Update googletest and include googlemock

Some tests in the Chromium verifier use gmock. Since upstream googletest considers them a single project now, just import both of them. Update-Note: As part of this, I've made gtest_main.cc now initializes gmock alongside gtest. This means BoringSSL's test targets now depend on both. Downstream builds where googletest and googlemock are separate build targets may need to add a dependency. (Though every downstream test I looked at treats them as one target, so this is most likely a no-op.) Bug: chromium:1322914 Change-Id: Ief38c675bc13a4639dee061d058580967ab99d41 Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/62945 Commit-Queue: Bob Beck <bbe@google.com> Reviewed-by: Bob Beck <bbe@google.com>
author: David Benjamin <davidben@google.com> 2023-09-01 21:23:01 -0400
committer: Boringssl LUCI CQ <boringssl-scoped@luci-project-accounts.iam.gserviceaccount.com> 2023-09-05 21:11:19 +0000
commit: fa343af32b77f5f005a651656732ae3f0b526774 (patch)
tree: d477a6527b92aa2fc074a263493581670dcd0df7 /third_party
parent: db1e9877fdabaf88494e2314cd527f09d5790281 (diff)
download: boringssl-fa343af32b77f5f005a651656732ae3f0b526774.zip
boringssl-fa343af32b77f5f005a651656732ae3f0b526774.tar.gz
boringssl-fa343af32b77f5f005a651656732ae3f0b526774.tar.bz2
244 files changed, 51320 insertions, 843 deletions
diff --git a/third_party/googletest/.clang-format b/third_party/googletest/.clang-format
new file mode 100644
index 0000000..5b9bfe6
--- /dev/null
+++ b/third_party/googletest/.clang-format
@@ -0,0 +1,4 @@
+# Run manually to reformat a file:
+# clang-format -i --style=file <file>
+Language:        Cpp
+BasedOnStyle:  Google
diff --git a/third_party/googletest/.github/ISSUE_TEMPLATE/00-bug_report.yml b/third_party/googletest/.github/ISSUE_TEMPLATE/00-bug_report.yml
new file mode 100644
index 0000000..586779a
--- /dev/null
+++ b/third_party/googletest/.github/ISSUE_TEMPLATE/00-bug_report.yml
@@ -0,0 +1,53 @@
+name: Bug Report
+description: Let us know that something does not work as expected.
+title: "[Bug]: Please title this bug report"
+body:
+  - type: textarea
+    id: what-happened
+    attributes:
+      label: Describe the issue
+      description: What happened, and what did you expect to happen?
+    validations:
+      required: true
+  - type: textarea
+    id: steps
+    attributes:
+      label: Steps to reproduce the problem
+      description: It is important that we are able to reproduce the problem that you are experiencing. Please provide all code and relevant steps to reproduce the problem, including your `BUILD`/`CMakeLists.txt` file and build commands. Links to a GitHub branch or [godbolt.org](https://godbolt.org/) that demonstrate the problem are also helpful.
+    validations:
+      required: true
+  - type: textarea
+    id: version
+    attributes:
+      label: What version of GoogleTest are you using?
+      description: Please include the output of `git rev-parse HEAD` or the GoogleTest release version number that you are using.
+    validations:
+      required: true
+  - type: textarea
+    id: os
+    attributes:
+      label: What operating system and version are you using?
+      description: If you are using a Linux distribution please include the name and version of the distribution as well.
+    validations:
+      required: true
+  - type: textarea
+    id: compiler
+    attributes:
+      label: What compiler and version are you using?
+      description: Please include the output of `gcc -v` or `clang -v`, or the equivalent for your compiler.
+    validations:
+      required: true
+  - type: textarea
+    id: buildsystem
+    attributes:
+      label: What build system are you using?
+      description: Please include the output of `bazel --version` or `cmake --version`, or the equivalent for your build system.
+    validations:
+      required: true
+  - type: textarea
+    id: additional
+    attributes:
+      label: Additional context
+      description: Add any other context about the problem here.
+    validations:
+      required: false
diff --git a/third_party/googletest/.github/ISSUE_TEMPLATE/10-feature_request.yml b/third_party/googletest/.github/ISSUE_TEMPLATE/10-feature_request.yml
new file mode 100644
index 0000000..f3bbc09
--- /dev/null
+++ b/third_party/googletest/.github/ISSUE_TEMPLATE/10-feature_request.yml
@@ -0,0 +1,33 @@
+name: Feature request
+description: Propose a new feature.
+title: "[FR]: Please title this feature request"
+labels: "enhancement"
+body:
+  - type: textarea
+    id: version
+    attributes:
+      label: Does the feature exist in the most recent commit?
+      description: We recommend using the latest commit from GitHub in your projects.
+    validations:
+      required: true
+  - type: textarea
+    id: why
+    attributes:
+      label: Why do we need this feature?
+      description: Ideally, explain why a combination of existing features cannot be used instead.
+    validations:
+      required: true
+  - type: textarea
+    id: proposal
+    attributes:
+      label: Describe the proposal.
+      description: Include a detailed description of the feature, with usage examples.
+    validations:
+      required: true
+  - type: textarea
+    id: platform
+    attributes:
+      label: Is the feature specific to an operating system, compiler, or build system version?
+      description: If it is, please specify which versions.
+    validations:
+      required: true
diff --git a/third_party/googletest/.github/ISSUE_TEMPLATE/config.yml b/third_party/googletest/.github/ISSUE_TEMPLATE/config.yml
new file mode 100644
index 0000000..65170d1
--- /dev/null
+++ b/third_party/googletest/.github/ISSUE_TEMPLATE/config.yml
@@ -0,0 +1,5 @@
+blank_issues_enabled: false
+contact_links:
+    - name: Get Help
+      url: https://github.com/google/googletest/discussions
+      about: Please ask and answer questions here.
diff --git a/third_party/googletest/.github/workflows/gtest-ci.yml b/third_party/googletest/.github/workflows/gtest-ci.yml
new file mode 100644
index 0000000..03a8cc5
--- /dev/null
+++ b/third_party/googletest/.github/workflows/gtest-ci.yml
@@ -0,0 +1,43 @@
+name: ci
+
+on:
+  push:
+  pull_request:
+
+env:
+  BAZEL_CXXOPTS: -std=c++14
+
+jobs:
+  Linux:
+    runs-on: ubuntu-latest
+    steps:
+
+    - uses: actions/checkout@v3
+      with:
+        fetch-depth: 0
+
+    - name: Tests
+      run: bazel test --cxxopt=-std=c++14 --features=external_include_paths --test_output=errors ...
+
+  macOS:
+    runs-on: macos-latest
+    steps:
+
+    - uses: actions/checkout@v3
+      with:
+        fetch-depth: 0
+
+    - name: Tests
+      run:  bazel test --cxxopt=-std=c++14 --features=external_include_paths --test_output=errors ...
+
+
+  Windows:
+    runs-on: windows-latest
+    steps:
+
+    - uses: actions/checkout@v3
+      with:
+        fetch-depth: 0
+
+    - name: Tests
+      run: bazel test --cxxopt=/std:c++14 --features=external_include_paths --test_output=errors ...
diff --git a/third_party/googletest/.gitignore b/third_party/googletest/.gitignore
new file mode 100644
index 0000000..fede02f
--- /dev/null
+++ b/third_party/googletest/.gitignore
@@ -0,0 +1,88 @@
+# Ignore CI build directory
+build/
+xcuserdata
+cmake-build-debug/
+.idea/
+bazel-bin
+bazel-genfiles
+bazel-googletest
+bazel-out
+bazel-testlogs
+# python
+*.pyc
+
+# Visual Studio files
+.vs
+*.sdf
+*.opensdf
+*.VC.opendb
+*.suo
+*.user
+_ReSharper.Caches/
+Win32-Debug/
+Win32-Release/
+x64-Debug/
+x64-Release/
+
+# VSCode files
+.cache/
+cmake-variants.yaml
+
+# Ignore autoconf / automake files
+Makefile.in
+aclocal.m4
+configure
+build-aux/
+autom4te.cache/
+googletest/m4/libtool.m4
+googletest/m4/ltoptions.m4
+googletest/m4/ltsugar.m4
+googletest/m4/ltversion.m4
+googletest/m4/lt~obsolete.m4
+googlemock/m4
+
+# Ignore generated directories.
+googlemock/fused-src/
+googletest/fused-src/
+
+# macOS files
+.DS_Store
+googletest/.DS_Store
+googletest/xcode/.DS_Store
+
+# Ignore cmake generated directories and files.
+CMakeFiles
+CTestTestfile.cmake
+Makefile
+cmake_install.cmake
+googlemock/CMakeFiles
+googlemock/CTestTestfile.cmake
+googlemock/Makefile
+googlemock/cmake_install.cmake
+googlemock/gtest
+/bin
+/googlemock/gmock.dir
+/googlemock/gmock_main.dir
+/googlemock/RUN_TESTS.vcxproj.filters
+/googlemock/RUN_TESTS.vcxproj
+/googlemock/INSTALL.vcxproj.filters
+/googlemock/INSTALL.vcxproj
+/googlemock/gmock_main.vcxproj.filters
+/googlemock/gmock_main.vcxproj
+/googlemock/gmock.vcxproj.filters
+/googlemock/gmock.vcxproj
+/googlemock/gmock.sln
+/googlemock/ALL_BUILD.vcxproj.filters
+/googlemock/ALL_BUILD.vcxproj
+/lib
+/Win32
+/ZERO_CHECK.vcxproj.filters
+/ZERO_CHECK.vcxproj
+/RUN_TESTS.vcxproj.filters
+/RUN_TESTS.vcxproj
+/INSTALL.vcxproj.filters
+/INSTALL.vcxproj
+/googletest-distribution.sln
+/CMakeCache.txt
+/ALL_BUILD.vcxproj.filters
+/ALL_BUILD.vcxproj
diff --git a/third_party/googletest/BUILD.bazel b/third_party/googletest/BUILD.bazel
new file mode 100644
index 0000000..b1e3b7f
--- /dev/null
+++ b/third_party/googletest/BUILD.bazel
@@ -0,0 +1,219 @@
+# Copyright 2017 Google Inc.
+# All Rights Reserved.
+#
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#
+#   Bazel Build for Google C++ Testing Framework(Google Test)
+
+package(default_visibility = ["//visibility:public"])
+
+licenses(["notice"])
+
+exports_files(["LICENSE"])
+
+config_setting(
+    name = "qnx",
+    constraint_values = ["@platforms//os:qnx"],
+)
+
+config_setting(
+    name = "windows",
+    constraint_values = ["@platforms//os:windows"],
+)
+
+config_setting(
+    name = "freebsd",
+    constraint_values = ["@platforms//os:freebsd"],
+)
+
+config_setting(
+    name = "openbsd",
+    constraint_values = ["@platforms//os:openbsd"],
+)
+
+config_setting(
+    name = "msvc_compiler",
+    flag_values = {
+        "@bazel_tools//tools/cpp:compiler": "msvc-cl",
+    },
+    visibility = [":__subpackages__"],
+)
+
+config_setting(
+    name = "has_absl",
+    values = {"define": "absl=1"},
+)
+
+# Library that defines the FRIEND_TEST macro.
+cc_library(
+    name = "gtest_prod",
+    hdrs = ["googletest/include/gtest/gtest_prod.h"],
+    includes = ["googletest/include"],
+)
+
+# Google Test including Google Mock
+cc_library(
+    name = "gtest",
+    srcs = glob(
+        include = [
+            "googletest/src/*.cc",
+            "googletest/src/*.h",
+            "googletest/include/gtest/**/*.h",
+            "googlemock/src/*.cc",
+            "googlemock/include/gmock/**/*.h",
+        ],
+        exclude = [
+            "googletest/src/gtest-all.cc",
+            "googletest/src/gtest_main.cc",
+            "googlemock/src/gmock-all.cc",
+            "googlemock/src/gmock_main.cc",
+        ],
+    ),
+    hdrs = glob([
+        "googletest/include/gtest/*.h",
+        "googlemock/include/gmock/*.h",
+    ]),
+    copts = select({
+        ":qnx": [],
+        ":windows": [],
+        "//conditions:default": ["-pthread"],
+    }),
+    defines = select({
+        ":has_absl": ["GTEST_HAS_ABSL=1"],
+        "//conditions:default": [],
+    }),
+    features = select({
+        ":windows": ["windows_export_all_symbols"],
+        "//conditions:default": [],
+    }),
+    includes = [
+        "googlemock",
+        "googlemock/include",
+        "googletest",
+        "googletest/include",
+    ],
+    linkopts = select({
+        ":qnx": ["-lregex"],
+        ":windows": [],
+        ":freebsd": [
+            "-lm",
+            "-pthread",
+        ],
+        ":openbsd": [
+            "-lm",
+            "-pthread",
+        ],
+        "//conditions:default": ["-pthread"],
+    }),
+    deps = select({
+        ":has_absl": [
+            "@com_google_absl//absl/container:flat_hash_set",
+            "@com_google_absl//absl/debugging:failure_signal_handler",
+            "@com_google_absl//absl/debugging:stacktrace",
+            "@com_google_absl//absl/debugging:symbolize",
+            "@com_google_absl//absl/flags:flag",
+            "@com_google_absl//absl/flags:parse",
+            "@com_google_absl//absl/flags:reflection",
+            "@com_google_absl//absl/flags:usage",
+            "@com_google_absl//absl/strings",
+            "@com_google_absl//absl/types:any",
+            "@com_google_absl//absl/types:optional",
+            "@com_google_absl//absl/types:variant",
+            "@com_googlesource_code_re2//:re2",
+        ],
+        "//conditions:default": [],
+    }),
+)
+
+cc_library(
+    name = "gtest_main",
+    srcs = ["googlemock/src/gmock_main.cc"],
+    features = select({
+        ":windows": ["windows_export_all_symbols"],
+        "//conditions:default": [],
+    }),
+    deps = [":gtest"],
+)
+
+# The following rules build samples of how to use gTest.
+cc_library(
+    name = "gtest_sample_lib",
+    srcs = [
+        "googletest/samples/sample1.cc",
+        "googletest/samples/sample2.cc",
+        "googletest/samples/sample4.cc",
+    ],
+    hdrs = [
+        "googletest/samples/prime_tables.h",
+        "googletest/samples/sample1.h",
+        "googletest/samples/sample2.h",
+        "googletest/samples/sample3-inl.h",
+        "googletest/samples/sample4.h",
+    ],
+    features = select({
+        ":windows": ["windows_export_all_symbols"],
+        "//conditions:default": [],
+    }),
+)
+
+cc_test(
+    name = "gtest_samples",
+    size = "small",
+    # All Samples except:
+    #   sample9 (main)
+    #   sample10 (main and takes a command line option and needs to be separate)
+    srcs = [
+        "googletest/samples/sample1_unittest.cc",
+        "googletest/samples/sample2_unittest.cc",
+        "googletest/samples/sample3_unittest.cc",
+        "googletest/samples/sample4_unittest.cc",
+        "googletest/samples/sample5_unittest.cc",
+        "googletest/samples/sample6_unittest.cc",
+        "googletest/samples/sample7_unittest.cc",
+        "googletest/samples/sample8_unittest.cc",
+    ],
+    linkstatic = 0,
+    deps = [
+        "gtest_sample_lib",
+        ":gtest_main",
+    ],
+)
+
+cc_test(
+    name = "sample9_unittest",
+    size = "small",
+    srcs = ["googletest/samples/sample9_unittest.cc"],
+    deps = [":gtest"],
+)
+
+cc_test(
+    name = "sample10_unittest",
+    size = "small",
+    srcs = ["googletest/samples/sample10_unittest.cc"],
+    deps = [":gtest"],
+)
diff --git a/third_party/googletest/CMakeLists.txt b/third_party/googletest/CMakeLists.txt
index 95bfa44..089ac98 100644
--- a/third_party/googletest/CMakeLists.txt
+++ b/third_party/googletest/CMakeLists.txt
@@ -1,338 +1,27 @@
-########################################################################
 # Note: CMake support is community-based. The maintainers do not use CMake
 # internally.
-#
-# CMake build script for Google Test.
-#
-# To run the tests for Google Test itself on Linux, use 'make test' or
-# ctest.  You can select which tests to run using 'ctest -R regex'.
-# For more options, run 'ctest --help'.
 
-# When other libraries are using a shared version of runtime libraries,
-# Google Test also has to use one.
-option(
-  gtest_force_shared_crt
-  "Use shared (DLL) run-time lib even when Google Test is built as static lib."
-  OFF)
+cmake_minimum_required(VERSION 3.13)
 
-option(gtest_build_tests "Build all of gtest's own tests." OFF)
+project(googletest-distribution)
+set(GOOGLETEST_VERSION 1.14.0)
 
-option(gtest_build_samples "Build gtest's sample programs." OFF)
-
-option(gtest_disable_pthreads "Disable uses of pthreads in gtest." OFF)
-
-option(
-  gtest_hide_internal_symbols
-  "Build gtest with internal symbols hidden in shared libraries."
-  OFF)
-
-# Defines pre_project_set_up_hermetic_build() and set_up_hermetic_build().
-include(cmake/hermetic_build.cmake OPTIONAL)
-
-if (COMMAND pre_project_set_up_hermetic_build)
-  pre_project_set_up_hermetic_build()
+if(NOT CYGWIN AND NOT MSYS AND NOT ${CMAKE_SYSTEM_NAME} STREQUAL QNX)
+  set(CMAKE_CXX_EXTENSIONS OFF)
 endif()
 
-########################################################################
-#
-# Project-wide settings
+enable_testing()
 
-# Name of the project.
-#
-# CMake files in this project can refer to the root source directory
-# as ${gtest_SOURCE_DIR} and to the root binary directory as
-# ${gtest_BINARY_DIR}.
-# Language "C" is required for find_package(Threads).
+include(CMakeDependentOption)
+include(GNUInstallDirs)
 
-# Project version:
-
-cmake_minimum_required(VERSION 3.5)
-cmake_policy(SET CMP0048 NEW)
-project(gtest VERSION ${GOOGLETEST_VERSION} LANGUAGES CXX C)
-
-if (POLICY CMP0063) # Visibility
-  cmake_policy(SET CMP0063 NEW)
-endif (POLICY CMP0063)
-
-if (COMMAND set_up_hermetic_build)
-  set_up_hermetic_build()
-endif()
-
-# These commands only run if this is the main project
-if(CMAKE_PROJECT_NAME STREQUAL "gtest" OR CMAKE_PROJECT_NAME STREQUAL "googletest-distribution")
-
-  # BUILD_SHARED_LIBS is a standard CMake variable, but we declare it here to
-  # make it prominent in the GUI.
-  option(BUILD_SHARED_LIBS "Build shared libraries (DLLs)." OFF)
+#Note that googlemock target already builds googletest
+option(BUILD_GMOCK "Builds the googlemock subproject" ON)
+option(INSTALL_GTEST "Enable installation of googletest. (Projects embedding googletest may want to turn this OFF.)" ON)
+option(GTEST_HAS_ABSL "Use Abseil and RE2. Requires Abseil and RE2 to be separately added to the build." OFF)
 
+if(BUILD_GMOCK)
+  add_subdirectory( googlemock )
 else()
-
-  mark_as_advanced(
-    gtest_force_shared_crt
-    gtest_build_tests
-    gtest_build_samples
-    gtest_disable_pthreads
-    gtest_hide_internal_symbols)
-
-endif()
-
-
-if (gtest_hide_internal_symbols)
-  set(CMAKE_CXX_VISIBILITY_PRESET hidden)
-  set(CMAKE_VISIBILITY_INLINES_HIDDEN 1)
-endif()
-
-# Define helper functions and macros used by Google Test.
-include(cmake/internal_utils.cmake)
-
-config_compiler_and_linker()  # Defined in internal_utils.cmake.
-
-# Needed to set the namespace for both the export targets and the
-# alias libraries
-set(cmake_package_name GTest CACHE INTERNAL "")
-
-# Create the CMake package file descriptors.
-if (INSTALL_GTEST)
-  include(CMakePackageConfigHelpers)
-  set(targets_export_name ${cmake_package_name}Targets CACHE INTERNAL "")
-  set(generated_dir "${CMAKE_CURRENT_BINARY_DIR}/generated" CACHE INTERNAL "")
-  set(cmake_files_install_dir "${CMAKE_INSTALL_LIBDIR}/cmake/${cmake_package_name}")
-  set(version_file "${generated_dir}/${cmake_package_name}ConfigVersion.cmake")
-  write_basic_package_version_file(${version_file} VERSION ${GOOGLETEST_VERSION} COMPATIBILITY AnyNewerVersion)
-  install(EXPORT ${targets_export_name}
-    NAMESPACE ${cmake_package_name}::
-    DESTINATION ${cmake_files_install_dir})
-  set(config_file "${generated_dir}/${cmake_package_name}Config.cmake")
-  configure_package_config_file("${gtest_SOURCE_DIR}/cmake/Config.cmake.in"
-    "${config_file}" INSTALL_DESTINATION ${cmake_files_install_dir})
-  install(FILES ${version_file} ${config_file}
-    DESTINATION ${cmake_files_install_dir})
-endif()
-
-# Where Google Test's .h files can be found.
-set(gtest_build_include_dirs
-  "${gtest_SOURCE_DIR}/include"
-  "${gtest_SOURCE_DIR}")
-include_directories(${gtest_build_include_dirs})
-
-########################################################################
-#
-# Defines the gtest & gtest_main libraries.  User tests should link
-# with one of them.
-
-# Google Test libraries.  We build them using more strict warnings than what
-# are used for other targets, to ensure that gtest can be compiled by a user
-# aggressive about warnings.
-cxx_library(gtest "${cxx_strict}" src/gtest-all.cc)
-set_target_properties(gtest PROPERTIES VERSION ${GOOGLETEST_VERSION})
-if(GTEST_HAS_ABSL)
-  target_compile_definitions(gtest PUBLIC GTEST_HAS_ABSL=1)
-  target_link_libraries(gtest PUBLIC
-    absl::failure_signal_handler
-    absl::stacktrace
-    absl::symbolize
-    absl::flags_parse
-    absl::flags_reflection
-    absl::flags_usage
-    absl::strings
-    absl::any
-    absl::optional
-    absl::variant
-    re2::re2
-  )
-endif()
-cxx_library(gtest_main "${cxx_strict}" src/gtest_main.cc)
-set_target_properties(gtest_main PROPERTIES VERSION ${GOOGLETEST_VERSION})
-# If the CMake version supports it, attach header directory information
-# to the targets for when we are part of a parent build (ie being pulled
-# in via add_subdirectory() rather than being a standalone build).
-if (DEFINED CMAKE_VERSION AND NOT "${CMAKE_VERSION}" VERSION_LESS "2.8.11")
-  string(REPLACE ";" "$<SEMICOLON>" dirs "${gtest_build_include_dirs}")
-  target_include_directories(gtest SYSTEM INTERFACE
-    "$<BUILD_INTERFACE:${dirs}>"
-    "$<INSTALL_INTERFACE:$<INSTALL_PREFIX>/${CMAKE_INSTALL_INCLUDEDIR}>")
-  target_include_directories(gtest_main SYSTEM INTERFACE
-    "$<BUILD_INTERFACE:${dirs}>"
-    "$<INSTALL_INTERFACE:$<INSTALL_PREFIX>/${CMAKE_INSTALL_INCLUDEDIR}>")
-endif()
-if(CMAKE_SYSTEM_NAME MATCHES "QNX")
-  target_link_libraries(gtest PUBLIC regex)
-endif()
-target_link_libraries(gtest_main PUBLIC gtest)
-
-########################################################################
-#
-# Install rules
-install_project(gtest gtest_main)
-
-########################################################################
-#
-# Samples on how to link user tests with gtest or gtest_main.
-#
-# They are not built by default.  To build them, set the
-# gtest_build_samples option to ON.  You can do it by running ccmake
-# or specifying the -Dgtest_build_samples=ON flag when running cmake.
-
-if (gtest_build_samples)
-  cxx_executable(sample1_unittest samples gtest_main samples/sample1.cc)
-  cxx_executable(sample2_unittest samples gtest_main samples/sample2.cc)
-  cxx_executable(sample3_unittest samples gtest_main)
-  cxx_executable(sample4_unittest samples gtest_main samples/sample4.cc)
-  cxx_executable(sample5_unittest samples gtest_main samples/sample1.cc)
-  cxx_executable(sample6_unittest samples gtest_main)
-  cxx_executable(sample7_unittest samples gtest_main)
-  cxx_executable(sample8_unittest samples gtest_main)
-  cxx_executable(sample9_unittest samples gtest)
-  cxx_executable(sample10_unittest samples gtest)
-endif()
-
-########################################################################
-#
-# Google Test's own tests.
-#
-# You can skip this section if you aren't interested in testing
-# Google Test itself.
-#
-# The tests are not built by default.  To build them, set the
-# gtest_build_tests option to ON.  You can do it by running ccmake
-# or specifying the -Dgtest_build_tests=ON flag when running cmake.
-
-if (gtest_build_tests)
-  # This must be set in the root directory for the tests to be run by
-  # 'make test' or ctest.
-  enable_testing()
-
-  ############################################################
-  # C++ tests built with standard compiler flags.
-
-  cxx_test(googletest-death-test-test gtest_main)
-  cxx_test(gtest_environment_test gtest)
-  cxx_test(googletest-filepath-test gtest_main)
-  cxx_test(googletest-listener-test gtest_main)
-  cxx_test(gtest_main_unittest gtest_main)
-  cxx_test(googletest-message-test gtest_main)
-  cxx_test(gtest_no_test_unittest gtest)
-  cxx_test(googletest-options-test gtest_main)
-  cxx_test(googletest-param-test-test gtest
-    test/googletest-param-test2-test.cc)
-  cxx_test(googletest-port-test gtest_main)
-  cxx_test(gtest_pred_impl_unittest gtest_main)
-  cxx_test(gtest_premature_exit_test gtest
-    test/gtest_premature_exit_test.cc)
-  cxx_test(googletest-printers-test gtest_main)
-  cxx_test(gtest_prod_test gtest_main
-    test/production.cc)
-  cxx_test(gtest_repeat_test gtest)
-  cxx_test(gtest_sole_header_test gtest_main)
-  cxx_test(gtest_stress_test gtest)
-  cxx_test(googletest-test-part-test gtest_main)
-  cxx_test(gtest_throw_on_failure_ex_test gtest)
-  cxx_test(gtest-typed-test_test gtest_main
-    test/gtest-typed-test2_test.cc)
-  cxx_test(gtest_unittest gtest_main)
-  cxx_test(gtest-unittest-api_test gtest)
-  cxx_test(gtest_skip_in_environment_setup_test gtest_main)
-  cxx_test(gtest_skip_test gtest_main)
-
-  ############################################################
-  # C++ tests built with non-standard compiler flags.
-
-  # MSVC 7.1 does not support STL with exceptions disabled.
-  if (NOT MSVC OR MSVC_VERSION GREATER 1310)
-    cxx_library(gtest_no_exception "${cxx_no_exception}"
-      src/gtest-all.cc)
-    cxx_library(gtest_main_no_exception "${cxx_no_exception}"
-      src/gtest-all.cc src/gtest_main.cc)
-  endif()
-  cxx_library(gtest_main_no_rtti "${cxx_no_rtti}"
-    src/gtest-all.cc src/gtest_main.cc)
-
-  cxx_test_with_flags(gtest-death-test_ex_nocatch_test
-    "${cxx_exception} -DGTEST_ENABLE_CATCH_EXCEPTIONS_=0"
-    gtest test/googletest-death-test_ex_test.cc)
-  cxx_test_with_flags(gtest-death-test_ex_catch_test
-    "${cxx_exception} -DGTEST_ENABLE_CATCH_EXCEPTIONS_=1"
-    gtest test/googletest-death-test_ex_test.cc)
-
-  cxx_test_with_flags(gtest_no_rtti_unittest "${cxx_no_rtti}"
-    gtest_main_no_rtti test/gtest_unittest.cc)
-
-  cxx_shared_library(gtest_dll "${cxx_default}"
-    src/gtest-all.cc src/gtest_main.cc)
-
-  cxx_executable_with_flags(gtest_dll_test_ "${cxx_default}"
-    gtest_dll test/gtest_all_test.cc)
-  set_target_properties(gtest_dll_test_
-                        PROPERTIES
-                        COMPILE_DEFINITIONS "GTEST_LINKED_AS_SHARED_LIBRARY=1")
-
-  ############################################################
-  # Python tests.
-
-  cxx_executable(googletest-break-on-failure-unittest_ test gtest)
-  py_test(googletest-break-on-failure-unittest)
-
-  py_test(gtest_skip_check_output_test)
-  py_test(gtest_skip_environment_check_output_test)
-
-  # Visual Studio .NET 2003 does not support STL with exceptions disabled.
-  if (NOT MSVC OR MSVC_VERSION GREATER 1310)  # 1310 is Visual Studio .NET 2003
-    cxx_executable_with_flags(
-      googletest-catch-exceptions-no-ex-test_
-      "${cxx_no_exception}"
-      gtest_main_no_exception
-      test/googletest-catch-exceptions-test_.cc)
-  endif()
-
-  cxx_executable_with_flags(
-    googletest-catch-exceptions-ex-test_
-    "${cxx_exception}"
-    gtest_main
-    test/googletest-catch-exceptions-test_.cc)
-  py_test(googletest-catch-exceptions-test)
-
-  cxx_executable(googletest-color-test_ test gtest)
-  py_test(googletest-color-test)
-
-  cxx_executable(googletest-env-var-test_ test gtest)
-  py_test(googletest-env-var-test)
-
-  cxx_executable(googletest-filter-unittest_ test gtest)
-  py_test(googletest-filter-unittest)
-
-  cxx_executable(gtest_help_test_ test gtest_main)
-  py_test(gtest_help_test)
-
-  cxx_executable(googletest-list-tests-unittest_ test gtest)
-  py_test(googletest-list-tests-unittest)
-
-  cxx_executable(googletest-output-test_ test gtest)
-  py_test(googletest-output-test --no_stacktrace_support)
-
-  cxx_executable(googletest-shuffle-test_ test gtest)
-  py_test(googletest-shuffle-test)
-
-  # MSVC 7.1 does not support STL with exceptions disabled.
-  if (NOT MSVC OR MSVC_VERSION GREATER 1310)
-    cxx_executable(googletest-throw-on-failure-test_ test gtest_no_exception)
-    set_target_properties(googletest-throw-on-failure-test_
-      PROPERTIES
-      COMPILE_FLAGS "${cxx_no_exception}")
-    py_test(googletest-throw-on-failure-test)
-  endif()
-
-  cxx_executable(googletest-uninitialized-test_ test gtest)
-  py_test(googletest-uninitialized-test)
-
-  cxx_executable(gtest_list_output_unittest_ test gtest)
-  py_test(gtest_list_output_unittest)
-
-  cxx_executable(gtest_xml_outfile1_test_ test gtest_main)
-  cxx_executable(gtest_xml_outfile2_test_ test gtest_main)
-  py_test(gtest_xml_outfiles_test)
-  py_test(googletest-json-outfiles-test)
-
-  cxx_executable(gtest_xml_output_unittest_ test gtest)
-  py_test(gtest_xml_output_unittest --no_stacktrace_support)
-  py_test(googletest-json-output-unittest --no_stacktrace_support)
+  add_subdirectory( googletest )
 endif()
diff --git a/third_party/googletest/CONTRIBUTING.md b/third_party/googletest/CONTRIBUTING.md
new file mode 100644
index 0000000..ab5a47b
--- /dev/null
+++ b/third_party/googletest/CONTRIBUTING.md
@@ -0,0 +1,141 @@
+# How to become a contributor and submit your own code
+
+## Contributor License Agreements
+
+We'd love to accept your patches! Before we can take them, we have to jump a
+couple of legal hurdles.
+
+Please fill out either the individual or corporate Contributor License Agreement
+(CLA).
+
+*   If you are an individual writing original source code and you're sure you
+    own the intellectual property, then you'll need to sign an
+    [individual CLA](https://developers.google.com/open-source/cla/individual).
+*   If you work for a company that wants to allow you to contribute your work,
+    then you'll need to sign a
+    [corporate CLA](https://developers.google.com/open-source/cla/corporate).
+
+Follow either of the two links above to access the appropriate CLA and
+instructions for how to sign and return it. Once we receive it, we'll be able to
+accept your pull requests.
+
+## Are you a Googler?
+
+If you are a Googler, please make an attempt to submit an internal contribution
+rather than a GitHub Pull Request. If you are not able to submit internally, a
+PR is acceptable as an alternative.
+
+## Contributing A Patch
+
+1.  Submit an issue describing your proposed change to the
+    [issue tracker](https://github.com/google/googletest/issues).
+2.  Please don't mix more than one logical change per submittal, because it
+    makes the history hard to follow. If you want to make a change that doesn't
+    have a corresponding issue in the issue tracker, please create one.
+3.  Also, coordinate with team members that are listed on the issue in question.
+    This ensures that work isn't being duplicated and communicating your plan
+    early also generally leads to better patches.
+4.  If your proposed change is accepted, and you haven't already done so, sign a
+    Contributor License Agreement
+    ([see details above](#contributor-license-agreements)).
+5.  Fork the desired repo, develop and test your code changes.
+6.  Ensure that your code adheres to the existing style in the sample to which
+    you are contributing.
+7.  Ensure that your code has an appropriate set of unit tests which all pass.
+8.  Submit a pull request.
+
+## The Google Test and Google Mock Communities
+
+The Google Test community exists primarily through the
+[discussion group](https://groups.google.com/group/googletestframework) and the
+GitHub repository. Likewise, the Google Mock community exists primarily through
+their own [discussion group](https://groups.google.com/group/googlemock). You
+are definitely encouraged to contribute to the discussion and you can also help
+us to keep the effectiveness of the group high by following and promoting the
+guidelines listed here.
+
+### Please Be Friendly
+
+Showing courtesy and respect to others is a vital part of the Google culture,
+and we strongly encourage everyone participating in Google Test development to
+join us in accepting nothing less. Of course, being courteous is not the same as
+failing to constructively disagree with each other, but it does mean that we
+should be respectful of each other when enumerating the 42 technical reasons
+that a particular proposal may not be the best choice. There's never a reason to
+be antagonistic or dismissive toward anyone who is sincerely trying to
+contribute to a discussion.
+
+Sure, C++ testing is serious business and all that, but it's also a lot of fun.
+Let's keep it that way. Let's strive to be one of the friendliest communities in
+all of open source.
+
+As always, discuss Google Test in the official GoogleTest discussion group. You
+don't have to actually submit code in order to sign up. Your participation
+itself is a valuable contribution.
+
+## Style
+
+To keep the source consistent, readable, diffable and easy to merge, we use a
+fairly rigid coding style, as defined by the
+[google-styleguide](https://github.com/google/styleguide) project. All patches
+will be expected to conform to the style outlined
+[here](https://google.github.io/styleguide/cppguide.html). Use
+[.clang-format](https://github.com/google/googletest/blob/main/.clang-format) to
+check your formatting.
+
+## Requirements for Contributors
+
+If you plan to contribute a patch, you need to build Google Test, Google Mock,
+and their own tests from a git checkout, which has further requirements:
+
+*   [Python](https://www.python.org/) v3.6 or newer (for running some of the
+    tests and re-generating certain source files from templates)
+*   [CMake](https://cmake.org/) v2.8.12 or newer
+
+## Developing Google Test and Google Mock
+
+This section discusses how to make your own changes to the Google Test project.
+
+### Testing Google Test and Google Mock Themselves
+
+To make sure your changes work as intended and don't break existing
+functionality, you'll want to compile and run Google Test and GoogleMock's own
+tests. For that you can use CMake:
+
+```
+mkdir mybuild
+cd mybuild
+cmake -Dgtest_build_tests=ON -Dgmock_build_tests=ON ${GTEST_REPO_DIR}
+```
+
+To choose between building only Google Test or Google Mock, you may modify your
+cmake command to be one of each
+
+```
+cmake -Dgtest_build_tests=ON ${GTEST_DIR} # sets up Google Test tests
+cmake -Dgmock_build_tests=ON ${GMOCK_DIR} # sets up Google Mock tests
+```
+
+Make sure you have Python installed, as some of Google Test's tests are written
+in Python. If the cmake command complains about not being able to find Python
+(`Could NOT find PythonInterp (missing: PYTHON_EXECUTABLE)`), try telling it
+explicitly where your Python executable can be found:
+
+```
+cmake -DPYTHON_EXECUTABLE=path/to/python ...
+```
+
+Next, you can build Google Test and / or Google Mock and all desired tests. On
+\*nix, this is usually done by
+
+```
+make
+```
+
+To run the tests, do
+
+```
+make test
+```
+
+All tests should pass.
diff --git a/third_party/googletest/METADATA b/third_party/googletest/METADATA
index a01eef8..0766f88 100644
--- a/third_party/googletest/METADATA
+++ b/third_party/googletest/METADATA
@@ -1,15 +1,11 @@
 name: "googletest"
-description: "googletest is Google's C++ test framework."
+description: "Google Testing and Mocking Framework"
 
 third_party {
   url {
     type: HOMEPAGE
     value: "https://github.com/google/googletest"
   }
-  version: "bb2941fcc611b9e4eaf16f156e8c723348bf0931"
-  last_upgrade_date { year: 2023 month: 5 day: 11 }
-
-  local_modifications:
-      "Only googletest, not googlemock, is included."
-      "CONTRIBUTORS and LICENSE files copied from the top-level."
+  version: "8a6feabf04bec8fb125e0df0ad1195c42350725f"
+  last_upgrade_date { year: 2023 month: 9 day: 1 }
 }
diff --git a/third_party/googletest/README.md b/third_party/googletest/README.md
index 995834e..c1c1446 100644
--- a/third_party/googletest/README.md
+++ b/third_party/googletest/README.md
@@ -1,231 +1,146 @@
-### Generic Build Instructions
-
-#### Setup
-
-To build GoogleTest and your tests that use it, you need to tell your build
-system where to find its headers and source files. The exact way to do it
-depends on which build system you use, and is usually straightforward.
-
-### Build with CMake
-
-GoogleTest comes with a CMake build script
-([CMakeLists.txt](https://github.com/google/googletest/blob/main/CMakeLists.txt))
-that can be used on a wide range of platforms ("C" stands for cross-platform.).
-If you don't have CMake installed already, you can download it for free from
-<http://www.cmake.org/>.
-
-CMake works by generating native makefiles or build projects that can be used in
-the compiler environment of your choice. You can either build GoogleTest as a
-standalone project or it can be incorporated into an existing CMake build for
-another project.
-
-#### Standalone CMake Project
-
-When building GoogleTest as a standalone project, the typical workflow starts
-with
-
-```
-git clone https://github.com/google/googletest.git -b v1.13.0
-cd googletest        # Main directory of the cloned repository.
-mkdir build          # Create a directory to hold the build output.
-cd build
-cmake ..             # Generate native build scripts for GoogleTest.
-```
-
-The above command also includes GoogleMock by default. And so, if you want to
-build only GoogleTest, you should replace the last command with
-
-```
-cmake .. -DBUILD_GMOCK=OFF
-```
-
-If you are on a \*nix system, you should now see a Makefile in the current
-directory. Just type `make` to build GoogleTest. And then you can simply install
-GoogleTest if you are a system administrator.
-
-```
-make
-sudo make install    # Install in /usr/local/ by default
-```
-
-If you use Windows and have Visual Studio installed, a `gtest.sln` file and
-several `.vcproj` files will be created. You can then build them using Visual
-Studio.
-
-On Mac OS X with Xcode installed, a `.xcodeproj` file will be generated.
-
-#### Incorporating Into An Existing CMake Project
-
-If you want to use GoogleTest in a project which already uses CMake, the easiest
-way is to get installed libraries and headers.
-
-*   Import GoogleTest by using `find_package` (or `pkg_check_modules`). For
-    example, if `find_package(GTest CONFIG REQUIRED)` succeeds, you can use the
-    libraries as `GTest::gtest`, `GTest::gmock`.
-
-And a more robust and flexible approach is to build GoogleTest as part of that
-project directly. This is done by making the GoogleTest source code available to
-the main build and adding it using CMake's `add_subdirectory()` command. This
-has the significant advantage that the same compiler and linker settings are
-used between GoogleTest and the rest of your project, so issues associated with
-using incompatible libraries (eg debug/release), etc. are avoided. This is
-particularly useful on Windows. Making GoogleTest's source code available to the
-main build can be done a few different ways:
-
-*   Download the GoogleTest source code manually and place it at a known
-    location. This is the least flexible approach and can make it more difficult
-    to use with continuous integration systems, etc.
-*   Embed the GoogleTest source code as a direct copy in the main project's
-    source tree. This is often the simplest approach, but is also the hardest to
-    keep up to date. Some organizations may not permit this method.
-*   Add GoogleTest as a git submodule or equivalent. This may not always be
-    possible or appropriate. Git submodules, for example, have their own set of
-    advantages and drawbacks.
-*   Use CMake to download GoogleTest as part of the build's configure step. This
-    approach doesn't have the limitations of the other methods.
-
-The last of the above methods is implemented with a small piece of CMake code
-that downloads and pulls the GoogleTest code into the main build.
-
-Just add to your `CMakeLists.txt`:
-
-```cmake
-include(FetchContent)
-FetchContent_Declare(
-  googletest
-  # Specify the commit you depend on and update it regularly.
-  URL https://github.com/google/googletest/archive/5376968f6948923e2411081fd9372e71a59d8e77.zip
-)
-# For Windows: Prevent overriding the parent project's compiler/linker settings
-set(gtest_force_shared_crt ON CACHE BOOL "" FORCE)
-FetchContent_MakeAvailable(googletest)
-
-# Now simply link against gtest or gtest_main as needed. Eg
-add_executable(example example.cpp)
-target_link_libraries(example gtest_main)
-add_test(NAME example_test COMMAND example)
-```
-
-Note that this approach requires CMake 3.14 or later due to its use of the
-`FetchContent_MakeAvailable()` command.
-
-##### Visual Studio Dynamic vs Static Runtimes
-
-By default, new Visual Studio projects link the C runtimes dynamically but
-GoogleTest links them statically. This will generate an error that looks
-something like the following: gtest.lib(gtest-all.obj) : error LNK2038: mismatch
-detected for 'RuntimeLibrary': value 'MTd_StaticDebug' doesn't match value
-'MDd_DynamicDebug' in main.obj
-
-GoogleTest already has a CMake option for this: `gtest_force_shared_crt`
-
-Enabling this option will make gtest link the runtimes dynamically too, and
-match the project in which it is included.
-
-#### C++ Standard Version
-
-An environment that supports C++11 is required in order to successfully build
-GoogleTest. One way to ensure this is to specify the standard in the top-level
-project, for example by using the `set(CMAKE_CXX_STANDARD 11)` command. If this
-is not feasible, for example in a C project using GoogleTest for validation,
-then it can be specified by adding it to the options for cmake via the
-`DCMAKE_CXX_FLAGS` option.
-
-### Tweaking GoogleTest
-
-GoogleTest can be used in diverse environments. The default configuration may
-not work (or may not work well) out of the box in some environments. However,
-you can easily tweak GoogleTest by defining control macros on the compiler
-command line. Generally, these macros are named like `GTEST_XYZ` and you define
-them to either 1 or 0 to enable or disable a certain feature.
-
-We list the most frequently used macros below. For a complete list, see file
-[include/gtest/internal/gtest-port.h](https://github.com/google/googletest/blob/main/googletest/include/gtest/internal/gtest-port.h).
-
-### Multi-threaded Tests
-
-GoogleTest is thread-safe where the pthread library is available. After
-`#include "gtest/gtest.h"`, you can check the
-`GTEST_IS_THREADSAFE` macro to see whether this is the case (yes if the macro is
-`#defined` to 1, no if it's undefined.).
-
-If GoogleTest doesn't correctly detect whether pthread is available in your
-environment, you can force it with
-
-```
--DGTEST_HAS_PTHREAD=1
-```
-
-or
-
-```
--DGTEST_HAS_PTHREAD=0
-```
-
-When GoogleTest uses pthread, you may need to add flags to your compiler and/or
-linker to select the pthread library, or you'll get link errors. If you use the
-CMake script, this is taken care of for you. If you use your own build script,
-you'll need to read your compiler and linker's manual to figure out what flags
-to add.
-
-### As a Shared Library (DLL)
-
-GoogleTest is compact, so most users can build and link it as a static library
-for the simplicity. You can choose to use GoogleTest as a shared library (known
-as a DLL on Windows) if you prefer.
-
-To compile *gtest* as a shared library, add
-
-```
--DGTEST_CREATE_SHARED_LIBRARY=1
-```
-
-to the compiler flags. You'll also need to tell the linker to produce a shared
-library instead - consult your linker's manual for how to do it.
-
-To compile your *tests* that use the gtest shared library, add
-
-```
--DGTEST_LINKED_AS_SHARED_LIBRARY=1
-```
-
-to the compiler flags.
-
-Note: while the above steps aren't technically necessary today when using some
-compilers (e.g. GCC), they may become necessary in the future, if we decide to
-improve the speed of loading the library (see
-<https://gcc.gnu.org/wiki/Visibility> for details). Therefore you are
-recommended to always add the above flags when using GoogleTest as a shared
-library. Otherwise a future release of GoogleTest may break your build script.
-
-### Avoiding Macro Name Clashes
-
-In C++, macros don't obey namespaces. Therefore two libraries that both define a
-macro of the same name will clash if you `#include` both definitions. In case a
-GoogleTest macro clashes with another library, you can force GoogleTest to
-rename its macro to avoid the conflict.
-
-Specifically, if both GoogleTest and some other code define macro FOO, you can
-add
-
-```
--DGTEST_DONT_DEFINE_FOO=1
-```
-
-to the compiler flags to tell GoogleTest to change the macro's name from `FOO`
-to `GTEST_FOO`. Currently `FOO` can be `ASSERT_EQ`, `ASSERT_FALSE`, `ASSERT_GE`,
-`ASSERT_GT`, `ASSERT_LE`, `ASSERT_LT`, `ASSERT_NE`, `ASSERT_TRUE`,
-`EXPECT_FALSE`, `EXPECT_TRUE`, `FAIL`, `SUCCEED`, `TEST`, or `TEST_F`. For
-example, with `-DGTEST_DONT_DEFINE_TEST=1`, you'll need to write
-
-```
-GTEST_TEST(SomeTest, DoesThis) { ... }
-```
-
-instead of
-
-```
-TEST(SomeTest, DoesThis) { ... }
-```
-
-in order to define a test.
+# GoogleTest
+
+### Announcements
+
+#### Live at Head
+
+GoogleTest now follows the
+[Abseil Live at Head philosophy](https://abseil.io/about/philosophy#upgrade-support).
+We recommend
+[updating to the latest commit in the `main` branch as often as possible](https://github.com/abseil/abseil-cpp/blob/master/FAQ.md#what-is-live-at-head-and-how-do-i-do-it).
+We do publish occasional semantic versions, tagged with
+`v${major}.${minor}.${patch}` (e.g. `v1.14.0`).
+
+#### Documentation Updates
+
+Our documentation is now live on GitHub Pages at
+https://google.github.io/googletest/. We recommend browsing the documentation on
+GitHub Pages rather than directly in the repository.
+
+#### Release 1.14.0
+
+[Release 1.14.0](https://github.com/google/googletest/releases/tag/v1.14.0) is
+now available.
+
+The 1.14.x branch requires at least C++14.
+
+#### Continuous Integration
+
+We use Google's internal systems for continuous integration. \
+GitHub Actions were added for the convenience of open-source contributors. They
+are exclusively maintained by the open-source community and not used by the
+GoogleTest team.
+
+#### Coming Soon
+
+*   We are planning to take a dependency on
+    [Abseil](https://github.com/abseil/abseil-cpp).
+*   More documentation improvements are planned.
+
+## Welcome to **GoogleTest**, Google's C++ test framework!
+
+This repository is a merger of the formerly separate GoogleTest and GoogleMock
+projects. These were so closely related that it makes sense to maintain and
+release them together.
+
+### Getting Started
+
+See the [GoogleTest User's Guide](https://google.github.io/googletest/) for
+documentation. We recommend starting with the
+[GoogleTest Primer](https://google.github.io/googletest/primer.html).
+
+More information about building GoogleTest can be found at
+[googletest/README.md](googletest/README.md).
+
+## Features
+
+*   xUnit test framework: \
+    Googletest is based on the [xUnit](https://en.wikipedia.org/wiki/XUnit)
+    testing framework, a popular architecture for unit testing
+*   Test discovery: \
+    Googletest automatically discovers and runs your tests, eliminating the need
+    to manually register your tests
+*   Rich set of assertions: \
+    Googletest provides a variety of assertions, such as equality, inequality,
+    exceptions, and more, making it easy to test your code
+*   User-defined assertions: \
+    You can define your own assertions with Googletest, making it simple to
+    write tests that are specific to your code
+*   Death tests: \
+    Googletest supports death tests, which verify that your code exits in a
+    certain way, making it useful for testing error-handling code
+*   Fatal and non-fatal failures: \
+    You can specify whether a test failure should be treated as fatal or
+    non-fatal with Googletest, allowing tests to continue running even if a
+    failure occurs
+*   Value-parameterized tests: \
+    Googletest supports value-parameterized tests, which run multiple times with
+    different input values, making it useful for testing functions that take
+    different inputs
+*   Type-parameterized tests: \
+    Googletest also supports type-parameterized tests, which run with different
+    data types, making it useful for testing functions that work with different
+    data types
+*   Various options for running tests: \
+    Googletest provides many options for running tests including running
+    individual tests, running tests in a specific order and running tests in
+    parallel
+
+## Supported Platforms
+
+GoogleTest follows Google's
+[Foundational C++ Support Policy](https://opensource.google/documentation/policies/cplusplus-support).
+See
+[this table](https://github.com/google/oss-policies-info/blob/main/foundational-cxx-support-matrix.md)
+for a list of currently supported versions of compilers, platforms, and build
+tools.
+
+## Who Is Using GoogleTest?
+
+In addition to many internal projects at Google, GoogleTest is also used by the
+following notable projects:
+
+*   The [Chromium projects](https://www.chromium.org/) (behind the Chrome
+    browser and Chrome OS).
+*   The [LLVM](https://llvm.org/) compiler.
+*   [Protocol Buffers](https://github.com/google/protobuf), Google's data
+    interchange format.
+*   The [OpenCV](https://opencv.org/) computer vision library.
+
+## Related Open Source Projects
+
+[GTest Runner](https://github.com/nholthaus/gtest-runner) is a Qt5 based
+automated test-runner and Graphical User Interface with powerful features for
+Windows and Linux platforms.
+
+[GoogleTest UI](https://github.com/ospector/gtest-gbar) is a test runner that
+runs your test binary, allows you to track its progress via a progress bar, and
+displays a list of test failures. Clicking on one shows failure text. GoogleTest
+UI is written in C#.
+
+[GTest TAP Listener](https://github.com/kinow/gtest-tap-listener) is an event
+listener for GoogleTest that implements the
+[TAP protocol](https://en.wikipedia.org/wiki/Test_Anything_Protocol) for test
+result output. If your test runner understands TAP, you may find it useful.
+
+[gtest-parallel](https://github.com/google/gtest-parallel) is a test runner that
+runs tests from your binary in parallel to provide significant speed-up.
+
+[GoogleTest Adapter](https://marketplace.visualstudio.com/items?itemName=DavidSchuldenfrei.gtest-adapter)
+is a VS Code extension allowing to view GoogleTest in a tree view and run/debug
+your tests.
+
+[C++ TestMate](https://github.com/matepek/vscode-catch2-test-adapter) is a VS
+Code extension allowing to view GoogleTest in a tree view and run/debug your
+tests.
+
+[Cornichon](https://pypi.org/project/cornichon/) is a small Gherkin DSL parser
+that generates stub code for GoogleTest.
+
+## Contributing Changes
+
+Please read
+[`CONTRIBUTING.md`](https://github.com/google/googletest/blob/main/CONTRIBUTING.md)
+for details on how to contribute to this project.
+
+Happy testing!
diff --git a/third_party/googletest/WORKSPACE b/third_party/googletest/WORKSPACE
new file mode 100644
index 0000000..f819ffe
--- /dev/null
+++ b/third_party/googletest/WORKSPACE
@@ -0,0 +1,27 @@
+workspace(name = "com_google_googletest")
+
+load("//:googletest_deps.bzl", "googletest_deps")
+googletest_deps()
+
+load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
+
+http_archive(
+  name = "rules_python",  # 2023-07-31T20:39:27Z
+  sha256 = "1250b59a33c591a1c4ba68c62e95fc88a84c334ec35a2e23f46cbc1b9a5a8b55",
+  strip_prefix = "rules_python-e355becc30275939d87116a4ec83dad4bb50d9e1",
+  urls = ["https://github.com/bazelbuild/rules_python/archive/e355becc30275939d87116a4ec83dad4bb50d9e1.zip"],
+)
+
+http_archive(
+  name = "bazel_skylib",  # 2023-05-31T19:24:07Z
+  sha256 = "08c0386f45821ce246bbbf77503c973246ed6ee5c3463e41efc197fa9bc3a7f4",
+  strip_prefix = "bazel-skylib-288731ef9f7f688932bd50e704a91a45ec185f9b",
+  urls = ["https://github.com/bazelbuild/bazel-skylib/archive/288731ef9f7f688932bd50e704a91a45ec185f9b.zip"],
+)
+
+http_archive(
+  name = "platforms",  # 2023-07-28T19:44:27Z
+  sha256 = "40eb313613ff00a5c03eed20aba58890046f4d38dec7344f00bb9a8867853526",
+  strip_prefix = "platforms-4ad40ef271da8176d4fc0194d2089b8a76e19d7b",
+  urls = ["https://github.com/bazelbuild/platforms/archive/4ad40ef271da8176d4fc0194d2089b8a76e19d7b.zip"],
+)
diff --git a/third_party/googletest/ci/linux-presubmit.sh b/third_party/googletest/ci/linux-presubmit.sh
new file mode 100644
index 0000000..a1caa27
--- /dev/null
+++ b/third_party/googletest/ci/linux-presubmit.sh
@@ -0,0 +1,137 @@
+#!/bin/bash
+#
+# Copyright 2020, Google Inc.
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+set -euox pipefail
+
+readonly LINUX_LATEST_CONTAINER="gcr.io/google.com/absl-177019/linux_hybrid-latest:20230816"
+readonly LINUX_GCC_FLOOR_CONTAINER="gcr.io/google.com/absl-177019/linux_gcc-floor:20230120"
+
+if [[ -z ${GTEST_ROOT:-} ]]; then
+  GTEST_ROOT="$(realpath $(dirname ${0})/..)"
+fi
+
+if [[ -z ${STD:-} ]]; then
+  STD="c++14 c++17 c++20"
+fi
+
+# Test the CMake build
+for cc in /usr/local/bin/gcc /opt/llvm/clang/bin/clang; do
+  for cmake_off_on in OFF ON; do
+    time docker run \
+      --volume="${GTEST_ROOT}:/src:ro" \
+      --tmpfs="/build:exec" \
+      --workdir="/build" \
+      --rm \
+      --env="CC=${cc}" \
+      --env=CXXFLAGS="-Werror -Wdeprecated" \
+      ${LINUX_LATEST_CONTAINER} \
+      /bin/bash -c "
+        cmake /src \
+          -DCMAKE_CXX_STANDARD=14 \
+          -Dgtest_build_samples=ON \
+          -Dgtest_build_tests=ON \
+          -Dgmock_build_tests=ON \
+          -Dcxx_no_exception=${cmake_off_on} \
+          -Dcxx_no_rtti=${cmake_off_on} && \
+        make -j$(nproc) && \
+        ctest -j$(nproc) --output-on-failure"
+  done
+done
+
+# Do one test with an older version of GCC
+time docker run \
+  --volume="${GTEST_ROOT}:/src:ro" \
+  --workdir="/src" \
+  --rm \
+  --env="CC=/usr/local/bin/gcc" \
+  --env="BAZEL_CXXOPTS=-std=c++14" \
+  ${LINUX_GCC_FLOOR_CONTAINER} \
+    /usr/local/bin/bazel test ... \
+      --copt="-Wall" \
+      --copt="-Werror" \
+      --copt="-Wuninitialized" \
+      --copt="-Wundef" \
+      --copt="-Wno-error=pragmas" \
+      --distdir="/bazel-distdir" \
+      --features=external_include_paths \
+      --keep_going \
+      --show_timestamps \
+      --test_output=errors
+
+# Test GCC
+for std in ${STD}; do
+  for absl in 0 1; do
+    time docker run \
+      --volume="${GTEST_ROOT}:/src:ro" \
+      --workdir="/src" \
+      --rm \
+      --env="CC=/usr/local/bin/gcc" \
+      --env="BAZEL_CXXOPTS=-std=${std}" \
+      ${LINUX_LATEST_CONTAINER} \
+      /usr/local/bin/bazel test ... \
+        --copt="-Wall" \
+        --copt="-Werror" \
+        --copt="-Wuninitialized" \
+        --copt="-Wundef" \
+        --define="absl=${absl}" \
+        --distdir="/bazel-distdir" \
+        --features=external_include_paths \
+        --keep_going \
+        --show_timestamps \
+        --test_output=errors
+  done
+done
+
+# Test Clang
+for std in ${STD}; do
+  for absl in 0 1; do
+    time docker run \
+      --volume="${GTEST_ROOT}:/src:ro" \
+      --workdir="/src" \
+      --rm \
+      --env="CC=/opt/llvm/clang/bin/clang" \
+      --env="BAZEL_CXXOPTS=-std=${std}" \
+      ${LINUX_LATEST_CONTAINER} \
+      /usr/local/bin/bazel test ... \
+        --copt="--gcc-toolchain=/usr/local" \
+        --copt="-Wall" \
+        --copt="-Werror" \
+        --copt="-Wuninitialized" \
+        --copt="-Wundef" \
+        --define="absl=${absl}" \
+        --distdir="/bazel-distdir" \
+        --features=external_include_paths \
+        --keep_going \
+        --linkopt="--gcc-toolchain=/usr/local" \
+        --show_timestamps \
+        --test_output=errors
+  done
+done
diff --git a/third_party/googletest/ci/macos-presubmit.sh b/third_party/googletest/ci/macos-presubmit.sh
new file mode 100644
index 0000000..681ebc2
--- /dev/null
+++ b/third_party/googletest/ci/macos-presubmit.sh
@@ -0,0 +1,76 @@
+#!/bin/bash
+#
+# Copyright 2020, Google Inc.
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+set -euox pipefail
+
+if [[ -z ${GTEST_ROOT:-} ]]; then
+  GTEST_ROOT="$(realpath $(dirname ${0})/..)"
+fi
+
+# Test the CMake build
+for cmake_off_on in OFF ON; do
+  BUILD_DIR=$(mktemp -d build_dir.XXXXXXXX)
+  cd ${BUILD_DIR}
+  time cmake ${GTEST_ROOT} \
+    -DCMAKE_CXX_STANDARD=14 \
+    -Dgtest_build_samples=ON \
+    -Dgtest_build_tests=ON \
+    -Dgmock_build_tests=ON \
+    -Dcxx_no_exception=${cmake_off_on} \
+    -Dcxx_no_rtti=${cmake_off_on}
+  time make
+  time ctest -j$(nproc) --output-on-failure
+done
+
+# Test the Bazel build
+
+# If we are running on Kokoro, check for a versioned Bazel binary.
+KOKORO_GFILE_BAZEL_BIN="bazel-5.1.1-darwin-x86_64"
+if [[ ${KOKORO_GFILE_DIR:-} ]] && [[ -f ${KOKORO_GFILE_DIR}/${KOKORO_GFILE_BAZEL_BIN} ]]; then
+  BAZEL_BIN="${KOKORO_GFILE_DIR}/${KOKORO_GFILE_BAZEL_BIN}"
+  chmod +x ${BAZEL_BIN}
+else
+  BAZEL_BIN="bazel"
+fi
+
+cd ${GTEST_ROOT}
+for absl in 0 1; do
+  ${BAZEL_BIN} test ... \
+    --copt="-Wall" \
+    --copt="-Werror" \
+    --copt="-Wundef" \
+    --cxxopt="-std=c++14" \
+    --define="absl=${absl}" \
+    --features=external_include_paths \
+    --keep_going \
+    --show_timestamps \
+    --test_output=errors
+done
diff --git a/third_party/googletest/ci/windows-presubmit.bat b/third_party/googletest/ci/windows-presubmit.bat
new file mode 100644
index 0000000..48962eb
--- /dev/null
+++ b/third_party/googletest/ci/windows-presubmit.bat
@@ -0,0 +1,58 @@
+SETLOCAL ENABLEDELAYEDEXPANSION
+
+SET BAZEL_EXE=%KOKORO_GFILE_DIR%\bazel-5.1.1-windows-x86_64.exe
+
+SET PATH=C:\Python34;%PATH%
+SET BAZEL_PYTHON=C:\python34\python.exe
+SET BAZEL_SH=C:\tools\msys64\usr\bin\bash.exe
+SET CMAKE_BIN="cmake.exe"
+SET CTEST_BIN="ctest.exe"
+SET CTEST_OUTPUT_ON_FAILURE=1
+SET CMAKE_BUILD_PARALLEL_LEVEL=16
+SET CTEST_PARALLEL_LEVEL=16
+
+IF EXIST git\googletest (
+  CD git\googletest
+) ELSE IF EXIST github\googletest (
+  CD github\googletest
+)
+
+IF %errorlevel% neq 0 EXIT /B 1
+
+:: ----------------------------------------------------------------------------
+:: CMake
+MKDIR cmake_msvc2022
+CD cmake_msvc2022
+
+%CMAKE_BIN% .. ^
+  -G "Visual Studio 17 2022" ^
+  -DPYTHON_EXECUTABLE:FILEPATH=c:\python37\python.exe ^
+  -DPYTHON_INCLUDE_DIR:PATH=c:\python37\include ^
+  -DPYTHON_LIBRARY:FILEPATH=c:\python37\lib\site-packages\pip ^
+  -Dgtest_build_samples=ON ^
+  -Dgtest_build_tests=ON ^
+  -Dgmock_build_tests=ON
+IF %errorlevel% neq 0 EXIT /B 1
+
+%CMAKE_BIN% --build . --target ALL_BUILD --config Debug -- -maxcpucount
+IF %errorlevel% neq 0 EXIT /B 1
+
+%CTEST_BIN% -C Debug --timeout 600
+IF %errorlevel% neq 0 EXIT /B 1
+
+CD ..
+RMDIR /S /Q cmake_msvc2022
+
+:: ----------------------------------------------------------------------------
+:: Bazel
+
+SET BAZEL_VS=C:\Program Files\Microsoft Visual Studio\2022\Community
+%BAZEL_EXE% test ... ^
+  --compilation_mode=dbg ^
+  --copt=/std:c++14 ^
+  --copt=/WX ^
+  --features=external_include_paths ^
+  --keep_going ^
+  --test_output=errors ^
+  --test_tag_filters=-no_test_msvc2017
+IF %errorlevel% neq 0 EXIT /B 1
diff --git a/third_party/googletest/docs/_config.yml b/third_party/googletest/docs/_config.yml
new file mode 100644
index 0000000..d12867e
--- /dev/null
+++ b/third_party/googletest/docs/_config.yml
@@ -0,0 +1 @@
+title: GoogleTest
diff --git a/third_party/googletest/docs/_data/navigation.yml b/third_party/googletest/docs/_data/navigation.yml
new file mode 100644
index 0000000..9f33327
--- /dev/null
+++ b/third_party/googletest/docs/_data/navigation.yml
@@ -0,0 +1,43 @@
+nav:
+- section: "Get Started"
+  items:
+  - title: "Supported Platforms"
+    url: "/platforms.html"
+  - title: "Quickstart: Bazel"
+    url: "/quickstart-bazel.html"
+  - title: "Quickstart: CMake"
+    url: "/quickstart-cmake.html"
+- section: "Guides"
+  items:
+  - title: "GoogleTest Primer"
+    url: "/primer.html"
+  - title: "Advanced Topics"
+    url: "/advanced.html"
+  - title: "Mocking for Dummies"
+    url: "/gmock_for_dummies.html"
+  - title: "Mocking Cookbook"
+    url: "/gmock_cook_book.html"
+  - title: "Mocking Cheat Sheet"
+    url: "/gmock_cheat_sheet.html"
+- section: "References"
+  items:
+  - title: "Testing Reference"
+    url: "/reference/testing.html"
+  - title: "Mocking Reference"
+    url: "/reference/mocking.html"
+  - title: "Assertions"
+    url: "/reference/assertions.html"
+  - title: "Matchers"
+    url: "/reference/matchers.html"
+  - title: "Actions"
+    url: "/reference/actions.html"
+  - title: "Testing FAQ"
+    url: "/faq.html"
+  - title: "Mocking FAQ"
+    url: "/gmock_faq.html"
+  - title: "Code Samples"
+    url: "/samples.html"
+  - title: "Using pkg-config"
+    url: "/pkgconfig.html"
+  - title: "Community Documentation"
+    url: "/community_created_documentation.html"
diff --git a/third_party/googletest/docs/_layouts/default.html b/third_party/googletest/docs/_layouts/default.html
new file mode 100644
index 0000000..c7f331b
--- /dev/null
+++ b/third_party/googletest/docs/_layouts/default.html
@@ -0,0 +1,58 @@
+<!DOCTYPE html>
+<html lang="{{ site.lang | default: "en-US" }}">
+  <head>
+    <meta charset="UTF-8">
+    <meta http-equiv="X-UA-Compatible" content="IE=edge">
+    <meta name="viewport" content="width=device-width, initial-scale=1">
+
+{% seo %}
+    <link rel="stylesheet" href="{{ "/assets/css/style.css?v=" | append: site.github.build_revision | relative_url }}">
+    <script>
+      window.ga=window.ga||function(){(ga.q=ga.q||[]).push(arguments)};ga.l=+new Date;
+      ga('create', 'UA-197576187-1', { 'storage': 'none' });
+      ga('set', 'referrer', document.referrer.split('?')[0]);
+      ga('set', 'location', window.location.href.split('?')[0]);
+      ga('set', 'anonymizeIp', true);
+      ga('send', 'pageview');
+    </script>
+    <script async src='https://www.google-analytics.com/analytics.js'></script>
+  </head>
+  <body>
+    <div class="sidebar">
+      <div class="header">
+        <h1><a href="{{ "/" | relative_url }}">{{ site.title | default: "Documentation" }}</a></h1>
+      </div>
+      <input type="checkbox" id="nav-toggle" class="nav-toggle">
+      <label for="nav-toggle" class="expander">
+        <span class="arrow"></span>
+      </label>
+      <nav>
+        {% for item in site.data.navigation.nav %}
+        <h2>{{ item.section }}</h2>
+        <ul>
+          {% for subitem in item.items %}
+          <a href="{{subitem.url | relative_url }}">
+            <li class="{% if subitem.url == page.url %}active{% endif %}">
+              {{ subitem.title }}
+            </li>
+          </a>
+          {% endfor %}
+        </ul>
+        {% endfor %}
+      </nav>
+    </div>
+    <div class="main markdown-body">
+      <div class="main-inner">
+        {{ content }}
+      </div>
+      <div class="footer">
+        GoogleTest &middot;
+        <a href="https://github.com/google/googletest">GitHub Repository</a> &middot;
+        <a href="https://github.com/google/googletest/blob/main/LICENSE">License</a> &middot;
+        <a href="https://policies.google.com/privacy">Privacy Policy</a>
+      </div>
+    </div>
+    <script src="https://cdnjs.cloudflare.com/ajax/libs/anchor-js/4.1.0/anchor.min.js" integrity="sha256-lZaRhKri35AyJSypXXs4o6OPFTbTmUoltBbDCbdzegg=" crossorigin="anonymous"></script>
+    <script>anchors.add('.main h2, .main h3, .main h4, .main h5, .main h6');</script>
+  </body>
+</html>
diff --git a/third_party/googletest/docs/_sass/main.scss b/third_party/googletest/docs/_sass/main.scss
new file mode 100644
index 0000000..92edc87
--- /dev/null
+++ b/third_party/googletest/docs/_sass/main.scss
@@ -0,0 +1,200 @@
+// Styles for GoogleTest docs website on GitHub Pages.
+// Color variables are defined in
+// https://github.com/pages-themes/primer/tree/master/_sass/primer-support/lib/variables
+
+$sidebar-width: 260px;
+
+body {
+  display: flex;
+  margin: 0;
+}
+
+.sidebar {
+  background: $black;
+  color: $text-white;
+  flex-shrink: 0;
+  height: 100vh;
+  overflow: auto;
+  position: sticky;
+  top: 0;
+  width: $sidebar-width;
+}
+
+.sidebar h1 {
+  font-size: 1.5em;
+}
+
+.sidebar h2 {
+  color: $gray-light;
+  font-size: 0.8em;
+  font-weight: normal;
+  margin-bottom: 0.8em;
+  padding-left: 2.5em;
+  text-transform: uppercase;
+}
+
+.sidebar .header {
+  background: $black;
+  padding: 2em;
+  position: sticky;
+  top: 0;
+  width: 100%;
+}
+
+.sidebar .header a {
+  color: $text-white;
+  text-decoration: none;
+}
+
+.sidebar .nav-toggle {
+  display: none;
+}
+
+.sidebar .expander {
+  cursor: pointer;
+  display: none;
+  height: 3em;
+  position: absolute;
+  right: 1em;
+  top: 1.5em;
+  width: 3em;
+}
+
+.sidebar .expander .arrow {
+  border: solid $white;
+  border-width: 0 3px 3px 0;
+  display: block;
+  height: 0.7em;
+  margin: 1em auto;
+  transform: rotate(45deg);
+  transition: transform 0.5s;
+  width: 0.7em;
+}
+
+.sidebar nav {
+  width: 100%;
+}
+
+.sidebar nav ul {
+  list-style-type: none;
+  margin-bottom: 1em;
+  padding: 0;
+
+  &:last-child {
+    margin-bottom: 2em;
+  }
+
+  a {
+   text-decoration: none;
+  }
+
+  li {
+    color: $text-white;
+    padding-left: 2em;
+    text-decoration: none;
+  }
+
+  li.active {
+    background: $border-gray-darker;
+    font-weight: bold;
+  }
+
+  li:hover {
+    background: $border-gray-darker;
+  }
+}
+
+.main {
+  background-color: $bg-gray;
+  width: calc(100% - #{$sidebar-width});
+}
+
+.main .main-inner {
+  background-color: $white;
+  padding: 2em;
+}
+
+.main .footer {
+  margin: 0;
+  padding: 2em;
+}
+
+.main table th {
+  text-align: left;
+}
+
+.main .callout {
+  border-left: 0.25em solid $white;
+  padding: 1em;
+
+  a {
+    text-decoration: underline;
+  }
+
+  &.important {
+    background-color: $bg-yellow-light;
+    border-color: $bg-yellow;
+    color: $black;
+  }
+
+  &.note {
+    background-color: $bg-blue-light;
+    border-color: $text-blue;
+    color: $text-blue;
+  }
+
+  &.tip {
+    background-color: $green-000;
+    border-color: $green-700;
+    color: $green-700;
+  }
+
+  &.warning {
+    background-color: $red-000;
+    border-color: $text-red;
+    color: $text-red;
+  }
+}
+
+.main .good pre {
+  background-color: $bg-green-light;
+}
+
+.main .bad pre {
+  background-color: $red-000;
+}
+
+@media all and (max-width: 768px) {
+  body {
+    flex-direction: column;
+  }
+
+  .sidebar {
+    height: auto;
+    position: relative;
+    width: 100%;
+  }
+
+  .sidebar .expander {
+    display: block;
+  }
+
+  .sidebar nav {
+    height: 0;
+    overflow: hidden;
+  }
+
+  .sidebar .nav-toggle:checked {
+    & ~ nav {
+      height: auto;
+    }
+
+    & + .expander .arrow {
+      transform: rotate(-135deg);
+    }
+  }
+
+  .main {
+    width: 100%;
+  }
+}
diff --git a/third_party/googletest/docs/advanced.md b/third_party/googletest/docs/advanced.md
new file mode 100644
index 0000000..0e1f812
--- /dev/null
+++ b/third_party/googletest/docs/advanced.md
@@ -0,0 +1,2436 @@
+# Advanced GoogleTest Topics
+
+## Introduction
+
+Now that you have read the [GoogleTest Primer](primer.md) and learned how to
+write tests using GoogleTest, it's time to learn some new tricks. This document
+will show you more assertions as well as how to construct complex failure
+messages, propagate fatal failures, reuse and speed up your test fixtures, and
+use various flags with your tests.
+
+## More Assertions
+
+This section covers some less frequently used, but still significant,
+assertions.
+
+### Explicit Success and Failure
+
+See [Explicit Success and Failure](reference/assertions.md#success-failure) in
+the Assertions Reference.
+
+### Exception Assertions
+
+See [Exception Assertions](reference/assertions.md#exceptions) in the Assertions
+Reference.
+
+### Predicate Assertions for Better Error Messages
+
+Even though GoogleTest has a rich set of assertions, they can never be complete,
+as it's impossible (nor a good idea) to anticipate all scenarios a user might
+run into. Therefore, sometimes a user has to use `EXPECT_TRUE()` to check a
+complex expression, for lack of a better macro. This has the problem of not
+showing you the values of the parts of the expression, making it hard to
+understand what went wrong. As a workaround, some users choose to construct the
+failure message by themselves, streaming it into `EXPECT_TRUE()`. However, this
+is awkward especially when the expression has side-effects or is expensive to
+evaluate.
+
+GoogleTest gives you three different options to solve this problem:
+
+#### Using an Existing Boolean Function
+
+If you already have a function or functor that returns `bool` (or a type that
+can be implicitly converted to `bool`), you can use it in a *predicate
+assertion* to get the function arguments printed for free. See
+[`EXPECT_PRED*`](reference/assertions.md#EXPECT_PRED) in the Assertions
+Reference for details.
+
+#### Using a Function That Returns an AssertionResult
+
+While `EXPECT_PRED*()` and friends are handy for a quick job, the syntax is not
+satisfactory: you have to use different macros for different arities, and it
+feels more like Lisp than C++. The `::testing::AssertionResult` class solves
+this problem.
+
+An `AssertionResult` object represents the result of an assertion (whether it's
+a success or a failure, and an associated message). You can create an
+`AssertionResult` using one of these factory functions:
+
+```c++
+namespace testing {
+
+// Returns an AssertionResult object to indicate that an assertion has
+// succeeded.
+AssertionResult AssertionSuccess();
+
+// Returns an AssertionResult object to indicate that an assertion has
+// failed.
+AssertionResult AssertionFailure();
+
+}
+```
+
+You can then use the `<<` operator to stream messages to the `AssertionResult`
+object.
+
+To provide more readable messages in Boolean assertions (e.g. `EXPECT_TRUE()`),
+write a predicate function that returns `AssertionResult` instead of `bool`. For
+example, if you define `IsEven()` as:
+
+```c++
+testing::AssertionResult IsEven(int n) {
+  if ((n % 2) == 0)
+    return testing::AssertionSuccess();
+  else
+    return testing::AssertionFailure() << n << " is odd";
+}
+```
+
+instead of:
+
+```c++
+bool IsEven(int n) {
+  return (n % 2) == 0;
+}
+```
+
+the failed assertion `EXPECT_TRUE(IsEven(Fib(4)))` will print:
+
+```none
+Value of: IsEven(Fib(4))
+  Actual: false (3 is odd)
+Expected: true
+```
+
+instead of a more opaque
+
+```none
+Value of: IsEven(Fib(4))
+  Actual: false
+Expected: true
+```
+
+If you want informative messages in `EXPECT_FALSE` and `ASSERT_FALSE` as well
+(one third of Boolean assertions in the Google code base are negative ones), and
+are fine with making the predicate slower in the success case, you can supply a
+success message:
+
+```c++
+testing::AssertionResult IsEven(int n) {
+  if ((n % 2) == 0)
+    return testing::AssertionSuccess() << n << " is even";
+  else
+    return testing::AssertionFailure() << n << " is odd";
+}
+```
+
+Then the statement `EXPECT_FALSE(IsEven(Fib(6)))` will print
+
+```none
+  Value of: IsEven(Fib(6))
+     Actual: true (8 is even)
+  Expected: false
+```
+
+#### Using a Predicate-Formatter
+
+If you find the default message generated by
+[`EXPECT_PRED*`](reference/assertions.md#EXPECT_PRED) and
+[`EXPECT_TRUE`](reference/assertions.md#EXPECT_TRUE) unsatisfactory, or some
+arguments to your predicate do not support streaming to `ostream`, you can
+instead use *predicate-formatter assertions* to *fully* customize how the
+message is formatted. See
+[`EXPECT_PRED_FORMAT*`](reference/assertions.md#EXPECT_PRED_FORMAT) in the
+Assertions Reference for details.
+
+### Floating-Point Comparison
+
+See [Floating-Point Comparison](reference/assertions.md#floating-point) in the
+Assertions Reference.
+
+#### Floating-Point Predicate-Format Functions
+
+Some floating-point operations are useful, but not that often used. In order to
+avoid an explosion of new macros, we provide them as predicate-format functions
+that can be used in the predicate assertion macro
+[`EXPECT_PRED_FORMAT2`](reference/assertions.md#EXPECT_PRED_FORMAT), for
+example:
+
+```c++
+using ::testing::FloatLE;
+using ::testing::DoubleLE;
+...
+EXPECT_PRED_FORMAT2(FloatLE, val1, val2);
+EXPECT_PRED_FORMAT2(DoubleLE, val1, val2);
+```
+
+The above code verifies that `val1` is less than, or approximately equal to,
+`val2`.
+
+### Asserting Using gMock Matchers
+
+See [`EXPECT_THAT`](reference/assertions.md#EXPECT_THAT) in the Assertions
+Reference.
+
+### More String Assertions
+
+(Please read the [previous](#asserting-using-gmock-matchers) section first if
+you haven't.)
+
+You can use the gMock [string matchers](reference/matchers.md#string-matchers)
+with [`EXPECT_THAT`](reference/assertions.md#EXPECT_THAT) to do more string
+comparison tricks (sub-string, prefix, suffix, regular expression, and etc). For
+example,
+
+```c++
+using ::testing::HasSubstr;
+using ::testing::MatchesRegex;
+...
+  ASSERT_THAT(foo_string, HasSubstr("needle"));
+  EXPECT_THAT(bar_string, MatchesRegex("\\w*\\d+"));
+```
+
+### Windows HRESULT assertions
+
+See [Windows HRESULT Assertions](reference/assertions.md#HRESULT) in the
+Assertions Reference.
+
+### Type Assertions
+
+You can call the function
+
+```c++
+::testing::StaticAssertTypeEq<T1, T2>();
+```
+
+to assert that types `T1` and `T2` are the same. The function does nothing if
+the assertion is satisfied. If the types are different, the function call will
+fail to compile, the compiler error message will say that `T1 and T2 are not the
+same type` and most likely (depending on the compiler) show you the actual
+values of `T1` and `T2`. This is mainly useful inside template code.
+
+**Caveat**: When used inside a member function of a class template or a function
+template, `StaticAssertTypeEq<T1, T2>()` is effective only if the function is
+instantiated. For example, given:
+
+```c++
+template <typename T> class Foo {
+ public:
+  void Bar() { testing::StaticAssertTypeEq<int, T>(); }
+};
+```
+
+the code:
+
+```c++
+void Test1() { Foo<bool> foo; }
+```
+
+will not generate a compiler error, as `Foo<bool>::Bar()` is never actually
+instantiated. Instead, you need:
+
+```c++
+void Test2() { Foo<bool> foo; foo.Bar(); }
+```
+
+to cause a compiler error.
+
+### Assertion Placement
+
+You can use assertions in any C++ function. In particular, it doesn't have to be
+a method of the test fixture class. The one constraint is that assertions that
+generate a fatal failure (`FAIL*` and `ASSERT_*`) can only be used in
+void-returning functions. This is a consequence of Google's not using
+exceptions. By placing it in a non-void function you'll get a confusing compile
+error like `"error: void value not ignored as it ought to be"` or `"cannot
+initialize return object of type 'bool' with an rvalue of type 'void'"` or
+`"error: no viable conversion from 'void' to 'string'"`.
+
+If you need to use fatal assertions in a function that returns non-void, one
+option is to make the function return the value in an out parameter instead. For
+example, you can rewrite `T2 Foo(T1 x)` to `void Foo(T1 x, T2* result)`. You
+need to make sure that `*result` contains some sensible value even when the
+function returns prematurely. As the function now returns `void`, you can use
+any assertion inside of it.
+
+If changing the function's type is not an option, you should just use assertions
+that generate non-fatal failures, such as `ADD_FAILURE*` and `EXPECT_*`.
+
+{: .callout .note}
+NOTE: Constructors and destructors are not considered void-returning functions,
+according to the C++ language specification, and so you may not use fatal
+assertions in them; you'll get a compilation error if you try. Instead, either
+call `abort` and crash the entire test executable, or put the fatal assertion in
+a `SetUp`/`TearDown` function; see
+[constructor/destructor vs. `SetUp`/`TearDown`](faq.md#CtorVsSetUp)
+
+{: .callout .warning}
+WARNING: A fatal assertion in a helper function (private void-returning method)
+called from a constructor or destructor does not terminate the current test, as
+your intuition might suggest: it merely returns from the constructor or
+destructor early, possibly leaving your object in a partially-constructed or
+partially-destructed state! You almost certainly want to `abort` or use
+`SetUp`/`TearDown` instead.
+
+## Skipping test execution
+
+Related to the assertions `SUCCEED()` and `FAIL()`, you can prevent further test
+execution at runtime with the `GTEST_SKIP()` macro. This is useful when you need
+to check for preconditions of the system under test during runtime and skip
+tests in a meaningful way.
+
+`GTEST_SKIP()` can be used in individual test cases or in the `SetUp()` methods
+of classes derived from either `::testing::Environment` or `::testing::Test`.
+For example:
+
+```c++
+TEST(SkipTest, DoesSkip) {
+  GTEST_SKIP() << "Skipping single test";
+  EXPECT_EQ(0, 1);  // Won't fail; it won't be executed
+}
+
+class SkipFixture : public ::testing::Test {
+ protected:
+  void SetUp() override {
+    GTEST_SKIP() << "Skipping all tests for this fixture";
+  }
+};
+
+// Tests for SkipFixture won't be executed.
+TEST_F(SkipFixture, SkipsOneTest) {
+  EXPECT_EQ(5, 7);  // Won't fail
+}
+```
+
+As with assertion macros, you can stream a custom message into `GTEST_SKIP()`.
+
+## Teaching GoogleTest How to Print Your Values
+
+When a test assertion such as `EXPECT_EQ` fails, GoogleTest prints the argument
+values to help you debug. It does this using a user-extensible value printer.
+
+This printer knows how to print built-in C++ types, native arrays, STL
+containers, and any type that supports the `<<` operator. For other types, it
+prints the raw bytes in the value and hopes that you the user can figure it out.
+
+As mentioned earlier, the printer is *extensible*. That means you can teach it
+to do a better job at printing your particular type than to dump the bytes. To
+do that, define an `AbslStringify()` overload as a `friend` function template
+for your type:
+
+```cpp
+namespace foo {
+
+class Point {  // We want GoogleTest to be able to print instances of this.
+  ...
+  // Provide a friend overload.
+  template <typename Sink>
+  friend void AbslStringify(Sink& sink, const Point& point) {
+    absl::Format(&sink, "(%d, %d)", point.x, point.y);
+  }
+
+  int x;
+  int y;
+};
+
+// If you can't declare the function in the class it's important that the
+// AbslStringify overload is defined in the SAME namespace that defines Point.
+// C++'s look-up rules rely on that.
+enum class EnumWithStringify { kMany = 0, kChoices = 1 };
+
+template <typename Sink>
+void AbslStringify(Sink& sink, EnumWithStringify e) {
+  absl::Format(&sink, "%s", e == EnumWithStringify::kMany ? "Many" : "Choices");
+}
+
+}  // namespace foo
+```
+
+{: .callout .note}
+Note: `AbslStringify()` utilizes a generic "sink" buffer to construct its
+string. For more information about supported operations on `AbslStringify()`'s
+sink, see go/abslstringify.
+
+`AbslStringify()` can also use `absl::StrFormat`'s catch-all `%v` type specifier
+within its own format strings to perform type deduction. `Point` above could be
+formatted as `"(%v, %v)"` for example, and deduce the `int` values as `%d`.
+
+Sometimes, `AbslStringify()` might not be an option: your team may wish to print
+types with extra debugging information for testing purposes only. If so, you can
+instead define a `PrintTo()` function like this:
+
+```c++
+#include <ostream>
+
+namespace foo {
+
+class Point {
+  ...
+  friend void PrintTo(const Point& point, std::ostream* os) {
+    *os << "(" << point.x << "," << point.y << ")";
+  }
+
+  int x;
+  int y;
+};
+
+// If you can't declare the function in the class it's important that PrintTo()
+// is defined in the SAME namespace that defines Point.  C++'s look-up rules
+// rely on that.
+void PrintTo(const Point& point, std::ostream* os) {
+    *os << "(" << point.x << "," << point.y << ")";
+}
+
+}  // namespace foo
+```
+
+If you have defined both `AbslStringify()` and `PrintTo()`, the latter will be
+used by GoogleTest. This allows you to customize how the value appears in
+GoogleTest's output without affecting code that relies on the behavior of
+`AbslStringify()`.
+
+If you have an existing `<<` operator and would like to define an
+`AbslStringify()`, the latter will be used for GoogleTest printing.
+
+If you want to print a value `x` using GoogleTest's value printer yourself, just
+call `::testing::PrintToString(x)`, which returns an `std::string`:
+
+```c++
+vector<pair<Point, int> > point_ints = GetPointIntVector();
+
+EXPECT_TRUE(IsCorrectPointIntVector(point_ints))
+    << "point_ints = " << testing::PrintToString(point_ints);
+```
+
+For more details regarding `AbslStringify()` and its integration with other
+libraries, see go/abslstringify.
+
+## Death Tests
+
+In many applications, there are assertions that can cause application failure if
+a condition is not met. These consistency checks, which ensure that the program
+is in a known good state, are there to fail at the earliest possible time after
+some program state is corrupted. If the assertion checks the wrong condition,
+then the program may proceed in an erroneous state, which could lead to memory
+corruption, security holes, or worse. Hence it is vitally important to test that
+such assertion statements work as expected.
+
+Since these precondition checks cause the processes to die, we call such tests
+_death tests_. More generally, any test that checks that a program terminates
+(except by throwing an exception) in an expected fashion is also a death test.
+
+Note that if a piece of code throws an exception, we don't consider it "death"
+for the purpose of death tests, as the caller of the code could catch the
+exception and avoid the crash. If you want to verify exceptions thrown by your
+code, see [Exception Assertions](#ExceptionAssertions).
+
+If you want to test `EXPECT_*()/ASSERT_*()` failures in your test code, see
+["Catching" Failures](#catching-failures).
+
+### How to Write a Death Test
+
+GoogleTest provides assertion macros to support death tests. See
+[Death Assertions](reference/assertions.md#death) in the Assertions Reference
+for details.
+
+To write a death test, simply use one of the macros inside your test function.
+For example,
+
+```c++
+TEST(MyDeathTest, Foo) {
+  // This death test uses a compound statement.
+  ASSERT_DEATH({
+    int n = 5;
+    Foo(&n);
+  }, "Error on line .* of Foo()");
+}
+
+TEST(MyDeathTest, NormalExit) {
+  EXPECT_EXIT(NormalExit(), testing::ExitedWithCode(0), "Success");
+}
+
+TEST(MyDeathTest, KillProcess) {
+  EXPECT_EXIT(KillProcess(), testing::KilledBySignal(SIGKILL),
+              "Sending myself unblockable signal");
+}
+```
+
+verifies that:
+
+*   calling `Foo(5)` causes the process to die with the given error message,
+*   calling `NormalExit()` causes the process to print `"Success"` to stderr and
+    exit with exit code 0, and
+*   calling `KillProcess()` kills the process with signal `SIGKILL`.
+
+The test function body may contain other assertions and statements as well, if
+necessary.
+
+Note that a death test only cares about three things:
+
+1.  does `statement` abort or exit the process?
+2.  (in the case of `ASSERT_EXIT` and `EXPECT_EXIT`) does the exit status
+    satisfy `predicate`? Or (in the case of `ASSERT_DEATH` and `EXPECT_DEATH`)
+    is the exit status non-zero? And
+3.  does the stderr output match `matcher`?
+
+In particular, if `statement` generates an `ASSERT_*` or `EXPECT_*` failure, it
+will **not** cause the death test to fail, as GoogleTest assertions don't abort
+the process.
+
+### Death Test Naming
+
+{: .callout .important}
+IMPORTANT: We strongly recommend you to follow the convention of naming your
+**test suite** (not test) `*DeathTest` when it contains a death test, as
+demonstrated in the above example. The
+[Death Tests And Threads](#death-tests-and-threads) section below explains why.
+
+If a test fixture class is shared by normal tests and death tests, you can use
+`using` or `typedef` to introduce an alias for the fixture class and avoid
+duplicating its code:
+
+```c++
+class FooTest : public testing::Test { ... };
+
+using FooDeathTest = FooTest;
+
+TEST_F(FooTest, DoesThis) {
+  // normal test
+}
+
+TEST_F(FooDeathTest, DoesThat) {
+  // death test
+}
+```
+
+### Regular Expression Syntax
+
+When built with Bazel and using Abseil, GoogleTest uses the
+[RE2](https://github.com/google/re2/wiki/Syntax) syntax. Otherwise, for POSIX
+systems (Linux, Cygwin, Mac), GoogleTest uses the
+[POSIX extended regular expression](https://www.opengroup.org/onlinepubs/009695399/basedefs/xbd_chap09.html#tag_09_04)
+syntax. To learn about POSIX syntax, you may want to read this
+[Wikipedia entry](https://en.wikipedia.org/wiki/Regular_expression#POSIX_extended).
+
+On Windows, GoogleTest uses its own simple regular expression implementation. It
+lacks many features. For example, we don't support union (`"x|y"`), grouping
+(`"(xy)"`), brackets (`"[xy]"`), and repetition count (`"x{5,7}"`), among
+others. Below is what we do support (`A` denotes a literal character, period
+(`.`), or a single `\\ ` escape sequence; `x` and `y` denote regular
+expressions.):
+
+Expression | Meaning
+---------- | --------------------------------------------------------------
+`c`        | matches any literal character `c`
+`\\d`      | matches any decimal digit
+`\\D`      | matches any character that's not a decimal digit
+`\\f`      | matches `\f`
+`\\n`      | matches `\n`
+`\\r`      | matches `\r`
+`\\s`      | matches any ASCII whitespace, including `\n`
+`\\S`      | matches any character that's not a whitespace
+`\\t`      | matches `\t`
+`\\v`      | matches `\v`
+`\\w`      | matches any letter, `_`, or decimal digit
+`\\W`      | matches any character that `\\w` doesn't match
+`\\c`      | matches any literal character `c`, which must be a punctuation
+`.`        | matches any single character except `\n`
+`A?`       | matches 0 or 1 occurrences of `A`
+`A*`       | matches 0 or many occurrences of `A`
+`A+`       | matches 1 or many occurrences of `A`
+`^`        | matches the beginning of a string (not that of each line)
+`$`        | matches the end of a string (not that of each line)
+`xy`       | matches `x` followed by `y`
+
+To help you determine which capability is available on your system, GoogleTest
+defines macros to govern which regular expression it is using. The macros are:
+`GTEST_USES_SIMPLE_RE=1` or `GTEST_USES_POSIX_RE=1`. If you want your death
+tests to work in all cases, you can either `#if` on these macros or use the more
+limited syntax only.
+
+### How It Works
+
+See [Death Assertions](reference/assertions.md#death) in the Assertions
+Reference.
+
+### Death Tests And Threads
+
+The reason for the two death test styles has to do with thread safety. Due to
+well-known problems with forking in the presence of threads, death tests should
+be run in a single-threaded context. Sometimes, however, it isn't feasible to
+arrange that kind of environment. For example, statically-initialized modules
+may start threads before main is ever reached. Once threads have been created,
+it may be difficult or impossible to clean them up.
+
+GoogleTest has three features intended to raise awareness of threading issues.
+
+1.  A warning is emitted if multiple threads are running when a death test is
+    encountered.
+2.  Test suites with a name ending in "DeathTest" are run before all other
+    tests.
+3.  It uses `clone()` instead of `fork()` to spawn the child process on Linux
+    (`clone()` is not available on Cygwin and Mac), as `fork()` is more likely
+    to cause the child to hang when the parent process has multiple threads.
+
+It's perfectly fine to create threads inside a death test statement; they are
+executed in a separate process and cannot affect the parent.
+
+### Death Test Styles
+
+The "threadsafe" death test style was introduced in order to help mitigate the
+risks of testing in a possibly multithreaded environment. It trades increased
+test execution time (potentially dramatically so) for improved thread safety.
+
+The automated testing framework does not set the style flag. You can choose a
+particular style of death tests by setting the flag programmatically:
+
+```c++
+GTEST_FLAG_SET(death_test_style, "threadsafe");
+```
+
+You can do this in `main()` to set the style for all death tests in the binary,
+or in individual tests. Recall that flags are saved before running each test and
+restored afterwards, so you need not do that yourself. For example:
+
+```c++
+int main(int argc, char** argv) {
+  testing::InitGoogleTest(&argc, argv);
+  GTEST_FLAG_SET(death_test_style, "fast");
+  return RUN_ALL_TESTS();
+}
+
+TEST(MyDeathTest, TestOne) {
+  GTEST_FLAG_SET(death_test_style, "threadsafe");
+  // This test is run in the "threadsafe" style:
+  ASSERT_DEATH(ThisShouldDie(), "");
+}
+
+TEST(MyDeathTest, TestTwo) {
+  // This test is run in the "fast" style:
+  ASSERT_DEATH(ThisShouldDie(), "");
+}
+```
+
+### Caveats
+
+The `statement` argument of `ASSERT_EXIT()` can be any valid C++ statement. If
+it leaves the current function via a `return` statement or by throwing an
+exception, the death test is considered to have failed. Some GoogleTest macros
+may return from the current function (e.g. `ASSERT_TRUE()`), so be sure to avoid
+them in `statement`.
+
+Since `statement` runs in the child process, any in-memory side effect (e.g.
+modifying a variable, releasing memory, etc) it causes will *not* be observable
+in the parent process. In particular, if you release memory in a death test,
+your program will fail the heap check as the parent process will never see the
+memory reclaimed. To solve this problem, you can
+
+1.  try not to free memory in a death test;
+2.  free the memory again in the parent process; or
+3.  do not use the heap checker in your program.
+
+Due to an implementation detail, you cannot place multiple death test assertions
+on the same line; otherwise, compilation will fail with an unobvious error
+message.
+
+Despite the improved thread safety afforded by the "threadsafe" style of death
+test, thread problems such as deadlock are still possible in the presence of
+handlers registered with `pthread_atfork(3)`.
+
+## Using Assertions in Sub-routines
+
+{: .callout .note}
+Note: If you want to put a series of test assertions in a subroutine to check
+for a complex condition, consider using
+[a custom GMock matcher](gmock_cook_book.md#NewMatchers) instead. This lets you
+provide a more readable error message in case of failure and avoid all of the
+issues described below.
+
+### Adding Traces to Assertions
+
+If a test sub-routine is called from several places, when an assertion inside it
+fails, it can be hard to tell which invocation of the sub-routine the failure is
+from. You can alleviate this problem using extra logging or custom failure
+messages, but that usually clutters up your tests. A better solution is to use
+the `SCOPED_TRACE` macro or the `ScopedTrace` utility:
+
+```c++
+SCOPED_TRACE(message);
+```
+
+```c++
+ScopedTrace trace("file_path", line_number, message);
+```
+
+where `message` can be anything streamable to `std::ostream`. `SCOPED_TRACE`
+macro will cause the current file name, line number, and the given message to be
+added in every failure message. `ScopedTrace` accepts explicit file name and
+line number in arguments, which is useful for writing test helpers. The effect
+will be undone when the control leaves the current lexical scope.
+
+For example,
+
+```c++
+10: void Sub1(int n) {
+11:   EXPECT_EQ(Bar(n), 1);
+12:   EXPECT_EQ(Bar(n + 1), 2);
+13: }
+14:
+15: TEST(FooTest, Bar) {
+16:   {
+17:     SCOPED_TRACE("A");  // This trace point will be included in
+18:                         // every failure in this scope.
+19:     Sub1(1);
+20:   }
+21:   // Now it won't.
+22:   Sub1(9);
+23: }
+```
+
+could result in messages like these:
+
+```none
+path/to/foo_test.cc:11: Failure
+Value of: Bar(n)
+Expected: 1
+  Actual: 2
+Google Test trace:
+path/to/foo_test.cc:17: A
+
+path/to/foo_test.cc:12: Failure
+Value of: Bar(n + 1)
+Expected: 2
+  Actual: 3
+```
+
+Without the trace, it would've been difficult to know which invocation of
+`Sub1()` the two failures come from respectively. (You could add an extra
+message to each assertion in `Sub1()` to indicate the value of `n`, but that's
+tedious.)
+
+Some tips on using `SCOPED_TRACE`:
+
+1.  With a suitable message, it's often enough to use `SCOPED_TRACE` at the
+    beginning of a sub-routine, instead of at each call site.
+2.  When calling sub-routines inside a loop, make the loop iterator part of the
+    message in `SCOPED_TRACE` such that you can know which iteration the failure
+    is from.
+3.  Sometimes the line number of the trace point is enough for identifying the
+    particular invocation of a sub-routine. In this case, you don't have to
+    choose a unique message for `SCOPED_TRACE`. You can simply use `""`.
+4.  You can use `SCOPED_TRACE` in an inner scope when there is one in the outer
+    scope. In this case, all active trace points will be included in the failure
+    messages, in reverse order they are encountered.
+5.  The trace dump is clickable in Emacs - hit `return` on a line number and
+    you'll be taken to that line in the source file!
+
+### Propagating Fatal Failures
+
+A common pitfall when using `ASSERT_*` and `FAIL*` is not understanding that
+when they fail they only abort the _current function_, not the entire test. For
+example, the following test will segfault:
+
+```c++
+void Subroutine() {
+  // Generates a fatal failure and aborts the current function.
+  ASSERT_EQ(1, 2);
+
+  // The following won't be executed.
+  ...
+}
+
+TEST(FooTest, Bar) {
+  Subroutine();  // The intended behavior is for the fatal failure
+                 // in Subroutine() to abort the entire test.
+
+  // The actual behavior: the function goes on after Subroutine() returns.
+  int* p = nullptr;
+  *p = 3;  // Segfault!
+}
+```
+
+To alleviate this, GoogleTest provides three different solutions. You could use
+either exceptions, the `(ASSERT|EXPECT)_NO_FATAL_FAILURE` assertions or the
+`HasFatalFailure()` function. They are described in the following two
+subsections.
+
+#### Asserting on Subroutines with an exception
+
+The following code can turn ASSERT-failure into an exception:
+
+```c++
+class ThrowListener : public testing::EmptyTestEventListener {
+  void OnTestPartResult(const testing::TestPartResult& result) override {
+    if (result.type() == testing::TestPartResult::kFatalFailure) {
+      throw testing::AssertionException(result);
+    }
+  }
+};
+int main(int argc, char** argv) {
+  ...
+  testing::UnitTest::GetInstance()->listeners().Append(new ThrowListener);
+  return RUN_ALL_TESTS();
+}
+```
+
+This listener should be added after other listeners if you have any, otherwise
+they won't see failed `OnTestPartResult`.
+
+#### Asserting on Subroutines
+
+As shown above, if your test calls a subroutine that has an `ASSERT_*` failure
+in it, the test will continue after the subroutine returns. This may not be what
+you want.
+
+Often people want fatal failures to propagate like exceptions. For that
+GoogleTest offers the following macros:
+
+Fatal assertion                       | Nonfatal assertion                    | Verifies
+------------------------------------- | ------------------------------------- | --------
+`ASSERT_NO_FATAL_FAILURE(statement);` | `EXPECT_NO_FATAL_FAILURE(statement);` | `statement` doesn't generate any new fatal failures in the current thread.
+
+Only failures in the thread that executes the assertion are checked to determine
+the result of this type of assertions. If `statement` creates new threads,
+failures in these threads are ignored.
+
+Examples:
+
+```c++
+ASSERT_NO_FATAL_FAILURE(Foo());
+
+int i;
+EXPECT_NO_FATAL_FAILURE({
+  i = Bar();
+});
+```
+
+Assertions from multiple threads are currently not supported on Windows.
+
+#### Checking for Failures in the Current Test
+
+`HasFatalFailure()` in the `::testing::Test` class returns `true` if an
+assertion in the current test has suffered a fatal failure. This allows
+functions to catch fatal failures in a sub-routine and return early.
+
+```c++
+class Test {
+ public:
+  ...
+  static bool HasFatalFailure();
+};
+```
+
+The typical usage, which basically simulates the behavior of a thrown exception,
+is:
+
+```c++
+TEST(FooTest, Bar) {
+  Subroutine();
+  // Aborts if Subroutine() had a fatal failure.
+  if (HasFatalFailure()) return;
+
+  // The following won't be executed.
+  ...
+}
+```
+
+If `HasFatalFailure()` is used outside of `TEST()` , `TEST_F()` , or a test
+fixture, you must add the `::testing::Test::` prefix, as in:
+
+```c++
+if (testing::Test::HasFatalFailure()) return;
+```
+
+Similarly, `HasNonfatalFailure()` returns `true` if the current test has at
+least one non-fatal failure, and `HasFailure()` returns `true` if the current
+test has at least one failure of either kind.
+
+## Logging Additional Information
+
+In your test code, you can call `RecordProperty("key", value)` to log additional
+information, where `value` can be either a string or an `int`. The *last* value
+recorded for a key will be emitted to the
+[XML output](#generating-an-xml-report) if you specify one. For example, the
+test
+
+```c++
+TEST_F(WidgetUsageTest, MinAndMaxWidgets) {
+  RecordProperty("MaximumWidgets", ComputeMaxUsage());
+  RecordProperty("MinimumWidgets", ComputeMinUsage());
+}
+```
+
+will output XML like this:
+
+```xml
+  ...
+    <testcase name="MinAndMaxWidgets" file="test.cpp" line="1" status="run" time="0.006" classname="WidgetUsageTest" MaximumWidgets="12" MinimumWidgets="9" />
+  ...
+```
+
+{: .callout .note}
+> NOTE:
+>
+> *   `RecordProperty()` is a static member of the `Test` class. Therefore it
+>     needs to be prefixed with `::testing::Test::` if used outside of the
+>     `TEST` body and the test fixture class.
+> *   *`key`* must be a valid XML attribute name, and cannot conflict with the
+>     ones already used by GoogleTest (`name`, `status`, `time`, `classname`,
+>     `type_param`, and `value_param`).
+> *   Calling `RecordProperty()` outside of the lifespan of a test is allowed.
+>     If it's called outside of a test but between a test suite's
+>     `SetUpTestSuite()` and `TearDownTestSuite()` methods, it will be
+>     attributed to the XML element for the test suite. If it's called outside
+>     of all test suites (e.g. in a test environment), it will be attributed to
+>     the top-level XML element.
+
+## Sharing Resources Between Tests in the Same Test Suite
+
+GoogleTest creates a new test fixture object for each test in order to make
+tests independent and easier to debug. However, sometimes tests use resources
+that are expensive to set up, making the one-copy-per-test model prohibitively
+expensive.
+
+If the tests don't change the resource, there's no harm in their sharing a
+single resource copy. So, in addition to per-test set-up/tear-down, GoogleTest
+also supports per-test-suite set-up/tear-down. To use it:
+
+1.  In your test fixture class (say `FooTest` ), declare as `static` some member
+    variables to hold the shared resources.
+2.  Outside your test fixture class (typically just below it), define those
+    member variables, optionally giving them initial values.
+3.  In the same test fixture class, define a public member function `static void
+    SetUpTestSuite()` (remember not to spell it as **`SetupTestSuite`** with a
+    small `u`!) to set up the shared resources and a `static void
+    TearDownTestSuite()` function to tear them down.
+
+That's it! GoogleTest automatically calls `SetUpTestSuite()` before running the
+*first test* in the `FooTest` test suite (i.e. before creating the first
+`FooTest` object), and calls `TearDownTestSuite()` after running the *last test*
+in it (i.e. after deleting the last `FooTest` object). In between, the tests can
+use the shared resources.
+
+Remember that the test order is undefined, so your code can't depend on a test
+preceding or following another. Also, the tests must either not modify the state
+of any shared resource, or, if they do modify the state, they must restore the
+state to its original value before passing control to the next test.
+
+Note that `SetUpTestSuite()` may be called multiple times for a test fixture
+class that has derived classes, so you should not expect code in the function
+body to be run only once. Also, derived classes still have access to shared
+resources defined as static members, so careful consideration is needed when
+managing shared resources to avoid memory leaks if shared resources are not
+properly cleaned up in `TearDownTestSuite()`.
+
+Here's an example of per-test-suite set-up and tear-down:
+
+```c++
+class FooTest : public testing::Test {
+ protected:
+  // Per-test-suite set-up.
+  // Called before the first test in this test suite.
+  // Can be omitted if not needed.
+  static void SetUpTestSuite() {
+    shared_resource_ = new ...;
+
+    // If `shared_resource_` is **not deleted** in `TearDownTestSuite()`,
+    // reallocation should be prevented because `SetUpTestSuite()` may be called
+    // in subclasses of FooTest and lead to memory leak.
+    //
+    // if (shared_resource_ == nullptr) {
+    //   shared_resource_ = new ...;
+    // }
+  }
+
+  // Per-test-suite tear-down.
+  // Called after the last test in this test suite.
+  // Can be omitted if not needed.
+  static void TearDownTestSuite() {
+    delete shared_resource_;
+    shared_resource_ = nullptr;
+  }
+
+  // You can define per-test set-up logic as usual.
+  void SetUp() override { ... }
+
+  // You can define per-test tear-down logic as usual.
+  void TearDown() override { ... }
+
+  // Some expensive resource shared by all tests.
+  static T* shared_resource_;
+};
+
+T* FooTest::shared_resource_ = nullptr;
+
+TEST_F(FooTest, Test1) {
+  ... you can refer to shared_resource_ here ...
+}
+
+TEST_F(FooTest, Test2) {
+  ... you can refer to shared_resource_ here ...
+}
+```
+
+{: .callout .note}
+NOTE: Though the above code declares `SetUpTestSuite()` protected, it may
+sometimes be necessary to declare it public, such as when using it with
+`TEST_P`.
+
+## Global Set-Up and Tear-Down
+
+Just as you can do set-up and tear-down at the test level and the test suite
+level, you can also do it at the test program level. Here's how.
+
+First, you subclass the `::testing::Environment` class to define a test
+environment, which knows how to set-up and tear-down:
+
+```c++
+class Environment : public ::testing::Environment {
+ public:
+  ~Environment() override {}
+
+  // Override this to define how to set up the environment.
+  void SetUp() override {}
+
+  // Override this to define how to tear down the environment.
+  void TearDown() override {}
+};
+```
+
+Then, you register an instance of your environment class with GoogleTest by
+calling the `::testing::AddGlobalTestEnvironment()` function:
+
+```c++
+Environment* AddGlobalTestEnvironment(Environment* env);
+```
+
+Now, when `RUN_ALL_TESTS()` is called, it first calls the `SetUp()` method of
+each environment object, then runs the tests if none of the environments
+reported fatal failures and `GTEST_SKIP()` was not called. `RUN_ALL_TESTS()`
+always calls `TearDown()` with each environment object, regardless of whether or
+not the tests were run.
+
+It's OK to register multiple environment objects. In this suite, their `SetUp()`
+will be called in the order they are registered, and their `TearDown()` will be
+called in the reverse order.
+
+Note that GoogleTest takes ownership of the registered environment objects.
+Therefore **do not delete them** by yourself.
+
+You should call `AddGlobalTestEnvironment()` before `RUN_ALL_TESTS()` is called,
+probably in `main()`. If you use `gtest_main`, you need to call this before
+`main()` starts for it to take effect. One way to do this is to define a global
+variable like this:
+
+```c++
+testing::Environment* const foo_env =
+    testing::AddGlobalTestEnvironment(new FooEnvironment);
+```
+
+However, we strongly recommend you to write your own `main()` and call
+`AddGlobalTestEnvironment()` there, as relying on initialization of global
+variables makes the code harder to read and may cause problems when you register
+multiple environments from different translation units and the environments have
+dependencies among them (remember that the compiler doesn't guarantee the order
+in which global variables from different translation units are initialized).
+
+## Value-Parameterized Tests
+
+*Value-parameterized tests* allow you to test your code with different
+parameters without writing multiple copies of the same test. This is useful in a
+number of situations, for example:
+
+*   You have a piece of code whose behavior is affected by one or more
+    command-line flags. You want to make sure your code performs correctly for
+    various values of those flags.
+*   You want to test different implementations of an OO interface.
+*   You want to test your code over various inputs (a.k.a. data-driven testing).
+    This feature is easy to abuse, so please exercise your good sense when doing
+    it!
+
+### How to Write Value-Parameterized Tests
+
+To write value-parameterized tests, first you should define a fixture class. It
+must be derived from both `testing::Test` and `testing::WithParamInterface<T>`
+(the latter is a pure interface), where `T` is the type of your parameter
+values. For convenience, you can just derive the fixture class from
+`testing::TestWithParam<T>`, which itself is derived from both `testing::Test`
+and `testing::WithParamInterface<T>`. `T` can be any copyable type. If it's a
+raw pointer, you are responsible for managing the lifespan of the pointed
+values.
+
+{: .callout .note}
+NOTE: If your test fixture defines `SetUpTestSuite()` or `TearDownTestSuite()`
+they must be declared **public** rather than **protected** in order to use
+`TEST_P`.
+
+```c++
+class FooTest :
+    public testing::TestWithParam<absl::string_view> {
+  // You can implement all the usual fixture class members here.
+  // To access the test parameter, call GetParam() from class
+  // TestWithParam<T>.
+};
+
+// Or, when you want to add parameters to a pre-existing fixture class:
+class BaseTest : public testing::Test {
+  ...
+};
+class BarTest : public BaseTest,
+                public testing::WithParamInterface<absl::string_view> {
+  ...
+};
+```
+
+Then, use the `TEST_P` macro to define as many test patterns using this fixture
+as you want. The `_P` suffix is for "parameterized" or "pattern", whichever you
+prefer to think.
+
+```c++
+TEST_P(FooTest, DoesBlah) {
+  // Inside a test, access the test parameter with the GetParam() method
+  // of the TestWithParam<T> class:
+  EXPECT_TRUE(foo.Blah(GetParam()));
+  ...
+}
+
+TEST_P(FooTest, HasBlahBlah) {
+  ...
+}
+```
+
+Finally, you can use the `INSTANTIATE_TEST_SUITE_P` macro to instantiate the
+test suite with any set of parameters you want. GoogleTest defines a number of
+functions for generating test parameters—see details at
+[`INSTANTIATE_TEST_SUITE_P`](reference/testing.md#INSTANTIATE_TEST_SUITE_P) in
+the Testing Reference.
+
+For example, the following statement will instantiate tests from the `FooTest`
+test suite each with parameter values `"meeny"`, `"miny"`, and `"moe"` using the
+[`Values`](reference/testing.md#param-generators) parameter generator:
+
+```c++
+INSTANTIATE_TEST_SUITE_P(MeenyMinyMoe,
+                         FooTest,
+                         testing::Values("meeny", "miny", "moe"));
+```
+
+{: .callout .note}
+NOTE: The code above must be placed at global or namespace scope, not at
+function scope.
+
+The first argument to `INSTANTIATE_TEST_SUITE_P` is a unique name for the
+instantiation of the test suite. The next argument is the name of the test
+pattern, and the last is the
+[parameter generator](reference/testing.md#param-generators).
+
+The parameter generator expression is not evaluated until GoogleTest is
+initialized (via `InitGoogleTest()`). Any prior initialization done in the
+`main` function will be accessible from the parameter generator, for example,
+the results of flag parsing.
+
+You can instantiate a test pattern more than once, so to distinguish different
+instances of the pattern, the instantiation name is added as a prefix to the
+actual test suite name. Remember to pick unique prefixes for different
+instantiations. The tests from the instantiation above will have these names:
+
+*   `MeenyMinyMoe/FooTest.DoesBlah/0` for `"meeny"`
+*   `MeenyMinyMoe/FooTest.DoesBlah/1` for `"miny"`
+*   `MeenyMinyMoe/FooTest.DoesBlah/2` for `"moe"`
+*   `MeenyMinyMoe/FooTest.HasBlahBlah/0` for `"meeny"`
+*   `MeenyMinyMoe/FooTest.HasBlahBlah/1` for `"miny"`
+*   `MeenyMinyMoe/FooTest.HasBlahBlah/2` for `"moe"`
+
+You can use these names in [`--gtest_filter`](#running-a-subset-of-the-tests).
+
+The following statement will instantiate all tests from `FooTest` again, each
+with parameter values `"cat"` and `"dog"` using the
+[`ValuesIn`](reference/testing.md#param-generators) parameter generator:
+
+```c++
+constexpr absl::string_view kPets[] = {"cat", "dog"};
+INSTANTIATE_TEST_SUITE_P(Pets, FooTest, testing::ValuesIn(kPets));
+```
+
+The tests from the instantiation above will have these names:
+
+*   `Pets/FooTest.DoesBlah/0` for `"cat"`
+*   `Pets/FooTest.DoesBlah/1` for `"dog"`
+*   `Pets/FooTest.HasBlahBlah/0` for `"cat"`
+*   `Pets/FooTest.HasBlahBlah/1` for `"dog"`
+
+Please note that `INSTANTIATE_TEST_SUITE_P` will instantiate *all* tests in the
+given test suite, whether their definitions come before or *after* the
+`INSTANTIATE_TEST_SUITE_P` statement.
+
+Additionally, by default, every `TEST_P` without a corresponding
+`INSTANTIATE_TEST_SUITE_P` causes a failing test in test suite
+`GoogleTestVerification`. If you have a test suite where that omission is not an
+error, for example it is in a library that may be linked in for other reasons or
+where the list of test cases is dynamic and may be empty, then this check can be
+suppressed by tagging the test suite:
+
+```c++
+GTEST_ALLOW_UNINSTANTIATED_PARAMETERIZED_TEST(FooTest);
+```
+
+You can see [sample7_unittest.cc] and [sample8_unittest.cc] for more examples.
+
+[sample7_unittest.cc]: https://github.com/google/googletest/blob/main/googletest/samples/sample7_unittest.cc "Parameterized Test example"
+[sample8_unittest.cc]: https://github.com/google/googletest/blob/main/googletest/samples/sample8_unittest.cc "Parameterized Test example with multiple parameters"
+
+### Creating Value-Parameterized Abstract Tests
+
+In the above, we define and instantiate `FooTest` in the *same* source file.
+Sometimes you may want to define value-parameterized tests in a library and let
+other people instantiate them later. This pattern is known as *abstract tests*.
+As an example of its application, when you are designing an interface you can
+write a standard suite of abstract tests (perhaps using a factory function as
+the test parameter) that all implementations of the interface are expected to
+pass. When someone implements the interface, they can instantiate your suite to
+get all the interface-conformance tests for free.
+
+To define abstract tests, you should organize your code like this:
+
+1.  Put the definition of the parameterized test fixture class (e.g. `FooTest`)
+    in a header file, say `foo_param_test.h`. Think of this as *declaring* your
+    abstract tests.
+2.  Put the `TEST_P` definitions in `foo_param_test.cc`, which includes
+    `foo_param_test.h`. Think of this as *implementing* your abstract tests.
+
+Once they are defined, you can instantiate them by including `foo_param_test.h`,
+invoking `INSTANTIATE_TEST_SUITE_P()`, and depending on the library target that
+contains `foo_param_test.cc`. You can instantiate the same abstract test suite
+multiple times, possibly in different source files.
+
+### Specifying Names for Value-Parameterized Test Parameters
+
+The optional last argument to `INSTANTIATE_TEST_SUITE_P()` allows the user to
+specify a function or functor that generates custom test name suffixes based on
+the test parameters. The function should accept one argument of type
+`testing::TestParamInfo<class ParamType>`, and return `std::string`.
+
+`testing::PrintToStringParamName` is a builtin test suffix generator that
+returns the value of `testing::PrintToString(GetParam())`. It does not work for
+`std::string` or C strings.
+
+{: .callout .note}
+NOTE: test names must be non-empty, unique, and may only contain ASCII
+alphanumeric characters. In particular, they
+[should not contain underscores](faq.md#why-should-test-suite-names-and-test-names-not-contain-underscore)
+
+```c++
+class MyTestSuite : public testing::TestWithParam<int> {};
+
+TEST_P(MyTestSuite, MyTest)
+{
+  std::cout << "Example Test Param: " << GetParam() << std::endl;
+}
+
+INSTANTIATE_TEST_SUITE_P(MyGroup, MyTestSuite, testing::Range(0, 10),
+                         testing::PrintToStringParamName());
+```
+
+Providing a custom functor allows for more control over test parameter name
+generation, especially for types where the automatic conversion does not
+generate helpful parameter names (e.g. strings as demonstrated above). The
+following example illustrates this for multiple parameters, an enumeration type
+and a string, and also demonstrates how to combine generators. It uses a lambda
+for conciseness:
+
+```c++
+enum class MyType { MY_FOO = 0, MY_BAR = 1 };
+
+class MyTestSuite : public testing::TestWithParam<std::tuple<MyType, std::string>> {
+};
+
+INSTANTIATE_TEST_SUITE_P(
+    MyGroup, MyTestSuite,
+    testing::Combine(
+        testing::Values(MyType::MY_FOO, MyType::MY_BAR),
+        testing::Values("A", "B")),
+    [](const testing::TestParamInfo<MyTestSuite::ParamType>& info) {
+      std::string name = absl::StrCat(
+          std::get<0>(info.param) == MyType::MY_FOO ? "Foo" : "Bar",
+          std::get<1>(info.param));
+      absl::c_replace_if(name, [](char c) { return !std::isalnum(c); }, '_');
+      return name;
+    });
+```
+
+## Typed Tests
+
+Suppose you have multiple implementations of the same interface and want to make
+sure that all of them satisfy some common requirements. Or, you may have defined
+several types that are supposed to conform to the same "concept" and you want to
+verify it. In both cases, you want the same test logic repeated for different
+types.
+
+While you can write one `TEST` or `TEST_F` for each type you want to test (and
+you may even factor the test logic into a function template that you invoke from
+the `TEST`), it's tedious and doesn't scale: if you want `m` tests over `n`
+types, you'll end up writing `m*n` `TEST`s.
+
+*Typed tests* allow you to repeat the same test logic over a list of types. You
+only need to write the test logic once, although you must know the type list
+when writing typed tests. Here's how you do it:
+
+First, define a fixture class template. It should be parameterized by a type.
+Remember to derive it from `::testing::Test`:
+
+```c++
+template <typename T>
+class FooTest : public testing::Test {
+ public:
+  ...
+  using List = std::list<T>;
+  static T shared_;
+  T value_;
+};
+```
+
+Next, associate a list of types with the test suite, which will be repeated for
+each type in the list:
+
+```c++
+using MyTypes = ::testing::Types<char, int, unsigned int>;
+TYPED_TEST_SUITE(FooTest, MyTypes);
+```
+
+The type alias (`using` or `typedef`) is necessary for the `TYPED_TEST_SUITE`
+macro to parse correctly. Otherwise the compiler will think that each comma in
+the type list introduces a new macro argument.
+
+Then, use `TYPED_TEST()` instead of `TEST_F()` to define a typed test for this
+test suite. You can repeat this as many times as you want:
+
+```c++
+TYPED_TEST(FooTest, DoesBlah) {
+  // Inside a test, refer to the special name TypeParam to get the type
+  // parameter.  Since we are inside a derived class template, C++ requires
+  // us to visit the members of FooTest via 'this'.
+  TypeParam n = this->value_;
+
+  // To visit static members of the fixture, add the 'TestFixture::'
+  // prefix.
+  n += TestFixture::shared_;
+
+  // To refer to typedefs in the fixture, add the 'typename TestFixture::'
+  // prefix.  The 'typename' is required to satisfy the compiler.
+  typename TestFixture::List values;
+
+  values.push_back(n);
+  ...
+}
+
+TYPED_TEST(FooTest, HasPropertyA) { ... }
+```
+
+You can see [sample6_unittest.cc] for a complete example.
+
+[sample6_unittest.cc]: https://github.com/google/googletest/blob/main/googletest/samples/sample6_unittest.cc "Typed Test example"
+
+## Type-Parameterized Tests
+
+*Type-parameterized tests* are like typed tests, except that they don't require
+you to know the list of types ahead of time. Instead, you can define the test
+logic first and instantiate it with different type lists later. You can even
+instantiate it more than once in the same program.
+
+If you are designing an interface or concept, you can define a suite of
+type-parameterized tests to verify properties that any valid implementation of
+the interface/concept should have. Then, the author of each implementation can
+just instantiate the test suite with their type to verify that it conforms to
+the requirements, without having to write similar tests repeatedly. Here's an
+example:
+
+First, define a fixture class template, as we did with typed tests:
+
+```c++
+template <typename T>
+class FooTest : public testing::Test {
+  void DoSomethingInteresting();
+  ...
+};
+```
+
+Next, declare that you will define a type-parameterized test suite:
+
+```c++
+TYPED_TEST_SUITE_P(FooTest);
+```
+
+Then, use `TYPED_TEST_P()` to define a type-parameterized test. You can repeat
+this as many times as you want:
+
+```c++
+TYPED_TEST_P(FooTest, DoesBlah) {
+  // Inside a test, refer to TypeParam to get the type parameter.
+  TypeParam n = 0;
+
+  // You will need to use `this` explicitly to refer to fixture members.
+  this->DoSomethingInteresting()
+  ...
+}
+
+TYPED_TEST_P(FooTest, HasPropertyA) { ... }
+```
+
+Now the tricky part: you need to register all test patterns using the
+`REGISTER_TYPED_TEST_SUITE_P` macro before you can instantiate them. The first
+argument of the macro is the test suite name; the rest are the names of the
+tests in this test suite:
+
+```c++
+REGISTER_TYPED_TEST_SUITE_P(FooTest,
+                            DoesBlah, HasPropertyA);
+```
+
+Finally, you are free to instantiate the pattern with the types you want. If you
+put the above code in a header file, you can `#include` it in multiple C++
+source files and instantiate it multiple times.
+
+```c++
+using MyTypes = ::testing::Types<char, int, unsigned int>;
+INSTANTIATE_TYPED_TEST_SUITE_P(My, FooTest, MyTypes);
+```
+
+To distinguish different instances of the pattern, the first argument to the
+`INSTANTIATE_TYPED_TEST_SUITE_P` macro is a prefix that will be added to the
+actual test suite name. Remember to pick unique prefixes for different
+instances.
+
+In the special case where the type list contains only one type, you can write
+that type directly without `::testing::Types<...>`, like this:
+
+```c++
+INSTANTIATE_TYPED_TEST_SUITE_P(My, FooTest, int);
+```
+
+You can see [sample6_unittest.cc] for a complete example.
+
+## Testing Private Code
+
+If you change your software's internal implementation, your tests should not
+break as long as the change is not observable by users. Therefore, **per the
+black-box testing principle, most of the time you should test your code through
+its public interfaces.**
+
+**If you still find yourself needing to test internal implementation code,
+consider if there's a better design.** The desire to test internal
+implementation is often a sign that the class is doing too much. Consider
+extracting an implementation class, and testing it. Then use that implementation
+class in the original class.
+
+If you absolutely have to test non-public interface code though, you can. There
+are two cases to consider:
+
+*   Static functions ( *not* the same as static member functions!) or unnamed
+    namespaces, and
+*   Private or protected class members
+
+To test them, we use the following special techniques:
+
+*   Both static functions and definitions/declarations in an unnamed namespace
+    are only visible within the same translation unit. To test them, you can
+    `#include` the entire `.cc` file being tested in your `*_test.cc` file.
+    (#including `.cc` files is not a good way to reuse code - you should not do
+    this in production code!)
+
+    However, a better approach is to move the private code into the
+    `foo::internal` namespace, where `foo` is the namespace your project
+    normally uses, and put the private declarations in a `*-internal.h` file.
+    Your production `.cc` files and your tests are allowed to include this
+    internal header, but your clients are not. This way, you can fully test your
+    internal implementation without leaking it to your clients.
+
+*   Private class members are only accessible from within the class or by
+    friends. To access a class' private members, you can declare your test
+    fixture as a friend to the class and define accessors in your fixture. Tests
+    using the fixture can then access the private members of your production
+    class via the accessors in the fixture. Note that even though your fixture
+    is a friend to your production class, your tests are not automatically
+    friends to it, as they are technically defined in sub-classes of the
+    fixture.
+
+    Another way to test private members is to refactor them into an
+    implementation class, which is then declared in a `*-internal.h` file. Your
+    clients aren't allowed to include this header but your tests can. Such is
+    called the
+    [Pimpl](https://www.gamedev.net/articles/programming/general-and-gameplay-programming/the-c-pimpl-r1794/)
+    (Private Implementation) idiom.
+
+    Or, you can declare an individual test as a friend of your class by adding
+    this line in the class body:
+
+    ```c++
+        FRIEND_TEST(TestSuiteName, TestName);
+    ```
+
+    For example,
+
+    ```c++
+    // foo.h
+    class Foo {
+      ...
+     private:
+      FRIEND_TEST(FooTest, BarReturnsZeroOnNull);
+
+      int Bar(void* x);
+    };
+
+    // foo_test.cc
+    ...
+    TEST(FooTest, BarReturnsZeroOnNull) {
+      Foo foo;
+      EXPECT_EQ(foo.Bar(NULL), 0);  // Uses Foo's private member Bar().
+    }
+    ```
+
+    Pay special attention when your class is defined in a namespace. If you want
+    your test fixtures and tests to be friends of your class, then they must be
+    defined in the exact same namespace (no anonymous or inline namespaces).
+
+    For example, if the code to be tested looks like:
+
+    ```c++
+    namespace my_namespace {
+
+    class Foo {
+      friend class FooTest;
+      FRIEND_TEST(FooTest, Bar);
+      FRIEND_TEST(FooTest, Baz);
+      ... definition of the class Foo ...
+    };
+
+    }  // namespace my_namespace
+    ```
+
+    Your test code should be something like:
+
+    ```c++
+    namespace my_namespace {
+
+    class FooTest : public testing::Test {
+     protected:
+      ...
+    };
+
+    TEST_F(FooTest, Bar) { ... }
+    TEST_F(FooTest, Baz) { ... }
+
+    }  // namespace my_namespace
+    ```
+
+## "Catching" Failures
+
+If you are building a testing utility on top of GoogleTest, you'll want to test
+your utility. What framework would you use to test it? GoogleTest, of course.
+
+The challenge is to verify that your testing utility reports failures correctly.
+In frameworks that report a failure by throwing an exception, you could catch
+the exception and assert on it. But GoogleTest doesn't use exceptions, so how do
+we test that a piece of code generates an expected failure?
+
+`"gtest/gtest-spi.h"` contains some constructs to do this.
+After #including this header, you can use
+
+```c++
+  EXPECT_FATAL_FAILURE(statement, substring);
+```
+
+to assert that `statement` generates a fatal (e.g. `ASSERT_*`) failure in the
+current thread whose message contains the given `substring`, or use
+
+```c++
+  EXPECT_NONFATAL_FAILURE(statement, substring);
+```
+
+if you are expecting a non-fatal (e.g. `EXPECT_*`) failure.
+
+Only failures in the current thread are checked to determine the result of this
+type of expectations. If `statement` creates new threads, failures in these
+threads are also ignored. If you want to catch failures in other threads as
+well, use one of the following macros instead:
+
+```c++
+  EXPECT_FATAL_FAILURE_ON_ALL_THREADS(statement, substring);
+  EXPECT_NONFATAL_FAILURE_ON_ALL_THREADS(statement, substring);
+```
+
+{: .callout .note}
+NOTE: Assertions from multiple threads are currently not supported on Windows.
+
+For technical reasons, there are some caveats:
+
+1.  You cannot stream a failure message to either macro.
+
+2.  `statement` in `EXPECT_FATAL_FAILURE{_ON_ALL_THREADS}()` cannot reference
+    local non-static variables or non-static members of `this` object.
+
+3.  `statement` in `EXPECT_FATAL_FAILURE{_ON_ALL_THREADS}()` cannot return a
+    value.
+
+## Registering tests programmatically
+
+The `TEST` macros handle the vast majority of all use cases, but there are few
+where runtime registration logic is required. For those cases, the framework
+provides the `::testing::RegisterTest` that allows callers to register arbitrary
+tests dynamically.
+
+This is an advanced API only to be used when the `TEST` macros are insufficient.
+The macros should be preferred when possible, as they avoid most of the
+complexity of calling this function.
+
+It provides the following signature:
+
+```c++
+template <typename Factory>
+TestInfo* RegisterTest(const char* test_suite_name, const char* test_name,
+                       const char* type_param, const char* value_param,
+                       const char* file, int line, Factory factory);
+```
+
+The `factory` argument is a factory callable (move-constructible) object or
+function pointer that creates a new instance of the Test object. It handles
+ownership to the caller. The signature of the callable is `Fixture*()`, where
+`Fixture` is the test fixture class for the test. All tests registered with the
+same `test_suite_name` must return the same fixture type. This is checked at
+runtime.
+
+The framework will infer the fixture class from the factory and will call the
+`SetUpTestSuite` and `TearDownTestSuite` for it.
+
+Must be called before `RUN_ALL_TESTS()` is invoked, otherwise behavior is
+undefined.
+
+Use case example:
+
+```c++
+class MyFixture : public testing::Test {
+ public:
+  // All of these optional, just like in regular macro usage.
+  static void SetUpTestSuite() { ... }
+  static void TearDownTestSuite() { ... }
+  void SetUp() override { ... }
+  void TearDown() override { ... }
+};
+
+class MyTest : public MyFixture {
+ public:
+  explicit MyTest(int data) : data_(data) {}
+  void TestBody() override { ... }
+
+ private:
+  int data_;
+};
+
+void RegisterMyTests(const std::vector<int>& values) {
+  for (int v : values) {
+    testing::RegisterTest(
+        "MyFixture", ("Test" + std::to_string(v)).c_str(), nullptr,
+        std::to_string(v).c_str(),
+        __FILE__, __LINE__,
+        // Important to use the fixture type as the return type here.
+        [=]() -> MyFixture* { return new MyTest(v); });
+  }
+}
+...
+int main(int argc, char** argv) {
+  testing::InitGoogleTest(&argc, argv);
+  std::vector<int> values_to_test = LoadValuesFromConfig();
+  RegisterMyTests(values_to_test);
+  ...
+  return RUN_ALL_TESTS();
+}
+```
+
+## Getting the Current Test's Name
+
+Sometimes a function may need to know the name of the currently running test.
+For example, you may be using the `SetUp()` method of your test fixture to set
+the golden file name based on which test is running. The
+[`TestInfo`](reference/testing.md#TestInfo) class has this information.
+
+To obtain a `TestInfo` object for the currently running test, call
+`current_test_info()` on the [`UnitTest`](reference/testing.md#UnitTest)
+singleton object:
+
+```c++
+  // Gets information about the currently running test.
+  // Do NOT delete the returned object - it's managed by the UnitTest class.
+  const testing::TestInfo* const test_info =
+      testing::UnitTest::GetInstance()->current_test_info();
+
+  printf("We are in test %s of test suite %s.\n",
+         test_info->name(),
+         test_info->test_suite_name());
+```
+
+`current_test_info()` returns a null pointer if no test is running. In
+particular, you cannot find the test suite name in `SetUpTestSuite()`,
+`TearDownTestSuite()` (where you know the test suite name implicitly), or
+functions called from them.
+
+## Extending GoogleTest by Handling Test Events
+
+GoogleTest provides an **event listener API** to let you receive notifications
+about the progress of a test program and test failures. The events you can
+listen to include the start and end of the test program, a test suite, or a test
+method, among others. You may use this API to augment or replace the standard
+console output, replace the XML output, or provide a completely different form
+of output, such as a GUI or a database. You can also use test events as
+checkpoints to implement a resource leak checker, for example.
+
+### Defining Event Listeners
+
+To define a event listener, you subclass either
+[`testing::TestEventListener`](reference/testing.md#TestEventListener) or
+[`testing::EmptyTestEventListener`](reference/testing.md#EmptyTestEventListener)
+The former is an (abstract) interface, where *each pure virtual method can be
+overridden to handle a test event* (For example, when a test starts, the
+`OnTestStart()` method will be called.). The latter provides an empty
+implementation of all methods in the interface, such that a subclass only needs
+to override the methods it cares about.
+
+When an event is fired, its context is passed to the handler function as an
+argument. The following argument types are used:
+
+*   UnitTest reflects the state of the entire test program,
+*   TestSuite has information about a test suite, which can contain one or more
+    tests,
+*   TestInfo contains the state of a test, and
+*   TestPartResult represents the result of a test assertion.
+
+An event handler function can examine the argument it receives to find out
+interesting information about the event and the test program's state.
+
+Here's an example:
+
+```c++
+  class MinimalistPrinter : public testing::EmptyTestEventListener {
+    // Called before a test starts.
+    void OnTestStart(const testing::TestInfo& test_info) override {
+      printf("*** Test %s.%s starting.\n",
+             test_info.test_suite_name(), test_info.name());
+    }
+
+    // Called after a failed assertion or a SUCCESS().
+    void OnTestPartResult(const testing::TestPartResult& test_part_result) override {
+      printf("%s in %s:%d\n%s\n",
+             test_part_result.failed() ? "*** Failure" : "Success",
+             test_part_result.file_name(),
+             test_part_result.line_number(),
+             test_part_result.summary());
+    }
+
+    // Called after a test ends.
+    void OnTestEnd(const testing::TestInfo& test_info) override {
+      printf("*** Test %s.%s ending.\n",
+             test_info.test_suite_name(), test_info.name());
+    }
+  };
+```
+
+### Using Event Listeners
+
+To use the event listener you have defined, add an instance of it to the
+GoogleTest event listener list (represented by class
+[`TestEventListeners`](reference/testing.md#TestEventListeners) - note the "s"
+at the end of the name) in your `main()` function, before calling
+`RUN_ALL_TESTS()`:
+
+```c++
+int main(int argc, char** argv) {
+  testing::InitGoogleTest(&argc, argv);
+  // Gets hold of the event listener list.
+  testing::TestEventListeners& listeners =
+      testing::UnitTest::GetInstance()->listeners();
+  // Adds a listener to the end.  GoogleTest takes the ownership.
+  listeners.Append(new MinimalistPrinter);
+  return RUN_ALL_TESTS();
+}
+```
+
+There's only one problem: the default test result printer is still in effect, so
+its output will mingle with the output from your minimalist printer. To suppress
+the default printer, just release it from the event listener list and delete it.
+You can do so by adding one line:
+
+```c++
+  ...
+  delete listeners.Release(listeners.default_result_printer());
+  listeners.Append(new MinimalistPrinter);
+  return RUN_ALL_TESTS();
+```
+
+Now, sit back and enjoy a completely different output from your tests. For more
+details, see [sample9_unittest.cc].
+
+[sample9_unittest.cc]: https://github.com/google/googletest/blob/main/googletest/samples/sample9_unittest.cc "Event listener example"
+
+You may append more than one listener to the list. When an `On*Start()` or
+`OnTestPartResult()` event is fired, the listeners will receive it in the order
+they appear in the list (since new listeners are added to the end of the list,
+the default text printer and the default XML generator will receive the event
+first). An `On*End()` event will be received by the listeners in the *reverse*
+order. This allows output by listeners added later to be framed by output from
+listeners added earlier.
+
+### Generating Failures in Listeners
+
+You may use failure-raising macros (`EXPECT_*()`, `ASSERT_*()`, `FAIL()`, etc)
+when processing an event. There are some restrictions:
+
+1.  You cannot generate any failure in `OnTestPartResult()` (otherwise it will
+    cause `OnTestPartResult()` to be called recursively).
+2.  A listener that handles `OnTestPartResult()` is not allowed to generate any
+    failure.
+
+When you add listeners to the listener list, you should put listeners that
+handle `OnTestPartResult()` *before* listeners that can generate failures. This
+ensures that failures generated by the latter are attributed to the right test
+by the former.
+
+See [sample10_unittest.cc] for an example of a failure-raising listener.
+
+[sample10_unittest.cc]: https://github.com/google/googletest/blob/main/googletest/samples/sample10_unittest.cc "Failure-raising listener example"
+
+## Running Test Programs: Advanced Options
+
+GoogleTest test programs are ordinary executables. Once built, you can run them
+directly and affect their behavior via the following environment variables
+and/or command line flags. For the flags to work, your programs must call
+`::testing::InitGoogleTest()` before calling `RUN_ALL_TESTS()`.
+
+To see a list of supported flags and their usage, please run your test program
+with the `--help` flag. You can also use `-h`, `-?`, or `/?` for short.
+
+If an option is specified both by an environment variable and by a flag, the
+latter takes precedence.
+
+### Selecting Tests
+
+#### Listing Test Names
+
+Sometimes it is necessary to list the available tests in a program before
+running them so that a filter may be applied if needed. Including the flag
+`--gtest_list_tests` overrides all other flags and lists tests in the following
+format:
+
+```none
+TestSuite1.
+  TestName1
+  TestName2
+TestSuite2.
+  TestName
+```
+
+None of the tests listed are actually run if the flag is provided. There is no
+corresponding environment variable for this flag.
+
+#### Running a Subset of the Tests
+
+By default, a GoogleTest program runs all tests the user has defined. Sometimes,
+you want to run only a subset of the tests (e.g. for debugging or quickly
+verifying a change). If you set the `GTEST_FILTER` environment variable or the
+`--gtest_filter` flag to a filter string, GoogleTest will only run the tests
+whose full names (in the form of `TestSuiteName.TestName`) match the filter.
+
+The format of a filter is a '`:`'-separated list of wildcard patterns (called
+the *positive patterns*) optionally followed by a '`-`' and another
+'`:`'-separated pattern list (called the *negative patterns*). A test matches
+the filter if and only if it matches any of the positive patterns but does not
+match any of the negative patterns.
+
+A pattern may contain `'*'` (matches any string) or `'?'` (matches any single
+character). For convenience, the filter `'*-NegativePatterns'` can be also
+written as `'-NegativePatterns'`.
+
+For example:
+
+*   `./foo_test` Has no flag, and thus runs all its tests.
+*   `./foo_test --gtest_filter=*` Also runs everything, due to the single
+    match-everything `*` value.
+*   `./foo_test --gtest_filter=FooTest.*` Runs everything in test suite
+    `FooTest` .
+*   `./foo_test --gtest_filter=*Null*:*Constructor*` Runs any test whose full
+    name contains either `"Null"` or `"Constructor"` .
+*   `./foo_test --gtest_filter=-*DeathTest.*` Runs all non-death tests.
+*   `./foo_test --gtest_filter=FooTest.*-FooTest.Bar` Runs everything in test
+    suite `FooTest` except `FooTest.Bar`.
+*   `./foo_test --gtest_filter=FooTest.*:BarTest.*-FooTest.Bar:BarTest.Foo` Runs
+    everything in test suite `FooTest` except `FooTest.Bar` and everything in
+    test suite `BarTest` except `BarTest.Foo`.
+
+#### Stop test execution upon first failure
+
+By default, a GoogleTest program runs all tests the user has defined. In some
+cases (e.g. iterative test development & execution) it may be desirable stop
+test execution upon first failure (trading improved latency for completeness).
+If `GTEST_FAIL_FAST` environment variable or `--gtest_fail_fast` flag is set,
+the test runner will stop execution as soon as the first test failure is found.
+
+#### Temporarily Disabling Tests
+
+If you have a broken test that you cannot fix right away, you can add the
+`DISABLED_` prefix to its name. This will exclude it from execution. This is
+better than commenting out the code or using `#if 0`, as disabled tests are
+still compiled (and thus won't rot).
+
+If you need to disable all tests in a test suite, you can either add `DISABLED_`
+to the front of the name of each test, or alternatively add it to the front of
+the test suite name.
+
+For example, the following tests won't be run by GoogleTest, even though they
+will still be compiled:
+
+```c++
+// Tests that Foo does Abc.
+TEST(FooTest, DISABLED_DoesAbc) { ... }
+
+class DISABLED_BarTest : public testing::Test { ... };
+
+// Tests that Bar does Xyz.
+TEST_F(DISABLED_BarTest, DoesXyz) { ... }
+```
+
+{: .callout .note}
+NOTE: This feature should only be used for temporary pain-relief. You still have
+to fix the disabled tests at a later date. As a reminder, GoogleTest will print
+a banner warning you if a test program contains any disabled tests.
+
+{: .callout .tip}
+TIP: You can easily count the number of disabled tests you have using
+`grep`. This number can be used as a metric for
+improving your test quality.
+
+#### Temporarily Enabling Disabled Tests
+
+To include disabled tests in test execution, just invoke the test program with
+the `--gtest_also_run_disabled_tests` flag or set the
+`GTEST_ALSO_RUN_DISABLED_TESTS` environment variable to a value other than `0`.
+You can combine this with the `--gtest_filter` flag to further select which
+disabled tests to run.
+
+### Repeating the Tests
+
+Once in a while you'll run into a test whose result is hit-or-miss. Perhaps it
+will fail only 1% of the time, making it rather hard to reproduce the bug under
+a debugger. This can be a major source of frustration.
+
+The `--gtest_repeat` flag allows you to repeat all (or selected) test methods in
+a program many times. Hopefully, a flaky test will eventually fail and give you
+a chance to debug. Here's how to use it:
+
+```none
+$ foo_test --gtest_repeat=1000
+Repeat foo_test 1000 times and don't stop at failures.
+
+$ foo_test --gtest_repeat=-1
+A negative count means repeating forever.
+
+$ foo_test --gtest_repeat=1000 --gtest_break_on_failure
+Repeat foo_test 1000 times, stopping at the first failure.  This
+is especially useful when running under a debugger: when the test
+fails, it will drop into the debugger and you can then inspect
+variables and stacks.
+
+$ foo_test --gtest_repeat=1000 --gtest_filter=FooBar.*
+Repeat the tests whose name matches the filter 1000 times.
+```
+
+If your test program contains
+[global set-up/tear-down](#global-set-up-and-tear-down) code, it will be
+repeated in each iteration as well, as the flakiness may be in it. To avoid
+repeating global set-up/tear-down, specify
+`--gtest_recreate_environments_when_repeating=false`{.nowrap}.
+
+You can also specify the repeat count by setting the `GTEST_REPEAT` environment
+variable.
+
+### Shuffling the Tests
+
+You can specify the `--gtest_shuffle` flag (or set the `GTEST_SHUFFLE`
+environment variable to `1`) to run the tests in a program in a random order.
+This helps to reveal bad dependencies between tests.
+
+By default, GoogleTest uses a random seed calculated from the current time.
+Therefore you'll get a different order every time. The console output includes
+the random seed value, such that you can reproduce an order-related test failure
+later. To specify the random seed explicitly, use the `--gtest_random_seed=SEED`
+flag (or set the `GTEST_RANDOM_SEED` environment variable), where `SEED` is an
+integer in the range [0, 99999]. The seed value 0 is special: it tells
+GoogleTest to do the default behavior of calculating the seed from the current
+time.
+
+If you combine this with `--gtest_repeat=N`, GoogleTest will pick a different
+random seed and re-shuffle the tests in each iteration.
+
+### Distributing Test Functions to Multiple Machines
+
+If you have more than one machine you can use to run a test program, you might
+want to run the test functions in parallel and get the result faster. We call
+this technique *sharding*, where each machine is called a *shard*.
+
+GoogleTest is compatible with test sharding. To take advantage of this feature,
+your test runner (not part of GoogleTest) needs to do the following:
+
+1.  Allocate a number of machines (shards) to run the tests.
+1.  On each shard, set the `GTEST_TOTAL_SHARDS` environment variable to the total
+    number of shards. It must be the same for all shards.
+1.  On each shard, set the `GTEST_SHARD_INDEX` environment variable to the index
+    of the shard. Different shards must be assigned different indices, which
+    must be in the range `[0, GTEST_TOTAL_SHARDS - 1]`.
+1.  Run the same test program on all shards. When GoogleTest sees the above two
+    environment variables, it will select a subset of the test functions to run.
+    Across all shards, each test function in the program will be run exactly
+    once.
+1.  Wait for all shards to finish, then collect and report the results.
+
+Your project may have tests that were written without GoogleTest and thus don't
+understand this protocol. In order for your test runner to figure out which test
+supports sharding, it can set the environment variable `GTEST_SHARD_STATUS_FILE`
+to a non-existent file path. If a test program supports sharding, it will create
+this file to acknowledge that fact; otherwise it will not create it. The actual
+contents of the file are not important at this time, although we may put some
+useful information in it in the future.
+
+Here's an example to make it clear. Suppose you have a test program `foo_test`
+that contains the following 5 test functions:
+
+```
+TEST(A, V)
+TEST(A, W)
+TEST(B, X)
+TEST(B, Y)
+TEST(B, Z)
+```
+
+Suppose you have 3 machines at your disposal. To run the test functions in
+parallel, you would set `GTEST_TOTAL_SHARDS` to 3 on all machines, and set
+`GTEST_SHARD_INDEX` to 0, 1, and 2 on the machines respectively. Then you would
+run the same `foo_test` on each machine.
+
+GoogleTest reserves the right to change how the work is distributed across the
+shards, but here's one possible scenario:
+
+*   Machine #0 runs `A.V` and `B.X`.
+*   Machine #1 runs `A.W` and `B.Y`.
+*   Machine #2 runs `B.Z`.
+
+### Controlling Test Output
+
+#### Colored Terminal Output
+
+GoogleTest can use colors in its terminal output to make it easier to spot the
+important information:
+
+<pre>...
+<font color="green">[----------]</font> 1 test from FooTest
+<font color="green">[ RUN      ]</font> FooTest.DoesAbc
+<font color="green">[       OK ]</font> FooTest.DoesAbc
+<font color="green">[----------]</font> 2 tests from BarTest
+<font color="green">[ RUN      ]</font> BarTest.HasXyzProperty
+<font color="green">[       OK ]</font> BarTest.HasXyzProperty
+<font color="green">[ RUN      ]</font> BarTest.ReturnsTrueOnSuccess
+... some error messages ...
+<font color="red">[   FAILED ]</font> BarTest.ReturnsTrueOnSuccess
+...
+<font color="green">[==========]</font> 30 tests from 14 test suites ran.
+<font color="green">[   PASSED ]</font> 28 tests.
+<font color="red">[   FAILED ]</font> 2 tests, listed below:
+<font color="red">[   FAILED ]</font> BarTest.ReturnsTrueOnSuccess
+<font color="red">[   FAILED ]</font> AnotherTest.DoesXyz
+
+ 2 FAILED TESTS
+</pre>
+
+You can set the `GTEST_COLOR` environment variable or the `--gtest_color`
+command line flag to `yes`, `no`, or `auto` (the default) to enable colors,
+disable colors, or let GoogleTest decide. When the value is `auto`, GoogleTest
+will use colors if and only if the output goes to a terminal and (on non-Windows
+platforms) the `TERM` environment variable is set to `xterm` or `xterm-color`.
+
+#### Suppressing test passes
+
+By default, GoogleTest prints 1 line of output for each test, indicating if it
+passed or failed. To show only test failures, run the test program with
+`--gtest_brief=1`, or set the GTEST_BRIEF environment variable to `1`.
+
+#### Suppressing the Elapsed Time
+
+By default, GoogleTest prints the time it takes to run each test. To disable
+that, run the test program with the `--gtest_print_time=0` command line flag, or
+set the GTEST_PRINT_TIME environment variable to `0`.
+
+#### Suppressing UTF-8 Text Output
+
+In case of assertion failures, GoogleTest prints expected and actual values of
+type `string` both as hex-encoded strings as well as in readable UTF-8 text if
+they contain valid non-ASCII UTF-8 characters. If you want to suppress the UTF-8
+text because, for example, you don't have an UTF-8 compatible output medium, run
+the test program with `--gtest_print_utf8=0` or set the `GTEST_PRINT_UTF8`
+environment variable to `0`.
+
+#### Generating an XML Report
+
+GoogleTest can emit a detailed XML report to a file in addition to its normal
+textual output. The report contains the duration of each test, and thus can help
+you identify slow tests.
+
+To generate the XML report, set the `GTEST_OUTPUT` environment variable or the
+`--gtest_output` flag to the string `"xml:path_to_output_file"`, which will
+create the file at the given location. You can also just use the string `"xml"`,
+in which case the output can be found in the `test_detail.xml` file in the
+current directory.
+
+If you specify a directory (for example, `"xml:output/directory/"` on Linux or
+`"xml:output\directory\"` on Windows), GoogleTest will create the XML file in
+that directory, named after the test executable (e.g. `foo_test.xml` for test
+program `foo_test` or `foo_test.exe`). If the file already exists (perhaps left
+over from a previous run), GoogleTest will pick a different name (e.g.
+`foo_test_1.xml`) to avoid overwriting it.
+
+The report is based on the `junitreport` Ant task. Since that format was
+originally intended for Java, a little interpretation is required to make it
+apply to GoogleTest tests, as shown here:
+
+```xml
+<testsuites name="AllTests" ...>
+  <testsuite name="test_case_name" ...>
+    <testcase    name="test_name" ...>
+      <failure message="..."/>
+      <failure message="..."/>
+      <failure message="..."/>
+    </testcase>
+  </testsuite>
+</testsuites>
+```
+
+*   The root `<testsuites>` element corresponds to the entire test program.
+*   `<testsuite>` elements correspond to GoogleTest test suites.
+*   `<testcase>` elements correspond to GoogleTest test functions.
+
+For instance, the following program
+
+```c++
+TEST(MathTest, Addition) { ... }
+TEST(MathTest, Subtraction) { ... }
+TEST(LogicTest, NonContradiction) { ... }
+```
+
+could generate this report:
+
+```xml
+<?xml version="1.0" encoding="UTF-8"?>
+<testsuites tests="3" failures="1" errors="0" time="0.035" timestamp="2011-10-31T18:52:42" name="AllTests">
+  <testsuite name="MathTest" tests="2" failures="1" errors="0" time="0.015">
+    <testcase name="Addition" file="test.cpp" line="1" status="run" time="0.007" classname="">
+      <failure message="Value of: add(1, 1)&#x0A;  Actual: 3&#x0A;Expected: 2" type="">...</failure>
+      <failure message="Value of: add(1, -1)&#x0A;  Actual: 1&#x0A;Expected: 0" type="">...</failure>
+    </testcase>
+    <testcase name="Subtraction" file="test.cpp" line="2" status="run" time="0.005" classname="">
+    </testcase>
+  </testsuite>
+  <testsuite name="LogicTest" tests="1" failures="0" errors="0" time="0.005">
+    <testcase name="NonContradiction" file="test.cpp" line="3" status="run" time="0.005" classname="">
+    </testcase>
+  </testsuite>
+</testsuites>
+```
+
+Things to note:
+
+*   The `tests` attribute of a `<testsuites>` or `<testsuite>` element tells how
+    many test functions the GoogleTest program or test suite contains, while the
+    `failures` attribute tells how many of them failed.
+
+*   The `time` attribute expresses the duration of the test, test suite, or
+    entire test program in seconds.
+
+*   The `timestamp` attribute records the local date and time of the test
+    execution.
+
+*   The `file` and `line` attributes record the source file location, where the
+    test was defined.
+
+*   Each `<failure>` element corresponds to a single failed GoogleTest
+    assertion.
+
+#### Generating a JSON Report
+
+GoogleTest can also emit a JSON report as an alternative format to XML. To
+generate the JSON report, set the `GTEST_OUTPUT` environment variable or the
+`--gtest_output` flag to the string `"json:path_to_output_file"`, which will
+create the file at the given location. You can also just use the string
+`"json"`, in which case the output can be found in the `test_detail.json` file
+in the current directory.
+
+The report format conforms to the following JSON Schema:
+
+```json
+{
+  "$schema": "https://json-schema.org/schema#",
+  "type": "object",
+  "definitions": {
+    "TestCase": {
+      "type": "object",
+      "properties": {
+        "name": { "type": "string" },
+        "tests": { "type": "integer" },
+        "failures": { "type": "integer" },
+        "disabled": { "type": "integer" },
+        "time": { "type": "string" },
+        "testsuite": {
+          "type": "array",
+          "items": {
+            "$ref": "#/definitions/TestInfo"
+          }
+        }
+      }
+    },
+    "TestInfo": {
+      "type": "object",
+      "properties": {
+        "name": { "type": "string" },
+        "file": { "type": "string" },
+        "line": { "type": "integer" },
+        "status": {
+          "type": "string",
+          "enum": ["RUN", "NOTRUN"]
+        },
+        "time": { "type": "string" },
+        "classname": { "type": "string" },
+        "failures": {
+          "type": "array",
+          "items": {
+            "$ref": "#/definitions/Failure"
+          }
+        }
+      }
+    },
+    "Failure": {
+      "type": "object",
+      "properties": {
+        "failures": { "type": "string" },
+        "type": { "type": "string" }
+      }
+    }
+  },
+  "properties": {
+    "tests": { "type": "integer" },
+    "failures": { "type": "integer" },
+    "disabled": { "type": "integer" },
+    "errors": { "type": "integer" },
+    "timestamp": {
+      "type": "string",
+      "format": "date-time"
+    },
+    "time": { "type": "string" },
+    "name": { "type": "string" },
+    "testsuites": {
+      "type": "array",
+      "items": {
+        "$ref": "#/definitions/TestCase"
+      }
+    }
+  }
+}
+```
+
+The report uses the format that conforms to the following Proto3 using the
+[JSON encoding](https://developers.google.com/protocol-buffers/docs/proto3#json):
+
+```proto
+syntax = "proto3";
+
+package googletest;
+
+import "google/protobuf/timestamp.proto";
+import "google/protobuf/duration.proto";
+
+message UnitTest {
+  int32 tests = 1;
+  int32 failures = 2;
+  int32 disabled = 3;
+  int32 errors = 4;
+  google.protobuf.Timestamp timestamp = 5;
+  google.protobuf.Duration time = 6;
+  string name = 7;
+  repeated TestCase testsuites = 8;
+}
+
+message TestCase {
+  string name = 1;
+  int32 tests = 2;
+  int32 failures = 3;
+  int32 disabled = 4;
+  int32 errors = 5;
+  google.protobuf.Duration time = 6;
+  repeated TestInfo testsuite = 7;
+}
+
+message TestInfo {
+  string name = 1;
+  string file = 6;
+  int32 line = 7;
+  enum Status {
+    RUN = 0;
+    NOTRUN = 1;
+  }
+  Status status = 2;
+  google.protobuf.Duration time = 3;
+  string classname = 4;
+  message Failure {
+    string failures = 1;
+    string type = 2;
+  }
+  repeated Failure failures = 5;
+}
+```
+
+For instance, the following program
+
+```c++
+TEST(MathTest, Addition) { ... }
+TEST(MathTest, Subtraction) { ... }
+TEST(LogicTest, NonContradiction) { ... }
+```
+
+could generate this report:
+
+```json
+{
+  "tests": 3,
+  "failures": 1,
+  "errors": 0,
+  "time": "0.035s",
+  "timestamp": "2011-10-31T18:52:42Z",
+  "name": "AllTests",
+  "testsuites": [
+    {
+      "name": "MathTest",
+      "tests": 2,
+      "failures": 1,
+      "errors": 0,
+      "time": "0.015s",
+      "testsuite": [
+        {
+          "name": "Addition",
+          "file": "test.cpp",
+          "line": 1,
+          "status": "RUN",
+          "time": "0.007s",
+          "classname": "",
+          "failures": [
+            {
+              "message": "Value of: add(1, 1)\n  Actual: 3\nExpected: 2",
+              "type": ""
+            },
+            {
+              "message": "Value of: add(1, -1)\n  Actual: 1\nExpected: 0",
+              "type": ""
+            }
+          ]
+        },
+        {
+          "name": "Subtraction",
+          "file": "test.cpp",
+          "line": 2,
+          "status": "RUN",
+          "time": "0.005s",
+          "classname": ""
+        }
+      ]
+    },
+    {
+      "name": "LogicTest",
+      "tests": 1,
+      "failures": 0,
+      "errors": 0,
+      "time": "0.005s",
+      "testsuite": [
+        {
+          "name": "NonContradiction",
+          "file": "test.cpp",
+          "line": 3,
+          "status": "RUN",
+          "time": "0.005s",
+          "classname": ""
+        }
+      ]
+    }
+  ]
+}
+```
+
+{: .callout .important}
+IMPORTANT: The exact format of the JSON document is subject to change.
+
+### Controlling How Failures Are Reported
+
+#### Detecting Test Premature Exit
+
+Google Test implements the _premature-exit-file_ protocol for test runners to
+catch any kind of unexpected exits of test programs. Upon start, Google Test
+creates the file which will be automatically deleted after all work has been
+finished. Then, the test runner can check if this file exists. In case the file
+remains undeleted, the inspected test has exited prematurely.
+
+This feature is enabled only if the `TEST_PREMATURE_EXIT_FILE` environment
+variable has been set.
+
+#### Turning Assertion Failures into Break-Points
+
+When running test programs under a debugger, it's very convenient if the
+debugger can catch an assertion failure and automatically drop into interactive
+mode. GoogleTest's *break-on-failure* mode supports this behavior.
+
+To enable it, set the `GTEST_BREAK_ON_FAILURE` environment variable to a value
+other than `0`. Alternatively, you can use the `--gtest_break_on_failure`
+command line flag.
+
+#### Disabling Catching Test-Thrown Exceptions
+
+GoogleTest can be used either with or without exceptions enabled. If a test
+throws a C++ exception or (on Windows) a structured exception (SEH), by default
+GoogleTest catches it, reports it as a test failure, and continues with the next
+test method. This maximizes the coverage of a test run. Also, on Windows an
+uncaught exception will cause a pop-up window, so catching the exceptions allows
+you to run the tests automatically.
+
+When debugging the test failures, however, you may instead want the exceptions
+to be handled by the debugger, such that you can examine the call stack when an
+exception is thrown. To achieve that, set the `GTEST_CATCH_EXCEPTIONS`
+environment variable to `0`, or use the `--gtest_catch_exceptions=0` flag when
+running the tests.
+
+### Sanitizer Integration
+
+The
+[Undefined Behavior Sanitizer](https://clang.llvm.org/docs/UndefinedBehaviorSanitizer.html),
+[Address Sanitizer](https://github.com/google/sanitizers/wiki/AddressSanitizer),
+and
+[Thread Sanitizer](https://github.com/google/sanitizers/wiki/ThreadSanitizerCppManual)
+all provide weak functions that you can override to trigger explicit failures
+when they detect sanitizer errors, such as creating a reference from `nullptr`.
+To override these functions, place definitions for them in a source file that
+you compile as part of your main binary:
+
+```
+extern "C" {
+void __ubsan_on_report() {
+  FAIL() << "Encountered an undefined behavior sanitizer error";
+}
+void __asan_on_error() {
+  FAIL() << "Encountered an address sanitizer error";
+}
+void __tsan_on_report() {
+  FAIL() << "Encountered a thread sanitizer error";
+}
+}  // extern "C"
+```
+
+After compiling your project with one of the sanitizers enabled, if a particular
+test triggers a sanitizer error, GoogleTest will report that it failed.
diff --git a/third_party/googletest/docs/assets/css/style.scss b/third_party/googletest/docs/assets/css/style.scss
new file mode 100644
index 0000000..bb30f41
--- /dev/null
+++ b/third_party/googletest/docs/assets/css/style.scss
@@ -0,0 +1,5 @@
+---
+---
+
+@import "jekyll-theme-primer";
+@import "main";
diff --git a/third_party/googletest/docs/community_created_documentation.md b/third_party/googletest/docs/community_created_documentation.md
new file mode 100644
index 0000000..4569075
--- /dev/null
+++ b/third_party/googletest/docs/community_created_documentation.md
@@ -0,0 +1,7 @@
+# Community-Created Documentation
+
+The following is a list, in no particular order, of links to documentation
+created by the Googletest community.
+
+*   [Googlemock Insights](https://github.com/ElectricRCAircraftGuy/eRCaGuy_dotfiles/blob/master/googletest/insights.md),
+    by [ElectricRCAircraftGuy](https://github.com/ElectricRCAircraftGuy)
diff --git a/third_party/googletest/docs/faq.md b/third_party/googletest/docs/faq.md
new file mode 100644
index 0000000..90c2497
--- /dev/null
+++ b/third_party/googletest/docs/faq.md
@@ -0,0 +1,692 @@
+# GoogleTest FAQ
+
+## Why should test suite names and test names not contain underscore?
+
+{: .callout .note}
+Note: GoogleTest reserves underscore (`_`) for special purpose keywords, such as
+[the `DISABLED_` prefix](advanced.md#temporarily-disabling-tests), in addition
+to the following rationale.
+
+Underscore (`_`) is special, as C++ reserves the following to be used by the
+compiler and the standard library:
+
+1.  any identifier that starts with an `_` followed by an upper-case letter, and
+2.  any identifier that contains two consecutive underscores (i.e. `__`)
+    *anywhere* in its name.
+
+User code is *prohibited* from using such identifiers.
+
+Now let's look at what this means for `TEST` and `TEST_F`.
+
+Currently `TEST(TestSuiteName, TestName)` generates a class named
+`TestSuiteName_TestName_Test`. What happens if `TestSuiteName` or `TestName`
+contains `_`?
+
+1.  If `TestSuiteName` starts with an `_` followed by an upper-case letter (say,
+    `_Foo`), we end up with `_Foo_TestName_Test`, which is reserved and thus
+    invalid.
+2.  If `TestSuiteName` ends with an `_` (say, `Foo_`), we get
+    `Foo__TestName_Test`, which is invalid.
+3.  If `TestName` starts with an `_` (say, `_Bar`), we get
+    `TestSuiteName__Bar_Test`, which is invalid.
+4.  If `TestName` ends with an `_` (say, `Bar_`), we get
+    `TestSuiteName_Bar__Test`, which is invalid.
+
+So clearly `TestSuiteName` and `TestName` cannot start or end with `_`
+(Actually, `TestSuiteName` can start with `_` -- as long as the `_` isn't
+followed by an upper-case letter. But that's getting complicated. So for
+simplicity we just say that it cannot start with `_`.).
+
+It may seem fine for `TestSuiteName` and `TestName` to contain `_` in the
+middle. However, consider this:
+
+```c++
+TEST(Time, Flies_Like_An_Arrow) { ... }
+TEST(Time_Flies, Like_An_Arrow) { ... }
+```
+
+Now, the two `TEST`s will both generate the same class
+(`Time_Flies_Like_An_Arrow_Test`). That's not good.
+
+So for simplicity, we just ask the users to avoid `_` in `TestSuiteName` and
+`TestName`. The rule is more constraining than necessary, but it's simple and
+easy to remember. It also gives GoogleTest some wiggle room in case its
+implementation needs to change in the future.
+
+If you violate the rule, there may not be immediate consequences, but your test
+may (just may) break with a new compiler (or a new version of the compiler you
+are using) or with a new version of GoogleTest. Therefore it's best to follow
+the rule.
+
+## Why does GoogleTest support `EXPECT_EQ(NULL, ptr)` and `ASSERT_EQ(NULL, ptr)` but not `EXPECT_NE(NULL, ptr)` and `ASSERT_NE(NULL, ptr)`?
+
+First of all, you can use `nullptr` with each of these macros, e.g.
+`EXPECT_EQ(ptr, nullptr)`, `EXPECT_NE(ptr, nullptr)`, `ASSERT_EQ(ptr, nullptr)`,
+`ASSERT_NE(ptr, nullptr)`. This is the preferred syntax in the style guide
+because `nullptr` does not have the type problems that `NULL` does.
+
+Due to some peculiarity of C++, it requires some non-trivial template meta
+programming tricks to support using `NULL` as an argument of the `EXPECT_XX()`
+and `ASSERT_XX()` macros. Therefore we only do it where it's most needed
+(otherwise we make the implementation of GoogleTest harder to maintain and more
+error-prone than necessary).
+
+Historically, the `EXPECT_EQ()` macro took the *expected* value as its first
+argument and the *actual* value as the second, though this argument order is now
+discouraged. It was reasonable that someone wanted
+to write `EXPECT_EQ(NULL, some_expression)`, and this indeed was requested
+several times. Therefore we implemented it.
+
+The need for `EXPECT_NE(NULL, ptr)` wasn't nearly as strong. When the assertion
+fails, you already know that `ptr` must be `NULL`, so it doesn't add any
+information to print `ptr` in this case. That means `EXPECT_TRUE(ptr != NULL)`
+works just as well.
+
+If we were to support `EXPECT_NE(NULL, ptr)`, for consistency we'd have to
+support `EXPECT_NE(ptr, NULL)` as well. This means using the template meta
+programming tricks twice in the implementation, making it even harder to
+understand and maintain. We believe the benefit doesn't justify the cost.
+
+Finally, with the growth of the gMock matcher library, we are encouraging people
+to use the unified `EXPECT_THAT(value, matcher)` syntax more often in tests. One
+significant advantage of the matcher approach is that matchers can be easily
+combined to form new matchers, while the `EXPECT_NE`, etc, macros cannot be
+easily combined. Therefore we want to invest more in the matchers than in the
+`EXPECT_XX()` macros.
+
+## I need to test that different implementations of an interface satisfy some common requirements. Should I use typed tests or value-parameterized tests?
+
+For testing various implementations of the same interface, either typed tests or
+value-parameterized tests can get it done. It's really up to you the user to
+decide which is more convenient for you, depending on your particular case. Some
+rough guidelines:
+
+*   Typed tests can be easier to write if instances of the different
+    implementations can be created the same way, modulo the type. For example,
+    if all these implementations have a public default constructor (such that
+    you can write `new TypeParam`), or if their factory functions have the same
+    form (e.g. `CreateInstance<TypeParam>()`).
+*   Value-parameterized tests can be easier to write if you need different code
+    patterns to create different implementations' instances, e.g. `new Foo` vs
+    `new Bar(5)`. To accommodate for the differences, you can write factory
+    function wrappers and pass these function pointers to the tests as their
+    parameters.
+*   When a typed test fails, the default output includes the name of the type,
+    which can help you quickly identify which implementation is wrong.
+    Value-parameterized tests only show the number of the failed iteration by
+    default. You will need to define a function that returns the iteration name
+    and pass it as the third parameter to INSTANTIATE_TEST_SUITE_P to have more
+    useful output.
+*   When using typed tests, you need to make sure you are testing against the
+    interface type, not the concrete types (in other words, you want to make
+    sure `implicit_cast<MyInterface*>(my_concrete_impl)` works, not just that
+    `my_concrete_impl` works). It's less likely to make mistakes in this area
+    when using value-parameterized tests.
+
+I hope I didn't confuse you more. :-) If you don't mind, I'd suggest you to give
+both approaches a try. Practice is a much better way to grasp the subtle
+differences between the two tools. Once you have some concrete experience, you
+can much more easily decide which one to use the next time.
+
+## I got some run-time errors about invalid proto descriptors when using `ProtocolMessageEquals`. Help!
+
+{: .callout .note}
+**Note:** `ProtocolMessageEquals` and `ProtocolMessageEquiv` are *deprecated*
+now. Please use `EqualsProto`, etc instead.
+
+`ProtocolMessageEquals` and `ProtocolMessageEquiv` were redefined recently and
+are now less tolerant of invalid protocol buffer definitions. In particular, if
+you have a `foo.proto` that doesn't fully qualify the type of a protocol message
+it references (e.g. `message<Bar>` where it should be `message<blah.Bar>`), you
+will now get run-time errors like:
+
+```
+... descriptor.cc:...] Invalid proto descriptor for file "path/to/foo.proto":
+... descriptor.cc:...]  blah.MyMessage.my_field: ".Bar" is not defined.
+```
+
+If you see this, your `.proto` file is broken and needs to be fixed by making
+the types fully qualified. The new definition of `ProtocolMessageEquals` and
+`ProtocolMessageEquiv` just happen to reveal your bug.
+
+## My death test modifies some state, but the change seems lost after the death test finishes. Why?
+
+Death tests (`EXPECT_DEATH`, etc) are executed in a sub-process s.t. the
+expected crash won't kill the test program (i.e. the parent process). As a
+result, any in-memory side effects they incur are observable in their respective
+sub-processes, but not in the parent process. You can think of them as running
+in a parallel universe, more or less.
+
+In particular, if you use mocking and the death test statement invokes some mock
+methods, the parent process will think the calls have never occurred. Therefore,
+you may want to move your `EXPECT_CALL` statements inside the `EXPECT_DEATH`
+macro.
+
+## EXPECT_EQ(htonl(blah), blah_blah) generates weird compiler errors in opt mode. Is this a GoogleTest bug?
+
+Actually, the bug is in `htonl()`.
+
+According to `'man htonl'`, `htonl()` is a *function*, which means it's valid to
+use `htonl` as a function pointer. However, in opt mode `htonl()` is defined as
+a *macro*, which breaks this usage.
+
+Worse, the macro definition of `htonl()` uses a `gcc` extension and is *not*
+standard C++. That hacky implementation has some ad hoc limitations. In
+particular, it prevents you from writing `Foo<sizeof(htonl(x))>()`, where `Foo`
+is a template that has an integral argument.
+
+The implementation of `EXPECT_EQ(a, b)` uses `sizeof(... a ...)` inside a
+template argument, and thus doesn't compile in opt mode when `a` contains a call
+to `htonl()`. It is difficult to make `EXPECT_EQ` bypass the `htonl()` bug, as
+the solution must work with different compilers on various platforms.
+
+## The compiler complains about "undefined references" to some static const member variables, but I did define them in the class body. What's wrong?
+
+If your class has a static data member:
+
+```c++
+// foo.h
+class Foo {
+  ...
+  static const int kBar = 100;
+};
+```
+
+You also need to define it *outside* of the class body in `foo.cc`:
+
+```c++
+const int Foo::kBar;  // No initializer here.
+```
+
+Otherwise your code is **invalid C++**, and may break in unexpected ways. In
+particular, using it in GoogleTest comparison assertions (`EXPECT_EQ`, etc) will
+generate an "undefined reference" linker error. The fact that "it used to work"
+doesn't mean it's valid. It just means that you were lucky. :-)
+
+If the declaration of the static data member is `constexpr` then it is
+implicitly an `inline` definition, and a separate definition in `foo.cc` is not
+needed:
+
+```c++
+// foo.h
+class Foo {
+  ...
+  static constexpr int kBar = 100;  // Defines kBar, no need to do it in foo.cc.
+};
+```
+
+## Can I derive a test fixture from another?
+
+Yes.
+
+Each test fixture has a corresponding and same named test suite. This means only
+one test suite can use a particular fixture. Sometimes, however, multiple test
+cases may want to use the same or slightly different fixtures. For example, you
+may want to make sure that all of a GUI library's test suites don't leak
+important system resources like fonts and brushes.
+
+In GoogleTest, you share a fixture among test suites by putting the shared logic
+in a base test fixture, then deriving from that base a separate fixture for each
+test suite that wants to use this common logic. You then use `TEST_F()` to write
+tests using each derived fixture.
+
+Typically, your code looks like this:
+
+```c++
+// Defines a base test fixture.
+class BaseTest : public ::testing::Test {
+ protected:
+  ...
+};
+
+// Derives a fixture FooTest from BaseTest.
+class FooTest : public BaseTest {
+ protected:
+  void SetUp() override {
+    BaseTest::SetUp();  // Sets up the base fixture first.
+    ... additional set-up work ...
+  }
+
+  void TearDown() override {
+    ... clean-up work for FooTest ...
+    BaseTest::TearDown();  // Remember to tear down the base fixture
+                           // after cleaning up FooTest!
+  }
+
+  ... functions and variables for FooTest ...
+};
+
+// Tests that use the fixture FooTest.
+TEST_F(FooTest, Bar) { ... }
+TEST_F(FooTest, Baz) { ... }
+
+... additional fixtures derived from BaseTest ...
+```
+
+If necessary, you can continue to derive test fixtures from a derived fixture.
+GoogleTest has no limit on how deep the hierarchy can be.
+
+For a complete example using derived test fixtures, see
+[sample5_unittest.cc](https://github.com/google/googletest/blob/main/googletest/samples/sample5_unittest.cc).
+
+## My compiler complains "void value not ignored as it ought to be." What does this mean?
+
+You're probably using an `ASSERT_*()` in a function that doesn't return `void`.
+`ASSERT_*()` can only be used in `void` functions, due to exceptions being
+disabled by our build system. Please see more details
+[here](advanced.md#assertion-placement).
+
+## My death test hangs (or seg-faults). How do I fix it?
+
+In GoogleTest, death tests are run in a child process and the way they work is
+delicate. To write death tests you really need to understand how they work—see
+the details at [Death Assertions](reference/assertions.md#death) in the
+Assertions Reference.
+
+In particular, death tests don't like having multiple threads in the parent
+process. So the first thing you can try is to eliminate creating threads outside
+of `EXPECT_DEATH()`. For example, you may want to use mocks or fake objects
+instead of real ones in your tests.
+
+Sometimes this is impossible as some library you must use may be creating
+threads before `main()` is even reached. In this case, you can try to minimize
+the chance of conflicts by either moving as many activities as possible inside
+`EXPECT_DEATH()` (in the extreme case, you want to move everything inside), or
+leaving as few things as possible in it. Also, you can try to set the death test
+style to `"threadsafe"`, which is safer but slower, and see if it helps.
+
+If you go with thread-safe death tests, remember that they rerun the test
+program from the beginning in the child process. Therefore make sure your
+program can run side-by-side with itself and is deterministic.
+
+In the end, this boils down to good concurrent programming. You have to make
+sure that there are no race conditions or deadlocks in your program. No silver
+bullet - sorry!
+
+## Should I use the constructor/destructor of the test fixture or SetUp()/TearDown()? {#CtorVsSetUp}
+
+The first thing to remember is that GoogleTest does **not** reuse the same test
+fixture object across multiple tests. For each `TEST_F`, GoogleTest will create
+a **fresh** test fixture object, immediately call `SetUp()`, run the test body,
+call `TearDown()`, and then delete the test fixture object.
+
+When you need to write per-test set-up and tear-down logic, you have the choice
+between using the test fixture constructor/destructor or `SetUp()/TearDown()`.
+The former is usually preferred, as it has the following benefits:
+
+*   By initializing a member variable in the constructor, we have the option to
+    make it `const`, which helps prevent accidental changes to its value and
+    makes the tests more obviously correct.
+*   In case we need to subclass the test fixture class, the subclass'
+    constructor is guaranteed to call the base class' constructor *first*, and
+    the subclass' destructor is guaranteed to call the base class' destructor
+    *afterward*. With `SetUp()/TearDown()`, a subclass may make the mistake of
+    forgetting to call the base class' `SetUp()/TearDown()` or call them at the
+    wrong time.
+
+You may still want to use `SetUp()/TearDown()` in the following cases:
+
+*   C++ does not allow virtual function calls in constructors and destructors.
+    You can call a method declared as virtual, but it will not use dynamic
+    dispatch. It will use the definition from the class the constructor of which
+    is currently executing. This is because calling a virtual method before the
+    derived class constructor has a chance to run is very dangerous - the
+    virtual method might operate on uninitialized data. Therefore, if you need
+    to call a method that will be overridden in a derived class, you have to use
+    `SetUp()/TearDown()`.
+*   In the body of a constructor (or destructor), it's not possible to use the
+    `ASSERT_xx` macros. Therefore, if the set-up operation could cause a fatal
+    test failure that should prevent the test from running, it's necessary to
+    use `abort` and abort the whole test
+    executable, or to use `SetUp()` instead of a constructor.
+*   If the tear-down operation could throw an exception, you must use
+    `TearDown()` as opposed to the destructor, as throwing in a destructor leads
+    to undefined behavior and usually will kill your program right away. Note
+    that many standard libraries (like STL) may throw when exceptions are
+    enabled in the compiler. Therefore you should prefer `TearDown()` if you
+    want to write portable tests that work with or without exceptions.
+*   The GoogleTest team is considering making the assertion macros throw on
+    platforms where exceptions are enabled (e.g. Windows, Mac OS, and Linux
+    client-side), which will eliminate the need for the user to propagate
+    failures from a subroutine to its caller. Therefore, you shouldn't use
+    GoogleTest assertions in a destructor if your code could run on such a
+    platform.
+
+## The compiler complains "no matching function to call" when I use ASSERT_PRED*. How do I fix it?
+
+See details for [`EXPECT_PRED*`](reference/assertions.md#EXPECT_PRED) in the
+Assertions Reference.
+
+## My compiler complains about "ignoring return value" when I call RUN_ALL_TESTS(). Why?
+
+Some people had been ignoring the return value of `RUN_ALL_TESTS()`. That is,
+instead of
+
+```c++
+  return RUN_ALL_TESTS();
+```
+
+they write
+
+```c++
+  RUN_ALL_TESTS();
+```
+
+This is **wrong and dangerous**. The testing services needs to see the return
+value of `RUN_ALL_TESTS()` in order to determine if a test has passed. If your
+`main()` function ignores it, your test will be considered successful even if it
+has a GoogleTest assertion failure. Very bad.
+
+We have decided to fix this (thanks to Michael Chastain for the idea). Now, your
+code will no longer be able to ignore `RUN_ALL_TESTS()` when compiled with
+`gcc`. If you do so, you'll get a compiler error.
+
+If you see the compiler complaining about you ignoring the return value of
+`RUN_ALL_TESTS()`, the fix is simple: just make sure its value is used as the
+return value of `main()`.
+
+But how could we introduce a change that breaks existing tests? Well, in this
+case, the code was already broken in the first place, so we didn't break it. :-)
+
+## My compiler complains that a constructor (or destructor) cannot return a value. What's going on?
+
+Due to a peculiarity of C++, in order to support the syntax for streaming
+messages to an `ASSERT_*`, e.g.
+
+```c++
+  ASSERT_EQ(1, Foo()) << "blah blah" << foo;
+```
+
+we had to give up using `ASSERT*` and `FAIL*` (but not `EXPECT*` and
+`ADD_FAILURE*`) in constructors and destructors. The workaround is to move the
+content of your constructor/destructor to a private void member function, or
+switch to `EXPECT_*()` if that works. This
+[section](advanced.md#assertion-placement) in the user's guide explains it.
+
+## My SetUp() function is not called. Why?
+
+C++ is case-sensitive. Did you spell it as `Setup()`?
+
+Similarly, sometimes people spell `SetUpTestSuite()` as `SetupTestSuite()` and
+wonder why it's never called.
+
+## I have several test suites which share the same test fixture logic, do I have to define a new test fixture class for each of them? This seems pretty tedious.
+
+You don't have to. Instead of
+
+```c++
+class FooTest : public BaseTest {};
+
+TEST_F(FooTest, Abc) { ... }
+TEST_F(FooTest, Def) { ... }
+
+class BarTest : public BaseTest {};
+
+TEST_F(BarTest, Abc) { ... }
+TEST_F(BarTest, Def) { ... }
+```
+
+you can simply `typedef` the test fixtures:
+
+```c++
+typedef BaseTest FooTest;
+
+TEST_F(FooTest, Abc) { ... }
+TEST_F(FooTest, Def) { ... }
+
+typedef BaseTest BarTest;
+
+TEST_F(BarTest, Abc) { ... }
+TEST_F(BarTest, Def) { ... }
+```
+
+## GoogleTest output is buried in a whole bunch of LOG messages. What do I do?
+
+The GoogleTest output is meant to be a concise and human-friendly report. If
+your test generates textual output itself, it will mix with the GoogleTest
+output, making it hard to read. However, there is an easy solution to this
+problem.
+
+Since `LOG` messages go to stderr, we decided to let GoogleTest output go to
+stdout. This way, you can easily separate the two using redirection. For
+example:
+
+```shell
+$ ./my_test > gtest_output.txt
+```
+
+## Why should I prefer test fixtures over global variables?
+
+There are several good reasons:
+
+1.  It's likely your test needs to change the states of its global variables.
+    This makes it difficult to keep side effects from escaping one test and
+    contaminating others, making debugging difficult. By using fixtures, each
+    test has a fresh set of variables that's different (but with the same
+    names). Thus, tests are kept independent of each other.
+2.  Global variables pollute the global namespace.
+3.  Test fixtures can be reused via subclassing, which cannot be done easily
+    with global variables. This is useful if many test suites have something in
+    common.
+
+## What can the statement argument in ASSERT_DEATH() be?
+
+`ASSERT_DEATH(statement, matcher)` (or any death assertion macro) can be used
+wherever *`statement`* is valid. So basically *`statement`* can be any C++
+statement that makes sense in the current context. In particular, it can
+reference global and/or local variables, and can be:
+
+*   a simple function call (often the case),
+*   a complex expression, or
+*   a compound statement.
+
+Some examples are shown here:
+
+```c++
+// A death test can be a simple function call.
+TEST(MyDeathTest, FunctionCall) {
+  ASSERT_DEATH(Xyz(5), "Xyz failed");
+}
+
+// Or a complex expression that references variables and functions.
+TEST(MyDeathTest, ComplexExpression) {
+  const bool c = Condition();
+  ASSERT_DEATH((c ? Func1(0) : object2.Method("test")),
+               "(Func1|Method) failed");
+}
+
+// Death assertions can be used anywhere in a function.  In
+// particular, they can be inside a loop.
+TEST(MyDeathTest, InsideLoop) {
+  // Verifies that Foo(0), Foo(1), ..., and Foo(4) all die.
+  for (int i = 0; i < 5; i++) {
+    EXPECT_DEATH_M(Foo(i), "Foo has \\d+ errors",
+                   ::testing::Message() << "where i is " << i);
+  }
+}
+
+// A death assertion can contain a compound statement.
+TEST(MyDeathTest, CompoundStatement) {
+  // Verifies that at lease one of Bar(0), Bar(1), ..., and
+  // Bar(4) dies.
+  ASSERT_DEATH({
+    for (int i = 0; i < 5; i++) {
+      Bar(i);
+    }
+  },
+  "Bar has \\d+ errors");
+}
+```
+
+## I have a fixture class `FooTest`, but `TEST_F(FooTest, Bar)` gives me error ``"no matching function for call to `FooTest::FooTest()'"``. Why?
+
+GoogleTest needs to be able to create objects of your test fixture class, so it
+must have a default constructor. Normally the compiler will define one for you.
+However, there are cases where you have to define your own:
+
+*   If you explicitly declare a non-default constructor for class `FooTest`
+    (`DISALLOW_EVIL_CONSTRUCTORS()` does this), then you need to define a
+    default constructor, even if it would be empty.
+*   If `FooTest` has a const non-static data member, then you have to define the
+    default constructor *and* initialize the const member in the initializer
+    list of the constructor. (Early versions of `gcc` doesn't force you to
+    initialize the const member. It's a bug that has been fixed in `gcc 4`.)
+
+## Why does ASSERT_DEATH complain about previous threads that were already joined?
+
+With the Linux pthread library, there is no turning back once you cross the line
+from a single thread to multiple threads. The first time you create a thread, a
+manager thread is created in addition, so you get 3, not 2, threads. Later when
+the thread you create joins the main thread, the thread count decrements by 1,
+but the manager thread will never be killed, so you still have 2 threads, which
+means you cannot safely run a death test.
+
+The new NPTL thread library doesn't suffer from this problem, as it doesn't
+create a manager thread. However, if you don't control which machine your test
+runs on, you shouldn't depend on this.
+
+## Why does GoogleTest require the entire test suite, instead of individual tests, to be named *DeathTest when it uses ASSERT_DEATH?
+
+GoogleTest does not interleave tests from different test suites. That is, it
+runs all tests in one test suite first, and then runs all tests in the next test
+suite, and so on. GoogleTest does this because it needs to set up a test suite
+before the first test in it is run, and tear it down afterwards. Splitting up
+the test case would require multiple set-up and tear-down processes, which is
+inefficient and makes the semantics unclean.
+
+If we were to determine the order of tests based on test name instead of test
+case name, then we would have a problem with the following situation:
+
+```c++
+TEST_F(FooTest, AbcDeathTest) { ... }
+TEST_F(FooTest, Uvw) { ... }
+
+TEST_F(BarTest, DefDeathTest) { ... }
+TEST_F(BarTest, Xyz) { ... }
+```
+
+Since `FooTest.AbcDeathTest` needs to run before `BarTest.Xyz`, and we don't
+interleave tests from different test suites, we need to run all tests in the
+`FooTest` case before running any test in the `BarTest` case. This contradicts
+with the requirement to run `BarTest.DefDeathTest` before `FooTest.Uvw`.
+
+## But I don't like calling my entire test suite \*DeathTest when it contains both death tests and non-death tests. What do I do?
+
+You don't have to, but if you like, you may split up the test suite into
+`FooTest` and `FooDeathTest`, where the names make it clear that they are
+related:
+
+```c++
+class FooTest : public ::testing::Test { ... };
+
+TEST_F(FooTest, Abc) { ... }
+TEST_F(FooTest, Def) { ... }
+
+using FooDeathTest = FooTest;
+
+TEST_F(FooDeathTest, Uvw) { ... EXPECT_DEATH(...) ... }
+TEST_F(FooDeathTest, Xyz) { ... ASSERT_DEATH(...) ... }
+```
+
+## GoogleTest prints the LOG messages in a death test's child process only when the test fails. How can I see the LOG messages when the death test succeeds?
+
+Printing the LOG messages generated by the statement inside `EXPECT_DEATH()`
+makes it harder to search for real problems in the parent's log. Therefore,
+GoogleTest only prints them when the death test has failed.
+
+If you really need to see such LOG messages, a workaround is to temporarily
+break the death test (e.g. by changing the regex pattern it is expected to
+match). Admittedly, this is a hack. We'll consider a more permanent solution
+after the fork-and-exec-style death tests are implemented.
+
+## The compiler complains about `no match for 'operator<<'` when I use an assertion. What gives?
+
+If you use a user-defined type `FooType` in an assertion, you must make sure
+there is an `std::ostream& operator<<(std::ostream&, const FooType&)` function
+defined such that we can print a value of `FooType`.
+
+In addition, if `FooType` is declared in a name space, the `<<` operator also
+needs to be defined in the *same* name space. See
+[Tip of the Week #49](https://abseil.io/tips/49) for details.
+
+## How do I suppress the memory leak messages on Windows?
+
+Since the statically initialized GoogleTest singleton requires allocations on
+the heap, the Visual C++ memory leak detector will report memory leaks at the
+end of the program run. The easiest way to avoid this is to use the
+`_CrtMemCheckpoint` and `_CrtMemDumpAllObjectsSince` calls to not report any
+statically initialized heap objects. See MSDN for more details and additional
+heap check/debug routines.
+
+## How can my code detect if it is running in a test?
+
+If you write code that sniffs whether it's running in a test and does different
+things accordingly, you are leaking test-only logic into production code and
+there is no easy way to ensure that the test-only code paths aren't run by
+mistake in production. Such cleverness also leads to
+[Heisenbugs](https://en.wikipedia.org/wiki/Heisenbug). Therefore we strongly
+advise against the practice, and GoogleTest doesn't provide a way to do it.
+
+In general, the recommended way to cause the code to behave differently under
+test is [Dependency Injection](https://en.wikipedia.org/wiki/Dependency_injection). You can inject
+different functionality from the test and from the production code. Since your
+production code doesn't link in the for-test logic at all (the
+[`testonly`](https://docs.bazel.build/versions/master/be/common-definitions.html#common.testonly) attribute for BUILD targets helps to ensure
+that), there is no danger in accidentally running it.
+
+However, if you *really*, *really*, *really* have no choice, and if you follow
+the rule of ending your test program names with `_test`, you can use the
+*horrible* hack of sniffing your executable name (`argv[0]` in `main()`) to know
+whether the code is under test.
+
+## How do I temporarily disable a test?
+
+If you have a broken test that you cannot fix right away, you can add the
+`DISABLED_` prefix to its name. This will exclude it from execution. This is
+better than commenting out the code or using `#if 0`, as disabled tests are
+still compiled (and thus won't rot).
+
+To include disabled tests in test execution, just invoke the test program with
+the `--gtest_also_run_disabled_tests` flag.
+
+## Is it OK if I have two separate `TEST(Foo, Bar)` test methods defined in different namespaces?
+
+Yes.
+
+The rule is **all test methods in the same test suite must use the same fixture
+class.** This means that the following is **allowed** because both tests use the
+same fixture class (`::testing::Test`).
+
+```c++
+namespace foo {
+TEST(CoolTest, DoSomething) {
+  SUCCEED();
+}
+}  // namespace foo
+
+namespace bar {
+TEST(CoolTest, DoSomething) {
+  SUCCEED();
+}
+}  // namespace bar
+```
+
+However, the following code is **not allowed** and will produce a runtime error
+from GoogleTest because the test methods are using different test fixture
+classes with the same test suite name.
+
+```c++
+namespace foo {
+class CoolTest : public ::testing::Test {};  // Fixture foo::CoolTest
+TEST_F(CoolTest, DoSomething) {
+  SUCCEED();
+}
+}  // namespace foo
+
+namespace bar {
+class CoolTest : public ::testing::Test {};  // Fixture: bar::CoolTest
+TEST_F(CoolTest, DoSomething) {
+  SUCCEED();
+}
+}  // namespace bar
+```
diff --git a/third_party/googletest/docs/gmock_cheat_sheet.md b/third_party/googletest/docs/gmock_cheat_sheet.md
new file mode 100644
index 0000000..ddafaaa
--- /dev/null
+++ b/third_party/googletest/docs/gmock_cheat_sheet.md
@@ -0,0 +1,241 @@
+# gMock Cheat Sheet
+
+## Defining a Mock Class
+
+### Mocking a Normal Class {#MockClass}
+
+Given
+
+```cpp
+class Foo {
+ public:
+  virtual ~Foo();
+  virtual int GetSize() const = 0;
+  virtual string Describe(const char* name) = 0;
+  virtual string Describe(int type) = 0;
+  virtual bool Process(Bar elem, int count) = 0;
+};
+```
+
+(note that `~Foo()` **must** be virtual) we can define its mock as
+
+```cpp
+#include <gmock/gmock.h>
+
+class MockFoo : public Foo {
+ public:
+  MOCK_METHOD(int, GetSize, (), (const, override));
+  MOCK_METHOD(string, Describe, (const char* name), (override));
+  MOCK_METHOD(string, Describe, (int type), (override));
+  MOCK_METHOD(bool, Process, (Bar elem, int count), (override));
+};
+```
+
+To create a "nice" mock, which ignores all uninteresting calls, a "naggy" mock,
+which warns on all uninteresting calls, or a "strict" mock, which treats them as
+failures:
+
+```cpp
+using ::testing::NiceMock;
+using ::testing::NaggyMock;
+using ::testing::StrictMock;
+
+NiceMock<MockFoo> nice_foo;      // The type is a subclass of MockFoo.
+NaggyMock<MockFoo> naggy_foo;    // The type is a subclass of MockFoo.
+StrictMock<MockFoo> strict_foo;  // The type is a subclass of MockFoo.
+```
+
+{: .callout .note}
+**Note:** A mock object is currently naggy by default. We may make it nice by
+default in the future.
+
+### Mocking a Class Template {#MockTemplate}
+
+Class templates can be mocked just like any class.
+
+To mock
+
+```cpp
+template <typename Elem>
+class StackInterface {
+ public:
+  virtual ~StackInterface();
+  virtual int GetSize() const = 0;
+  virtual void Push(const Elem& x) = 0;
+};
+```
+
+(note that all member functions that are mocked, including `~StackInterface()`
+**must** be virtual).
+
+```cpp
+template <typename Elem>
+class MockStack : public StackInterface<Elem> {
+ public:
+  MOCK_METHOD(int, GetSize, (), (const, override));
+  MOCK_METHOD(void, Push, (const Elem& x), (override));
+};
+```
+
+### Specifying Calling Conventions for Mock Functions
+
+If your mock function doesn't use the default calling convention, you can
+specify it by adding `Calltype(convention)` to `MOCK_METHOD`'s 4th parameter.
+For example,
+
+```cpp
+  MOCK_METHOD(bool, Foo, (int n), (Calltype(STDMETHODCALLTYPE)));
+  MOCK_METHOD(int, Bar, (double x, double y),
+              (const, Calltype(STDMETHODCALLTYPE)));
+```
+
+where `STDMETHODCALLTYPE` is defined by `<objbase.h>` on Windows.
+
+## Using Mocks in Tests {#UsingMocks}
+
+The typical work flow is:
+
+1.  Import the gMock names you need to use. All gMock symbols are in the
+    `testing` namespace unless they are macros or otherwise noted.
+2.  Create the mock objects.
+3.  Optionally, set the default actions of the mock objects.
+4.  Set your expectations on the mock objects (How will they be called? What
+    will they do?).
+5.  Exercise code that uses the mock objects; if necessary, check the result
+    using googletest assertions.
+6.  When a mock object is destructed, gMock automatically verifies that all
+    expectations on it have been satisfied.
+
+Here's an example:
+
+```cpp
+using ::testing::Return;                          // #1
+
+TEST(BarTest, DoesThis) {
+  MockFoo foo;                                    // #2
+
+  ON_CALL(foo, GetSize())                         // #3
+      .WillByDefault(Return(1));
+  // ... other default actions ...
+
+  EXPECT_CALL(foo, Describe(5))                   // #4
+      .Times(3)
+      .WillRepeatedly(Return("Category 5"));
+  // ... other expectations ...
+
+  EXPECT_EQ(MyProductionFunction(&foo), "good");  // #5
+}                                                 // #6
+```
+
+## Setting Default Actions {#OnCall}
+
+gMock has a **built-in default action** for any function that returns `void`,
+`bool`, a numeric value, or a pointer. In C++11, it will additionally returns
+the default-constructed value, if one exists for the given type.
+
+To customize the default action for functions with return type `T`, use
+[`DefaultValue<T>`](reference/mocking.md#DefaultValue). For example:
+
+```cpp
+  // Sets the default action for return type std::unique_ptr<Buzz> to
+  // creating a new Buzz every time.
+  DefaultValue<std::unique_ptr<Buzz>>::SetFactory(
+      [] { return std::make_unique<Buzz>(AccessLevel::kInternal); });
+
+  // When this fires, the default action of MakeBuzz() will run, which
+  // will return a new Buzz object.
+  EXPECT_CALL(mock_buzzer_, MakeBuzz("hello")).Times(AnyNumber());
+
+  auto buzz1 = mock_buzzer_.MakeBuzz("hello");
+  auto buzz2 = mock_buzzer_.MakeBuzz("hello");
+  EXPECT_NE(buzz1, nullptr);
+  EXPECT_NE(buzz2, nullptr);
+  EXPECT_NE(buzz1, buzz2);
+
+  // Resets the default action for return type std::unique_ptr<Buzz>,
+  // to avoid interfere with other tests.
+  DefaultValue<std::unique_ptr<Buzz>>::Clear();
+```
+
+To customize the default action for a particular method of a specific mock
+object, use [`ON_CALL`](reference/mocking.md#ON_CALL). `ON_CALL` has a similar
+syntax to `EXPECT_CALL`, but it is used for setting default behaviors when you
+do not require that the mock method is called. See
+[Knowing When to Expect](gmock_cook_book.md#UseOnCall) for a more detailed
+discussion.
+
+## Setting Expectations {#ExpectCall}
+
+See [`EXPECT_CALL`](reference/mocking.md#EXPECT_CALL) in the Mocking Reference.
+
+## Matchers {#MatcherList}
+
+See the [Matchers Reference](reference/matchers.md).
+
+## Actions {#ActionList}
+
+See the [Actions Reference](reference/actions.md).
+
+## Cardinalities {#CardinalityList}
+
+See the [`Times` clause](reference/mocking.md#EXPECT_CALL.Times) of
+`EXPECT_CALL` in the Mocking Reference.
+
+## Expectation Order
+
+By default, expectations can be matched in *any* order. If some or all
+expectations must be matched in a given order, you can use the
+[`After` clause](reference/mocking.md#EXPECT_CALL.After) or
+[`InSequence` clause](reference/mocking.md#EXPECT_CALL.InSequence) of
+`EXPECT_CALL`, or use an [`InSequence` object](reference/mocking.md#InSequence).
+
+## Verifying and Resetting a Mock
+
+gMock will verify the expectations on a mock object when it is destructed, or
+you can do it earlier:
+
+```cpp
+using ::testing::Mock;
+...
+// Verifies and removes the expectations on mock_obj;
+// returns true if and only if successful.
+Mock::VerifyAndClearExpectations(&mock_obj);
+...
+// Verifies and removes the expectations on mock_obj;
+// also removes the default actions set by ON_CALL();
+// returns true if and only if successful.
+Mock::VerifyAndClear(&mock_obj);
+```
+
+Do not set new expectations after verifying and clearing a mock after its use.
+Setting expectations after code that exercises the mock has undefined behavior.
+See [Using Mocks in Tests](gmock_for_dummies.md#using-mocks-in-tests) for more
+information.
+
+You can also tell gMock that a mock object can be leaked and doesn't need to be
+verified:
+
+```cpp
+Mock::AllowLeak(&mock_obj);
+```
+
+## Mock Classes
+
+gMock defines a convenient mock class template
+
+```cpp
+class MockFunction<R(A1, ..., An)> {
+ public:
+  MOCK_METHOD(R, Call, (A1, ..., An));
+};
+```
+
+See this [recipe](gmock_cook_book.md#UsingCheckPoints) for one application of
+it.
+
+## Flags
+
+| Flag                           | Description                               |
+| :----------------------------- | :---------------------------------------- |
+| `--gmock_catch_leaked_mocks=0` | Don't report leaked mock objects as failures. |
+| `--gmock_verbose=LEVEL` | Sets the default verbosity level (`info`, `warning`, or `error`) of Google Mock messages. |
diff --git a/third_party/googletest/docs/gmock_cook_book.md b/third_party/googletest/docs/gmock_cook_book.md
new file mode 100644
index 0000000..da10918
--- /dev/null
+++ b/third_party/googletest/docs/gmock_cook_book.md
@@ -0,0 +1,4344 @@
+# gMock Cookbook
+
+You can find recipes for using gMock here. If you haven't yet, please read
+[the dummy guide](gmock_for_dummies.md) first to make sure you understand the
+basics.
+
+{: .callout .note}
+**Note:** gMock lives in the `testing` name space. For readability, it is
+recommended to write `using ::testing::Foo;` once in your file before using the
+name `Foo` defined by gMock. We omit such `using` statements in this section for
+brevity, but you should do it in your own code.
+
+## Creating Mock Classes
+
+Mock classes are defined as normal classes, using the `MOCK_METHOD` macro to
+generate mocked methods. The macro gets 3 or 4 parameters:
+
+```cpp
+class MyMock {
+ public:
+  MOCK_METHOD(ReturnType, MethodName, (Args...));
+  MOCK_METHOD(ReturnType, MethodName, (Args...), (Specs...));
+};
+```
+
+The first 3 parameters are simply the method declaration, split into 3 parts.
+The 4th parameter accepts a closed list of qualifiers, which affect the
+generated method:
+
+*   **`const`** - Makes the mocked method a `const` method. Required if
+    overriding a `const` method.
+*   **`override`** - Marks the method with `override`. Recommended if overriding
+    a `virtual` method.
+*   **`noexcept`** - Marks the method with `noexcept`. Required if overriding a
+    `noexcept` method.
+*   **`Calltype(...)`** - Sets the call type for the method (e.g. to
+    `STDMETHODCALLTYPE`), useful in Windows.
+*   **`ref(...)`** - Marks the method with the reference qualification
+    specified. Required if overriding a method that has reference
+    qualifications. Eg `ref(&)` or `ref(&&)`.
+
+### Dealing with unprotected commas
+
+Unprotected commas, i.e. commas which are not surrounded by parentheses, prevent
+`MOCK_METHOD` from parsing its arguments correctly:
+
+{: .bad}
+```cpp
+class MockFoo {
+ public:
+  MOCK_METHOD(std::pair<bool, int>, GetPair, ());  // Won't compile!
+  MOCK_METHOD(bool, CheckMap, (std::map<int, double>, bool));  // Won't compile!
+};
+```
+
+Solution 1 - wrap with parentheses:
+
+{: .good}
+```cpp
+class MockFoo {
+ public:
+  MOCK_METHOD((std::pair<bool, int>), GetPair, ());
+  MOCK_METHOD(bool, CheckMap, ((std::map<int, double>), bool));
+};
+```
+
+Note that wrapping a return or argument type with parentheses is, in general,
+invalid C++. `MOCK_METHOD` removes the parentheses.
+
+Solution 2 - define an alias:
+
+{: .good}
+```cpp
+class MockFoo {
+ public:
+  using BoolAndInt = std::pair<bool, int>;
+  MOCK_METHOD(BoolAndInt, GetPair, ());
+  using MapIntDouble = std::map<int, double>;
+  MOCK_METHOD(bool, CheckMap, (MapIntDouble, bool));
+};
+```
+
+### Mocking Private or Protected Methods
+
+You must always put a mock method definition (`MOCK_METHOD`) in a `public:`
+section of the mock class, regardless of the method being mocked being `public`,
+`protected`, or `private` in the base class. This allows `ON_CALL` and
+`EXPECT_CALL` to reference the mock function from outside of the mock class.
+(Yes, C++ allows a subclass to change the access level of a virtual function in
+the base class.) Example:
+
+```cpp
+class Foo {
+ public:
+  ...
+  virtual bool Transform(Gadget* g) = 0;
+
+ protected:
+  virtual void Resume();
+
+ private:
+  virtual int GetTimeOut();
+};
+
+class MockFoo : public Foo {
+ public:
+  ...
+  MOCK_METHOD(bool, Transform, (Gadget* g), (override));
+
+  // The following must be in the public section, even though the
+  // methods are protected or private in the base class.
+  MOCK_METHOD(void, Resume, (), (override));
+  MOCK_METHOD(int, GetTimeOut, (), (override));
+};
+```
+
+### Mocking Overloaded Methods
+
+You can mock overloaded functions as usual. No special attention is required:
+
+```cpp
+class Foo {
+  ...
+
+  // Must be virtual as we'll inherit from Foo.
+  virtual ~Foo();
+
+  // Overloaded on the types and/or numbers of arguments.
+  virtual int Add(Element x);
+  virtual int Add(int times, Element x);
+
+  // Overloaded on the const-ness of this object.
+  virtual Bar& GetBar();
+  virtual const Bar& GetBar() const;
+};
+
+class MockFoo : public Foo {
+  ...
+  MOCK_METHOD(int, Add, (Element x), (override));
+  MOCK_METHOD(int, Add, (int times, Element x), (override));
+
+  MOCK_METHOD(Bar&, GetBar, (), (override));
+  MOCK_METHOD(const Bar&, GetBar, (), (const, override));
+};
+```
+
+{: .callout .note}
+**Note:** if you don't mock all versions of the overloaded method, the compiler
+will give you a warning about some methods in the base class being hidden. To
+fix that, use `using` to bring them in scope:
+
+```cpp
+class MockFoo : public Foo {
+  ...
+  using Foo::Add;
+  MOCK_METHOD(int, Add, (Element x), (override));
+  // We don't want to mock int Add(int times, Element x);
+  ...
+};
+```
+
+### Mocking Class Templates
+
+You can mock class templates just like any class.
+
+```cpp
+template <typename Elem>
+class StackInterface {
+  ...
+  // Must be virtual as we'll inherit from StackInterface.
+  virtual ~StackInterface();
+
+  virtual int GetSize() const = 0;
+  virtual void Push(const Elem& x) = 0;
+};
+
+template <typename Elem>
+class MockStack : public StackInterface<Elem> {
+  ...
+  MOCK_METHOD(int, GetSize, (), (override));
+  MOCK_METHOD(void, Push, (const Elem& x), (override));
+};
+```
+
+### Mocking Non-virtual Methods {#MockingNonVirtualMethods}
+
+gMock can mock non-virtual functions to be used in Hi-perf dependency injection.
+
+In this case, instead of sharing a common base class with the real class, your
+mock class will be *unrelated* to the real class, but contain methods with the
+same signatures. The syntax for mocking non-virtual methods is the *same* as
+mocking virtual methods (just don't add `override`):
+
+```cpp
+// A simple packet stream class.  None of its members is virtual.
+class ConcretePacketStream {
+ public:
+  void AppendPacket(Packet* new_packet);
+  const Packet* GetPacket(size_t packet_number) const;
+  size_t NumberOfPackets() const;
+  ...
+};
+
+// A mock packet stream class.  It inherits from no other, but defines
+// GetPacket() and NumberOfPackets().
+class MockPacketStream {
+ public:
+  MOCK_METHOD(const Packet*, GetPacket, (size_t packet_number), (const));
+  MOCK_METHOD(size_t, NumberOfPackets, (), (const));
+  ...
+};
+```
+
+Note that the mock class doesn't define `AppendPacket()`, unlike the real class.
+That's fine as long as the test doesn't need to call it.
+
+Next, you need a way to say that you want to use `ConcretePacketStream` in
+production code, and use `MockPacketStream` in tests. Since the functions are
+not virtual and the two classes are unrelated, you must specify your choice at
+*compile time* (as opposed to run time).
+
+One way to do it is to templatize your code that needs to use a packet stream.
+More specifically, you will give your code a template type argument for the type
+of the packet stream. In production, you will instantiate your template with
+`ConcretePacketStream` as the type argument. In tests, you will instantiate the
+same template with `MockPacketStream`. For example, you may write:
+
+```cpp
+template <class PacketStream>
+void CreateConnection(PacketStream* stream) { ... }
+
+template <class PacketStream>
+class PacketReader {
+ public:
+  void ReadPackets(PacketStream* stream, size_t packet_num);
+};
+```
+
+Then you can use `CreateConnection<ConcretePacketStream>()` and
+`PacketReader<ConcretePacketStream>` in production code, and use
+`CreateConnection<MockPacketStream>()` and `PacketReader<MockPacketStream>` in
+tests.
+
+```cpp
+  MockPacketStream mock_stream;
+  EXPECT_CALL(mock_stream, ...)...;
+  .. set more expectations on mock_stream ...
+  PacketReader<MockPacketStream> reader(&mock_stream);
+  ... exercise reader ...
+```
+
+### Mocking Free Functions
+
+It is not possible to directly mock a free function (i.e. a C-style function or
+a static method). If you need to, you can rewrite your code to use an interface
+(abstract class).
+
+Instead of calling a free function (say, `OpenFile`) directly, introduce an
+interface for it and have a concrete subclass that calls the free function:
+
+```cpp
+class FileInterface {
+ public:
+  ...
+  virtual bool Open(const char* path, const char* mode) = 0;
+};
+
+class File : public FileInterface {
+ public:
+  ...
+  bool Open(const char* path, const char* mode) override {
+     return OpenFile(path, mode);
+  }
+};
+```
+
+Your code should talk to `FileInterface` to open a file. Now it's easy to mock
+out the function.
+
+This may seem like a lot of hassle, but in practice you often have multiple
+related functions that you can put in the same interface, so the per-function
+syntactic overhead will be much lower.
+
+If you are concerned about the performance overhead incurred by virtual
+functions, and profiling confirms your concern, you can combine this with the
+recipe for [mocking non-virtual methods](#MockingNonVirtualMethods).
+
+Alternatively, instead of introducing a new interface, you can rewrite your code
+to accept a std::function instead of the free function, and then use
+[MockFunction](#MockFunction) to mock the std::function.
+
+### Old-Style `MOCK_METHODn` Macros
+
+Before the generic `MOCK_METHOD` macro
+[was introduced in 2018](https://github.com/google/googletest/commit/c5f08bf91944ce1b19bcf414fa1760e69d20afc2),
+mocks where created using a family of macros collectively called `MOCK_METHODn`.
+These macros are still supported, though migration to the new `MOCK_METHOD` is
+recommended.
+
+The macros in the `MOCK_METHODn` family differ from `MOCK_METHOD`:
+
+*   The general structure is `MOCK_METHODn(MethodName, ReturnType(Args))`,
+    instead of `MOCK_METHOD(ReturnType, MethodName, (Args))`.
+*   The number `n` must equal the number of arguments.
+*   When mocking a const method, one must use `MOCK_CONST_METHODn`.
+*   When mocking a class template, the macro name must be suffixed with `_T`.
+*   In order to specify the call type, the macro name must be suffixed with
+    `_WITH_CALLTYPE`, and the call type is the first macro argument.
+
+Old macros and their new equivalents:
+
+<table>
+  <tr><th colspan=2>Simple</th></tr>
+  <tr>
+    <td>Old</td>
+    <td><code>MOCK_METHOD1(Foo, bool(int))</code></td>
+  </tr>
+  <tr>
+    <td>New</td>
+    <td><code>MOCK_METHOD(bool, Foo, (int))</code></td>
+  </tr>
+
+  <tr><th colspan=2>Const Method</th></tr>
+  <tr>
+    <td>Old</td>
+    <td><code>MOCK_CONST_METHOD1(Foo, bool(int))</code></td>
+  </tr>
+  <tr>
+    <td>New</td>
+    <td><code>MOCK_METHOD(bool, Foo, (int), (const))</code></td>
+  </tr>
+
+  <tr><th colspan=2>Method in a Class Template</th></tr>
+  <tr>
+    <td>Old</td>
+    <td><code>MOCK_METHOD1_T(Foo, bool(int))</code></td>
+  </tr>
+  <tr>
+    <td>New</td>
+    <td><code>MOCK_METHOD(bool, Foo, (int))</code></td>
+  </tr>
+
+  <tr><th colspan=2>Const Method in a Class Template</th></tr>
+  <tr>
+    <td>Old</td>
+    <td><code>MOCK_CONST_METHOD1_T(Foo, bool(int))</code></td>
+  </tr>
+  <tr>
+    <td>New</td>
+    <td><code>MOCK_METHOD(bool, Foo, (int), (const))</code></td>
+  </tr>
+
+  <tr><th colspan=2>Method with Call Type</th></tr>
+  <tr>
+    <td>Old</td>
+    <td><code>MOCK_METHOD1_WITH_CALLTYPE(STDMETHODCALLTYPE, Foo, bool(int))</code></td>
+  </tr>
+  <tr>
+    <td>New</td>
+    <td><code>MOCK_METHOD(bool, Foo, (int), (Calltype(STDMETHODCALLTYPE)))</code></td>
+  </tr>
+
+  <tr><th colspan=2>Const Method with Call Type</th></tr>
+  <tr>
+    <td>Old</td>
+    <td><code>MOCK_CONST_METHOD1_WITH_CALLTYPE(STDMETHODCALLTYPE, Foo, bool(int))</code></td>
+  </tr>
+  <tr>
+    <td>New</td>
+    <td><code>MOCK_METHOD(bool, Foo, (int), (const, Calltype(STDMETHODCALLTYPE)))</code></td>
+  </tr>
+
+  <tr><th colspan=2>Method with Call Type in a Class Template</th></tr>
+  <tr>
+    <td>Old</td>
+    <td><code>MOCK_METHOD1_T_WITH_CALLTYPE(STDMETHODCALLTYPE, Foo, bool(int))</code></td>
+  </tr>
+  <tr>
+    <td>New</td>
+    <td><code>MOCK_METHOD(bool, Foo, (int), (Calltype(STDMETHODCALLTYPE)))</code></td>
+  </tr>
+
+  <tr><th colspan=2>Const Method with Call Type in a Class Template</th></tr>
+  <tr>
+    <td>Old</td>
+    <td><code>MOCK_CONST_METHOD1_T_WITH_CALLTYPE(STDMETHODCALLTYPE, Foo, bool(int))</code></td>
+  </tr>
+  <tr>
+    <td>New</td>
+    <td><code>MOCK_METHOD(bool, Foo, (int), (const, Calltype(STDMETHODCALLTYPE)))</code></td>
+  </tr>
+</table>
+
+### The Nice, the Strict, and the Naggy {#NiceStrictNaggy}
+
+If a mock method has no `EXPECT_CALL` spec but is called, we say that it's an
+"uninteresting call", and the default action (which can be specified using
+`ON_CALL()`) of the method will be taken. Currently, an uninteresting call will
+also by default cause gMock to print a warning.
+
+However, sometimes you may want to ignore these uninteresting calls, and
+sometimes you may want to treat them as errors. gMock lets you make the decision
+on a per-mock-object basis.
+
+Suppose your test uses a mock class `MockFoo`:
+
+```cpp
+TEST(...) {
+  MockFoo mock_foo;
+  EXPECT_CALL(mock_foo, DoThis());
+  ... code that uses mock_foo ...
+}
+```
+
+If a method of `mock_foo` other than `DoThis()` is called, you will get a
+warning. However, if you rewrite your test to use `NiceMock<MockFoo>` instead,
+you can suppress the warning:
+
+```cpp
+using ::testing::NiceMock;
+
+TEST(...) {
+  NiceMock<MockFoo> mock_foo;
+  EXPECT_CALL(mock_foo, DoThis());
+  ... code that uses mock_foo ...
+}
+```
+
+`NiceMock<MockFoo>` is a subclass of `MockFoo`, so it can be used wherever
+`MockFoo` is accepted.
+
+It also works if `MockFoo`'s constructor takes some arguments, as
+`NiceMock<MockFoo>` "inherits" `MockFoo`'s constructors:
+
+```cpp
+using ::testing::NiceMock;
+
+TEST(...) {
+  NiceMock<MockFoo> mock_foo(5, "hi");  // Calls MockFoo(5, "hi").
+  EXPECT_CALL(mock_foo, DoThis());
+  ... code that uses mock_foo ...
+}
+```
+
+The usage of `StrictMock` is similar, except that it makes all uninteresting
+calls failures:
+
+```cpp
+using ::testing::StrictMock;
+
+TEST(...) {
+  StrictMock<MockFoo> mock_foo;
+  EXPECT_CALL(mock_foo, DoThis());
+  ... code that uses mock_foo ...
+
+  // The test will fail if a method of mock_foo other than DoThis()
+  // is called.
+}
+```
+
+{: .callout .note}
+NOTE: `NiceMock` and `StrictMock` only affects *uninteresting* calls (calls of
+*methods* with no expectations); they do not affect *unexpected* calls (calls of
+methods with expectations, but they don't match). See
+[Understanding Uninteresting vs Unexpected Calls](#uninteresting-vs-unexpected).
+
+There are some caveats though (sadly they are side effects of C++'s
+limitations):
+
+1.  `NiceMock<MockFoo>` and `StrictMock<MockFoo>` only work for mock methods
+    defined using the `MOCK_METHOD` macro **directly** in the `MockFoo` class.
+    If a mock method is defined in a **base class** of `MockFoo`, the "nice" or
+    "strict" modifier may not affect it, depending on the compiler. In
+    particular, nesting `NiceMock` and `StrictMock` (e.g.
+    `NiceMock<StrictMock<MockFoo> >`) is **not** supported.
+2.  `NiceMock<MockFoo>` and `StrictMock<MockFoo>` may not work correctly if the
+    destructor of `MockFoo` is not virtual. We would like to fix this, but it
+    requires cleaning up existing tests.
+
+Finally, you should be **very cautious** about when to use naggy or strict
+mocks, as they tend to make tests more brittle and harder to maintain. When you
+refactor your code without changing its externally visible behavior, ideally you
+shouldn't need to update any tests. If your code interacts with a naggy mock,
+however, you may start to get spammed with warnings as the result of your
+change. Worse, if your code interacts with a strict mock, your tests may start
+to fail and you'll be forced to fix them. Our general recommendation is to use
+nice mocks (not yet the default) most of the time, use naggy mocks (the current
+default) when developing or debugging tests, and use strict mocks only as the
+last resort.
+
+### Simplifying the Interface without Breaking Existing Code {#SimplerInterfaces}
+
+Sometimes a method has a long list of arguments that is mostly uninteresting.
+For example:
+
+```cpp
+class LogSink {
+ public:
+  ...
+  virtual void send(LogSeverity severity, const char* full_filename,
+                    const char* base_filename, int line,
+                    const struct tm* tm_time,
+                    const char* message, size_t message_len) = 0;
+};
+```
+
+This method's argument list is lengthy and hard to work with (the `message`
+argument is not even 0-terminated). If we mock it as is, using the mock will be
+awkward. If, however, we try to simplify this interface, we'll need to fix all
+clients depending on it, which is often infeasible.
+
+The trick is to redispatch the method in the mock class:
+
+```cpp
+class ScopedMockLog : public LogSink {
+ public:
+  ...
+  void send(LogSeverity severity, const char* full_filename,
+                    const char* base_filename, int line, const tm* tm_time,
+                    const char* message, size_t message_len) override {
+    // We are only interested in the log severity, full file name, and
+    // log message.
+    Log(severity, full_filename, std::string(message, message_len));
+  }
+
+  // Implements the mock method:
+  //
+  //   void Log(LogSeverity severity,
+  //            const string& file_path,
+  //            const string& message);
+  MOCK_METHOD(void, Log,
+              (LogSeverity severity, const string& file_path,
+               const string& message));
+};
+```
+
+By defining a new mock method with a trimmed argument list, we make the mock
+class more user-friendly.
+
+This technique may also be applied to make overloaded methods more amenable to
+mocking. For example, when overloads have been used to implement default
+arguments:
+
+```cpp
+class MockTurtleFactory : public TurtleFactory {
+ public:
+  Turtle* MakeTurtle(int length, int weight) override { ... }
+  Turtle* MakeTurtle(int length, int weight, int speed) override { ... }
+
+  // the above methods delegate to this one:
+  MOCK_METHOD(Turtle*, DoMakeTurtle, ());
+};
+```
+
+This allows tests that don't care which overload was invoked to avoid specifying
+argument matchers:
+
+```cpp
+ON_CALL(factory, DoMakeTurtle)
+    .WillByDefault(Return(MakeMockTurtle()));
+```
+
+### Alternative to Mocking Concrete Classes
+
+Often you may find yourself using classes that don't implement interfaces. In
+order to test your code that uses such a class (let's call it `Concrete`), you
+may be tempted to make the methods of `Concrete` virtual and then mock it.
+
+Try not to do that.
+
+Making a non-virtual function virtual is a big decision. It creates an extension
+point where subclasses can tweak your class' behavior. This weakens your control
+on the class because now it's harder to maintain the class invariants. You
+should make a function virtual only when there is a valid reason for a subclass
+to override it.
+
+Mocking concrete classes directly is problematic as it creates a tight coupling
+between the class and the tests - any small change in the class may invalidate
+your tests and make test maintenance a pain.
+
+To avoid such problems, many programmers have been practicing "coding to
+interfaces": instead of talking to the `Concrete` class, your code would define
+an interface and talk to it. Then you implement that interface as an adaptor on
+top of `Concrete`. In tests, you can easily mock that interface to observe how
+your code is doing.
+
+This technique incurs some overhead:
+
+*   You pay the cost of virtual function calls (usually not a problem).
+*   There is more abstraction for the programmers to learn.
+
+However, it can also bring significant benefits in addition to better
+testability:
+
+*   `Concrete`'s API may not fit your problem domain very well, as you may not
+    be the only client it tries to serve. By designing your own interface, you
+    have a chance to tailor it to your need - you may add higher-level
+    functionalities, rename stuff, etc instead of just trimming the class. This
+    allows you to write your code (user of the interface) in a more natural way,
+    which means it will be more readable, more maintainable, and you'll be more
+    productive.
+*   If `Concrete`'s implementation ever has to change, you don't have to rewrite
+    everywhere it is used. Instead, you can absorb the change in your
+    implementation of the interface, and your other code and tests will be
+    insulated from this change.
+
+Some people worry that if everyone is practicing this technique, they will end
+up writing lots of redundant code. This concern is totally understandable.
+However, there are two reasons why it may not be the case:
+
+*   Different projects may need to use `Concrete` in different ways, so the best
+    interfaces for them will be different. Therefore, each of them will have its
+    own domain-specific interface on top of `Concrete`, and they will not be the
+    same code.
+*   If enough projects want to use the same interface, they can always share it,
+    just like they have been sharing `Concrete`. You can check in the interface
+    and the adaptor somewhere near `Concrete` (perhaps in a `contrib`
+    sub-directory) and let many projects use it.
+
+You need to weigh the pros and cons carefully for your particular problem, but
+I'd like to assure you that the Java community has been practicing this for a
+long time and it's a proven effective technique applicable in a wide variety of
+situations. :-)
+
+### Delegating Calls to a Fake {#DelegatingToFake}
+
+Some times you have a non-trivial fake implementation of an interface. For
+example:
+
+```cpp
+class Foo {
+ public:
+  virtual ~Foo() {}
+  virtual char DoThis(int n) = 0;
+  virtual void DoThat(const char* s, int* p) = 0;
+};
+
+class FakeFoo : public Foo {
+ public:
+  char DoThis(int n) override {
+    return (n > 0) ? '+' :
+           (n < 0) ? '-' : '0';
+  }
+
+  void DoThat(const char* s, int* p) override {
+    *p = strlen(s);
+  }
+};
+```
+
+Now you want to mock this interface such that you can set expectations on it.
+However, you also want to use `FakeFoo` for the default behavior, as duplicating
+it in the mock object is, well, a lot of work.
+
+When you define the mock class using gMock, you can have it delegate its default
+action to a fake class you already have, using this pattern:
+
+```cpp
+class MockFoo : public Foo {
+ public:
+  // Normal mock method definitions using gMock.
+  MOCK_METHOD(char, DoThis, (int n), (override));
+  MOCK_METHOD(void, DoThat, (const char* s, int* p), (override));
+
+  // Delegates the default actions of the methods to a FakeFoo object.
+  // This must be called *before* the custom ON_CALL() statements.
+  void DelegateToFake() {
+    ON_CALL(*this, DoThis).WillByDefault([this](int n) {
+      return fake_.DoThis(n);
+    });
+    ON_CALL(*this, DoThat).WillByDefault([this](const char* s, int* p) {
+      fake_.DoThat(s, p);
+    });
+  }
+
+ private:
+  FakeFoo fake_;  // Keeps an instance of the fake in the mock.
+};
+```
+
+With that, you can use `MockFoo` in your tests as usual. Just remember that if
+you don't explicitly set an action in an `ON_CALL()` or `EXPECT_CALL()`, the
+fake will be called upon to do it.:
+
+```cpp
+using ::testing::_;
+
+TEST(AbcTest, Xyz) {
+  MockFoo foo;
+
+  foo.DelegateToFake();  // Enables the fake for delegation.
+
+  // Put your ON_CALL(foo, ...)s here, if any.
+
+  // No action specified, meaning to use the default action.
+  EXPECT_CALL(foo, DoThis(5));
+  EXPECT_CALL(foo, DoThat(_, _));
+
+  int n = 0;
+  EXPECT_EQ(foo.DoThis(5), '+');  // FakeFoo::DoThis() is invoked.
+  foo.DoThat("Hi", &n);  // FakeFoo::DoThat() is invoked.
+  EXPECT_EQ(n, 2);
+}
+```
+
+**Some tips:**
+
+*   If you want, you can still override the default action by providing your own
+    `ON_CALL()` or using `.WillOnce()` / `.WillRepeatedly()` in `EXPECT_CALL()`.
+*   In `DelegateToFake()`, you only need to delegate the methods whose fake
+    implementation you intend to use.
+
+*   The general technique discussed here works for overloaded methods, but
+    you'll need to tell the compiler which version you mean. To disambiguate a
+    mock function (the one you specify inside the parentheses of `ON_CALL()`),
+    use [this technique](#SelectOverload); to disambiguate a fake function (the
+    one you place inside `Invoke()`), use a `static_cast` to specify the
+    function's type. For instance, if class `Foo` has methods `char DoThis(int
+    n)` and `bool DoThis(double x) const`, and you want to invoke the latter,
+    you need to write `Invoke(&fake_, static_cast<bool (FakeFoo::*)(double)
+    const>(&FakeFoo::DoThis))` instead of `Invoke(&fake_, &FakeFoo::DoThis)`
+    (The strange-looking thing inside the angled brackets of `static_cast` is
+    the type of a function pointer to the second `DoThis()` method.).
+
+*   Having to mix a mock and a fake is often a sign of something gone wrong.
+    Perhaps you haven't got used to the interaction-based way of testing yet. Or
+    perhaps your interface is taking on too many roles and should be split up.
+    Therefore, **don't abuse this**. We would only recommend to do it as an
+    intermediate step when you are refactoring your code.
+
+Regarding the tip on mixing a mock and a fake, here's an example on why it may
+be a bad sign: Suppose you have a class `System` for low-level system
+operations. In particular, it does file and I/O operations. And suppose you want
+to test how your code uses `System` to do I/O, and you just want the file
+operations to work normally. If you mock out the entire `System` class, you'll
+have to provide a fake implementation for the file operation part, which
+suggests that `System` is taking on too many roles.
+
+Instead, you can define a `FileOps` interface and an `IOOps` interface and split
+`System`'s functionalities into the two. Then you can mock `IOOps` without
+mocking `FileOps`.
+
+### Delegating Calls to a Real Object
+
+When using testing doubles (mocks, fakes, stubs, and etc), sometimes their
+behaviors will differ from those of the real objects. This difference could be
+either intentional (as in simulating an error such that you can test the error
+handling code) or unintentional. If your mocks have different behaviors than the
+real objects by mistake, you could end up with code that passes the tests but
+fails in production.
+
+You can use the *delegating-to-real* technique to ensure that your mock has the
+same behavior as the real object while retaining the ability to validate calls.
+This technique is very similar to the [delegating-to-fake](#DelegatingToFake)
+technique, the difference being that we use a real object instead of a fake.
+Here's an example:
+
+```cpp
+using ::testing::AtLeast;
+
+class MockFoo : public Foo {
+ public:
+  MockFoo() {
+    // By default, all calls are delegated to the real object.
+    ON_CALL(*this, DoThis).WillByDefault([this](int n) {
+      return real_.DoThis(n);
+    });
+    ON_CALL(*this, DoThat).WillByDefault([this](const char* s, int* p) {
+      real_.DoThat(s, p);
+    });
+    ...
+  }
+  MOCK_METHOD(char, DoThis, ...);
+  MOCK_METHOD(void, DoThat, ...);
+  ...
+ private:
+  Foo real_;
+};
+
+...
+  MockFoo mock;
+  EXPECT_CALL(mock, DoThis())
+      .Times(3);
+  EXPECT_CALL(mock, DoThat("Hi"))
+      .Times(AtLeast(1));
+  ... use mock in test ...
+```
+
+With this, gMock will verify that your code made the right calls (with the right
+arguments, in the right order, called the right number of times, etc), and a
+real object will answer the calls (so the behavior will be the same as in
+production). This gives you the best of both worlds.
+
+### Delegating Calls to a Parent Class
+
+Ideally, you should code to interfaces, whose methods are all pure virtual. In
+reality, sometimes you do need to mock a virtual method that is not pure (i.e,
+it already has an implementation). For example:
+
+```cpp
+class Foo {
+ public:
+  virtual ~Foo();
+
+  virtual void Pure(int n) = 0;
+  virtual int Concrete(const char* str) { ... }
+};
+
+class MockFoo : public Foo {
+ public:
+  // Mocking a pure method.
+  MOCK_METHOD(void, Pure, (int n), (override));
+  // Mocking a concrete method.  Foo::Concrete() is shadowed.
+  MOCK_METHOD(int, Concrete, (const char* str), (override));
+};
+```
+
+Sometimes you may want to call `Foo::Concrete()` instead of
+`MockFoo::Concrete()`. Perhaps you want to do it as part of a stub action, or
+perhaps your test doesn't need to mock `Concrete()` at all (but it would be
+oh-so painful to have to define a new mock class whenever you don't need to mock
+one of its methods).
+
+You can call `Foo::Concrete()` inside an action by:
+
+```cpp
+...
+  EXPECT_CALL(foo, Concrete).WillOnce([&foo](const char* str) {
+    return foo.Foo::Concrete(str);
+  });
+```
+
+or tell the mock object that you don't want to mock `Concrete()`:
+
+```cpp
+...
+  ON_CALL(foo, Concrete).WillByDefault([&foo](const char* str) {
+    return foo.Foo::Concrete(str);
+  });
+```
+
+(Why don't we just write `{ return foo.Concrete(str); }`? If you do that,
+`MockFoo::Concrete()` will be called (and cause an infinite recursion) since
+`Foo::Concrete()` is virtual. That's just how C++ works.)
+
+## Using Matchers
+
+### Matching Argument Values Exactly
+
+You can specify exactly which arguments a mock method is expecting:
+
+```cpp
+using ::testing::Return;
+...
+  EXPECT_CALL(foo, DoThis(5))
+      .WillOnce(Return('a'));
+  EXPECT_CALL(foo, DoThat("Hello", bar));
+```
+
+### Using Simple Matchers
+
+You can use matchers to match arguments that have a certain property:
+
+```cpp
+using ::testing::NotNull;
+using ::testing::Return;
+...
+  EXPECT_CALL(foo, DoThis(Ge(5)))  // The argument must be >= 5.
+      .WillOnce(Return('a'));
+  EXPECT_CALL(foo, DoThat("Hello", NotNull()));
+      // The second argument must not be NULL.
+```
+
+A frequently used matcher is `_`, which matches anything:
+
+```cpp
+  EXPECT_CALL(foo, DoThat(_, NotNull()));
+```
+
+### Combining Matchers {#CombiningMatchers}
+
+You can build complex matchers from existing ones using `AllOf()`,
+`AllOfArray()`, `AnyOf()`, `AnyOfArray()` and `Not()`:
+
+```cpp
+using ::testing::AllOf;
+using ::testing::Gt;
+using ::testing::HasSubstr;
+using ::testing::Ne;
+using ::testing::Not;
+...
+  // The argument must be > 5 and != 10.
+  EXPECT_CALL(foo, DoThis(AllOf(Gt(5),
+                                Ne(10))));
+
+  // The first argument must not contain sub-string "blah".
+  EXPECT_CALL(foo, DoThat(Not(HasSubstr("blah")),
+                          NULL));
+```
+
+Matchers are function objects, and parametrized matchers can be composed just
+like any other function. However because their types can be long and rarely
+provide meaningful information, it can be easier to express them with C++14
+generic lambdas to avoid specifying types. For example,
+
+```cpp
+using ::testing::Contains;
+using ::testing::Property;
+
+inline constexpr auto HasFoo = [](const auto& f) {
+  return Property("foo", &MyClass::foo, Contains(f));
+};
+...
+  EXPECT_THAT(x, HasFoo("blah"));
+```
+
+### Casting Matchers {#SafeMatcherCast}
+
+gMock matchers are statically typed, meaning that the compiler can catch your
+mistake if you use a matcher of the wrong type (for example, if you use `Eq(5)`
+to match a `string` argument). Good for you!
+
+Sometimes, however, you know what you're doing and want the compiler to give you
+some slack. One example is that you have a matcher for `long` and the argument
+you want to match is `int`. While the two types aren't exactly the same, there
+is nothing really wrong with using a `Matcher<long>` to match an `int` - after
+all, we can first convert the `int` argument to a `long` losslessly before
+giving it to the matcher.
+
+To support this need, gMock gives you the `SafeMatcherCast<T>(m)` function. It
+casts a matcher `m` to type `Matcher<T>`. To ensure safety, gMock checks that
+(let `U` be the type `m` accepts :
+
+1.  Type `T` can be *implicitly* cast to type `U`;
+2.  When both `T` and `U` are built-in arithmetic types (`bool`, integers, and
+    floating-point numbers), the conversion from `T` to `U` is not lossy (in
+    other words, any value representable by `T` can also be represented by `U`);
+    and
+3.  When `U` is a reference, `T` must also be a reference (as the underlying
+    matcher may be interested in the address of the `U` value).
+
+The code won't compile if any of these conditions isn't met.
+
+Here's one example:
+
+```cpp
+using ::testing::SafeMatcherCast;
+
+// A base class and a child class.
+class Base { ... };
+class Derived : public Base { ... };
+
+class MockFoo : public Foo {
+ public:
+  MOCK_METHOD(void, DoThis, (Derived* derived), (override));
+};
+
+...
+  MockFoo foo;
+  // m is a Matcher<Base*> we got from somewhere.
+  EXPECT_CALL(foo, DoThis(SafeMatcherCast<Derived*>(m)));
+```
+
+If you find `SafeMatcherCast<T>(m)` too limiting, you can use a similar function
+`MatcherCast<T>(m)`. The difference is that `MatcherCast` works as long as you
+can `static_cast` type `T` to type `U`.
+
+`MatcherCast` essentially lets you bypass C++'s type system (`static_cast` isn't
+always safe as it could throw away information, for example), so be careful not
+to misuse/abuse it.
+
+### Selecting Between Overloaded Functions {#SelectOverload}
+
+If you expect an overloaded function to be called, the compiler may need some
+help on which overloaded version it is.
+
+To disambiguate functions overloaded on the const-ness of this object, use the
+`Const()` argument wrapper.
+
+```cpp
+using ::testing::ReturnRef;
+
+class MockFoo : public Foo {
+  ...
+  MOCK_METHOD(Bar&, GetBar, (), (override));
+  MOCK_METHOD(const Bar&, GetBar, (), (const, override));
+};
+
+...
+  MockFoo foo;
+  Bar bar1, bar2;
+  EXPECT_CALL(foo, GetBar())         // The non-const GetBar().
+      .WillOnce(ReturnRef(bar1));
+  EXPECT_CALL(Const(foo), GetBar())  // The const GetBar().
+      .WillOnce(ReturnRef(bar2));
+```
+
+(`Const()` is defined by gMock and returns a `const` reference to its argument.)
+
+To disambiguate overloaded functions with the same number of arguments but
+different argument types, you may need to specify the exact type of a matcher,
+either by wrapping your matcher in `Matcher<type>()`, or using a matcher whose
+type is fixed (`TypedEq<type>`, `An<type>()`, etc):
+
+```cpp
+using ::testing::An;
+using ::testing::Matcher;
+using ::testing::TypedEq;
+
+class MockPrinter : public Printer {
+ public:
+  MOCK_METHOD(void, Print, (int n), (override));
+  MOCK_METHOD(void, Print, (char c), (override));
+};
+
+TEST(PrinterTest, Print) {
+  MockPrinter printer;
+
+  EXPECT_CALL(printer, Print(An<int>()));            // void Print(int);
+  EXPECT_CALL(printer, Print(Matcher<int>(Lt(5))));  // void Print(int);
+  EXPECT_CALL(printer, Print(TypedEq<char>('a')));   // void Print(char);
+
+  printer.Print(3);
+  printer.Print(6);
+  printer.Print('a');
+}
+```
+
+### Performing Different Actions Based on the Arguments
+
+When a mock method is called, the *last* matching expectation that's still
+active will be selected (think "newer overrides older"). So, you can make a
+method do different things depending on its argument values like this:
+
+```cpp
+using ::testing::_;
+using ::testing::Lt;
+using ::testing::Return;
+...
+  // The default case.
+  EXPECT_CALL(foo, DoThis(_))
+      .WillRepeatedly(Return('b'));
+  // The more specific case.
+  EXPECT_CALL(foo, DoThis(Lt(5)))
+      .WillRepeatedly(Return('a'));
+```
+
+Now, if `foo.DoThis()` is called with a value less than 5, `'a'` will be
+returned; otherwise `'b'` will be returned.
+
+### Matching Multiple Arguments as a Whole
+
+Sometimes it's not enough to match the arguments individually. For example, we
+may want to say that the first argument must be less than the second argument.
+The `With()` clause allows us to match all arguments of a mock function as a
+whole. For example,
+
+```cpp
+using ::testing::_;
+using ::testing::Ne;
+using ::testing::Lt;
+...
+  EXPECT_CALL(foo, InRange(Ne(0), _))
+      .With(Lt());
+```
+
+says that the first argument of `InRange()` must not be 0, and must be less than
+the second argument.
+
+The expression inside `With()` must be a matcher of type `Matcher<std::tuple<A1,
+..., An>>`, where `A1`, ..., `An` are the types of the function arguments.
+
+You can also write `AllArgs(m)` instead of `m` inside `.With()`. The two forms
+are equivalent, but `.With(AllArgs(Lt()))` is more readable than `.With(Lt())`.
+
+You can use `Args<k1, ..., kn>(m)` to match the `n` selected arguments (as a
+tuple) against `m`. For example,
+
+```cpp
+using ::testing::_;
+using ::testing::AllOf;
+using ::testing::Args;
+using ::testing::Lt;
+...
+  EXPECT_CALL(foo, Blah)
+      .With(AllOf(Args<0, 1>(Lt()), Args<1, 2>(Lt())));
+```
+
+says that `Blah` will be called with arguments `x`, `y`, and `z` where `x < y <
+z`. Note that in this example, it wasn't necessary to specify the positional
+matchers.
+
+As a convenience and example, gMock provides some matchers for 2-tuples,
+including the `Lt()` matcher above. See
+[Multi-argument Matchers](reference/matchers.md#MultiArgMatchers) for the
+complete list.
+
+Note that if you want to pass the arguments to a predicate of your own (e.g.
+`.With(Args<0, 1>(Truly(&MyPredicate)))`), that predicate MUST be written to
+take a `std::tuple` as its argument; gMock will pass the `n` selected arguments
+as *one* single tuple to the predicate.
+
+### Using Matchers as Predicates
+
+Have you noticed that a matcher is just a fancy predicate that also knows how to
+describe itself? Many existing algorithms take predicates as arguments (e.g.
+those defined in STL's `<algorithm>` header), and it would be a shame if gMock
+matchers were not allowed to participate.
+
+Luckily, you can use a matcher where a unary predicate functor is expected by
+wrapping it inside the `Matches()` function. For example,
+
+```cpp
+#include <algorithm>
+#include <vector>
+
+using ::testing::Matches;
+using ::testing::Ge;
+
+vector<int> v;
+...
+// How many elements in v are >= 10?
+const int count = count_if(v.begin(), v.end(), Matches(Ge(10)));
+```
+
+Since you can build complex matchers from simpler ones easily using gMock, this
+gives you a way to conveniently construct composite predicates (doing the same
+using STL's `<functional>` header is just painful). For example, here's a
+predicate that's satisfied by any number that is >= 0, <= 100, and != 50:
+
+```cpp
+using ::testing::AllOf;
+using ::testing::Ge;
+using ::testing::Le;
+using ::testing::Matches;
+using ::testing::Ne;
+...
+Matches(AllOf(Ge(0), Le(100), Ne(50)))
+```
+
+### Using Matchers in googletest Assertions
+
+See [`EXPECT_THAT`](reference/assertions.md#EXPECT_THAT) in the Assertions
+Reference.
+
+### Using Predicates as Matchers
+
+gMock provides a set of built-in matchers for matching arguments with expected
+values—see the [Matchers Reference](reference/matchers.md) for more information.
+In case you find the built-in set lacking, you can use an arbitrary unary
+predicate function or functor as a matcher - as long as the predicate accepts a
+value of the type you want. You do this by wrapping the predicate inside the
+`Truly()` function, for example:
+
+```cpp
+using ::testing::Truly;
+
+int IsEven(int n) { return (n % 2) == 0 ? 1 : 0; }
+...
+  // Bar() must be called with an even number.
+  EXPECT_CALL(foo, Bar(Truly(IsEven)));
+```
+
+Note that the predicate function / functor doesn't have to return `bool`. It
+works as long as the return value can be used as the condition in the statement
+`if (condition) ...`.
+
+### Matching Arguments that Are Not Copyable
+
+When you do an `EXPECT_CALL(mock_obj, Foo(bar))`, gMock saves away a copy of
+`bar`. When `Foo()` is called later, gMock compares the argument to `Foo()` with
+the saved copy of `bar`. This way, you don't need to worry about `bar` being
+modified or destroyed after the `EXPECT_CALL()` is executed. The same is true
+when you use matchers like `Eq(bar)`, `Le(bar)`, and so on.
+
+But what if `bar` cannot be copied (i.e. has no copy constructor)? You could
+define your own matcher function or callback and use it with `Truly()`, as the
+previous couple of recipes have shown. Or, you may be able to get away from it
+if you can guarantee that `bar` won't be changed after the `EXPECT_CALL()` is
+executed. Just tell gMock that it should save a reference to `bar`, instead of a
+copy of it. Here's how:
+
+```cpp
+using ::testing::Eq;
+using ::testing::Lt;
+...
+  // Expects that Foo()'s argument == bar.
+  EXPECT_CALL(mock_obj, Foo(Eq(std::ref(bar))));
+
+  // Expects that Foo()'s argument < bar.
+  EXPECT_CALL(mock_obj, Foo(Lt(std::ref(bar))));
+```
+
+Remember: if you do this, don't change `bar` after the `EXPECT_CALL()`, or the
+result is undefined.
+
+### Validating a Member of an Object
+
+Often a mock function takes a reference to object as an argument. When matching
+the argument, you may not want to compare the entire object against a fixed
+object, as that may be over-specification. Instead, you may need to validate a
+certain member variable or the result of a certain getter method of the object.
+You can do this with `Field()` and `Property()`. More specifically,
+
+```cpp
+Field(&Foo::bar, m)
+```
+
+is a matcher that matches a `Foo` object whose `bar` member variable satisfies
+matcher `m`.
+
+```cpp
+Property(&Foo::baz, m)
+```
+
+is a matcher that matches a `Foo` object whose `baz()` method returns a value
+that satisfies matcher `m`.
+
+For example:
+
+| Expression                   | Description                              |
+| :--------------------------- | :--------------------------------------- |
+| `Field(&Foo::number, Ge(3))` | Matches `x` where `x.number >= 3`.       |
+| `Property(&Foo::name,  StartsWith("John "))` | Matches `x` where `x.name()` starts with  `"John "`. |
+
+Note that in `Property(&Foo::baz, ...)`, method `baz()` must take no argument
+and be declared as `const`. Don't use `Property()` against member functions that
+you do not own, because taking addresses of functions is fragile and generally
+not part of the contract of the function.
+
+`Field()` and `Property()` can also match plain pointers to objects. For
+instance,
+
+```cpp
+using ::testing::Field;
+using ::testing::Ge;
+...
+Field(&Foo::number, Ge(3))
+```
+
+matches a plain pointer `p` where `p->number >= 3`. If `p` is `NULL`, the match
+will always fail regardless of the inner matcher.
+
+What if you want to validate more than one members at the same time? Remember
+that there are [`AllOf()` and `AllOfArray()`](#CombiningMatchers).
+
+Finally `Field()` and `Property()` provide overloads that take the field or
+property names as the first argument to include it in the error message. This
+can be useful when creating combined matchers.
+
+```cpp
+using ::testing::AllOf;
+using ::testing::Field;
+using ::testing::Matcher;
+using ::testing::SafeMatcherCast;
+
+Matcher<Foo> IsFoo(const Foo& foo) {
+  return AllOf(Field("some_field", &Foo::some_field, foo.some_field),
+               Field("other_field", &Foo::other_field, foo.other_field),
+               Field("last_field", &Foo::last_field, foo.last_field));
+}
+```
+
+### Validating the Value Pointed to by a Pointer Argument
+
+C++ functions often take pointers as arguments. You can use matchers like
+`IsNull()`, `NotNull()`, and other comparison matchers to match a pointer, but
+what if you want to make sure the value *pointed to* by the pointer, instead of
+the pointer itself, has a certain property? Well, you can use the `Pointee(m)`
+matcher.
+
+`Pointee(m)` matches a pointer if and only if `m` matches the value the pointer
+points to. For example:
+
+```cpp
+using ::testing::Ge;
+using ::testing::Pointee;
+...
+  EXPECT_CALL(foo, Bar(Pointee(Ge(3))));
+```
+
+expects `foo.Bar()` to be called with a pointer that points to a value greater
+than or equal to 3.
+
+One nice thing about `Pointee()` is that it treats a `NULL` pointer as a match
+failure, so you can write `Pointee(m)` instead of
+
+```cpp
+using ::testing::AllOf;
+using ::testing::NotNull;
+using ::testing::Pointee;
+...
+  AllOf(NotNull(), Pointee(m))
+```
+
+without worrying that a `NULL` pointer will crash your test.
+
+Also, did we tell you that `Pointee()` works with both raw pointers **and**
+smart pointers (`std::unique_ptr`, `std::shared_ptr`, etc)?
+
+What if you have a pointer to pointer? You guessed it - you can use nested
+`Pointee()` to probe deeper inside the value. For example,
+`Pointee(Pointee(Lt(3)))` matches a pointer that points to a pointer that points
+to a number less than 3 (what a mouthful...).
+
+### Defining a Custom Matcher Class {#CustomMatcherClass}
+
+Most matchers can be simply defined using [the MATCHER* macros](#NewMatchers),
+which are terse and flexible, and produce good error messages. However, these
+macros are not very explicit about the interfaces they create and are not always
+suitable, especially for matchers that will be widely reused.
+
+For more advanced cases, you may need to define your own matcher class. A custom
+matcher allows you to test a specific invariant property of that object. Let's
+take a look at how to do so.
+
+Imagine you have a mock function that takes an object of type `Foo`, which has
+an `int bar()` method and an `int baz()` method. You want to constrain that the
+argument's `bar()` value plus its `baz()` value is a given number. (This is an
+invariant.) Here's how we can write and use a matcher class to do so:
+
+```cpp
+class BarPlusBazEqMatcher {
+ public:
+  using is_gtest_matcher = void;
+
+  explicit BarPlusBazEqMatcher(int expected_sum)
+      : expected_sum_(expected_sum) {}
+
+  bool MatchAndExplain(const Foo& foo,
+                       std::ostream* /* listener */) const {
+    return (foo.bar() + foo.baz()) == expected_sum_;
+  }
+
+  void DescribeTo(std::ostream* os) const {
+    *os << "bar() + baz() equals " << expected_sum_;
+  }
+
+  void DescribeNegationTo(std::ostream* os) const {
+    *os << "bar() + baz() does not equal " << expected_sum_;
+  }
+ private:
+  const int expected_sum_;
+};
+
+::testing::Matcher<const Foo&> BarPlusBazEq(int expected_sum) {
+  return BarPlusBazEqMatcher(expected_sum);
+}
+
+...
+  Foo foo;
+  EXPECT_THAT(foo, BarPlusBazEq(5))...;
+```
+
+### Matching Containers
+
+Sometimes an STL container (e.g. list, vector, map, ...) is passed to a mock
+function and you may want to validate it. Since most STL containers support the
+`==` operator, you can write `Eq(expected_container)` or simply
+`expected_container` to match a container exactly.
+
+Sometimes, though, you may want to be more flexible (for example, the first
+element must be an exact match, but the second element can be any positive
+number, and so on). Also, containers used in tests often have a small number of
+elements, and having to define the expected container out-of-line is a bit of a
+hassle.
+
+You can use the `ElementsAre()` or `UnorderedElementsAre()` matcher in such
+cases:
+
+```cpp
+using ::testing::_;
+using ::testing::ElementsAre;
+using ::testing::Gt;
+...
+  MOCK_METHOD(void, Foo, (const vector<int>& numbers), (override));
+...
+  EXPECT_CALL(mock, Foo(ElementsAre(1, Gt(0), _, 5)));
+```
+
+The above matcher says that the container must have 4 elements, which must be 1,
+greater than 0, anything, and 5 respectively.
+
+If you instead write:
+
+```cpp
+using ::testing::_;
+using ::testing::Gt;
+using ::testing::UnorderedElementsAre;
+...
+  MOCK_METHOD(void, Foo, (const vector<int>& numbers), (override));
+...
+  EXPECT_CALL(mock, Foo(UnorderedElementsAre(1, Gt(0), _, 5)));
+```
+
+It means that the container must have 4 elements, which (under some permutation)
+must be 1, greater than 0, anything, and 5 respectively.
+
+As an alternative you can place the arguments in a C-style array and use
+`ElementsAreArray()` or `UnorderedElementsAreArray()` instead:
+
+```cpp
+using ::testing::ElementsAreArray;
+...
+  // ElementsAreArray accepts an array of element values.
+  const int expected_vector1[] = {1, 5, 2, 4, ...};
+  EXPECT_CALL(mock, Foo(ElementsAreArray(expected_vector1)));
+
+  // Or, an array of element matchers.
+  Matcher<int> expected_vector2[] = {1, Gt(2), _, 3, ...};
+  EXPECT_CALL(mock, Foo(ElementsAreArray(expected_vector2)));
+```
+
+In case the array needs to be dynamically created (and therefore the array size
+cannot be inferred by the compiler), you can give `ElementsAreArray()` an
+additional argument to specify the array size:
+
+```cpp
+using ::testing::ElementsAreArray;
+...
+  int* const expected_vector3 = new int[count];
+  ... fill expected_vector3 with values ...
+  EXPECT_CALL(mock, Foo(ElementsAreArray(expected_vector3, count)));
+```
+
+Use `Pair` when comparing maps or other associative containers.
+
+{% raw %}
+
+```cpp
+using ::testing::UnorderedElementsAre;
+using ::testing::Pair;
+...
+  absl::flat_hash_map<string, int> m = {{"a", 1}, {"b", 2}, {"c", 3}};
+  EXPECT_THAT(m, UnorderedElementsAre(
+      Pair("a", 1), Pair("b", 2), Pair("c", 3)));
+```
+
+{% endraw %}
+
+**Tips:**
+
+*   `ElementsAre*()` can be used to match *any* container that implements the
+    STL iterator pattern (i.e. it has a `const_iterator` type and supports
+    `begin()/end()`), not just the ones defined in STL. It will even work with
+    container types yet to be written - as long as they follows the above
+    pattern.
+*   You can use nested `ElementsAre*()` to match nested (multi-dimensional)
+    containers.
+*   If the container is passed by pointer instead of by reference, just write
+    `Pointee(ElementsAre*(...))`.
+*   The order of elements *matters* for `ElementsAre*()`. If you are using it
+    with containers whose element order are undefined (such as a
+    `std::unordered_map`) you should use `UnorderedElementsAre`.
+
+### Sharing Matchers
+
+Under the hood, a gMock matcher object consists of a pointer to a ref-counted
+implementation object. Copying matchers is allowed and very efficient, as only
+the pointer is copied. When the last matcher that references the implementation
+object dies, the implementation object will be deleted.
+
+Therefore, if you have some complex matcher that you want to use again and
+again, there is no need to build it every time. Just assign it to a matcher
+variable and use that variable repeatedly! For example,
+
+```cpp
+using ::testing::AllOf;
+using ::testing::Gt;
+using ::testing::Le;
+using ::testing::Matcher;
+...
+  Matcher<int> in_range = AllOf(Gt(5), Le(10));
+  ... use in_range as a matcher in multiple EXPECT_CALLs ...
+```
+
+### Matchers must have no side-effects {#PureMatchers}
+
+{: .callout .warning}
+WARNING: gMock does not guarantee when or how many times a matcher will be
+invoked. Therefore, all matchers must be *purely functional*: they cannot have
+any side effects, and the match result must not depend on anything other than
+the matcher's parameters and the value being matched.
+
+This requirement must be satisfied no matter how a matcher is defined (e.g., if
+it is one of the standard matchers, or a custom matcher). In particular, a
+matcher can never call a mock function, as that will affect the state of the
+mock object and gMock.
+
+## Setting Expectations
+
+### Knowing When to Expect {#UseOnCall}
+
+**`ON_CALL`** is likely the *single most under-utilized construct* in gMock.
+
+There are basically two constructs for defining the behavior of a mock object:
+`ON_CALL` and `EXPECT_CALL`. The difference? `ON_CALL` defines what happens when
+a mock method is called, but <em>doesn't imply any expectation on the method
+being called</em>. `EXPECT_CALL` not only defines the behavior, but also sets an
+expectation that <em>the method will be called with the given arguments, for the
+given number of times</em> (and *in the given order* when you specify the order
+too).
+
+Since `EXPECT_CALL` does more, isn't it better than `ON_CALL`? Not really. Every
+`EXPECT_CALL` adds a constraint on the behavior of the code under test. Having
+more constraints than necessary is *baaad* - even worse than not having enough
+constraints.
+
+This may be counter-intuitive. How could tests that verify more be worse than
+tests that verify less? Isn't verification the whole point of tests?
+
+The answer lies in *what* a test should verify. **A good test verifies the
+contract of the code.** If a test over-specifies, it doesn't leave enough
+freedom to the implementation. As a result, changing the implementation without
+breaking the contract (e.g. refactoring and optimization), which should be
+perfectly fine to do, can break such tests. Then you have to spend time fixing
+them, only to see them broken again the next time the implementation is changed.
+
+Keep in mind that one doesn't have to verify more than one property in one test.
+In fact, **it's a good style to verify only one thing in one test.** If you do
+that, a bug will likely break only one or two tests instead of dozens (which
+case would you rather debug?). If you are also in the habit of giving tests
+descriptive names that tell what they verify, you can often easily guess what's
+wrong just from the test log itself.
+
+So use `ON_CALL` by default, and only use `EXPECT_CALL` when you actually intend
+to verify that the call is made. For example, you may have a bunch of `ON_CALL`s
+in your test fixture to set the common mock behavior shared by all tests in the
+same group, and write (scarcely) different `EXPECT_CALL`s in different `TEST_F`s
+to verify different aspects of the code's behavior. Compared with the style
+where each `TEST` has many `EXPECT_CALL`s, this leads to tests that are more
+resilient to implementational changes (and thus less likely to require
+maintenance) and makes the intent of the tests more obvious (so they are easier
+to maintain when you do need to maintain them).
+
+If you are bothered by the "Uninteresting mock function call" message printed
+when a mock method without an `EXPECT_CALL` is called, you may use a `NiceMock`
+instead to suppress all such messages for the mock object, or suppress the
+message for specific methods by adding `EXPECT_CALL(...).Times(AnyNumber())`. DO
+NOT suppress it by blindly adding an `EXPECT_CALL(...)`, or you'll have a test
+that's a pain to maintain.
+
+### Ignoring Uninteresting Calls
+
+If you are not interested in how a mock method is called, just don't say
+anything about it. In this case, if the method is ever called, gMock will
+perform its default action to allow the test program to continue. If you are not
+happy with the default action taken by gMock, you can override it using
+`DefaultValue<T>::Set()` (described [here](#DefaultValue)) or `ON_CALL()`.
+
+Please note that once you expressed interest in a particular mock method (via
+`EXPECT_CALL()`), all invocations to it must match some expectation. If this
+function is called but the arguments don't match any `EXPECT_CALL()` statement,
+it will be an error.
+
+### Disallowing Unexpected Calls
+
+If a mock method shouldn't be called at all, explicitly say so:
+
+```cpp
+using ::testing::_;
+...
+  EXPECT_CALL(foo, Bar(_))
+      .Times(0);
+```
+
+If some calls to the method are allowed, but the rest are not, just list all the
+expected calls:
+
+```cpp
+using ::testing::AnyNumber;
+using ::testing::Gt;
+...
+  EXPECT_CALL(foo, Bar(5));
+  EXPECT_CALL(foo, Bar(Gt(10)))
+      .Times(AnyNumber());
+```
+
+A call to `foo.Bar()` that doesn't match any of the `EXPECT_CALL()` statements
+will be an error.
+
+### Understanding Uninteresting vs Unexpected Calls {#uninteresting-vs-unexpected}
+
+*Uninteresting* calls and *unexpected* calls are different concepts in gMock.
+*Very* different.
+
+A call `x.Y(...)` is **uninteresting** if there's *not even a single*
+`EXPECT_CALL(x, Y(...))` set. In other words, the test isn't interested in the
+`x.Y()` method at all, as evident in that the test doesn't care to say anything
+about it.
+
+A call `x.Y(...)` is **unexpected** if there are *some* `EXPECT_CALL(x,
+Y(...))`s set, but none of them matches the call. Put another way, the test is
+interested in the `x.Y()` method (therefore it explicitly sets some
+`EXPECT_CALL` to verify how it's called); however, the verification fails as the
+test doesn't expect this particular call to happen.
+
+**An unexpected call is always an error,** as the code under test doesn't behave
+the way the test expects it to behave.
+
+**By default, an uninteresting call is not an error,** as it violates no
+constraint specified by the test. (gMock's philosophy is that saying nothing
+means there is no constraint.) However, it leads to a warning, as it *might*
+indicate a problem (e.g. the test author might have forgotten to specify a
+constraint).
+
+In gMock, `NiceMock` and `StrictMock` can be used to make a mock class "nice" or
+"strict". How does this affect uninteresting calls and unexpected calls?
+
+A **nice mock** suppresses uninteresting call *warnings*. It is less chatty than
+the default mock, but otherwise is the same. If a test fails with a default
+mock, it will also fail using a nice mock instead. And vice versa. Don't expect
+making a mock nice to change the test's result.
+
+A **strict mock** turns uninteresting call warnings into errors. So making a
+mock strict may change the test's result.
+
+Let's look at an example:
+
+```cpp
+TEST(...) {
+  NiceMock<MockDomainRegistry> mock_registry;
+  EXPECT_CALL(mock_registry, GetDomainOwner("google.com"))
+          .WillRepeatedly(Return("Larry Page"));
+
+  // Use mock_registry in code under test.
+  ... &mock_registry ...
+}
+```
+
+The sole `EXPECT_CALL` here says that all calls to `GetDomainOwner()` must have
+`"google.com"` as the argument. If `GetDomainOwner("yahoo.com")` is called, it
+will be an unexpected call, and thus an error. *Having a nice mock doesn't
+change the severity of an unexpected call.*
+
+So how do we tell gMock that `GetDomainOwner()` can be called with some other
+arguments as well? The standard technique is to add a "catch all" `EXPECT_CALL`:
+
+```cpp
+  EXPECT_CALL(mock_registry, GetDomainOwner(_))
+        .Times(AnyNumber());  // catches all other calls to this method.
+  EXPECT_CALL(mock_registry, GetDomainOwner("google.com"))
+        .WillRepeatedly(Return("Larry Page"));
+```
+
+Remember that `_` is the wildcard matcher that matches anything. With this, if
+`GetDomainOwner("google.com")` is called, it will do what the second
+`EXPECT_CALL` says; if it is called with a different argument, it will do what
+the first `EXPECT_CALL` says.
+
+Note that the order of the two `EXPECT_CALL`s is important, as a newer
+`EXPECT_CALL` takes precedence over an older one.
+
+For more on uninteresting calls, nice mocks, and strict mocks, read
+["The Nice, the Strict, and the Naggy"](#NiceStrictNaggy).
+
+### Ignoring Uninteresting Arguments {#ParameterlessExpectations}
+
+If your test doesn't care about the parameters (it only cares about the number
+or order of calls), you can often simply omit the parameter list:
+
+```cpp
+  // Expect foo.Bar( ... ) twice with any arguments.
+  EXPECT_CALL(foo, Bar).Times(2);
+
+  // Delegate to the given method whenever the factory is invoked.
+  ON_CALL(foo_factory, MakeFoo)
+      .WillByDefault(&BuildFooForTest);
+```
+
+This functionality is only available when a method is not overloaded; to prevent
+unexpected behavior it is a compilation error to try to set an expectation on a
+method where the specific overload is ambiguous. You can work around this by
+supplying a [simpler mock interface](#SimplerInterfaces) than the mocked class
+provides.
+
+This pattern is also useful when the arguments are interesting, but match logic
+is substantially complex. You can leave the argument list unspecified and use
+SaveArg actions to [save the values for later verification](#SaveArgVerify). If
+you do that, you can easily differentiate calling the method the wrong number of
+times from calling it with the wrong arguments.
+
+### Expecting Ordered Calls {#OrderedCalls}
+
+Although an `EXPECT_CALL()` statement defined later takes precedence when gMock
+tries to match a function call with an expectation, by default calls don't have
+to happen in the order `EXPECT_CALL()` statements are written. For example, if
+the arguments match the matchers in the second `EXPECT_CALL()`, but not those in
+the first and third, then the second expectation will be used.
+
+If you would rather have all calls occur in the order of the expectations, put
+the `EXPECT_CALL()` statements in a block where you define a variable of type
+`InSequence`:
+
+```cpp
+using ::testing::_;
+using ::testing::InSequence;
+
+  {
+    InSequence s;
+
+    EXPECT_CALL(foo, DoThis(5));
+    EXPECT_CALL(bar, DoThat(_))
+        .Times(2);
+    EXPECT_CALL(foo, DoThis(6));
+  }
+```
+
+In this example, we expect a call to `foo.DoThis(5)`, followed by two calls to
+`bar.DoThat()` where the argument can be anything, which are in turn followed by
+a call to `foo.DoThis(6)`. If a call occurred out-of-order, gMock will report an
+error.
+
+### Expecting Partially Ordered Calls {#PartialOrder}
+
+Sometimes requiring everything to occur in a predetermined order can lead to
+brittle tests. For example, we may care about `A` occurring before both `B` and
+`C`, but aren't interested in the relative order of `B` and `C`. In this case,
+the test should reflect our real intent, instead of being overly constraining.
+
+gMock allows you to impose an arbitrary DAG (directed acyclic graph) on the
+calls. One way to express the DAG is to use the
+[`After` clause](reference/mocking.md#EXPECT_CALL.After) of `EXPECT_CALL`.
+
+Another way is via the `InSequence()` clause (not the same as the `InSequence`
+class), which we borrowed from jMock 2. It's less flexible than `After()`, but
+more convenient when you have long chains of sequential calls, as it doesn't
+require you to come up with different names for the expectations in the chains.
+Here's how it works:
+
+If we view `EXPECT_CALL()` statements as nodes in a graph, and add an edge from
+node A to node B wherever A must occur before B, we can get a DAG. We use the
+term "sequence" to mean a directed path in this DAG. Now, if we decompose the
+DAG into sequences, we just need to know which sequences each `EXPECT_CALL()`
+belongs to in order to be able to reconstruct the original DAG.
+
+So, to specify the partial order on the expectations we need to do two things:
+first to define some `Sequence` objects, and then for each `EXPECT_CALL()` say
+which `Sequence` objects it is part of.
+
+Expectations in the same sequence must occur in the order they are written. For
+example,
+
+```cpp
+using ::testing::Sequence;
+...
+  Sequence s1, s2;
+
+  EXPECT_CALL(foo, A())
+      .InSequence(s1, s2);
+  EXPECT_CALL(bar, B())
+      .InSequence(s1);
+  EXPECT_CALL(bar, C())
+      .InSequence(s2);
+  EXPECT_CALL(foo, D())
+      .InSequence(s2);
+```
+
+specifies the following DAG (where `s1` is `A -> B`, and `s2` is `A -> C -> D`):
+
+```text
+       +---> B
+       |
+  A ---|
+       |
+       +---> C ---> D
+```
+
+This means that A must occur before B and C, and C must occur before D. There's
+no restriction about the order other than these.
+
+### Controlling When an Expectation Retires
+
+When a mock method is called, gMock only considers expectations that are still
+active. An expectation is active when created, and becomes inactive (aka
+*retires*) when a call that has to occur later has occurred. For example, in
+
+```cpp
+using ::testing::_;
+using ::testing::Sequence;
+...
+  Sequence s1, s2;
+
+  EXPECT_CALL(log, Log(WARNING, _, "File too large."))      // #1
+      .Times(AnyNumber())
+      .InSequence(s1, s2);
+  EXPECT_CALL(log, Log(WARNING, _, "Data set is empty."))   // #2
+      .InSequence(s1);
+  EXPECT_CALL(log, Log(WARNING, _, "User not found."))      // #3
+      .InSequence(s2);
+```
+
+as soon as either #2 or #3 is matched, #1 will retire. If a warning `"File too
+large."` is logged after this, it will be an error.
+
+Note that an expectation doesn't retire automatically when it's saturated. For
+example,
+
+```cpp
+using ::testing::_;
+...
+  EXPECT_CALL(log, Log(WARNING, _, _));                     // #1
+  EXPECT_CALL(log, Log(WARNING, _, "File too large."));     // #2
+```
+
+says that there will be exactly one warning with the message `"File too
+large."`. If the second warning contains this message too, #2 will match again
+and result in an upper-bound-violated error.
+
+If this is not what you want, you can ask an expectation to retire as soon as it
+becomes saturated:
+
+```cpp
+using ::testing::_;
+...
+  EXPECT_CALL(log, Log(WARNING, _, _));                     // #1
+  EXPECT_CALL(log, Log(WARNING, _, "File too large."))      // #2
+      .RetiresOnSaturation();
+```
+
+Here #2 can be used only once, so if you have two warnings with the message
+`"File too large."`, the first will match #2 and the second will match #1 -
+there will be no error.
+
+## Using Actions
+
+### Returning References from Mock Methods
+
+If a mock function's return type is a reference, you need to use `ReturnRef()`
+instead of `Return()` to return a result:
+
+```cpp
+using ::testing::ReturnRef;
+
+class MockFoo : public Foo {
+ public:
+  MOCK_METHOD(Bar&, GetBar, (), (override));
+};
+...
+  MockFoo foo;
+  Bar bar;
+  EXPECT_CALL(foo, GetBar())
+      .WillOnce(ReturnRef(bar));
+...
+```
+
+### Returning Live Values from Mock Methods
+
+The `Return(x)` action saves a copy of `x` when the action is created, and
+always returns the same value whenever it's executed. Sometimes you may want to
+instead return the *live* value of `x` (i.e. its value at the time when the
+action is *executed*.). Use either `ReturnRef()` or `ReturnPointee()` for this
+purpose.
+
+If the mock function's return type is a reference, you can do it using
+`ReturnRef(x)`, as shown in the previous recipe ("Returning References from Mock
+Methods"). However, gMock doesn't let you use `ReturnRef()` in a mock function
+whose return type is not a reference, as doing that usually indicates a user
+error. So, what shall you do?
+
+Though you may be tempted, DO NOT use `std::ref()`:
+
+```cpp
+using ::testing::Return;
+
+class MockFoo : public Foo {
+ public:
+  MOCK_METHOD(int, GetValue, (), (override));
+};
+...
+  int x = 0;
+  MockFoo foo;
+  EXPECT_CALL(foo, GetValue())
+      .WillRepeatedly(Return(std::ref(x)));  // Wrong!
+  x = 42;
+  EXPECT_EQ(foo.GetValue(), 42);
+```
+
+Unfortunately, it doesn't work here. The above code will fail with error:
+
+```text
+Value of: foo.GetValue()
+  Actual: 0
+Expected: 42
+```
+
+The reason is that `Return(*value*)` converts `value` to the actual return type
+of the mock function at the time when the action is *created*, not when it is
+*executed*. (This behavior was chosen for the action to be safe when `value` is
+a proxy object that references some temporary objects.) As a result,
+`std::ref(x)` is converted to an `int` value (instead of a `const int&`) when
+the expectation is set, and `Return(std::ref(x))` will always return 0.
+
+`ReturnPointee(pointer)` was provided to solve this problem specifically. It
+returns the value pointed to by `pointer` at the time the action is *executed*:
+
+```cpp
+using ::testing::ReturnPointee;
+...
+  int x = 0;
+  MockFoo foo;
+  EXPECT_CALL(foo, GetValue())
+      .WillRepeatedly(ReturnPointee(&x));  // Note the & here.
+  x = 42;
+  EXPECT_EQ(foo.GetValue(), 42);  // This will succeed now.
+```
+
+### Combining Actions
+
+Want to do more than one thing when a function is called? That's fine. `DoAll()`
+allows you to do a sequence of actions every time. Only the return value of the
+last action in the sequence will be used.
+
+```cpp
+using ::testing::_;
+using ::testing::DoAll;
+
+class MockFoo : public Foo {
+ public:
+  MOCK_METHOD(bool, Bar, (int n), (override));
+};
+...
+  EXPECT_CALL(foo, Bar(_))
+      .WillOnce(DoAll(action_1,
+                      action_2,
+                      ...
+                      action_n));
+```
+
+### Verifying Complex Arguments {#SaveArgVerify}
+
+If you want to verify that a method is called with a particular argument but the
+match criteria is complex, it can be difficult to distinguish between
+cardinality failures (calling the method the wrong number of times) and argument
+match failures. Similarly, if you are matching multiple parameters, it may not
+be easy to distinguishing which argument failed to match. For example:
+
+```cpp
+  // Not ideal: this could fail because of a problem with arg1 or arg2, or maybe
+  // just the method wasn't called.
+  EXPECT_CALL(foo, SendValues(_, ElementsAre(1, 4, 4, 7), EqualsProto( ... )));
+```
+
+You can instead save the arguments and test them individually:
+
+```cpp
+  EXPECT_CALL(foo, SendValues)
+      .WillOnce(DoAll(SaveArg<1>(&actual_array), SaveArg<2>(&actual_proto)));
+  ... run the test
+  EXPECT_THAT(actual_array, ElementsAre(1, 4, 4, 7));
+  EXPECT_THAT(actual_proto, EqualsProto( ... ));
+```
+
+### Mocking Side Effects {#MockingSideEffects}
+
+Sometimes a method exhibits its effect not via returning a value but via side
+effects. For example, it may change some global state or modify an output
+argument. To mock side effects, in general you can define your own action by
+implementing `::testing::ActionInterface`.
+
+If all you need to do is to change an output argument, the built-in
+`SetArgPointee()` action is convenient:
+
+```cpp
+using ::testing::_;
+using ::testing::SetArgPointee;
+
+class MockMutator : public Mutator {
+ public:
+  MOCK_METHOD(void, Mutate, (bool mutate, int* value), (override));
+  ...
+}
+...
+  MockMutator mutator;
+  EXPECT_CALL(mutator, Mutate(true, _))
+      .WillOnce(SetArgPointee<1>(5));
+```
+
+In this example, when `mutator.Mutate()` is called, we will assign 5 to the
+`int` variable pointed to by argument #1 (0-based).
+
+`SetArgPointee()` conveniently makes an internal copy of the value you pass to
+it, removing the need to keep the value in scope and alive. The implication
+however is that the value must have a copy constructor and assignment operator.
+
+If the mock method also needs to return a value as well, you can chain
+`SetArgPointee()` with `Return()` using `DoAll()`, remembering to put the
+`Return()` statement last:
+
+```cpp
+using ::testing::_;
+using ::testing::DoAll;
+using ::testing::Return;
+using ::testing::SetArgPointee;
+
+class MockMutator : public Mutator {
+ public:
+  ...
+  MOCK_METHOD(bool, MutateInt, (int* value), (override));
+}
+...
+  MockMutator mutator;
+  EXPECT_CALL(mutator, MutateInt(_))
+      .WillOnce(DoAll(SetArgPointee<0>(5),
+                      Return(true)));
+```
+
+Note, however, that if you use the `ReturnOKWith()` method, it will override the
+values provided by `SetArgPointee()` in the response parameters of your function
+call.
+
+If the output argument is an array, use the `SetArrayArgument<N>(first, last)`
+action instead. It copies the elements in source range `[first, last)` to the
+array pointed to by the `N`-th (0-based) argument:
+
+```cpp
+using ::testing::NotNull;
+using ::testing::SetArrayArgument;
+
+class MockArrayMutator : public ArrayMutator {
+ public:
+  MOCK_METHOD(void, Mutate, (int* values, int num_values), (override));
+  ...
+}
+...
+  MockArrayMutator mutator;
+  int values[5] = {1, 2, 3, 4, 5};
+  EXPECT_CALL(mutator, Mutate(NotNull(), 5))
+      .WillOnce(SetArrayArgument<0>(values, values + 5));
+```
+
+This also works when the argument is an output iterator:
+
+```cpp
+using ::testing::_;
+using ::testing::SetArrayArgument;
+
+class MockRolodex : public Rolodex {
+ public:
+  MOCK_METHOD(void, GetNames, (std::back_insert_iterator<vector<string>>),
+              (override));
+  ...
+}
+...
+  MockRolodex rolodex;
+  vector<string> names = {"George", "John", "Thomas"};
+  EXPECT_CALL(rolodex, GetNames(_))
+      .WillOnce(SetArrayArgument<0>(names.begin(), names.end()));
+```
+
+### Changing a Mock Object's Behavior Based on the State
+
+If you expect a call to change the behavior of a mock object, you can use
+`::testing::InSequence` to specify different behaviors before and after the
+call:
+
+```cpp
+using ::testing::InSequence;
+using ::testing::Return;
+
+...
+  {
+     InSequence seq;
+     EXPECT_CALL(my_mock, IsDirty())
+         .WillRepeatedly(Return(true));
+     EXPECT_CALL(my_mock, Flush());
+     EXPECT_CALL(my_mock, IsDirty())
+         .WillRepeatedly(Return(false));
+  }
+  my_mock.FlushIfDirty();
+```
+
+This makes `my_mock.IsDirty()` return `true` before `my_mock.Flush()` is called
+and return `false` afterwards.
+
+If the behavior change is more complex, you can store the effects in a variable
+and make a mock method get its return value from that variable:
+
+```cpp
+using ::testing::_;
+using ::testing::SaveArg;
+using ::testing::Return;
+
+ACTION_P(ReturnPointee, p) { return *p; }
+...
+  int previous_value = 0;
+  EXPECT_CALL(my_mock, GetPrevValue)
+      .WillRepeatedly(ReturnPointee(&previous_value));
+  EXPECT_CALL(my_mock, UpdateValue)
+      .WillRepeatedly(SaveArg<0>(&previous_value));
+  my_mock.DoSomethingToUpdateValue();
+```
+
+Here `my_mock.GetPrevValue()` will always return the argument of the last
+`UpdateValue()` call.
+
+### Setting the Default Value for a Return Type {#DefaultValue}
+
+If a mock method's return type is a built-in C++ type or pointer, by default it
+will return 0 when invoked. Also, in C++ 11 and above, a mock method whose
+return type has a default constructor will return a default-constructed value by
+default. You only need to specify an action if this default value doesn't work
+for you.
+
+Sometimes, you may want to change this default value, or you may want to specify
+a default value for types gMock doesn't know about. You can do this using the
+`::testing::DefaultValue` class template:
+
+```cpp
+using ::testing::DefaultValue;
+
+class MockFoo : public Foo {
+ public:
+  MOCK_METHOD(Bar, CalculateBar, (), (override));
+};
+
+
+...
+  Bar default_bar;
+  // Sets the default return value for type Bar.
+  DefaultValue<Bar>::Set(default_bar);
+
+  MockFoo foo;
+
+  // We don't need to specify an action here, as the default
+  // return value works for us.
+  EXPECT_CALL(foo, CalculateBar());
+
+  foo.CalculateBar();  // This should return default_bar.
+
+  // Unsets the default return value.
+  DefaultValue<Bar>::Clear();
+```
+
+Please note that changing the default value for a type can make your tests hard
+to understand. We recommend you to use this feature judiciously. For example,
+you may want to make sure the `Set()` and `Clear()` calls are right next to the
+code that uses your mock.
+
+### Setting the Default Actions for a Mock Method
+
+You've learned how to change the default value of a given type. However, this
+may be too coarse for your purpose: perhaps you have two mock methods with the
+same return type and you want them to have different behaviors. The `ON_CALL()`
+macro allows you to customize your mock's behavior at the method level:
+
+```cpp
+using ::testing::_;
+using ::testing::AnyNumber;
+using ::testing::Gt;
+using ::testing::Return;
+...
+  ON_CALL(foo, Sign(_))
+      .WillByDefault(Return(-1));
+  ON_CALL(foo, Sign(0))
+      .WillByDefault(Return(0));
+  ON_CALL(foo, Sign(Gt(0)))
+      .WillByDefault(Return(1));
+
+  EXPECT_CALL(foo, Sign(_))
+      .Times(AnyNumber());
+
+  foo.Sign(5);   // This should return 1.
+  foo.Sign(-9);  // This should return -1.
+  foo.Sign(0);   // This should return 0.
+```
+
+As you may have guessed, when there are more than one `ON_CALL()` statements,
+the newer ones in the order take precedence over the older ones. In other words,
+the **last** one that matches the function arguments will be used. This matching
+order allows you to set up the common behavior in a mock object's constructor or
+the test fixture's set-up phase and specialize the mock's behavior later.
+
+Note that both `ON_CALL` and `EXPECT_CALL` have the same "later statements take
+precedence" rule, but they don't interact. That is, `EXPECT_CALL`s have their
+own precedence order distinct from the `ON_CALL` precedence order.
+
+### Using Functions/Methods/Functors/Lambdas as Actions {#FunctionsAsActions}
+
+If the built-in actions don't suit you, you can use an existing callable
+(function, `std::function`, method, functor, lambda) as an action.
+
+```cpp
+using ::testing::_; using ::testing::Invoke;
+
+class MockFoo : public Foo {
+ public:
+  MOCK_METHOD(int, Sum, (int x, int y), (override));
+  MOCK_METHOD(bool, ComplexJob, (int x), (override));
+};
+
+int CalculateSum(int x, int y) { return x + y; }
+int Sum3(int x, int y, int z) { return x + y + z; }
+
+class Helper {
+ public:
+  bool ComplexJob(int x);
+};
+
+...
+  MockFoo foo;
+  Helper helper;
+  EXPECT_CALL(foo, Sum(_, _))
+      .WillOnce(&CalculateSum)
+      .WillRepeatedly(Invoke(NewPermanentCallback(Sum3, 1)));
+  EXPECT_CALL(foo, ComplexJob(_))
+      .WillOnce(Invoke(&helper, &Helper::ComplexJob))
+      .WillOnce([] { return true; })
+      .WillRepeatedly([](int x) { return x > 0; });
+
+  foo.Sum(5, 6);         // Invokes CalculateSum(5, 6).
+  foo.Sum(2, 3);         // Invokes Sum3(1, 2, 3).
+  foo.ComplexJob(10);    // Invokes helper.ComplexJob(10).
+  foo.ComplexJob(-1);    // Invokes the inline lambda.
+```
+
+The only requirement is that the type of the function, etc must be *compatible*
+with the signature of the mock function, meaning that the latter's arguments (if
+it takes any) can be implicitly converted to the corresponding arguments of the
+former, and the former's return type can be implicitly converted to that of the
+latter. So, you can invoke something whose type is *not* exactly the same as the
+mock function, as long as it's safe to do so - nice, huh?
+
+Note that:
+
+*   The action takes ownership of the callback and will delete it when the
+    action itself is destructed.
+*   If the type of a callback is derived from a base callback type `C`, you need
+    to implicitly cast it to `C` to resolve the overloading, e.g.
+
+    ```cpp
+    using ::testing::Invoke;
+    ...
+      ResultCallback<bool>* is_ok = ...;
+      ... Invoke(is_ok) ...;  // This works.
+
+      BlockingClosure* done = new BlockingClosure;
+      ... Invoke(implicit_cast<Closure*>(done)) ...;  // The cast is necessary.
+    ```
+
+### Using Functions with Extra Info as Actions
+
+The function or functor you call using `Invoke()` must have the same number of
+arguments as the mock function you use it for. Sometimes you may have a function
+that takes more arguments, and you are willing to pass in the extra arguments
+yourself to fill the gap. You can do this in gMock using callbacks with
+pre-bound arguments. Here's an example:
+
+```cpp
+using ::testing::Invoke;
+
+class MockFoo : public Foo {
+ public:
+  MOCK_METHOD(char, DoThis, (int n), (override));
+};
+
+char SignOfSum(int x, int y) {
+  const int sum = x + y;
+  return (sum > 0) ? '+' : (sum < 0) ? '-' : '0';
+}
+
+TEST_F(FooTest, Test) {
+  MockFoo foo;
+
+  EXPECT_CALL(foo, DoThis(2))
+      .WillOnce(Invoke(NewPermanentCallback(SignOfSum, 5)));
+  EXPECT_EQ(foo.DoThis(2), '+');  // Invokes SignOfSum(5, 2).
+}
+```
+
+### Invoking a Function/Method/Functor/Lambda/Callback Without Arguments
+
+`Invoke()` passes the mock function's arguments to the function, etc being
+invoked such that the callee has the full context of the call to work with. If
+the invoked function is not interested in some or all of the arguments, it can
+simply ignore them.
+
+Yet, a common pattern is that a test author wants to invoke a function without
+the arguments of the mock function. She could do that using a wrapper function
+that throws away the arguments before invoking an underlining nullary function.
+Needless to say, this can be tedious and obscures the intent of the test.
+
+There are two solutions to this problem. First, you can pass any callable of
+zero args as an action. Alternatively, use `InvokeWithoutArgs()`, which is like
+`Invoke()` except that it doesn't pass the mock function's arguments to the
+callee. Here's an example of each:
+
+```cpp
+using ::testing::_;
+using ::testing::InvokeWithoutArgs;
+
+class MockFoo : public Foo {
+ public:
+  MOCK_METHOD(bool, ComplexJob, (int n), (override));
+};
+
+bool Job1() { ... }
+bool Job2(int n, char c) { ... }
+
+...
+  MockFoo foo;
+  EXPECT_CALL(foo, ComplexJob(_))
+      .WillOnce([] { Job1(); });
+      .WillOnce(InvokeWithoutArgs(NewPermanentCallback(Job2, 5, 'a')));
+
+  foo.ComplexJob(10);  // Invokes Job1().
+  foo.ComplexJob(20);  // Invokes Job2(5, 'a').
+```
+
+Note that:
+
+*   The action takes ownership of the callback and will delete it when the
+    action itself is destructed.
+*   If the type of a callback is derived from a base callback type `C`, you need
+    to implicitly cast it to `C` to resolve the overloading, e.g.
+
+    ```cpp
+    using ::testing::InvokeWithoutArgs;
+    ...
+      ResultCallback<bool>* is_ok = ...;
+      ... InvokeWithoutArgs(is_ok) ...;  // This works.
+
+      BlockingClosure* done = ...;
+      ... InvokeWithoutArgs(implicit_cast<Closure*>(done)) ...;
+      // The cast is necessary.
+    ```
+
+### Invoking an Argument of the Mock Function
+
+Sometimes a mock function will receive a function pointer, a functor (in other
+words, a "callable") as an argument, e.g.
+
+```cpp
+class MockFoo : public Foo {
+ public:
+  MOCK_METHOD(bool, DoThis, (int n, (ResultCallback1<bool, int>* callback)),
+              (override));
+};
+```
+
+and you may want to invoke this callable argument:
+
+```cpp
+using ::testing::_;
+...
+  MockFoo foo;
+  EXPECT_CALL(foo, DoThis(_, _))
+      .WillOnce(...);
+      // Will execute callback->Run(5), where callback is the
+      // second argument DoThis() receives.
+```
+
+{: .callout .note}
+NOTE: The section below is legacy documentation from before C++ had lambdas:
+
+Arghh, you need to refer to a mock function argument but C++ has no lambda
+(yet), so you have to define your own action. :-( Or do you really?
+
+Well, gMock has an action to solve *exactly* this problem:
+
+```cpp
+InvokeArgument<N>(arg_1, arg_2, ..., arg_m)
+```
+
+will invoke the `N`-th (0-based) argument the mock function receives, with
+`arg_1`, `arg_2`, ..., and `arg_m`. No matter if the argument is a function
+pointer, a functor, or a callback. gMock handles them all.
+
+With that, you could write:
+
+```cpp
+using ::testing::_;
+using ::testing::InvokeArgument;
+...
+  EXPECT_CALL(foo, DoThis(_, _))
+      .WillOnce(InvokeArgument<1>(5));
+      // Will execute callback->Run(5), where callback is the
+      // second argument DoThis() receives.
+```
+
+What if the callable takes an argument by reference? No problem - just wrap it
+inside `std::ref()`:
+
+```cpp
+  ...
+  MOCK_METHOD(bool, Bar,
+              ((ResultCallback2<bool, int, const Helper&>* callback)),
+              (override));
+  ...
+  using ::testing::_;
+  using ::testing::InvokeArgument;
+  ...
+  MockFoo foo;
+  Helper helper;
+  ...
+  EXPECT_CALL(foo, Bar(_))
+      .WillOnce(InvokeArgument<0>(5, std::ref(helper)));
+      // std::ref(helper) guarantees that a reference to helper, not a copy of
+      // it, will be passed to the callback.
+```
+
+What if the callable takes an argument by reference and we do **not** wrap the
+argument in `std::ref()`? Then `InvokeArgument()` will *make a copy* of the
+argument, and pass a *reference to the copy*, instead of a reference to the
+original value, to the callable. This is especially handy when the argument is a
+temporary value:
+
+```cpp
+  ...
+  MOCK_METHOD(bool, DoThat, (bool (*f)(const double& x, const string& s)),
+              (override));
+  ...
+  using ::testing::_;
+  using ::testing::InvokeArgument;
+  ...
+  MockFoo foo;
+  ...
+  EXPECT_CALL(foo, DoThat(_))
+      .WillOnce(InvokeArgument<0>(5.0, string("Hi")));
+      // Will execute (*f)(5.0, string("Hi")), where f is the function pointer
+      // DoThat() receives.  Note that the values 5.0 and string("Hi") are
+      // temporary and dead once the EXPECT_CALL() statement finishes.  Yet
+      // it's fine to perform this action later, since a copy of the values
+      // are kept inside the InvokeArgument action.
+```
+
+### Ignoring an Action's Result
+
+Sometimes you have an action that returns *something*, but you need an action
+that returns `void` (perhaps you want to use it in a mock function that returns
+`void`, or perhaps it needs to be used in `DoAll()` and it's not the last in the
+list). `IgnoreResult()` lets you do that. For example:
+
+```cpp
+using ::testing::_;
+using ::testing::DoAll;
+using ::testing::IgnoreResult;
+using ::testing::Return;
+
+int Process(const MyData& data);
+string DoSomething();
+
+class MockFoo : public Foo {
+ public:
+  MOCK_METHOD(void, Abc, (const MyData& data), (override));
+  MOCK_METHOD(bool, Xyz, (), (override));
+};
+
+  ...
+  MockFoo foo;
+  EXPECT_CALL(foo, Abc(_))
+      // .WillOnce(Invoke(Process));
+      // The above line won't compile as Process() returns int but Abc() needs
+      // to return void.
+      .WillOnce(IgnoreResult(Process));
+  EXPECT_CALL(foo, Xyz())
+      .WillOnce(DoAll(IgnoreResult(DoSomething),
+                      // Ignores the string DoSomething() returns.
+                      Return(true)));
+```
+
+Note that you **cannot** use `IgnoreResult()` on an action that already returns
+`void`. Doing so will lead to ugly compiler errors.
+
+### Selecting an Action's Arguments {#SelectingArgs}
+
+Say you have a mock function `Foo()` that takes seven arguments, and you have a
+custom action that you want to invoke when `Foo()` is called. Trouble is, the
+custom action only wants three arguments:
+
+```cpp
+using ::testing::_;
+using ::testing::Invoke;
+...
+  MOCK_METHOD(bool, Foo,
+              (bool visible, const string& name, int x, int y,
+               (const map<pair<int, int>>), double& weight, double min_weight,
+               double max_wight));
+...
+bool IsVisibleInQuadrant1(bool visible, int x, int y) {
+  return visible && x >= 0 && y >= 0;
+}
+...
+  EXPECT_CALL(mock, Foo)
+      .WillOnce(Invoke(IsVisibleInQuadrant1));  // Uh, won't compile. :-(
+```
+
+To please the compiler God, you need to define an "adaptor" that has the same
+signature as `Foo()` and calls the custom action with the right arguments:
+
+```cpp
+using ::testing::_;
+using ::testing::Invoke;
+...
+bool MyIsVisibleInQuadrant1(bool visible, const string& name, int x, int y,
+                            const map<pair<int, int>, double>& weight,
+                            double min_weight, double max_wight) {
+  return IsVisibleInQuadrant1(visible, x, y);
+}
+...
+  EXPECT_CALL(mock, Foo)
+      .WillOnce(Invoke(MyIsVisibleInQuadrant1));  // Now it works.
+```
+
+But isn't this awkward?
+
+gMock provides a generic *action adaptor*, so you can spend your time minding
+more important business than writing your own adaptors. Here's the syntax:
+
+```cpp
+WithArgs<N1, N2, ..., Nk>(action)
+```
+
+creates an action that passes the arguments of the mock function at the given
+indices (0-based) to the inner `action` and performs it. Using `WithArgs`, our
+original example can be written as:
+
+```cpp
+using ::testing::_;
+using ::testing::Invoke;
+using ::testing::WithArgs;
+...
+  EXPECT_CALL(mock, Foo)
+      .WillOnce(WithArgs<0, 2, 3>(Invoke(IsVisibleInQuadrant1)));  // No need to define your own adaptor.
+```
+
+For better readability, gMock also gives you:
+
+*   `WithoutArgs(action)` when the inner `action` takes *no* argument, and
+*   `WithArg<N>(action)` (no `s` after `Arg`) when the inner `action` takes
+    *one* argument.
+
+As you may have realized, `InvokeWithoutArgs(...)` is just syntactic sugar for
+`WithoutArgs(Invoke(...))`.
+
+Here are more tips:
+
+*   The inner action used in `WithArgs` and friends does not have to be
+    `Invoke()` -- it can be anything.
+*   You can repeat an argument in the argument list if necessary, e.g.
+    `WithArgs<2, 3, 3, 5>(...)`.
+*   You can change the order of the arguments, e.g. `WithArgs<3, 2, 1>(...)`.
+*   The types of the selected arguments do *not* have to match the signature of
+    the inner action exactly. It works as long as they can be implicitly
+    converted to the corresponding arguments of the inner action. For example,
+    if the 4-th argument of the mock function is an `int` and `my_action` takes
+    a `double`, `WithArg<4>(my_action)` will work.
+
+### Ignoring Arguments in Action Functions
+
+The [selecting-an-action's-arguments](#SelectingArgs) recipe showed us one way
+to make a mock function and an action with incompatible argument lists fit
+together. The downside is that wrapping the action in `WithArgs<...>()` can get
+tedious for people writing the tests.
+
+If you are defining a function (or method, functor, lambda, callback) to be used
+with `Invoke*()`, and you are not interested in some of its arguments, an
+alternative to `WithArgs` is to declare the uninteresting arguments as `Unused`.
+This makes the definition less cluttered and less fragile in case the types of
+the uninteresting arguments change. It could also increase the chance the action
+function can be reused. For example, given
+
+```cpp
+ public:
+  MOCK_METHOD(double, Foo, double(const string& label, double x, double y),
+              (override));
+  MOCK_METHOD(double, Bar, (int index, double x, double y), (override));
+```
+
+instead of
+
+```cpp
+using ::testing::_;
+using ::testing::Invoke;
+
+double DistanceToOriginWithLabel(const string& label, double x, double y) {
+  return sqrt(x*x + y*y);
+}
+double DistanceToOriginWithIndex(int index, double x, double y) {
+  return sqrt(x*x + y*y);
+}
+...
+  EXPECT_CALL(mock, Foo("abc", _, _))
+      .WillOnce(Invoke(DistanceToOriginWithLabel));
+  EXPECT_CALL(mock, Bar(5, _, _))
+      .WillOnce(Invoke(DistanceToOriginWithIndex));
+```
+
+you could write
+
+```cpp
+using ::testing::_;
+using ::testing::Invoke;
+using ::testing::Unused;
+
+double DistanceToOrigin(Unused, double x, double y) {
+  return sqrt(x*x + y*y);
+}
+...
+  EXPECT_CALL(mock, Foo("abc", _, _))
+      .WillOnce(Invoke(DistanceToOrigin));
+  EXPECT_CALL(mock, Bar(5, _, _))
+      .WillOnce(Invoke(DistanceToOrigin));
+```
+
+### Sharing Actions
+
+Just like matchers, a gMock action object consists of a pointer to a ref-counted
+implementation object. Therefore copying actions is also allowed and very
+efficient. When the last action that references the implementation object dies,
+the implementation object will be deleted.
+
+If you have some complex action that you want to use again and again, you may
+not have to build it from scratch every time. If the action doesn't have an
+internal state (i.e. if it always does the same thing no matter how many times
+it has been called), you can assign it to an action variable and use that
+variable repeatedly. For example:
+
+```cpp
+using ::testing::Action;
+using ::testing::DoAll;
+using ::testing::Return;
+using ::testing::SetArgPointee;
+...
+  Action<bool(int*)> set_flag = DoAll(SetArgPointee<0>(5),
+                                      Return(true));
+  ... use set_flag in .WillOnce() and .WillRepeatedly() ...
+```
+
+However, if the action has its own state, you may be surprised if you share the
+action object. Suppose you have an action factory `IncrementCounter(init)` which
+creates an action that increments and returns a counter whose initial value is
+`init`, using two actions created from the same expression and using a shared
+action will exhibit different behaviors. Example:
+
+```cpp
+  EXPECT_CALL(foo, DoThis())
+      .WillRepeatedly(IncrementCounter(0));
+  EXPECT_CALL(foo, DoThat())
+      .WillRepeatedly(IncrementCounter(0));
+  foo.DoThis();  // Returns 1.
+  foo.DoThis();  // Returns 2.
+  foo.DoThat();  // Returns 1 - DoThat() uses a different
+                 // counter than DoThis()'s.
+```
+
+versus
+
+```cpp
+using ::testing::Action;
+...
+  Action<int()> increment = IncrementCounter(0);
+  EXPECT_CALL(foo, DoThis())
+      .WillRepeatedly(increment);
+  EXPECT_CALL(foo, DoThat())
+      .WillRepeatedly(increment);
+  foo.DoThis();  // Returns 1.
+  foo.DoThis();  // Returns 2.
+  foo.DoThat();  // Returns 3 - the counter is shared.
+```
+
+### Testing Asynchronous Behavior
+
+One oft-encountered problem with gMock is that it can be hard to test
+asynchronous behavior. Suppose you had a `EventQueue` class that you wanted to
+test, and you created a separate `EventDispatcher` interface so that you could
+easily mock it out. However, the implementation of the class fired all the
+events on a background thread, which made test timings difficult. You could just
+insert `sleep()` statements and hope for the best, but that makes your test
+behavior nondeterministic. A better way is to use gMock actions and
+`Notification` objects to force your asynchronous test to behave synchronously.
+
+```cpp
+class MockEventDispatcher : public EventDispatcher {
+  MOCK_METHOD(bool, DispatchEvent, (int32), (override));
+};
+
+TEST(EventQueueTest, EnqueueEventTest) {
+  MockEventDispatcher mock_event_dispatcher;
+  EventQueue event_queue(&mock_event_dispatcher);
+
+  const int32 kEventId = 321;
+  absl::Notification done;
+  EXPECT_CALL(mock_event_dispatcher, DispatchEvent(kEventId))
+      .WillOnce([&done] { done.Notify(); });
+
+  event_queue.EnqueueEvent(kEventId);
+  done.WaitForNotification();
+}
+```
+
+In the example above, we set our normal gMock expectations, but then add an
+additional action to notify the `Notification` object. Now we can just call
+`Notification::WaitForNotification()` in the main thread to wait for the
+asynchronous call to finish. After that, our test suite is complete and we can
+safely exit.
+
+{: .callout .note}
+Note: this example has a downside: namely, if the expectation is not satisfied,
+our test will run forever. It will eventually time-out and fail, but it will
+take longer and be slightly harder to debug. To alleviate this problem, you can
+use `WaitForNotificationWithTimeout(ms)` instead of `WaitForNotification()`.
+
+## Misc Recipes on Using gMock
+
+### Mocking Methods That Use Move-Only Types
+
+C++11 introduced *move-only types*. A move-only-typed value can be moved from
+one object to another, but cannot be copied. `std::unique_ptr<T>` is probably
+the most commonly used move-only type.
+
+Mocking a method that takes and/or returns move-only types presents some
+challenges, but nothing insurmountable. This recipe shows you how you can do it.
+Note that the support for move-only method arguments was only introduced to
+gMock in April 2017; in older code, you may find more complex
+[workarounds](#LegacyMoveOnly) for lack of this feature.
+
+Let’s say we are working on a fictional project that lets one post and share
+snippets called “buzzes”. Your code uses these types:
+
+```cpp
+enum class AccessLevel { kInternal, kPublic };
+
+class Buzz {
+ public:
+  explicit Buzz(AccessLevel access) { ... }
+  ...
+};
+
+class Buzzer {
+ public:
+  virtual ~Buzzer() {}
+  virtual std::unique_ptr<Buzz> MakeBuzz(StringPiece text) = 0;
+  virtual bool ShareBuzz(std::unique_ptr<Buzz> buzz, int64_t timestamp) = 0;
+  ...
+};
+```
+
+A `Buzz` object represents a snippet being posted. A class that implements the
+`Buzzer` interface is capable of creating and sharing `Buzz`es. Methods in
+`Buzzer` may return a `unique_ptr<Buzz>` or take a `unique_ptr<Buzz>`. Now we
+need to mock `Buzzer` in our tests.
+
+To mock a method that accepts or returns move-only types, you just use the
+familiar `MOCK_METHOD` syntax as usual:
+
+```cpp
+class MockBuzzer : public Buzzer {
+ public:
+  MOCK_METHOD(std::unique_ptr<Buzz>, MakeBuzz, (StringPiece text), (override));
+  MOCK_METHOD(bool, ShareBuzz, (std::unique_ptr<Buzz> buzz, int64_t timestamp),
+              (override));
+};
+```
+
+Now that we have the mock class defined, we can use it in tests. In the
+following code examples, we assume that we have defined a `MockBuzzer` object
+named `mock_buzzer_`:
+
+```cpp
+  MockBuzzer mock_buzzer_;
+```
+
+First let’s see how we can set expectations on the `MakeBuzz()` method, which
+returns a `unique_ptr<Buzz>`.
+
+As usual, if you set an expectation without an action (i.e. the `.WillOnce()` or
+`.WillRepeatedly()` clause), when that expectation fires, the default action for
+that method will be taken. Since `unique_ptr<>` has a default constructor that
+returns a null `unique_ptr`, that’s what you’ll get if you don’t specify an
+action:
+
+```cpp
+using ::testing::IsNull;
+...
+  // Use the default action.
+  EXPECT_CALL(mock_buzzer_, MakeBuzz("hello"));
+
+  // Triggers the previous EXPECT_CALL.
+  EXPECT_THAT(mock_buzzer_.MakeBuzz("hello"), IsNull());
+```
+
+If you are not happy with the default action, you can tweak it as usual; see
+[Setting Default Actions](#OnCall).
+
+If you just need to return a move-only value, you can use it in combination with
+`WillOnce`. For example:
+
+```cpp
+  EXPECT_CALL(mock_buzzer_, MakeBuzz("hello"))
+      .WillOnce(Return(std::make_unique<Buzz>(AccessLevel::kInternal)));
+  EXPECT_NE(nullptr, mock_buzzer_.MakeBuzz("hello"));
+```
+
+Quiz time! What do you think will happen if a `Return` action is performed more
+than once (e.g. you write `... .WillRepeatedly(Return(std::move(...)));`)? Come
+think of it, after the first time the action runs, the source value will be
+consumed (since it’s a move-only value), so the next time around, there’s no
+value to move from -- you’ll get a run-time error that `Return(std::move(...))`
+can only be run once.
+
+If you need your mock method to do more than just moving a pre-defined value,
+remember that you can always use a lambda or a callable object, which can do
+pretty much anything you want:
+
+```cpp
+  EXPECT_CALL(mock_buzzer_, MakeBuzz("x"))
+      .WillRepeatedly([](StringPiece text) {
+        return std::make_unique<Buzz>(AccessLevel::kInternal);
+      });
+
+  EXPECT_NE(nullptr, mock_buzzer_.MakeBuzz("x"));
+  EXPECT_NE(nullptr, mock_buzzer_.MakeBuzz("x"));
+```
+
+Every time this `EXPECT_CALL` fires, a new `unique_ptr<Buzz>` will be created
+and returned. You cannot do this with `Return(std::make_unique<...>(...))`.
+
+That covers returning move-only values; but how do we work with methods
+accepting move-only arguments? The answer is that they work normally, although
+some actions will not compile when any of method's arguments are move-only. You
+can always use `Return`, or a [lambda or functor](#FunctionsAsActions):
+
+```cpp
+  using ::testing::Unused;
+
+  EXPECT_CALL(mock_buzzer_, ShareBuzz(NotNull(), _)).WillOnce(Return(true));
+  EXPECT_TRUE(mock_buzzer_.ShareBuzz(std::make_unique<Buzz>(AccessLevel::kInternal)),
+              0);
+
+  EXPECT_CALL(mock_buzzer_, ShareBuzz(_, _)).WillOnce(
+      [](std::unique_ptr<Buzz> buzz, Unused) { return buzz != nullptr; });
+  EXPECT_FALSE(mock_buzzer_.ShareBuzz(nullptr, 0));
+```
+
+Many built-in actions (`WithArgs`, `WithoutArgs`,`DeleteArg`, `SaveArg`, ...)
+could in principle support move-only arguments, but the support for this is not
+implemented yet. If this is blocking you, please file a bug.
+
+A few actions (e.g. `DoAll`) copy their arguments internally, so they can never
+work with non-copyable objects; you'll have to use functors instead.
+
+#### Legacy workarounds for move-only types {#LegacyMoveOnly}
+
+Support for move-only function arguments was only introduced to gMock in April
+of 2017. In older code, you may encounter the following workaround for the lack
+of this feature (it is no longer necessary - we're including it just for
+reference):
+
+```cpp
+class MockBuzzer : public Buzzer {
+ public:
+  MOCK_METHOD(bool, DoShareBuzz, (Buzz* buzz, Time timestamp));
+  bool ShareBuzz(std::unique_ptr<Buzz> buzz, Time timestamp) override {
+    return DoShareBuzz(buzz.get(), timestamp);
+  }
+};
+```
+
+The trick is to delegate the `ShareBuzz()` method to a mock method (let’s call
+it `DoShareBuzz()`) that does not take move-only parameters. Then, instead of
+setting expectations on `ShareBuzz()`, you set them on the `DoShareBuzz()` mock
+method:
+
+```cpp
+  MockBuzzer mock_buzzer_;
+  EXPECT_CALL(mock_buzzer_, DoShareBuzz(NotNull(), _));
+
+  // When one calls ShareBuzz() on the MockBuzzer like this, the call is
+  // forwarded to DoShareBuzz(), which is mocked.  Therefore this statement
+  // will trigger the above EXPECT_CALL.
+  mock_buzzer_.ShareBuzz(std::make_unique<Buzz>(AccessLevel::kInternal), 0);
+```
+
+### Making the Compilation Faster
+
+Believe it or not, the *vast majority* of the time spent on compiling a mock
+class is in generating its constructor and destructor, as they perform
+non-trivial tasks (e.g. verification of the expectations). What's more, mock
+methods with different signatures have different types and thus their
+constructors/destructors need to be generated by the compiler separately. As a
+result, if you mock many different types of methods, compiling your mock class
+can get really slow.
+
+If you are experiencing slow compilation, you can move the definition of your
+mock class' constructor and destructor out of the class body and into a `.cc`
+file. This way, even if you `#include` your mock class in N files, the compiler
+only needs to generate its constructor and destructor once, resulting in a much
+faster compilation.
+
+Let's illustrate the idea using an example. Here's the definition of a mock
+class before applying this recipe:
+
+```cpp
+// File mock_foo.h.
+...
+class MockFoo : public Foo {
+ public:
+  // Since we don't declare the constructor or the destructor,
+  // the compiler will generate them in every translation unit
+  // where this mock class is used.
+
+  MOCK_METHOD(int, DoThis, (), (override));
+  MOCK_METHOD(bool, DoThat, (const char* str), (override));
+  ... more mock methods ...
+};
+```
+
+After the change, it would look like:
+
+```cpp
+// File mock_foo.h.
+...
+class MockFoo : public Foo {
+ public:
+  // The constructor and destructor are declared, but not defined, here.
+  MockFoo();
+  virtual ~MockFoo();
+
+  MOCK_METHOD(int, DoThis, (), (override));
+  MOCK_METHOD(bool, DoThat, (const char* str), (override));
+  ... more mock methods ...
+};
+```
+
+and
+
+```cpp
+// File mock_foo.cc.
+#include "path/to/mock_foo.h"
+
+// The definitions may appear trivial, but the functions actually do a
+// lot of things through the constructors/destructors of the member
+// variables used to implement the mock methods.
+MockFoo::MockFoo() {}
+MockFoo::~MockFoo() {}
+```
+
+### Forcing a Verification
+
+When it's being destroyed, your friendly mock object will automatically verify
+that all expectations on it have been satisfied, and will generate googletest
+failures if not. This is convenient as it leaves you with one less thing to
+worry about. That is, unless you are not sure if your mock object will be
+destroyed.
+
+How could it be that your mock object won't eventually be destroyed? Well, it
+might be created on the heap and owned by the code you are testing. Suppose
+there's a bug in that code and it doesn't delete the mock object properly - you
+could end up with a passing test when there's actually a bug.
+
+Using a heap checker is a good idea and can alleviate the concern, but its
+implementation is not 100% reliable. So, sometimes you do want to *force* gMock
+to verify a mock object before it is (hopefully) destructed. You can do this
+with `Mock::VerifyAndClearExpectations(&mock_object)`:
+
+```cpp
+TEST(MyServerTest, ProcessesRequest) {
+  using ::testing::Mock;
+
+  MockFoo* const foo = new MockFoo;
+  EXPECT_CALL(*foo, ...)...;
+  // ... other expectations ...
+
+  // server now owns foo.
+  MyServer server(foo);
+  server.ProcessRequest(...);
+
+  // In case that server's destructor will forget to delete foo,
+  // this will verify the expectations anyway.
+  Mock::VerifyAndClearExpectations(foo);
+}  // server is destroyed when it goes out of scope here.
+```
+
+{: .callout .tip}
+**Tip:** The `Mock::VerifyAndClearExpectations()` function returns a `bool` to
+indicate whether the verification was successful (`true` for yes), so you can
+wrap that function call inside a `ASSERT_TRUE()` if there is no point going
+further when the verification has failed.
+
+Do not set new expectations after verifying and clearing a mock after its use.
+Setting expectations after code that exercises the mock has undefined behavior.
+See [Using Mocks in Tests](gmock_for_dummies.md#using-mocks-in-tests) for more
+information.
+
+### Using Checkpoints {#UsingCheckPoints}
+
+Sometimes you might want to test a mock object's behavior in phases whose sizes
+are each manageable, or you might want to set more detailed expectations about
+which API calls invoke which mock functions.
+
+A technique you can use is to put the expectations in a sequence and insert
+calls to a dummy "checkpoint" function at specific places. Then you can verify
+that the mock function calls do happen at the right time. For example, if you
+are exercising the code:
+
+```cpp
+  Foo(1);
+  Foo(2);
+  Foo(3);
+```
+
+and want to verify that `Foo(1)` and `Foo(3)` both invoke `mock.Bar("a")`, but
+`Foo(2)` doesn't invoke anything, you can write:
+
+```cpp
+using ::testing::MockFunction;
+
+TEST(FooTest, InvokesBarCorrectly) {
+  MyMock mock;
+  // Class MockFunction<F> has exactly one mock method.  It is named
+  // Call() and has type F.
+  MockFunction<void(string check_point_name)> check;
+  {
+    InSequence s;
+
+    EXPECT_CALL(mock, Bar("a"));
+    EXPECT_CALL(check, Call("1"));
+    EXPECT_CALL(check, Call("2"));
+    EXPECT_CALL(mock, Bar("a"));
+  }
+  Foo(1);
+  check.Call("1");
+  Foo(2);
+  check.Call("2");
+  Foo(3);
+}
+```
+
+The expectation spec says that the first `Bar("a")` call must happen before
+checkpoint "1", the second `Bar("a")` call must happen after checkpoint "2", and
+nothing should happen between the two checkpoints. The explicit checkpoints make
+it clear which `Bar("a")` is called by which call to `Foo()`.
+
+### Mocking Destructors
+
+Sometimes you want to make sure a mock object is destructed at the right time,
+e.g. after `bar->A()` is called but before `bar->B()` is called. We already know
+that you can specify constraints on the [order](#OrderedCalls) of mock function
+calls, so all we need to do is to mock the destructor of the mock function.
+
+This sounds simple, except for one problem: a destructor is a special function
+with special syntax and special semantics, and the `MOCK_METHOD` macro doesn't
+work for it:
+
+```cpp
+MOCK_METHOD(void, ~MockFoo, ());  // Won't compile!
+```
+
+The good news is that you can use a simple pattern to achieve the same effect.
+First, add a mock function `Die()` to your mock class and call it in the
+destructor, like this:
+
+```cpp
+class MockFoo : public Foo {
+  ...
+  // Add the following two lines to the mock class.
+  MOCK_METHOD(void, Die, ());
+  ~MockFoo() override { Die(); }
+};
+```
+
+(If the name `Die()` clashes with an existing symbol, choose another name.) Now,
+we have translated the problem of testing when a `MockFoo` object dies to
+testing when its `Die()` method is called:
+
+```cpp
+  MockFoo* foo = new MockFoo;
+  MockBar* bar = new MockBar;
+  ...
+  {
+    InSequence s;
+
+    // Expects *foo to die after bar->A() and before bar->B().
+    EXPECT_CALL(*bar, A());
+    EXPECT_CALL(*foo, Die());
+    EXPECT_CALL(*bar, B());
+  }
+```
+
+And that's that.
+
+### Using gMock and Threads {#UsingThreads}
+
+In a **unit** test, it's best if you could isolate and test a piece of code in a
+single-threaded context. That avoids race conditions and dead locks, and makes
+debugging your test much easier.
+
+Yet most programs are multi-threaded, and sometimes to test something we need to
+pound on it from more than one thread. gMock works for this purpose too.
+
+Remember the steps for using a mock:
+
+1.  Create a mock object `foo`.
+2.  Set its default actions and expectations using `ON_CALL()` and
+    `EXPECT_CALL()`.
+3.  The code under test calls methods of `foo`.
+4.  Optionally, verify and reset the mock.
+5.  Destroy the mock yourself, or let the code under test destroy it. The
+    destructor will automatically verify it.
+
+If you follow the following simple rules, your mocks and threads can live
+happily together:
+
+*   Execute your *test code* (as opposed to the code being tested) in *one*
+    thread. This makes your test easy to follow.
+*   Obviously, you can do step #1 without locking.
+*   When doing step #2 and #5, make sure no other thread is accessing `foo`.
+    Obvious too, huh?
+*   #3 and #4 can be done either in one thread or in multiple threads - anyway
+    you want. gMock takes care of the locking, so you don't have to do any -
+    unless required by your test logic.
+
+If you violate the rules (for example, if you set expectations on a mock while
+another thread is calling its methods), you get undefined behavior. That's not
+fun, so don't do it.
+
+gMock guarantees that the action for a mock function is done in the same thread
+that called the mock function. For example, in
+
+```cpp
+  EXPECT_CALL(mock, Foo(1))
+      .WillOnce(action1);
+  EXPECT_CALL(mock, Foo(2))
+      .WillOnce(action2);
+```
+
+if `Foo(1)` is called in thread 1 and `Foo(2)` is called in thread 2, gMock will
+execute `action1` in thread 1 and `action2` in thread 2.
+
+gMock does *not* impose a sequence on actions performed in different threads
+(doing so may create deadlocks as the actions may need to cooperate). This means
+that the execution of `action1` and `action2` in the above example *may*
+interleave. If this is a problem, you should add proper synchronization logic to
+`action1` and `action2` to make the test thread-safe.
+
+Also, remember that `DefaultValue<T>` is a global resource that potentially
+affects *all* living mock objects in your program. Naturally, you won't want to
+mess with it from multiple threads or when there still are mocks in action.
+
+### Controlling How Much Information gMock Prints
+
+When gMock sees something that has the potential of being an error (e.g. a mock
+function with no expectation is called, a.k.a. an uninteresting call, which is
+allowed but perhaps you forgot to explicitly ban the call), it prints some
+warning messages, including the arguments of the function, the return value, and
+the stack trace. Hopefully this will remind you to take a look and see if there
+is indeed a problem.
+
+Sometimes you are confident that your tests are correct and may not appreciate
+such friendly messages. Some other times, you are debugging your tests or
+learning about the behavior of the code you are testing, and wish you could
+observe every mock call that happens (including argument values, the return
+value, and the stack trace). Clearly, one size doesn't fit all.
+
+You can control how much gMock tells you using the `--gmock_verbose=LEVEL`
+command-line flag, where `LEVEL` is a string with three possible values:
+
+*   `info`: gMock will print all informational messages, warnings, and errors
+    (most verbose). At this setting, gMock will also log any calls to the
+    `ON_CALL/EXPECT_CALL` macros. It will include a stack trace in
+    "uninteresting call" warnings.
+*   `warning`: gMock will print both warnings and errors (less verbose); it will
+    omit the stack traces in "uninteresting call" warnings. This is the default.
+*   `error`: gMock will print errors only (least verbose).
+
+Alternatively, you can adjust the value of that flag from within your tests like
+so:
+
+```cpp
+  ::testing::FLAGS_gmock_verbose = "error";
+```
+
+If you find gMock printing too many stack frames with its informational or
+warning messages, remember that you can control their amount with the
+`--gtest_stack_trace_depth=max_depth` flag.
+
+Now, judiciously use the right flag to enable gMock serve you better!
+
+### Gaining Super Vision into Mock Calls
+
+You have a test using gMock. It fails: gMock tells you some expectations aren't
+satisfied. However, you aren't sure why: Is there a typo somewhere in the
+matchers? Did you mess up the order of the `EXPECT_CALL`s? Or is the code under
+test doing something wrong? How can you find out the cause?
+
+Won't it be nice if you have X-ray vision and can actually see the trace of all
+`EXPECT_CALL`s and mock method calls as they are made? For each call, would you
+like to see its actual argument values and which `EXPECT_CALL` gMock thinks it
+matches? If you still need some help to figure out who made these calls, how
+about being able to see the complete stack trace at each mock call?
+
+You can unlock this power by running your test with the `--gmock_verbose=info`
+flag. For example, given the test program:
+
+```cpp
+#include <gmock/gmock.h>
+
+using ::testing::_;
+using ::testing::HasSubstr;
+using ::testing::Return;
+
+class MockFoo {
+ public:
+  MOCK_METHOD(void, F, (const string& x, const string& y));
+};
+
+TEST(Foo, Bar) {
+  MockFoo mock;
+  EXPECT_CALL(mock, F(_, _)).WillRepeatedly(Return());
+  EXPECT_CALL(mock, F("a", "b"));
+  EXPECT_CALL(mock, F("c", HasSubstr("d")));
+
+  mock.F("a", "good");
+  mock.F("a", "b");
+}
+```
+
+if you run it with `--gmock_verbose=info`, you will see this output:
+
+```shell
+[ RUN       ] Foo.Bar
+
+foo_test.cc:14: EXPECT_CALL(mock, F(_, _)) invoked
+Stack trace: ...
+
+foo_test.cc:15: EXPECT_CALL(mock, F("a", "b")) invoked
+Stack trace: ...
+
+foo_test.cc:16: EXPECT_CALL(mock, F("c", HasSubstr("d"))) invoked
+Stack trace: ...
+
+foo_test.cc:14: Mock function call matches EXPECT_CALL(mock, F(_, _))...
+    Function call: F(@0x7fff7c8dad40"a",@0x7fff7c8dad10"good")
+Stack trace: ...
+
+foo_test.cc:15: Mock function call matches EXPECT_CALL(mock, F("a", "b"))...
+    Function call: F(@0x7fff7c8dada0"a",@0x7fff7c8dad70"b")
+Stack trace: ...
+
+foo_test.cc:16: Failure
+Actual function call count doesn't match EXPECT_CALL(mock, F("c", HasSubstr("d")))...
+         Expected: to be called once
+           Actual: never called - unsatisfied and active
+[  FAILED  ] Foo.Bar
+```
+
+Suppose the bug is that the `"c"` in the third `EXPECT_CALL` is a typo and
+should actually be `"a"`. With the above message, you should see that the actual
+`F("a", "good")` call is matched by the first `EXPECT_CALL`, not the third as
+you thought. From that it should be obvious that the third `EXPECT_CALL` is
+written wrong. Case solved.
+
+If you are interested in the mock call trace but not the stack traces, you can
+combine `--gmock_verbose=info` with `--gtest_stack_trace_depth=0` on the test
+command line.
+
+### Running Tests in Emacs
+
+If you build and run your tests in Emacs using the `M-x google-compile` command
+(as many googletest users do), the source file locations of gMock and googletest
+errors will be highlighted. Just press `<Enter>` on one of them and you'll be
+taken to the offending line. Or, you can just type `C-x`` to jump to the next
+error.
+
+To make it even easier, you can add the following lines to your `~/.emacs` file:
+
+```text
+(global-set-key "\M-m"  'google-compile)  ; m is for make
+(global-set-key [M-down] 'next-error)
+(global-set-key [M-up]  '(lambda () (interactive) (next-error -1)))
+```
+
+Then you can type `M-m` to start a build (if you want to run the test as well,
+just make sure `foo_test.run` or `runtests` is in the build command you supply
+after typing `M-m`), or `M-up`/`M-down` to move back and forth between errors.
+
+## Extending gMock
+
+### Writing New Matchers Quickly {#NewMatchers}
+
+{: .callout .warning}
+WARNING: gMock does not guarantee when or how many times a matcher will be
+invoked. Therefore, all matchers must be functionally pure. See
+[this section](#PureMatchers) for more details.
+
+The `MATCHER*` family of macros can be used to define custom matchers easily.
+The syntax:
+
+```cpp
+MATCHER(name, description_string_expression) { statements; }
+```
+
+will define a matcher with the given name that executes the statements, which
+must return a `bool` to indicate if the match succeeds. Inside the statements,
+you can refer to the value being matched by `arg`, and refer to its type by
+`arg_type`.
+
+The *description string* is a `string`-typed expression that documents what the
+matcher does, and is used to generate the failure message when the match fails.
+It can (and should) reference the special `bool` variable `negation`, and should
+evaluate to the description of the matcher when `negation` is `false`, or that
+of the matcher's negation when `negation` is `true`.
+
+For convenience, we allow the description string to be empty (`""`), in which
+case gMock will use the sequence of words in the matcher name as the
+description.
+
+For example:
+
+```cpp
+MATCHER(IsDivisibleBy7, "") { return (arg % 7) == 0; }
+```
+
+allows you to write
+
+```cpp
+  // Expects mock_foo.Bar(n) to be called where n is divisible by 7.
+  EXPECT_CALL(mock_foo, Bar(IsDivisibleBy7()));
+```
+
+or,
+
+```cpp
+  using ::testing::Not;
+  ...
+  // Verifies that a value is divisible by 7 and the other is not.
+  EXPECT_THAT(some_expression, IsDivisibleBy7());
+  EXPECT_THAT(some_other_expression, Not(IsDivisibleBy7()));
+```
+
+If the above assertions fail, they will print something like:
+
+```shell
+  Value of: some_expression
+  Expected: is divisible by 7
+    Actual: 27
+  ...
+  Value of: some_other_expression
+  Expected: not (is divisible by 7)
+    Actual: 21
+```
+
+where the descriptions `"is divisible by 7"` and `"not (is divisible by 7)"` are
+automatically calculated from the matcher name `IsDivisibleBy7`.
+
+As you may have noticed, the auto-generated descriptions (especially those for
+the negation) may not be so great. You can always override them with a `string`
+expression of your own:
+
+```cpp
+MATCHER(IsDivisibleBy7,
+        absl::StrCat(negation ? "isn't" : "is", " divisible by 7")) {
+  return (arg % 7) == 0;
+}
+```
+
+Optionally, you can stream additional information to a hidden argument named
+`result_listener` to explain the match result. For example, a better definition
+of `IsDivisibleBy7` is:
+
+```cpp
+MATCHER(IsDivisibleBy7, "") {
+  if ((arg % 7) == 0)
+    return true;
+
+  *result_listener << "the remainder is " << (arg % 7);
+  return false;
+}
+```
+
+With this definition, the above assertion will give a better message:
+
+```shell
+  Value of: some_expression
+  Expected: is divisible by 7
+    Actual: 27 (the remainder is 6)
+```
+
+You should let `MatchAndExplain()` print *any additional information* that can
+help a user understand the match result. Note that it should explain why the
+match succeeds in case of a success (unless it's obvious) - this is useful when
+the matcher is used inside `Not()`. There is no need to print the argument value
+itself, as gMock already prints it for you.
+
+{: .callout .note}
+NOTE: The type of the value being matched (`arg_type`) is determined by the
+context in which you use the matcher and is supplied to you by the compiler, so
+you don't need to worry about declaring it (nor can you). This allows the
+matcher to be polymorphic. For example, `IsDivisibleBy7()` can be used to match
+any type where the value of `(arg % 7) == 0` can be implicitly converted to a
+`bool`. In the `Bar(IsDivisibleBy7())` example above, if method `Bar()` takes an
+`int`, `arg_type` will be `int`; if it takes an `unsigned long`, `arg_type` will
+be `unsigned long`; and so on.
+
+### Writing New Parameterized Matchers Quickly
+
+Sometimes you'll want to define a matcher that has parameters. For that you can
+use the macro:
+
+```cpp
+MATCHER_P(name, param_name, description_string) { statements; }
+```
+
+where the description string can be either `""` or a `string` expression that
+references `negation` and `param_name`.
+
+For example:
+
+```cpp
+MATCHER_P(HasAbsoluteValue, value, "") { return abs(arg) == value; }
+```
+
+will allow you to write:
+
+```cpp
+  EXPECT_THAT(Blah("a"), HasAbsoluteValue(n));
+```
+
+which may lead to this message (assuming `n` is 10):
+
+```shell
+  Value of: Blah("a")
+  Expected: has absolute value 10
+    Actual: -9
+```
+
+Note that both the matcher description and its parameter are printed, making the
+message human-friendly.
+
+In the matcher definition body, you can write `foo_type` to reference the type
+of a parameter named `foo`. For example, in the body of
+`MATCHER_P(HasAbsoluteValue, value)` above, you can write `value_type` to refer
+to the type of `value`.
+
+gMock also provides `MATCHER_P2`, `MATCHER_P3`, ..., up to `MATCHER_P10` to
+support multi-parameter matchers:
+
+```cpp
+MATCHER_Pk(name, param_1, ..., param_k, description_string) { statements; }
+```
+
+Please note that the custom description string is for a particular *instance* of
+the matcher, where the parameters have been bound to actual values. Therefore
+usually you'll want the parameter values to be part of the description. gMock
+lets you do that by referencing the matcher parameters in the description string
+expression.
+
+For example,
+
+```cpp
+using ::testing::PrintToString;
+MATCHER_P2(InClosedRange, low, hi,
+           absl::StrFormat("%s in range [%s, %s]", negation ? "isn't" : "is",
+                           PrintToString(low), PrintToString(hi))) {
+  return low <= arg && arg <= hi;
+}
+...
+EXPECT_THAT(3, InClosedRange(4, 6));
+```
+
+would generate a failure that contains the message:
+
+```shell
+  Expected: is in range [4, 6]
+```
+
+If you specify `""` as the description, the failure message will contain the
+sequence of words in the matcher name followed by the parameter values printed
+as a tuple. For example,
+
+```cpp
+  MATCHER_P2(InClosedRange, low, hi, "") { ... }
+  ...
+  EXPECT_THAT(3, InClosedRange(4, 6));
+```
+
+would generate a failure that contains the text:
+
+```shell
+  Expected: in closed range (4, 6)
+```
+
+For the purpose of typing, you can view
+
+```cpp
+MATCHER_Pk(Foo, p1, ..., pk, description_string) { ... }
+```
+
+as shorthand for
+
+```cpp
+template <typename p1_type, ..., typename pk_type>
+FooMatcherPk<p1_type, ..., pk_type>
+Foo(p1_type p1, ..., pk_type pk) { ... }
+```
+
+When you write `Foo(v1, ..., vk)`, the compiler infers the types of the
+parameters `v1`, ..., and `vk` for you. If you are not happy with the result of
+the type inference, you can specify the types by explicitly instantiating the
+template, as in `Foo<long, bool>(5, false)`. As said earlier, you don't get to
+(or need to) specify `arg_type` as that's determined by the context in which the
+matcher is used.
+
+You can assign the result of expression `Foo(p1, ..., pk)` to a variable of type
+`FooMatcherPk<p1_type, ..., pk_type>`. This can be useful when composing
+matchers. Matchers that don't have a parameter or have only one parameter have
+special types: you can assign `Foo()` to a `FooMatcher`-typed variable, and
+assign `Foo(p)` to a `FooMatcherP<p_type>`-typed variable.
+
+While you can instantiate a matcher template with reference types, passing the
+parameters by pointer usually makes your code more readable. If, however, you
+still want to pass a parameter by reference, be aware that in the failure
+message generated by the matcher you will see the value of the referenced object
+but not its address.
+
+You can overload matchers with different numbers of parameters:
+
+```cpp
+MATCHER_P(Blah, a, description_string_1) { ... }
+MATCHER_P2(Blah, a, b, description_string_2) { ... }
+```
+
+While it's tempting to always use the `MATCHER*` macros when defining a new
+matcher, you should also consider implementing the matcher interface directly
+instead (see the recipes that follow), especially if you need to use the matcher
+a lot. While these approaches require more work, they give you more control on
+the types of the value being matched and the matcher parameters, which in
+general leads to better compiler error messages that pay off in the long run.
+They also allow overloading matchers based on parameter types (as opposed to
+just based on the number of parameters).
+
+### Writing New Monomorphic Matchers
+
+A matcher of argument type `T` implements the matcher interface for `T` and does
+two things: it tests whether a value of type `T` matches the matcher, and can
+describe what kind of values it matches. The latter ability is used for
+generating readable error messages when expectations are violated.
+
+A matcher of `T` must declare a typedef like:
+
+```cpp
+using is_gtest_matcher = void;
+```
+
+and supports the following operations:
+
+```cpp
+// Match a value and optionally explain into an ostream.
+bool matched = matcher.MatchAndExplain(value, maybe_os);
+// where `value` is of type `T` and
+// `maybe_os` is of type `std::ostream*`, where it can be null if the caller
+// is not interested in there textual explanation.
+
+matcher.DescribeTo(os);
+matcher.DescribeNegationTo(os);
+// where `os` is of type `std::ostream*`.
+```
+
+If you need a custom matcher but `Truly()` is not a good option (for example,
+you may not be happy with the way `Truly(predicate)` describes itself, or you
+may want your matcher to be polymorphic as `Eq(value)` is), you can define a
+matcher to do whatever you want in two steps: first implement the matcher
+interface, and then define a factory function to create a matcher instance. The
+second step is not strictly needed but it makes the syntax of using the matcher
+nicer.
+
+For example, you can define a matcher to test whether an `int` is divisible by 7
+and then use it like this:
+
+```cpp
+using ::testing::Matcher;
+
+class DivisibleBy7Matcher {
+ public:
+  using is_gtest_matcher = void;
+
+  bool MatchAndExplain(int n, std::ostream*) const {
+    return (n % 7) == 0;
+  }
+
+  void DescribeTo(std::ostream* os) const {
+    *os << "is divisible by 7";
+  }
+
+  void DescribeNegationTo(std::ostream* os) const {
+    *os << "is not divisible by 7";
+  }
+};
+
+Matcher<int> DivisibleBy7() {
+  return DivisibleBy7Matcher();
+}
+
+...
+  EXPECT_CALL(foo, Bar(DivisibleBy7()));
+```
+
+You may improve the matcher message by streaming additional information to the
+`os` argument in `MatchAndExplain()`:
+
+```cpp
+class DivisibleBy7Matcher {
+ public:
+  bool MatchAndExplain(int n, std::ostream* os) const {
+    const int remainder = n % 7;
+    if (remainder != 0 && os != nullptr) {
+      *os << "the remainder is " << remainder;
+    }
+    return remainder == 0;
+  }
+  ...
+};
+```
+
+Then, `EXPECT_THAT(x, DivisibleBy7());` may generate a message like this:
+
+```shell
+Value of: x
+Expected: is divisible by 7
+  Actual: 23 (the remainder is 2)
+```
+
+{: .callout .tip}
+Tip: for convenience, `MatchAndExplain()` can take a `MatchResultListener*`
+instead of `std::ostream*`.
+
+### Writing New Polymorphic Matchers
+
+Expanding what we learned above to *polymorphic* matchers is now just as simple
+as adding templates in the right place.
+
+```cpp
+
+class NotNullMatcher {
+ public:
+  using is_gtest_matcher = void;
+
+  // To implement a polymorphic matcher, we just need to make MatchAndExplain a
+  // template on its first argument.
+
+  // In this example, we want to use NotNull() with any pointer, so
+  // MatchAndExplain() accepts a pointer of any type as its first argument.
+  // In general, you can define MatchAndExplain() as an ordinary method or
+  // a method template, or even overload it.
+  template <typename T>
+  bool MatchAndExplain(T* p, std::ostream*) const {
+    return p != nullptr;
+  }
+
+  // Describes the property of a value matching this matcher.
+  void DescribeTo(std::ostream* os) const { *os << "is not NULL"; }
+
+  // Describes the property of a value NOT matching this matcher.
+  void DescribeNegationTo(std::ostream* os) const { *os << "is NULL"; }
+};
+
+NotNullMatcher NotNull() {
+  return NotNullMatcher();
+}
+
+...
+
+  EXPECT_CALL(foo, Bar(NotNull()));  // The argument must be a non-NULL pointer.
+```
+
+### Legacy Matcher Implementation
+
+Defining matchers used to be somewhat more complicated, in which it required
+several supporting classes and virtual functions. To implement a matcher for
+type `T` using the legacy API you have to derive from `MatcherInterface<T>` and
+call `MakeMatcher` to construct the object.
+
+The interface looks like this:
+
+```cpp
+class MatchResultListener {
+ public:
+  ...
+  // Streams x to the underlying ostream; does nothing if the ostream
+  // is NULL.
+  template <typename T>
+  MatchResultListener& operator<<(const T& x);
+
+  // Returns the underlying ostream.
+  std::ostream* stream();
+};
+
+template <typename T>
+class MatcherInterface {
+ public:
+  virtual ~MatcherInterface();
+
+  // Returns true if and only if the matcher matches x; also explains the match
+  // result to 'listener'.
+  virtual bool MatchAndExplain(T x, MatchResultListener* listener) const = 0;
+
+  // Describes this matcher to an ostream.
+  virtual void DescribeTo(std::ostream* os) const = 0;
+
+  // Describes the negation of this matcher to an ostream.
+  virtual void DescribeNegationTo(std::ostream* os) const;
+};
+```
+
+Fortunately, most of the time you can define a polymorphic matcher easily with
+the help of `MakePolymorphicMatcher()`. Here's how you can define `NotNull()` as
+an example:
+
+```cpp
+using ::testing::MakePolymorphicMatcher;
+using ::testing::MatchResultListener;
+using ::testing::PolymorphicMatcher;
+
+class NotNullMatcher {
+ public:
+  // To implement a polymorphic matcher, first define a COPYABLE class
+  // that has three members MatchAndExplain(), DescribeTo(), and
+  // DescribeNegationTo(), like the following.
+
+  // In this example, we want to use NotNull() with any pointer, so
+  // MatchAndExplain() accepts a pointer of any type as its first argument.
+  // In general, you can define MatchAndExplain() as an ordinary method or
+  // a method template, or even overload it.
+  template <typename T>
+  bool MatchAndExplain(T* p,
+                       MatchResultListener* /* listener */) const {
+    return p != NULL;
+  }
+
+  // Describes the property of a value matching this matcher.
+  void DescribeTo(std::ostream* os) const { *os << "is not NULL"; }
+
+  // Describes the property of a value NOT matching this matcher.
+  void DescribeNegationTo(std::ostream* os) const { *os << "is NULL"; }
+};
+
+// To construct a polymorphic matcher, pass an instance of the class
+// to MakePolymorphicMatcher().  Note the return type.
+PolymorphicMatcher<NotNullMatcher> NotNull() {
+  return MakePolymorphicMatcher(NotNullMatcher());
+}
+
+...
+
+  EXPECT_CALL(foo, Bar(NotNull()));  // The argument must be a non-NULL pointer.
+```
+
+{: .callout .note}
+**Note:** Your polymorphic matcher class does **not** need to inherit from
+`MatcherInterface` or any other class, and its methods do **not** need to be
+virtual.
+
+Like in a monomorphic matcher, you may explain the match result by streaming
+additional information to the `listener` argument in `MatchAndExplain()`.
+
+### Writing New Cardinalities
+
+A cardinality is used in `Times()` to tell gMock how many times you expect a
+call to occur. It doesn't have to be exact. For example, you can say
+`AtLeast(5)` or `Between(2, 4)`.
+
+If the [built-in set](gmock_cheat_sheet.md#CardinalityList) of cardinalities
+doesn't suit you, you are free to define your own by implementing the following
+interface (in namespace `testing`):
+
+```cpp
+class CardinalityInterface {
+ public:
+  virtual ~CardinalityInterface();
+
+  // Returns true if and only if call_count calls will satisfy this cardinality.
+  virtual bool IsSatisfiedByCallCount(int call_count) const = 0;
+
+  // Returns true if and only if call_count calls will saturate this
+  // cardinality.
+  virtual bool IsSaturatedByCallCount(int call_count) const = 0;
+
+  // Describes self to an ostream.
+  virtual void DescribeTo(std::ostream* os) const = 0;
+};
+```
+
+For example, to specify that a call must occur even number of times, you can
+write
+
+```cpp
+using ::testing::Cardinality;
+using ::testing::CardinalityInterface;
+using ::testing::MakeCardinality;
+
+class EvenNumberCardinality : public CardinalityInterface {
+ public:
+  bool IsSatisfiedByCallCount(int call_count) const override {
+    return (call_count % 2) == 0;
+  }
+
+  bool IsSaturatedByCallCount(int call_count) const override {
+    return false;
+  }
+
+  void DescribeTo(std::ostream* os) const {
+    *os << "called even number of times";
+  }
+};
+
+Cardinality EvenNumber() {
+  return MakeCardinality(new EvenNumberCardinality);
+}
+
+...
+  EXPECT_CALL(foo, Bar(3))
+      .Times(EvenNumber());
+```
+
+### Writing New Actions {#QuickNewActions}
+
+If the built-in actions don't work for you, you can easily define your own one.
+All you need is a call operator with a signature compatible with the mocked
+function. So you can use a lambda:
+
+```cpp
+MockFunction<int(int)> mock;
+EXPECT_CALL(mock, Call).WillOnce([](const int input) { return input * 7; });
+EXPECT_EQ(mock.AsStdFunction()(2), 14);
+```
+
+Or a struct with a call operator (even a templated one):
+
+```cpp
+struct MultiplyBy {
+  template <typename T>
+  T operator()(T arg) { return arg * multiplier; }
+
+  int multiplier;
+};
+
+// Then use:
+// EXPECT_CALL(...).WillOnce(MultiplyBy{7});
+```
+
+It's also fine for the callable to take no arguments, ignoring the arguments
+supplied to the mock function:
+
+```cpp
+MockFunction<int(int)> mock;
+EXPECT_CALL(mock, Call).WillOnce([] { return 17; });
+EXPECT_EQ(mock.AsStdFunction()(0), 17);
+```
+
+When used with `WillOnce`, the callable can assume it will be called at most
+once and is allowed to be a move-only type:
+
+```cpp
+// An action that contains move-only types and has an &&-qualified operator,
+// demanding in the type system that it be called at most once. This can be
+// used with WillOnce, but the compiler will reject it if handed to
+// WillRepeatedly.
+struct MoveOnlyAction {
+  std::unique_ptr<int> move_only_state;
+  std::unique_ptr<int> operator()() && { return std::move(move_only_state); }
+};
+
+MockFunction<std::unique_ptr<int>()> mock;
+EXPECT_CALL(mock, Call).WillOnce(MoveOnlyAction{std::make_unique<int>(17)});
+EXPECT_THAT(mock.AsStdFunction()(), Pointee(Eq(17)));
+```
+
+More generally, to use with a mock function whose signature is `R(Args...)` the
+object can be anything convertible to `OnceAction<R(Args...)>` or
+`Action<R(Args...)`>. The difference between the two is that `OnceAction` has
+weaker requirements (`Action` requires a copy-constructible input that can be
+called repeatedly whereas `OnceAction` requires only move-constructible and
+supports `&&`-qualified call operators), but can be used only with `WillOnce`.
+`OnceAction` is typically relevant only when supporting move-only types or
+actions that want a type-system guarantee that they will be called at most once.
+
+Typically the `OnceAction` and `Action` templates need not be referenced
+directly in your actions: a struct or class with a call operator is sufficient,
+as in the examples above. But fancier polymorphic actions that need to know the
+specific return type of the mock function can define templated conversion
+operators to make that possible. See `gmock-actions.h` for examples.
+
+#### Legacy macro-based Actions
+
+Before C++11, the functor-based actions were not supported; the old way of
+writing actions was through a set of `ACTION*` macros. We suggest to avoid them
+in new code; they hide a lot of logic behind the macro, potentially leading to
+harder-to-understand compiler errors. Nevertheless, we cover them here for
+completeness.
+
+By writing
+
+```cpp
+ACTION(name) { statements; }
+```
+
+in a namespace scope (i.e. not inside a class or function), you will define an
+action with the given name that executes the statements. The value returned by
+`statements` will be used as the return value of the action. Inside the
+statements, you can refer to the K-th (0-based) argument of the mock function as
+`argK`. For example:
+
+```cpp
+ACTION(IncrementArg1) { return ++(*arg1); }
+```
+
+allows you to write
+
+```cpp
+... WillOnce(IncrementArg1());
+```
+
+Note that you don't need to specify the types of the mock function arguments.
+Rest assured that your code is type-safe though: you'll get a compiler error if
+`*arg1` doesn't support the `++` operator, or if the type of `++(*arg1)` isn't
+compatible with the mock function's return type.
+
+Another example:
+
+```cpp
+ACTION(Foo) {
+  (*arg2)(5);
+  Blah();
+  *arg1 = 0;
+  return arg0;
+}
+```
+
+defines an action `Foo()` that invokes argument #2 (a function pointer) with 5,
+calls function `Blah()`, sets the value pointed to by argument #1 to 0, and
+returns argument #0.
+
+For more convenience and flexibility, you can also use the following pre-defined
+symbols in the body of `ACTION`:
+
+`argK_type`     | The type of the K-th (0-based) argument of the mock function
+:-------------- | :-----------------------------------------------------------
+`args`          | All arguments of the mock function as a tuple
+`args_type`     | The type of all arguments of the mock function as a tuple
+`return_type`   | The return type of the mock function
+`function_type` | The type of the mock function
+
+For example, when using an `ACTION` as a stub action for mock function:
+
+```cpp
+int DoSomething(bool flag, int* ptr);
+```
+
+we have:
+
+Pre-defined Symbol | Is Bound To
+------------------ | ---------------------------------
+`arg0`             | the value of `flag`
+`arg0_type`        | the type `bool`
+`arg1`             | the value of `ptr`
+`arg1_type`        | the type `int*`
+`args`             | the tuple `(flag, ptr)`
+`args_type`        | the type `std::tuple<bool, int*>`
+`return_type`      | the type `int`
+`function_type`    | the type `int(bool, int*)`
+
+#### Legacy macro-based parameterized Actions
+
+Sometimes you'll want to parameterize an action you define. For that we have
+another macro
+
+```cpp
+ACTION_P(name, param) { statements; }
+```
+
+For example,
+
+```cpp
+ACTION_P(Add, n) { return arg0 + n; }
+```
+
+will allow you to write
+
+```cpp
+// Returns argument #0 + 5.
+... WillOnce(Add(5));
+```
+
+For convenience, we use the term *arguments* for the values used to invoke the
+mock function, and the term *parameters* for the values used to instantiate an
+action.
+
+Note that you don't need to provide the type of the parameter either. Suppose
+the parameter is named `param`, you can also use the gMock-defined symbol
+`param_type` to refer to the type of the parameter as inferred by the compiler.
+For example, in the body of `ACTION_P(Add, n)` above, you can write `n_type` for
+the type of `n`.
+
+gMock also provides `ACTION_P2`, `ACTION_P3`, and etc to support multi-parameter
+actions. For example,
+
+```cpp
+ACTION_P2(ReturnDistanceTo, x, y) {
+  double dx = arg0 - x;
+  double dy = arg1 - y;
+  return sqrt(dx*dx + dy*dy);
+}
+```
+
+lets you write
+
+```cpp
+... WillOnce(ReturnDistanceTo(5.0, 26.5));
+```
+
+You can view `ACTION` as a degenerated parameterized action where the number of
+parameters is 0.
+
+You can also easily define actions overloaded on the number of parameters:
+
+```cpp
+ACTION_P(Plus, a) { ... }
+ACTION_P2(Plus, a, b) { ... }
+```
+
+### Restricting the Type of an Argument or Parameter in an ACTION
+
+For maximum brevity and reusability, the `ACTION*` macros don't ask you to
+provide the types of the mock function arguments and the action parameters.
+Instead, we let the compiler infer the types for us.
+
+Sometimes, however, we may want to be more explicit about the types. There are
+several tricks to do that. For example:
+
+```cpp
+ACTION(Foo) {
+  // Makes sure arg0 can be converted to int.
+  int n = arg0;
+  ... use n instead of arg0 here ...
+}
+
+ACTION_P(Bar, param) {
+  // Makes sure the type of arg1 is const char*.
+  ::testing::StaticAssertTypeEq<const char*, arg1_type>();
+
+  // Makes sure param can be converted to bool.
+  bool flag = param;
+}
+```
+
+where `StaticAssertTypeEq` is a compile-time assertion in googletest that
+verifies two types are the same.
+
+### Writing New Action Templates Quickly
+
+Sometimes you want to give an action explicit template parameters that cannot be
+inferred from its value parameters. `ACTION_TEMPLATE()` supports that and can be
+viewed as an extension to `ACTION()` and `ACTION_P*()`.
+
+The syntax:
+
+```cpp
+ACTION_TEMPLATE(ActionName,
+                HAS_m_TEMPLATE_PARAMS(kind1, name1, ..., kind_m, name_m),
+                AND_n_VALUE_PARAMS(p1, ..., p_n)) { statements; }
+```
+
+defines an action template that takes *m* explicit template parameters and *n*
+value parameters, where *m* is in [1, 10] and *n* is in [0, 10]. `name_i` is the
+name of the *i*-th template parameter, and `kind_i` specifies whether it's a
+`typename`, an integral constant, or a template. `p_i` is the name of the *i*-th
+value parameter.
+
+Example:
+
+```cpp
+// DuplicateArg<k, T>(output) converts the k-th argument of the mock
+// function to type T and copies it to *output.
+ACTION_TEMPLATE(DuplicateArg,
+                // Note the comma between int and k:
+                HAS_2_TEMPLATE_PARAMS(int, k, typename, T),
+                AND_1_VALUE_PARAMS(output)) {
+  *output = T(std::get<k>(args));
+}
+```
+
+To create an instance of an action template, write:
+
+```cpp
+ActionName<t1, ..., t_m>(v1, ..., v_n)
+```
+
+where the `t`s are the template arguments and the `v`s are the value arguments.
+The value argument types are inferred by the compiler. For example:
+
+```cpp
+using ::testing::_;
+...
+  int n;
+  EXPECT_CALL(mock, Foo).WillOnce(DuplicateArg<1, unsigned char>(&n));
+```
+
+If you want to explicitly specify the value argument types, you can provide
+additional template arguments:
+
+```cpp
+ActionName<t1, ..., t_m, u1, ..., u_k>(v1, ..., v_n)
+```
+
+where `u_i` is the desired type of `v_i`.
+
+`ACTION_TEMPLATE` and `ACTION`/`ACTION_P*` can be overloaded on the number of
+value parameters, but not on the number of template parameters. Without the
+restriction, the meaning of the following is unclear:
+
+```cpp
+  OverloadedAction<int, bool>(x);
+```
+
+Are we using a single-template-parameter action where `bool` refers to the type
+of `x`, or a two-template-parameter action where the compiler is asked to infer
+the type of `x`?
+
+### Using the ACTION Object's Type
+
+If you are writing a function that returns an `ACTION` object, you'll need to
+know its type. The type depends on the macro used to define the action and the
+parameter types. The rule is relatively simple:
+
+
+| Given Definition              | Expression          | Has Type              |
+| ----------------------------- | ------------------- | --------------------- |
+| `ACTION(Foo)`                 | `Foo()`             | `FooAction`           |
+| `ACTION_TEMPLATE(Foo, HAS_m_TEMPLATE_PARAMS(...), AND_0_VALUE_PARAMS())` | `Foo<t1, ..., t_m>()` | `FooAction<t1, ..., t_m>` |
+| `ACTION_P(Bar, param)`        | `Bar(int_value)`    | `BarActionP<int>`     |
+| `ACTION_TEMPLATE(Bar, HAS_m_TEMPLATE_PARAMS(...), AND_1_VALUE_PARAMS(p1))` | `Bar<t1, ..., t_m>(int_value)` | `BarActionP<t1, ..., t_m, int>` |
+| `ACTION_P2(Baz, p1, p2)`      | `Baz(bool_value, int_value)` | `BazActionP2<bool, int>` |
+| `ACTION_TEMPLATE(Baz, HAS_m_TEMPLATE_PARAMS(...), AND_2_VALUE_PARAMS(p1, p2))` | `Baz<t1, ..., t_m>(bool_value, int_value)` | `BazActionP2<t1, ..., t_m, bool, int>` |
+| ...                           | ...                 | ...                   |
+
+
+Note that we have to pick different suffixes (`Action`, `ActionP`, `ActionP2`,
+and etc) for actions with different numbers of value parameters, or the action
+definitions cannot be overloaded on the number of them.
+
+### Writing New Monomorphic Actions {#NewMonoActions}
+
+While the `ACTION*` macros are very convenient, sometimes they are
+inappropriate. For example, despite the tricks shown in the previous recipes,
+they don't let you directly specify the types of the mock function arguments and
+the action parameters, which in general leads to unoptimized compiler error
+messages that can baffle unfamiliar users. They also don't allow overloading
+actions based on parameter types without jumping through some hoops.
+
+An alternative to the `ACTION*` macros is to implement
+`::testing::ActionInterface<F>`, where `F` is the type of the mock function in
+which the action will be used. For example:
+
+```cpp
+template <typename F>
+class ActionInterface {
+ public:
+  virtual ~ActionInterface();
+
+  // Performs the action.  Result is the return type of function type
+  // F, and ArgumentTuple is the tuple of arguments of F.
+  //
+
+  // For example, if F is int(bool, const string&), then Result would
+  // be int, and ArgumentTuple would be std::tuple<bool, const string&>.
+  virtual Result Perform(const ArgumentTuple& args) = 0;
+};
+```
+
+```cpp
+using ::testing::_;
+using ::testing::Action;
+using ::testing::ActionInterface;
+using ::testing::MakeAction;
+
+typedef int IncrementMethod(int*);
+
+class IncrementArgumentAction : public ActionInterface<IncrementMethod> {
+ public:
+  int Perform(const std::tuple<int*>& args) override {
+    int* p = std::get<0>(args);  // Grabs the first argument.
+    return *p++;
+  }
+};
+
+Action<IncrementMethod> IncrementArgument() {
+  return MakeAction(new IncrementArgumentAction);
+}
+
+...
+  EXPECT_CALL(foo, Baz(_))
+      .WillOnce(IncrementArgument());
+
+  int n = 5;
+  foo.Baz(&n);  // Should return 5 and change n to 6.
+```
+
+### Writing New Polymorphic Actions {#NewPolyActions}
+
+The previous recipe showed you how to define your own action. This is all good,
+except that you need to know the type of the function in which the action will
+be used. Sometimes that can be a problem. For example, if you want to use the
+action in functions with *different* types (e.g. like `Return()` and
+`SetArgPointee()`).
+
+If an action can be used in several types of mock functions, we say it's
+*polymorphic*. The `MakePolymorphicAction()` function template makes it easy to
+define such an action:
+
+```cpp
+namespace testing {
+template <typename Impl>
+PolymorphicAction<Impl> MakePolymorphicAction(const Impl& impl);
+}  // namespace testing
+```
+
+As an example, let's define an action that returns the second argument in the
+mock function's argument list. The first step is to define an implementation
+class:
+
+```cpp
+class ReturnSecondArgumentAction {
+ public:
+  template <typename Result, typename ArgumentTuple>
+  Result Perform(const ArgumentTuple& args) const {
+    // To get the i-th (0-based) argument, use std::get(args).
+    return std::get<1>(args);
+  }
+};
+```
+
+This implementation class does *not* need to inherit from any particular class.
+What matters is that it must have a `Perform()` method template. This method
+template takes the mock function's arguments as a tuple in a **single**
+argument, and returns the result of the action. It can be either `const` or not,
+but must be invocable with exactly one template argument, which is the result
+type. In other words, you must be able to call `Perform<R>(args)` where `R` is
+the mock function's return type and `args` is its arguments in a tuple.
+
+Next, we use `MakePolymorphicAction()` to turn an instance of the implementation
+class into the polymorphic action we need. It will be convenient to have a
+wrapper for this:
+
+```cpp
+using ::testing::MakePolymorphicAction;
+using ::testing::PolymorphicAction;
+
+PolymorphicAction<ReturnSecondArgumentAction> ReturnSecondArgument() {
+  return MakePolymorphicAction(ReturnSecondArgumentAction());
+}
+```
+
+Now, you can use this polymorphic action the same way you use the built-in ones:
+
+```cpp
+using ::testing::_;
+
+class MockFoo : public Foo {
+ public:
+  MOCK_METHOD(int, DoThis, (bool flag, int n), (override));
+  MOCK_METHOD(string, DoThat, (int x, const char* str1, const char* str2),
+              (override));
+};
+
+  ...
+  MockFoo foo;
+  EXPECT_CALL(foo, DoThis).WillOnce(ReturnSecondArgument());
+  EXPECT_CALL(foo, DoThat).WillOnce(ReturnSecondArgument());
+  ...
+  foo.DoThis(true, 5);  // Will return 5.
+  foo.DoThat(1, "Hi", "Bye");  // Will return "Hi".
+```
+
+### Teaching gMock How to Print Your Values
+
+When an uninteresting or unexpected call occurs, gMock prints the argument
+values and the stack trace to help you debug. Assertion macros like
+`EXPECT_THAT` and `EXPECT_EQ` also print the values in question when the
+assertion fails. gMock and googletest do this using googletest's user-extensible
+value printer.
+
+This printer knows how to print built-in C++ types, native arrays, STL
+containers, and any type that supports the `<<` operator. For other types, it
+prints the raw bytes in the value and hopes that you the user can figure it out.
+[The GoogleTest advanced guide](advanced.md#teaching-googletest-how-to-print-your-values)
+explains how to extend the printer to do a better job at printing your
+particular type than to dump the bytes.
+
+## Useful Mocks Created Using gMock
+
+<!--#include file="includes/g3_testing_LOGs.md"-->
+<!--#include file="includes/g3_mock_callbacks.md"-->
+
+### Mock std::function {#MockFunction}
+
+`std::function` is a general function type introduced in C++11. It is a
+preferred way of passing callbacks to new interfaces. Functions are copyable,
+and are not usually passed around by pointer, which makes them tricky to mock.
+But fear not - `MockFunction` can help you with that.
+
+`MockFunction<R(T1, ..., Tn)>` has a mock method `Call()` with the signature:
+
+```cpp
+  R Call(T1, ..., Tn);
+```
+
+It also has a `AsStdFunction()` method, which creates a `std::function` proxy
+forwarding to Call:
+
+```cpp
+  std::function<R(T1, ..., Tn)> AsStdFunction();
+```
+
+To use `MockFunction`, first create `MockFunction` object and set up
+expectations on its `Call` method. Then pass proxy obtained from
+`AsStdFunction()` to the code you are testing. For example:
+
+```cpp
+TEST(FooTest, RunsCallbackWithBarArgument) {
+  // 1. Create a mock object.
+  MockFunction<int(string)> mock_function;
+
+  // 2. Set expectations on Call() method.
+  EXPECT_CALL(mock_function, Call("bar")).WillOnce(Return(1));
+
+  // 3. Exercise code that uses std::function.
+  Foo(mock_function.AsStdFunction());
+  // Foo's signature can be either of:
+  // void Foo(const std::function<int(string)>& fun);
+  // void Foo(std::function<int(string)> fun);
+
+  // 4. All expectations will be verified when mock_function
+  //     goes out of scope and is destroyed.
+}
+```
+
+Remember that function objects created with `AsStdFunction()` are just
+forwarders. If you create multiple of them, they will share the same set of
+expectations.
+
+Although `std::function` supports unlimited number of arguments, `MockFunction`
+implementation is limited to ten. If you ever hit that limit... well, your
+callback has bigger problems than being mockable. :-)
diff --git a/third_party/googletest/docs/gmock_faq.md b/third_party/googletest/docs/gmock_faq.md
new file mode 100644
index 0000000..8f220bf
--- /dev/null
+++ b/third_party/googletest/docs/gmock_faq.md
@@ -0,0 +1,390 @@
+# Legacy gMock FAQ
+
+### When I call a method on my mock object, the method for the real object is invoked instead. What's the problem?
+
+In order for a method to be mocked, it must be *virtual*, unless you use the
+[high-perf dependency injection technique](gmock_cook_book.md#MockingNonVirtualMethods).
+
+### Can I mock a variadic function?
+
+You cannot mock a variadic function (i.e. a function taking ellipsis (`...`)
+arguments) directly in gMock.
+
+The problem is that in general, there is *no way* for a mock object to know how
+many arguments are passed to the variadic method, and what the arguments' types
+are. Only the *author of the base class* knows the protocol, and we cannot look
+into his or her head.
+
+Therefore, to mock such a function, the *user* must teach the mock object how to
+figure out the number of arguments and their types. One way to do it is to
+provide overloaded versions of the function.
+
+Ellipsis arguments are inherited from C and not really a C++ feature. They are
+unsafe to use and don't work with arguments that have constructors or
+destructors. Therefore we recommend to avoid them in C++ as much as possible.
+
+### MSVC gives me warning C4301 or C4373 when I define a mock method with a const parameter. Why?
+
+If you compile this using Microsoft Visual C++ 2005 SP1:
+
+```cpp
+class Foo {
+  ...
+  virtual void Bar(const int i) = 0;
+};
+
+class MockFoo : public Foo {
+  ...
+  MOCK_METHOD(void, Bar, (const int i), (override));
+};
+```
+
+You may get the following warning:
+
+```shell
+warning C4301: 'MockFoo::Bar': overriding virtual function only differs from 'Foo::Bar' by const/volatile qualifier
+```
+
+This is a MSVC bug. The same code compiles fine with gcc, for example. If you
+use Visual C++ 2008 SP1, you would get the warning:
+
+```shell
+warning C4373: 'MockFoo::Bar': virtual function overrides 'Foo::Bar', previous versions of the compiler did not override when parameters only differed by const/volatile qualifiers
+```
+
+In C++, if you *declare* a function with a `const` parameter, the `const`
+modifier is ignored. Therefore, the `Foo` base class above is equivalent to:
+
+```cpp
+class Foo {
+  ...
+  virtual void Bar(int i) = 0;  // int or const int?  Makes no difference.
+};
+```
+
+In fact, you can *declare* `Bar()` with an `int` parameter, and define it with a
+`const int` parameter. The compiler will still match them up.
+
+Since making a parameter `const` is meaningless in the method declaration, we
+recommend to remove it in both `Foo` and `MockFoo`. That should workaround the
+VC bug.
+
+Note that we are talking about the *top-level* `const` modifier here. If the
+function parameter is passed by pointer or reference, declaring the pointee or
+referee as `const` is still meaningful. For example, the following two
+declarations are *not* equivalent:
+
+```cpp
+void Bar(int* p);         // Neither p nor *p is const.
+void Bar(const int* p);  // p is not const, but *p is.
+```
+
+### I can't figure out why gMock thinks my expectations are not satisfied. What should I do?
+
+You might want to run your test with `--gmock_verbose=info`. This flag lets
+gMock print a trace of every mock function call it receives. By studying the
+trace, you'll gain insights on why the expectations you set are not met.
+
+If you see the message "The mock function has no default action set, and its
+return type has no default value set.", then try
+[adding a default action](gmock_cheat_sheet.md#OnCall). Due to a known issue,
+unexpected calls on mocks without default actions don't print out a detailed
+comparison between the actual arguments and the expected arguments.
+
+### My program crashed and `ScopedMockLog` spit out tons of messages. Is it a gMock bug?
+
+gMock and `ScopedMockLog` are likely doing the right thing here.
+
+When a test crashes, the failure signal handler will try to log a lot of
+information (the stack trace, and the address map, for example). The messages
+are compounded if you have many threads with depth stacks. When `ScopedMockLog`
+intercepts these messages and finds that they don't match any expectations, it
+prints an error for each of them.
+
+You can learn to ignore the errors, or you can rewrite your expectations to make
+your test more robust, for example, by adding something like:
+
+```cpp
+using ::testing::AnyNumber;
+using ::testing::Not;
+...
+  // Ignores any log not done by us.
+  EXPECT_CALL(log, Log(_, Not(EndsWith("/my_file.cc")), _))
+      .Times(AnyNumber());
+```
+
+### How can I assert that a function is NEVER called?
+
+```cpp
+using ::testing::_;
+...
+  EXPECT_CALL(foo, Bar(_))
+      .Times(0);
+```
+
+### I have a failed test where gMock tells me TWICE that a particular expectation is not satisfied. Isn't this redundant?
+
+When gMock detects a failure, it prints relevant information (the mock function
+arguments, the state of relevant expectations, and etc) to help the user debug.
+If another failure is detected, gMock will do the same, including printing the
+state of relevant expectations.
+
+Sometimes an expectation's state didn't change between two failures, and you'll
+see the same description of the state twice. They are however *not* redundant,
+as they refer to *different points in time*. The fact they are the same *is*
+interesting information.
+
+### I get a heapcheck failure when using a mock object, but using a real object is fine. What can be wrong?
+
+Does the class (hopefully a pure interface) you are mocking have a virtual
+destructor?
+
+Whenever you derive from a base class, make sure its destructor is virtual.
+Otherwise Bad Things will happen. Consider the following code:
+
+```cpp
+class Base {
+ public:
+  // Not virtual, but should be.
+  ~Base() { ... }
+  ...
+};
+
+class Derived : public Base {
+ public:
+  ...
+ private:
+  std::string value_;
+};
+
+...
+  Base* p = new Derived;
+  ...
+  delete p;  // Surprise! ~Base() will be called, but ~Derived() will not
+                 // - value_ is leaked.
+```
+
+By changing `~Base()` to virtual, `~Derived()` will be correctly called when
+`delete p` is executed, and the heap checker will be happy.
+
+### The "newer expectations override older ones" rule makes writing expectations awkward. Why does gMock do that?
+
+When people complain about this, often they are referring to code like:
+
+```cpp
+using ::testing::Return;
+...
+  // foo.Bar() should be called twice, return 1 the first time, and return
+  // 2 the second time.  However, I have to write the expectations in the
+  // reverse order.  This sucks big time!!!
+  EXPECT_CALL(foo, Bar())
+      .WillOnce(Return(2))
+      .RetiresOnSaturation();
+  EXPECT_CALL(foo, Bar())
+      .WillOnce(Return(1))
+      .RetiresOnSaturation();
+```
+
+The problem, is that they didn't pick the **best** way to express the test's
+intent.
+
+By default, expectations don't have to be matched in *any* particular order. If
+you want them to match in a certain order, you need to be explicit. This is
+gMock's (and jMock's) fundamental philosophy: it's easy to accidentally
+over-specify your tests, and we want to make it harder to do so.
+
+There are two better ways to write the test spec. You could either put the
+expectations in sequence:
+
+```cpp
+using ::testing::Return;
+...
+  // foo.Bar() should be called twice, return 1 the first time, and return
+  // 2 the second time.  Using a sequence, we can write the expectations
+  // in their natural order.
+  {
+    InSequence s;
+    EXPECT_CALL(foo, Bar())
+        .WillOnce(Return(1))
+        .RetiresOnSaturation();
+    EXPECT_CALL(foo, Bar())
+        .WillOnce(Return(2))
+        .RetiresOnSaturation();
+  }
+```
+
+or you can put the sequence of actions in the same expectation:
+
+```cpp
+using ::testing::Return;
+...
+  // foo.Bar() should be called twice, return 1 the first time, and return
+  // 2 the second time.
+  EXPECT_CALL(foo, Bar())
+      .WillOnce(Return(1))
+      .WillOnce(Return(2))
+      .RetiresOnSaturation();
+```
+
+Back to the original questions: why does gMock search the expectations (and
+`ON_CALL`s) from back to front? Because this allows a user to set up a mock's
+behavior for the common case early (e.g. in the mock's constructor or the test
+fixture's set-up phase) and customize it with more specific rules later. If
+gMock searches from front to back, this very useful pattern won't be possible.
+
+### gMock prints a warning when a function without EXPECT_CALL is called, even if I have set its behavior using ON_CALL. Would it be reasonable not to show the warning in this case?
+
+When choosing between being neat and being safe, we lean toward the latter. So
+the answer is that we think it's better to show the warning.
+
+Often people write `ON_CALL`s in the mock object's constructor or `SetUp()`, as
+the default behavior rarely changes from test to test. Then in the test body
+they set the expectations, which are often different for each test. Having an
+`ON_CALL` in the set-up part of a test doesn't mean that the calls are expected.
+If there's no `EXPECT_CALL` and the method is called, it's possibly an error. If
+we quietly let the call go through without notifying the user, bugs may creep in
+unnoticed.
+
+If, however, you are sure that the calls are OK, you can write
+
+```cpp
+using ::testing::_;
+...
+  EXPECT_CALL(foo, Bar(_))
+      .WillRepeatedly(...);
+```
+
+instead of
+
+```cpp
+using ::testing::_;
+...
+  ON_CALL(foo, Bar(_))
+      .WillByDefault(...);
+```
+
+This tells gMock that you do expect the calls and no warning should be printed.
+
+Also, you can control the verbosity by specifying `--gmock_verbose=error`. Other
+values are `info` and `warning`. If you find the output too noisy when
+debugging, just choose a less verbose level.
+
+### How can I delete the mock function's argument in an action?
+
+If your mock function takes a pointer argument and you want to delete that
+argument, you can use testing::DeleteArg<N>() to delete the N'th (zero-indexed)
+argument:
+
+```cpp
+using ::testing::_;
+  ...
+  MOCK_METHOD(void, Bar, (X* x, const Y& y));
+  ...
+  EXPECT_CALL(mock_foo_, Bar(_, _))
+      .WillOnce(testing::DeleteArg<0>()));
+```
+
+### How can I perform an arbitrary action on a mock function's argument?
+
+If you find yourself needing to perform some action that's not supported by
+gMock directly, remember that you can define your own actions using
+[`MakeAction()`](#NewMonoActions) or
+[`MakePolymorphicAction()`](#NewPolyActions), or you can write a stub function
+and invoke it using [`Invoke()`](#FunctionsAsActions).
+
+```cpp
+using ::testing::_;
+using ::testing::Invoke;
+  ...
+  MOCK_METHOD(void, Bar, (X* p));
+  ...
+  EXPECT_CALL(mock_foo_, Bar(_))
+      .WillOnce(Invoke(MyAction(...)));
+```
+
+### My code calls a static/global function. Can I mock it?
+
+You can, but you need to make some changes.
+
+In general, if you find yourself needing to mock a static function, it's a sign
+that your modules are too tightly coupled (and less flexible, less reusable,
+less testable, etc). You are probably better off defining a small interface and
+call the function through that interface, which then can be easily mocked. It's
+a bit of work initially, but usually pays for itself quickly.
+
+This Google Testing Blog
+[post](https://testing.googleblog.com/2008/06/defeat-static-cling.html) says it
+excellently. Check it out.
+
+### My mock object needs to do complex stuff. It's a lot of pain to specify the actions. gMock sucks!
+
+I know it's not a question, but you get an answer for free any way. :-)
+
+With gMock, you can create mocks in C++ easily. And people might be tempted to
+use them everywhere. Sometimes they work great, and sometimes you may find them,
+well, a pain to use. So, what's wrong in the latter case?
+
+When you write a test without using mocks, you exercise the code and assert that
+it returns the correct value or that the system is in an expected state. This is
+sometimes called "state-based testing".
+
+Mocks are great for what some call "interaction-based" testing: instead of
+checking the system state at the very end, mock objects verify that they are
+invoked the right way and report an error as soon as it arises, giving you a
+handle on the precise context in which the error was triggered. This is often
+more effective and economical to do than state-based testing.
+
+If you are doing state-based testing and using a test double just to simulate
+the real object, you are probably better off using a fake. Using a mock in this
+case causes pain, as it's not a strong point for mocks to perform complex
+actions. If you experience this and think that mocks suck, you are just not
+using the right tool for your problem. Or, you might be trying to solve the
+wrong problem. :-)
+
+### I got a warning "Uninteresting function call encountered - default action taken.." Should I panic?
+
+By all means, NO! It's just an FYI. :-)
+
+What it means is that you have a mock function, you haven't set any expectations
+on it (by gMock's rule this means that you are not interested in calls to this
+function and therefore it can be called any number of times), and it is called.
+That's OK - you didn't say it's not OK to call the function!
+
+What if you actually meant to disallow this function to be called, but forgot to
+write `EXPECT_CALL(foo, Bar()).Times(0)`? While one can argue that it's the
+user's fault, gMock tries to be nice and prints you a note.
+
+So, when you see the message and believe that there shouldn't be any
+uninteresting calls, you should investigate what's going on. To make your life
+easier, gMock dumps the stack trace when an uninteresting call is encountered.
+From that you can figure out which mock function it is, and how it is called.
+
+### I want to define a custom action. Should I use Invoke() or implement the ActionInterface interface?
+
+Either way is fine - you want to choose the one that's more convenient for your
+circumstance.
+
+Usually, if your action is for a particular function type, defining it using
+`Invoke()` should be easier; if your action can be used in functions of
+different types (e.g. if you are defining `Return(*value*)`),
+`MakePolymorphicAction()` is easiest. Sometimes you want precise control on what
+types of functions the action can be used in, and implementing `ActionInterface`
+is the way to go here. See the implementation of `Return()` in `gmock-actions.h`
+for an example.
+
+### I use SetArgPointee() in WillOnce(), but gcc complains about "conflicting return type specified". What does it mean?
+
+You got this error as gMock has no idea what value it should return when the
+mock method is called. `SetArgPointee()` says what the side effect is, but
+doesn't say what the return value should be. You need `DoAll()` to chain a
+`SetArgPointee()` with a `Return()` that provides a value appropriate to the API
+being mocked.
+
+See this [recipe](gmock_cook_book.md#mocking-side-effects) for more details and
+an example.
+
+### I have a huge mock class, and Microsoft Visual C++ runs out of memory when compiling it. What can I do?
+
+We've noticed that when the `/clr` compiler flag is used, Visual C++ uses 5~6
+times as much memory when compiling a mock class. We suggest to avoid `/clr`
+when compiling native C++ mocks.
diff --git a/third_party/googletest/docs/gmock_for_dummies.md b/third_party/googletest/docs/gmock_for_dummies.md
new file mode 100644
index 0000000..9f24dca
--- /dev/null
+++ b/third_party/googletest/docs/gmock_for_dummies.md
@@ -0,0 +1,700 @@
+# gMock for Dummies
+
+## What Is gMock?
+
+When you write a prototype or test, often it's not feasible or wise to rely on
+real objects entirely. A **mock object** implements the same interface as a real
+object (so it can be used as one), but lets you specify at run time how it will
+be used and what it should do (which methods will be called? in which order? how
+many times? with what arguments? what will they return? etc).
+
+It is easy to confuse the term *fake objects* with mock objects. Fakes and mocks
+actually mean very different things in the Test-Driven Development (TDD)
+community:
+
+*   **Fake** objects have working implementations, but usually take some
+    shortcut (perhaps to make the operations less expensive), which makes them
+    not suitable for production. An in-memory file system would be an example of
+    a fake.
+*   **Mocks** are objects pre-programmed with *expectations*, which form a
+    specification of the calls they are expected to receive.
+
+If all this seems too abstract for you, don't worry - the most important thing
+to remember is that a mock allows you to check the *interaction* between itself
+and code that uses it. The difference between fakes and mocks shall become much
+clearer once you start to use mocks.
+
+**gMock** is a library (sometimes we also call it a "framework" to make it sound
+cool) for creating mock classes and using them. It does to C++ what
+jMock/EasyMock does to Java (well, more or less).
+
+When using gMock,
+
+1.  first, you use some simple macros to describe the interface you want to
+    mock, and they will expand to the implementation of your mock class;
+2.  next, you create some mock objects and specify its expectations and behavior
+    using an intuitive syntax;
+3.  then you exercise code that uses the mock objects. gMock will catch any
+    violation to the expectations as soon as it arises.
+
+## Why gMock?
+
+While mock objects help you remove unnecessary dependencies in tests and make
+them fast and reliable, using mocks manually in C++ is *hard*:
+
+*   Someone has to implement the mocks. The job is usually tedious and
+    error-prone. No wonder people go great distance to avoid it.
+*   The quality of those manually written mocks is a bit, uh, unpredictable. You
+    may see some really polished ones, but you may also see some that were
+    hacked up in a hurry and have all sorts of ad hoc restrictions.
+*   The knowledge you gained from using one mock doesn't transfer to the next
+    one.
+
+In contrast, Java and Python programmers have some fine mock frameworks (jMock,
+EasyMock, etc), which automate the creation of mocks. As a result, mocking is a
+proven effective technique and widely adopted practice in those communities.
+Having the right tool absolutely makes the difference.
+
+gMock was built to help C++ programmers. It was inspired by jMock and EasyMock,
+but designed with C++'s specifics in mind. It is your friend if any of the
+following problems is bothering you:
+
+*   You are stuck with a sub-optimal design and wish you had done more
+    prototyping before it was too late, but prototyping in C++ is by no means
+    "rapid".
+*   Your tests are slow as they depend on too many libraries or use expensive
+    resources (e.g. a database).
+*   Your tests are brittle as some resources they use are unreliable (e.g. the
+    network).
+*   You want to test how your code handles a failure (e.g. a file checksum
+    error), but it's not easy to cause one.
+*   You need to make sure that your module interacts with other modules in the
+    right way, but it's hard to observe the interaction; therefore you resort to
+    observing the side effects at the end of the action, but it's awkward at
+    best.
+*   You want to "mock out" your dependencies, except that they don't have mock
+    implementations yet; and, frankly, you aren't thrilled by some of those
+    hand-written mocks.
+
+We encourage you to use gMock as
+
+*   a *design* tool, for it lets you experiment with your interface design early
+    and often. More iterations lead to better designs!
+*   a *testing* tool to cut your tests' outbound dependencies and probe the
+    interaction between your module and its collaborators.
+
+## Getting Started
+
+gMock is bundled with googletest.
+
+## A Case for Mock Turtles
+
+Let's look at an example. Suppose you are developing a graphics program that
+relies on a [LOGO](https://en.wikipedia.org/wiki/Logo_programming_language)-like
+API for drawing. How would you test that it does the right thing? Well, you can
+run it and compare the screen with a golden screen snapshot, but let's admit it:
+tests like this are expensive to run and fragile (What if you just upgraded to a
+shiny new graphics card that has better anti-aliasing? Suddenly you have to
+update all your golden images.). It would be too painful if all your tests are
+like this. Fortunately, you learned about
+[Dependency Injection](https://en.wikipedia.org/wiki/Dependency_injection) and know the right thing
+to do: instead of having your application talk to the system API directly, wrap
+the API in an interface (say, `Turtle`) and code to that interface:
+
+```cpp
+class Turtle {
+  ...
+  virtual ~Turtle() {}
+  virtual void PenUp() = 0;
+  virtual void PenDown() = 0;
+  virtual void Forward(int distance) = 0;
+  virtual void Turn(int degrees) = 0;
+  virtual void GoTo(int x, int y) = 0;
+  virtual int GetX() const = 0;
+  virtual int GetY() const = 0;
+};
+```
+
+(Note that the destructor of `Turtle` **must** be virtual, as is the case for
+**all** classes you intend to inherit from - otherwise the destructor of the
+derived class will not be called when you delete an object through a base
+pointer, and you'll get corrupted program states like memory leaks.)
+
+You can control whether the turtle's movement will leave a trace using `PenUp()`
+and `PenDown()`, and control its movement using `Forward()`, `Turn()`, and
+`GoTo()`. Finally, `GetX()` and `GetY()` tell you the current position of the
+turtle.
+
+Your program will normally use a real implementation of this interface. In
+tests, you can use a mock implementation instead. This allows you to easily
+check what drawing primitives your program is calling, with what arguments, and
+in which order. Tests written this way are much more robust (they won't break
+because your new machine does anti-aliasing differently), easier to read and
+maintain (the intent of a test is expressed in the code, not in some binary
+images), and run *much, much faster*.
+
+## Writing the Mock Class
+
+If you are lucky, the mocks you need to use have already been implemented by
+some nice people. If, however, you find yourself in the position to write a mock
+class, relax - gMock turns this task into a fun game! (Well, almost.)
+
+### How to Define It
+
+Using the `Turtle` interface as example, here are the simple steps you need to
+follow:
+
+*   Derive a class `MockTurtle` from `Turtle`.
+*   Take a *virtual* function of `Turtle` (while it's possible to
+    [mock non-virtual methods using templates](gmock_cook_book.md#MockingNonVirtualMethods),
+    it's much more involved).
+*   In the `public:` section of the child class, write `MOCK_METHOD();`
+*   Now comes the fun part: you take the function signature, cut-and-paste it
+    into the macro, and add two commas - one between the return type and the
+    name, another between the name and the argument list.
+*   If you're mocking a const method, add a 4th parameter containing `(const)`
+    (the parentheses are required).
+*   Since you're overriding a virtual method, we suggest adding the `override`
+    keyword. For const methods the 4th parameter becomes `(const, override)`,
+    for non-const methods just `(override)`. This isn't mandatory.
+*   Repeat until all virtual functions you want to mock are done. (It goes
+    without saying that *all* pure virtual methods in your abstract class must
+    be either mocked or overridden.)
+
+After the process, you should have something like:
+
+```cpp
+#include <gmock/gmock.h>  // Brings in gMock.
+
+class MockTurtle : public Turtle {
+ public:
+  ...
+  MOCK_METHOD(void, PenUp, (), (override));
+  MOCK_METHOD(void, PenDown, (), (override));
+  MOCK_METHOD(void, Forward, (int distance), (override));
+  MOCK_METHOD(void, Turn, (int degrees), (override));
+  MOCK_METHOD(void, GoTo, (int x, int y), (override));
+  MOCK_METHOD(int, GetX, (), (const, override));
+  MOCK_METHOD(int, GetY, (), (const, override));
+};
+```
+
+You don't need to define these mock methods somewhere else - the `MOCK_METHOD`
+macro will generate the definitions for you. It's that simple!
+
+### Where to Put It
+
+When you define a mock class, you need to decide where to put its definition.
+Some people put it in a `_test.cc`. This is fine when the interface being mocked
+(say, `Foo`) is owned by the same person or team. Otherwise, when the owner of
+`Foo` changes it, your test could break. (You can't really expect `Foo`'s
+maintainer to fix every test that uses `Foo`, can you?)
+
+Generally, you should not mock classes you don't own. If you must mock such a
+class owned by others, define the mock class in `Foo`'s Bazel package (usually
+the same directory or a `testing` sub-directory), and put it in a `.h` and a
+`cc_library` with `testonly=True`. Then everyone can reference them from their
+tests. If `Foo` ever changes, there is only one copy of `MockFoo` to change, and
+only tests that depend on the changed methods need to be fixed.
+
+Another way to do it: you can introduce a thin layer `FooAdaptor` on top of
+`Foo` and code to this new interface. Since you own `FooAdaptor`, you can absorb
+changes in `Foo` much more easily. While this is more work initially, carefully
+choosing the adaptor interface can make your code easier to write and more
+readable (a net win in the long run), as you can choose `FooAdaptor` to fit your
+specific domain much better than `Foo` does.
+
+## Using Mocks in Tests
+
+Once you have a mock class, using it is easy. The typical work flow is:
+
+1.  Import the gMock names from the `testing` namespace such that you can use
+    them unqualified (You only have to do it once per file). Remember that
+    namespaces are a good idea.
+2.  Create some mock objects.
+3.  Specify your expectations on them (How many times will a method be called?
+    With what arguments? What should it do? etc.).
+4.  Exercise some code that uses the mocks; optionally, check the result using
+    googletest assertions. If a mock method is called more than expected or with
+    wrong arguments, you'll get an error immediately.
+5.  When a mock is destructed, gMock will automatically check whether all
+    expectations on it have been satisfied.
+
+Here's an example:
+
+```cpp
+#include "path/to/mock-turtle.h"
+#include <gmock/gmock.h>
+#include <gtest/gtest.h>
+
+using ::testing::AtLeast;                         // #1
+
+TEST(PainterTest, CanDrawSomething) {
+  MockTurtle turtle;                              // #2
+  EXPECT_CALL(turtle, PenDown())                  // #3
+      .Times(AtLeast(1));
+
+  Painter painter(&turtle);                       // #4
+
+  EXPECT_TRUE(painter.DrawCircle(0, 0, 10));      // #5
+}
+```
+
+As you might have guessed, this test checks that `PenDown()` is called at least
+once. If the `painter` object didn't call this method, your test will fail with
+a message like this:
+
+```text
+path/to/my_test.cc:119: Failure
+Actual function call count doesn't match this expectation:
+Actually: never called;
+Expected: called at least once.
+Stack trace:
+...
+```
+
+**Tip 1:** If you run the test from an Emacs buffer, you can hit `<Enter>` on
+the line number to jump right to the failed expectation.
+
+**Tip 2:** If your mock objects are never deleted, the final verification won't
+happen. Therefore it's a good idea to turn on the heap checker in your tests
+when you allocate mocks on the heap. You get that automatically if you use the
+`gtest_main` library already.
+
+**Important note:** gMock requires expectations to be set **before** the mock
+functions are called, otherwise the behavior is **undefined**. Do not alternate
+between calls to `EXPECT_CALL()` and calls to the mock functions, and do not set
+any expectations on a mock after passing the mock to an API.
+
+This means `EXPECT_CALL()` should be read as expecting that a call will occur
+*in the future*, not that a call has occurred. Why does gMock work like that?
+Well, specifying the expectation beforehand allows gMock to report a violation
+as soon as it rises, when the context (stack trace, etc) is still available.
+This makes debugging much easier.
+
+Admittedly, this test is contrived and doesn't do much. You can easily achieve
+the same effect without using gMock. However, as we shall reveal soon, gMock
+allows you to do *so much more* with the mocks.
+
+## Setting Expectations
+
+The key to using a mock object successfully is to set the *right expectations*
+on it. If you set the expectations too strict, your test will fail as the result
+of unrelated changes. If you set them too loose, bugs can slip through. You want
+to do it just right such that your test can catch exactly the kind of bugs you
+intend it to catch. gMock provides the necessary means for you to do it "just
+right."
+
+### General Syntax
+
+In gMock we use the `EXPECT_CALL()` macro to set an expectation on a mock
+method. The general syntax is:
+
+```cpp
+EXPECT_CALL(mock_object, method(matchers))
+    .Times(cardinality)
+    .WillOnce(action)
+    .WillRepeatedly(action);
+```
+
+The macro has two arguments: first the mock object, and then the method and its
+arguments. Note that the two are separated by a comma (`,`), not a period (`.`).
+(Why using a comma? The answer is that it was necessary for technical reasons.)
+If the method is not overloaded, the macro can also be called without matchers:
+
+```cpp
+EXPECT_CALL(mock_object, non-overloaded-method)
+    .Times(cardinality)
+    .WillOnce(action)
+    .WillRepeatedly(action);
+```
+
+This syntax allows the test writer to specify "called with any arguments"
+without explicitly specifying the number or types of arguments. To avoid
+unintended ambiguity, this syntax may only be used for methods that are not
+overloaded.
+
+Either form of the macro can be followed by some optional *clauses* that provide
+more information about the expectation. We'll discuss how each clause works in
+the coming sections.
+
+This syntax is designed to make an expectation read like English. For example,
+you can probably guess that
+
+```cpp
+using ::testing::Return;
+...
+EXPECT_CALL(turtle, GetX())
+    .Times(5)
+    .WillOnce(Return(100))
+    .WillOnce(Return(150))
+    .WillRepeatedly(Return(200));
+```
+
+says that the `turtle` object's `GetX()` method will be called five times, it
+will return 100 the first time, 150 the second time, and then 200 every time.
+Some people like to call this style of syntax a Domain-Specific Language (DSL).
+
+{: .callout .note}
+**Note:** Why do we use a macro to do this? Well it serves two purposes: first
+it makes expectations easily identifiable (either by `grep` or by a human
+reader), and second it allows gMock to include the source file location of a
+failed expectation in messages, making debugging easier.
+
+### Matchers: What Arguments Do We Expect?
+
+When a mock function takes arguments, we may specify what arguments we are
+expecting, for example:
+
+```cpp
+// Expects the turtle to move forward by 100 units.
+EXPECT_CALL(turtle, Forward(100));
+```
+
+Oftentimes you do not want to be too specific. Remember that talk about tests
+being too rigid? Over specification leads to brittle tests and obscures the
+intent of tests. Therefore we encourage you to specify only what's necessary—no
+more, no less. If you aren't interested in the value of an argument, write `_`
+as the argument, which means "anything goes":
+
+```cpp
+using ::testing::_;
+...
+// Expects that the turtle jumps to somewhere on the x=50 line.
+EXPECT_CALL(turtle, GoTo(50, _));
+```
+
+`_` is an instance of what we call **matchers**. A matcher is like a predicate
+and can test whether an argument is what we'd expect. You can use a matcher
+inside `EXPECT_CALL()` wherever a function argument is expected. `_` is a
+convenient way of saying "any value".
+
+In the above examples, `100` and `50` are also matchers; implicitly, they are
+the same as `Eq(100)` and `Eq(50)`, which specify that the argument must be
+equal (using `operator==`) to the matcher argument. There are many
+[built-in matchers](reference/matchers.md) for common types (as well as
+[custom matchers](gmock_cook_book.md#NewMatchers)); for example:
+
+```cpp
+using ::testing::Ge;
+...
+// Expects the turtle moves forward by at least 100.
+EXPECT_CALL(turtle, Forward(Ge(100)));
+```
+
+If you don't care about *any* arguments, rather than specify `_` for each of
+them you may instead omit the parameter list:
+
+```cpp
+// Expects the turtle to move forward.
+EXPECT_CALL(turtle, Forward);
+// Expects the turtle to jump somewhere.
+EXPECT_CALL(turtle, GoTo);
+```
+
+This works for all non-overloaded methods; if a method is overloaded, you need
+to help gMock resolve which overload is expected by specifying the number of
+arguments and possibly also the
+[types of the arguments](gmock_cook_book.md#SelectOverload).
+
+### Cardinalities: How Many Times Will It Be Called?
+
+The first clause we can specify following an `EXPECT_CALL()` is `Times()`. We
+call its argument a **cardinality** as it tells *how many times* the call should
+occur. It allows us to repeat an expectation many times without actually writing
+it as many times. More importantly, a cardinality can be "fuzzy", just like a
+matcher can be. This allows a user to express the intent of a test exactly.
+
+An interesting special case is when we say `Times(0)`. You may have guessed - it
+means that the function shouldn't be called with the given arguments at all, and
+gMock will report a googletest failure whenever the function is (wrongfully)
+called.
+
+We've seen `AtLeast(n)` as an example of fuzzy cardinalities earlier. For the
+list of built-in cardinalities you can use, see
+[here](gmock_cheat_sheet.md#CardinalityList).
+
+The `Times()` clause can be omitted. **If you omit `Times()`, gMock will infer
+the cardinality for you.** The rules are easy to remember:
+
+*   If **neither** `WillOnce()` **nor** `WillRepeatedly()` is in the
+    `EXPECT_CALL()`, the inferred cardinality is `Times(1)`.
+*   If there are *n* `WillOnce()`'s but **no** `WillRepeatedly()`, where *n* >=
+    1, the cardinality is `Times(n)`.
+*   If there are *n* `WillOnce()`'s and **one** `WillRepeatedly()`, where *n* >=
+    0, the cardinality is `Times(AtLeast(n))`.
+
+**Quick quiz:** what do you think will happen if a function is expected to be
+called twice but actually called four times?
+
+### Actions: What Should It Do?
+
+Remember that a mock object doesn't really have a working implementation? We as
+users have to tell it what to do when a method is invoked. This is easy in
+gMock.
+
+First, if the return type of a mock function is a built-in type or a pointer,
+the function has a **default action** (a `void` function will just return, a
+`bool` function will return `false`, and other functions will return 0). In
+addition, in C++ 11 and above, a mock function whose return type is
+default-constructible (i.e. has a default constructor) has a default action of
+returning a default-constructed value. If you don't say anything, this behavior
+will be used.
+
+Second, if a mock function doesn't have a default action, or the default action
+doesn't suit you, you can specify the action to be taken each time the
+expectation matches using a series of `WillOnce()` clauses followed by an
+optional `WillRepeatedly()`. For example,
+
+```cpp
+using ::testing::Return;
+...
+EXPECT_CALL(turtle, GetX())
+     .WillOnce(Return(100))
+     .WillOnce(Return(200))
+     .WillOnce(Return(300));
+```
+
+says that `turtle.GetX()` will be called *exactly three times* (gMock inferred
+this from how many `WillOnce()` clauses we've written, since we didn't
+explicitly write `Times()`), and will return 100, 200, and 300 respectively.
+
+```cpp
+using ::testing::Return;
+...
+EXPECT_CALL(turtle, GetY())
+     .WillOnce(Return(100))
+     .WillOnce(Return(200))
+     .WillRepeatedly(Return(300));
+```
+
+says that `turtle.GetY()` will be called *at least twice* (gMock knows this as
+we've written two `WillOnce()` clauses and a `WillRepeatedly()` while having no
+explicit `Times()`), will return 100 and 200 respectively the first two times,
+and 300 from the third time on.
+
+Of course, if you explicitly write a `Times()`, gMock will not try to infer the
+cardinality itself. What if the number you specified is larger than there are
+`WillOnce()` clauses? Well, after all `WillOnce()`s are used up, gMock will do
+the *default* action for the function every time (unless, of course, you have a
+`WillRepeatedly()`.).
+
+What can we do inside `WillOnce()` besides `Return()`? You can return a
+reference using `ReturnRef(`*`variable`*`)`, or invoke a pre-defined function,
+among [others](gmock_cook_book.md#using-actions).
+
+**Important note:** The `EXPECT_CALL()` statement evaluates the action clause
+only once, even though the action may be performed many times. Therefore you
+must be careful about side effects. The following may not do what you want:
+
+```cpp
+using ::testing::Return;
+...
+int n = 100;
+EXPECT_CALL(turtle, GetX())
+    .Times(4)
+    .WillRepeatedly(Return(n++));
+```
+
+Instead of returning 100, 101, 102, ..., consecutively, this mock function will
+always return 100 as `n++` is only evaluated once. Similarly, `Return(new Foo)`
+will create a new `Foo` object when the `EXPECT_CALL()` is executed, and will
+return the same pointer every time. If you want the side effect to happen every
+time, you need to define a custom action, which we'll teach in the
+[cook book](gmock_cook_book.md).
+
+Time for another quiz! What do you think the following means?
+
+```cpp
+using ::testing::Return;
+...
+EXPECT_CALL(turtle, GetY())
+    .Times(4)
+    .WillOnce(Return(100));
+```
+
+Obviously `turtle.GetY()` is expected to be called four times. But if you think
+it will return 100 every time, think twice! Remember that one `WillOnce()`
+clause will be consumed each time the function is invoked and the default action
+will be taken afterwards. So the right answer is that `turtle.GetY()` will
+return 100 the first time, but **return 0 from the second time on**, as
+returning 0 is the default action for `int` functions.
+
+### Using Multiple Expectations {#MultiExpectations}
+
+So far we've only shown examples where you have a single expectation. More
+realistically, you'll specify expectations on multiple mock methods which may be
+from multiple mock objects.
+
+By default, when a mock method is invoked, gMock will search the expectations in
+the **reverse order** they are defined, and stop when an active expectation that
+matches the arguments is found (you can think of it as "newer rules override
+older ones."). If the matching expectation cannot take any more calls, you will
+get an upper-bound-violated failure. Here's an example:
+
+```cpp
+using ::testing::_;
+...
+EXPECT_CALL(turtle, Forward(_));  // #1
+EXPECT_CALL(turtle, Forward(10))  // #2
+    .Times(2);
+```
+
+If `Forward(10)` is called three times in a row, the third time it will be an
+error, as the last matching expectation (#2) has been saturated. If, however,
+the third `Forward(10)` call is replaced by `Forward(20)`, then it would be OK,
+as now #1 will be the matching expectation.
+
+{: .callout .note}
+**Note:** Why does gMock search for a match in the *reverse* order of the
+expectations? The reason is that this allows a user to set up the default
+expectations in a mock object's constructor or the test fixture's set-up phase
+and then customize the mock by writing more specific expectations in the test
+body. So, if you have two expectations on the same method, you want to put the
+one with more specific matchers **after** the other, or the more specific rule
+would be shadowed by the more general one that comes after it.
+
+{: .callout .tip}
+**Tip:** It is very common to start with a catch-all expectation for a method
+and `Times(AnyNumber())` (omitting arguments, or with `_` for all arguments, if
+overloaded). This makes any calls to the method expected. This is not necessary
+for methods that are not mentioned at all (these are "uninteresting"), but is
+useful for methods that have some expectations, but for which other calls are
+ok. See
+[Understanding Uninteresting vs Unexpected Calls](gmock_cook_book.md#uninteresting-vs-unexpected).
+
+### Ordered vs Unordered Calls {#OrderedCalls}
+
+By default, an expectation can match a call even though an earlier expectation
+hasn't been satisfied. In other words, the calls don't have to occur in the
+order the expectations are specified.
+
+Sometimes, you may want all the expected calls to occur in a strict order. To
+say this in gMock is easy:
+
+```cpp
+using ::testing::InSequence;
+...
+TEST(FooTest, DrawsLineSegment) {
+  ...
+  {
+    InSequence seq;
+
+    EXPECT_CALL(turtle, PenDown());
+    EXPECT_CALL(turtle, Forward(100));
+    EXPECT_CALL(turtle, PenUp());
+  }
+  Foo();
+}
+```
+
+By creating an object of type `InSequence`, all expectations in its scope are
+put into a *sequence* and have to occur *sequentially*. Since we are just
+relying on the constructor and destructor of this object to do the actual work,
+its name is really irrelevant.
+
+In this example, we test that `Foo()` calls the three expected functions in the
+order as written. If a call is made out-of-order, it will be an error.
+
+(What if you care about the relative order of some of the calls, but not all of
+them? Can you specify an arbitrary partial order? The answer is ... yes! The
+details can be found [here](gmock_cook_book.md#OrderedCalls).)
+
+### All Expectations Are Sticky (Unless Said Otherwise) {#StickyExpectations}
+
+Now let's do a quick quiz to see how well you can use this mock stuff already.
+How would you test that the turtle is asked to go to the origin *exactly twice*
+(you want to ignore any other instructions it receives)?
+
+After you've come up with your answer, take a look at ours and compare notes
+(solve it yourself first - don't cheat!):
+
+```cpp
+using ::testing::_;
+using ::testing::AnyNumber;
+...
+EXPECT_CALL(turtle, GoTo(_, _))  // #1
+     .Times(AnyNumber());
+EXPECT_CALL(turtle, GoTo(0, 0))  // #2
+     .Times(2);
+```
+
+Suppose `turtle.GoTo(0, 0)` is called three times. In the third time, gMock will
+see that the arguments match expectation #2 (remember that we always pick the
+last matching expectation). Now, since we said that there should be only two
+such calls, gMock will report an error immediately. This is basically what we've
+told you in the [Using Multiple Expectations](#MultiExpectations) section above.
+
+This example shows that **expectations in gMock are "sticky" by default**, in
+the sense that they remain active even after we have reached their invocation
+upper bounds. This is an important rule to remember, as it affects the meaning
+of the spec, and is **different** to how it's done in many other mocking
+frameworks (Why'd we do that? Because we think our rule makes the common cases
+easier to express and understand.).
+
+Simple? Let's see if you've really understood it: what does the following code
+say?
+
+```cpp
+using ::testing::Return;
+...
+for (int i = n; i > 0; i--) {
+  EXPECT_CALL(turtle, GetX())
+      .WillOnce(Return(10*i));
+}
+```
+
+If you think it says that `turtle.GetX()` will be called `n` times and will
+return 10, 20, 30, ..., consecutively, think twice! The problem is that, as we
+said, expectations are sticky. So, the second time `turtle.GetX()` is called,
+the last (latest) `EXPECT_CALL()` statement will match, and will immediately
+lead to an "upper bound violated" error - this piece of code is not very useful!
+
+One correct way of saying that `turtle.GetX()` will return 10, 20, 30, ..., is
+to explicitly say that the expectations are *not* sticky. In other words, they
+should *retire* as soon as they are saturated:
+
+```cpp
+using ::testing::Return;
+...
+for (int i = n; i > 0; i--) {
+  EXPECT_CALL(turtle, GetX())
+      .WillOnce(Return(10*i))
+      .RetiresOnSaturation();
+}
+```
+
+And, there's a better way to do it: in this case, we expect the calls to occur
+in a specific order, and we line up the actions to match the order. Since the
+order is important here, we should make it explicit using a sequence:
+
+```cpp
+using ::testing::InSequence;
+using ::testing::Return;
+...
+{
+  InSequence s;
+
+  for (int i = 1; i <= n; i++) {
+    EXPECT_CALL(turtle, GetX())
+        .WillOnce(Return(10*i))
+        .RetiresOnSaturation();
+  }
+}
+```
+
+By the way, the other situation where an expectation may *not* be sticky is when
+it's in a sequence - as soon as another expectation that comes after it in the
+sequence has been used, it automatically retires (and will never be used to
+match any call).
+
+### Uninteresting Calls
+
+A mock object may have many methods, and not all of them are that interesting.
+For example, in some tests we may not care about how many times `GetX()` and
+`GetY()` get called.
+
+In gMock, if you are not interested in a method, just don't say anything about
+it. If a call to this method occurs, you'll see a warning in the test output,
+but it won't be a failure. This is called "naggy" behavior; to change, see
+[The Nice, the Strict, and the Naggy](gmock_cook_book.md#NiceStrictNaggy).
diff --git a/third_party/googletest/docs/index.md b/third_party/googletest/docs/index.md
new file mode 100644
index 0000000..b162c74
--- /dev/null
+++ b/third_party/googletest/docs/index.md
@@ -0,0 +1,22 @@
+# GoogleTest User's Guide
+
+## Welcome to GoogleTest!
+
+GoogleTest is Google's C++ testing and mocking framework. This user's guide has
+the following contents:
+
+*   [GoogleTest Primer](primer.md) - Teaches you how to write simple tests using
+    GoogleTest. Read this first if you are new to GoogleTest.
+*   [GoogleTest Advanced](advanced.md) - Read this when you've finished the
+    Primer and want to utilize GoogleTest to its full potential.
+*   [GoogleTest Samples](samples.md) - Describes some GoogleTest samples.
+*   [GoogleTest FAQ](faq.md) - Have a question? Want some tips? Check here
+    first.
+*   [Mocking for Dummies](gmock_for_dummies.md) - Teaches you how to create mock
+    objects and use them in tests.
+*   [Mocking Cookbook](gmock_cook_book.md) - Includes tips and approaches to
+    common mocking use cases.
+*   [Mocking Cheat Sheet](gmock_cheat_sheet.md) - A handy reference for
+    matchers, actions, invariants, and more.
+*   [Mocking FAQ](gmock_faq.md) - Contains answers to some mocking-specific
+    questions.
diff --git a/third_party/googletest/docs/pkgconfig.md b/third_party/googletest/docs/pkgconfig.md
new file mode 100644
index 0000000..bf05d59
--- /dev/null
+++ b/third_party/googletest/docs/pkgconfig.md
@@ -0,0 +1,144 @@
+## Using GoogleTest from various build systems
+
+GoogleTest comes with pkg-config files that can be used to determine all
+necessary flags for compiling and linking to GoogleTest (and GoogleMock).
+Pkg-config is a standardised plain-text format containing
+
+*   the includedir (-I) path
+*   necessary macro (-D) definitions
+*   further required flags (-pthread)
+*   the library (-L) path
+*   the library (-l) to link to
+
+All current build systems support pkg-config in one way or another. For all
+examples here we assume you want to compile the sample
+`samples/sample3_unittest.cc`.
+
+### CMake
+
+Using `pkg-config` in CMake is fairly easy:
+
+```cmake
+find_package(PkgConfig)
+pkg_search_module(GTEST REQUIRED gtest_main)
+
+add_executable(testapp)
+target_sources(testapp PRIVATE samples/sample3_unittest.cc)
+target_link_libraries(testapp PRIVATE ${GTEST_LDFLAGS})
+target_compile_options(testapp PRIVATE ${GTEST_CFLAGS})
+
+enable_testing()
+add_test(first_and_only_test testapp)
+```
+
+It is generally recommended that you use `target_compile_options` + `_CFLAGS`
+over `target_include_directories` + `_INCLUDE_DIRS` as the former includes not
+just -I flags (GoogleTest might require a macro indicating to internal headers
+that all libraries have been compiled with threading enabled. In addition,
+GoogleTest might also require `-pthread` in the compiling step, and as such
+splitting the pkg-config `Cflags` variable into include dirs and macros for
+`target_compile_definitions()` might still miss this). The same recommendation
+goes for using `_LDFLAGS` over the more commonplace `_LIBRARIES`, which happens
+to discard `-L` flags and `-pthread`.
+
+### Help! pkg-config can't find GoogleTest!
+
+Let's say you have a `CMakeLists.txt` along the lines of the one in this
+tutorial and you try to run `cmake`. It is very possible that you get a failure
+along the lines of:
+
+```
+-- Checking for one of the modules 'gtest_main'
+CMake Error at /usr/share/cmake/Modules/FindPkgConfig.cmake:640 (message):
+  None of the required 'gtest_main' found
+```
+
+These failures are common if you installed GoogleTest yourself and have not
+sourced it from a distro or other package manager. If so, you need to tell
+pkg-config where it can find the `.pc` files containing the information. Say you
+installed GoogleTest to `/usr/local`, then it might be that the `.pc` files are
+installed under `/usr/local/lib64/pkgconfig`. If you set
+
+```
+export PKG_CONFIG_PATH=/usr/local/lib64/pkgconfig
+```
+
+pkg-config will also try to look in `PKG_CONFIG_PATH` to find `gtest_main.pc`.
+
+### Using pkg-config in a cross-compilation setting
+
+Pkg-config can be used in a cross-compilation setting too. To do this, let's
+assume the final prefix of the cross-compiled installation will be `/usr`, and
+your sysroot is `/home/MYUSER/sysroot`. Configure and install GTest using
+
+```
+mkdir build && cmake -DCMAKE_INSTALL_PREFIX=/usr ..
+```
+
+Install into the sysroot using `DESTDIR`:
+
+```
+make -j install DESTDIR=/home/MYUSER/sysroot
+```
+
+Before we continue, it is recommended to **always** define the following two
+variables for pkg-config in a cross-compilation setting:
+
+```
+export PKG_CONFIG_ALLOW_SYSTEM_CFLAGS=yes
+export PKG_CONFIG_ALLOW_SYSTEM_LIBS=yes
+```
+
+otherwise `pkg-config` will filter `-I` and `-L` flags against standard prefixes
+such as `/usr` (see https://bugs.freedesktop.org/show_bug.cgi?id=28264#c3 for
+reasons why this stripping needs to occur usually).
+
+If you look at the generated pkg-config file, it will look something like
+
+```
+libdir=/usr/lib64
+includedir=/usr/include
+
+Name: gtest
+Description: GoogleTest (without main() function)
+Version: 1.11.0
+URL: https://github.com/google/googletest
+Libs: -L${libdir} -lgtest -lpthread
+Cflags: -I${includedir} -DGTEST_HAS_PTHREAD=1 -lpthread
+```
+
+Notice that the sysroot is not included in `libdir` and `includedir`! If you try
+to run `pkg-config` with the correct
+`PKG_CONFIG_LIBDIR=/home/MYUSER/sysroot/usr/lib64/pkgconfig` against this `.pc`
+file, you will get
+
+```
+$ pkg-config --cflags gtest
+-DGTEST_HAS_PTHREAD=1 -lpthread -I/usr/include
+$ pkg-config --libs gtest
+-L/usr/lib64 -lgtest -lpthread
+```
+
+which is obviously wrong and points to the `CBUILD` and not `CHOST` root. In
+order to use this in a cross-compilation setting, we need to tell pkg-config to
+inject the actual sysroot into `-I` and `-L` variables. Let us now tell
+pkg-config about the actual sysroot
+
+```
+export PKG_CONFIG_DIR=
+export PKG_CONFIG_SYSROOT_DIR=/home/MYUSER/sysroot
+export PKG_CONFIG_LIBDIR=${PKG_CONFIG_SYSROOT_DIR}/usr/lib64/pkgconfig
+```
+
+and running `pkg-config` again we get
+
+```
+$ pkg-config --cflags gtest
+-DGTEST_HAS_PTHREAD=1 -lpthread -I/home/MYUSER/sysroot/usr/include
+$ pkg-config --libs gtest
+-L/home/MYUSER/sysroot/usr/lib64 -lgtest -lpthread
+```
+
+which contains the correct sysroot now. For a more comprehensive guide to also
+including `${CHOST}` in build system calls, see the excellent tutorial by Diego
+Elio Pettenò: <https://autotools.io/pkgconfig/cross-compiling.html>
diff --git a/third_party/googletest/docs/platforms.md b/third_party/googletest/docs/platforms.md
new file mode 100644
index 0000000..d35a7be
--- /dev/null
+++ b/third_party/googletest/docs/platforms.md
@@ -0,0 +1,8 @@
+# Supported Platforms
+
+GoogleTest follows Google's
+[Foundational C++ Support Policy](https://opensource.google/documentation/policies/cplusplus-support).
+See
+[this table](https://github.com/google/oss-policies-info/blob/main/foundational-cxx-support-matrix.md)
+for a list of currently supported versions compilers, platforms, and build
+tools.
diff --git a/third_party/googletest/docs/primer.md b/third_party/googletest/docs/primer.md
new file mode 100644
index 0000000..4901e1a
--- /dev/null
+++ b/third_party/googletest/docs/primer.md
@@ -0,0 +1,483 @@
+# GoogleTest Primer
+
+## Introduction: Why GoogleTest?
+
+*GoogleTest* helps you write better C++ tests.
+
+GoogleTest is a testing framework developed by the Testing Technology team with
+Google's specific requirements and constraints in mind. Whether you work on
+Linux, Windows, or a Mac, if you write C++ code, GoogleTest can help you. And it
+supports *any* kind of tests, not just unit tests.
+
+So what makes a good test, and how does GoogleTest fit in? We believe:
+
+1.  Tests should be *independent* and *repeatable*. It's a pain to debug a test
+    that succeeds or fails as a result of other tests. GoogleTest isolates the
+    tests by running each of them on a different object. When a test fails,
+    GoogleTest allows you to run it in isolation for quick debugging.
+2.  Tests should be well *organized* and reflect the structure of the tested
+    code. GoogleTest groups related tests into test suites that can share data
+    and subroutines. This common pattern is easy to recognize and makes tests
+    easy to maintain. Such consistency is especially helpful when people switch
+    projects and start to work on a new code base.
+3.  Tests should be *portable* and *reusable*. Google has a lot of code that is
+    platform-neutral; its tests should also be platform-neutral. GoogleTest
+    works on different OSes, with different compilers, with or without
+    exceptions, so GoogleTest tests can work with a variety of configurations.
+4.  When tests fail, they should provide as much *information* about the problem
+    as possible. GoogleTest doesn't stop at the first test failure. Instead, it
+    only stops the current test and continues with the next. You can also set up
+    tests that report non-fatal failures after which the current test continues.
+    Thus, you can detect and fix multiple bugs in a single run-edit-compile
+    cycle.
+5.  The testing framework should liberate test writers from housekeeping chores
+    and let them focus on the test *content*. GoogleTest automatically keeps
+    track of all tests defined, and doesn't require the user to enumerate them
+    in order to run them.
+6.  Tests should be *fast*. With GoogleTest, you can reuse shared resources
+    across tests and pay for the set-up/tear-down only once, without making
+    tests depend on each other.
+
+Since GoogleTest is based on the popular xUnit architecture, you'll feel right
+at home if you've used JUnit or PyUnit before. If not, it will take you about 10
+minutes to learn the basics and get started. So let's go!
+
+## Beware of the Nomenclature
+
+{: .callout .note}
+*Note:* There might be some confusion arising from different definitions of the
+terms *Test*, *Test Case* and *Test Suite*, so beware of misunderstanding these.
+
+Historically, GoogleTest started to use the term *Test Case* for grouping
+related tests, whereas current publications, including International Software
+Testing Qualifications Board ([ISTQB](https://www.istqb.org/)) materials and
+various textbooks on software quality, use the term
+*[Test Suite][istqb test suite]* for this.
+
+The related term *Test*, as it is used in GoogleTest, corresponds to the term
+*[Test Case][istqb test case]* of ISTQB and others.
+
+The term *Test* is commonly of broad enough sense, including ISTQB's definition
+of *Test Case*, so it's not much of a problem here. But the term *Test Case* as
+was used in Google Test is of contradictory sense and thus confusing.
+
+GoogleTest recently started replacing the term *Test Case* with *Test Suite*.
+The preferred API is *TestSuite*. The older TestCase API is being slowly
+deprecated and refactored away.
+
+So please be aware of the different definitions of the terms:
+
+
+Meaning                                                                              | GoogleTest Term         | [ISTQB](https://www.istqb.org/) Term
+:----------------------------------------------------------------------------------- | :---------------------- | :----------------------------------
+Exercise a particular program path with specific input values and verify the results | [TEST()](#simple-tests) | [Test Case][istqb test case]
+
+
+[istqb test case]: https://glossary.istqb.org/en/search/test%20case
+[istqb test suite]: https://glossary.istqb.org/en/search/test%20suite
+
+## Basic Concepts
+
+When using GoogleTest, you start by writing *assertions*, which are statements
+that check whether a condition is true. An assertion's result can be *success*,
+*nonfatal failure*, or *fatal failure*. If a fatal failure occurs, it aborts the
+current function; otherwise the program continues normally.
+
+*Tests* use assertions to verify the tested code's behavior. If a test crashes
+or has a failed assertion, then it *fails*; otherwise it *succeeds*.
+
+A *test suite* contains one or many tests. You should group your tests into test
+suites that reflect the structure of the tested code. When multiple tests in a
+test suite need to share common objects and subroutines, you can put them into a
+*test fixture* class.
+
+A *test program* can contain multiple test suites.
+
+We'll now explain how to write a test program, starting at the individual
+assertion level and building up to tests and test suites.
+
+## Assertions
+
+GoogleTest assertions are macros that resemble function calls. You test a class
+or function by making assertions about its behavior. When an assertion fails,
+GoogleTest prints the assertion's source file and line number location, along
+with a failure message. You may also supply a custom failure message which will
+be appended to GoogleTest's message.
+
+The assertions come in pairs that test the same thing but have different effects
+on the current function. `ASSERT_*` versions generate fatal failures when they
+fail, and **abort the current function**. `EXPECT_*` versions generate nonfatal
+failures, which don't abort the current function. Usually `EXPECT_*` are
+preferred, as they allow more than one failure to be reported in a test.
+However, you should use `ASSERT_*` if it doesn't make sense to continue when the
+assertion in question fails.
+
+Since a failed `ASSERT_*` returns from the current function immediately,
+possibly skipping clean-up code that comes after it, it may cause a space leak.
+Depending on the nature of the leak, it may or may not be worth fixing - so keep
+this in mind if you get a heap checker error in addition to assertion errors.
+
+To provide a custom failure message, simply stream it into the macro using the
+`<<` operator or a sequence of such operators. See the following example, using
+the [`ASSERT_EQ` and `EXPECT_EQ`](reference/assertions.md#EXPECT_EQ) macros to
+verify value equality:
+
+```c++
+ASSERT_EQ(x.size(), y.size()) << "Vectors x and y are of unequal length";
+
+for (int i = 0; i < x.size(); ++i) {
+  EXPECT_EQ(x[i], y[i]) << "Vectors x and y differ at index " << i;
+}
+```
+
+Anything that can be streamed to an `ostream` can be streamed to an assertion
+macro--in particular, C strings and `string` objects. If a wide string
+(`wchar_t*`, `TCHAR*` in `UNICODE` mode on Windows, or `std::wstring`) is
+streamed to an assertion, it will be translated to UTF-8 when printed.
+
+GoogleTest provides a collection of assertions for verifying the behavior of
+your code in various ways. You can check Boolean conditions, compare values
+based on relational operators, verify string values, floating-point values, and
+much more. There are even assertions that enable you to verify more complex
+states by providing custom predicates. For the complete list of assertions
+provided by GoogleTest, see the [Assertions Reference](reference/assertions.md).
+
+## Simple Tests
+
+To create a test:
+
+1.  Use the `TEST()` macro to define and name a test function. These are
+    ordinary C++ functions that don't return a value.
+2.  In this function, along with any valid C++ statements you want to include,
+    use the various GoogleTest assertions to check values.
+3.  The test's result is determined by the assertions; if any assertion in the
+    test fails (either fatally or non-fatally), or if the test crashes, the
+    entire test fails. Otherwise, it succeeds.
+
+```c++
+TEST(TestSuiteName, TestName) {
+  ... test body ...
+}
+```
+
+`TEST()` arguments go from general to specific. The *first* argument is the name
+of the test suite, and the *second* argument is the test's name within the test
+suite. Both names must be valid C++ identifiers, and they should not contain any
+underscores (`_`). A test's *full name* consists of its containing test suite
+and its individual name. Tests from different test suites can have the same
+individual name.
+
+For example, let's take a simple integer function:
+
+```c++
+int Factorial(int n);  // Returns the factorial of n
+```
+
+A test suite for this function might look like:
+
+```c++
+// Tests factorial of 0.
+TEST(FactorialTest, HandlesZeroInput) {
+  EXPECT_EQ(Factorial(0), 1);
+}
+
+// Tests factorial of positive numbers.
+TEST(FactorialTest, HandlesPositiveInput) {
+  EXPECT_EQ(Factorial(1), 1);
+  EXPECT_EQ(Factorial(2), 2);
+  EXPECT_EQ(Factorial(3), 6);
+  EXPECT_EQ(Factorial(8), 40320);
+}
+```
+
+GoogleTest groups the test results by test suites, so logically related tests
+should be in the same test suite; in other words, the first argument to their
+`TEST()` should be the same. In the above example, we have two tests,
+`HandlesZeroInput` and `HandlesPositiveInput`, that belong to the same test
+suite `FactorialTest`.
+
+When naming your test suites and tests, you should follow the same convention as
+for
+[naming functions and classes](https://google.github.io/styleguide/cppguide.html#Function_Names).
+
+**Availability**: Linux, Windows, Mac.
+
+## Test Fixtures: Using the Same Data Configuration for Multiple Tests {#same-data-multiple-tests}
+
+If you find yourself writing two or more tests that operate on similar data, you
+can use a *test fixture*. This allows you to reuse the same configuration of
+objects for several different tests.
+
+To create a fixture:
+
+1.  Derive a class from `::testing::Test` . Start its body with `protected:`, as
+    we'll want to access fixture members from sub-classes.
+2.  Inside the class, declare any objects you plan to use.
+3.  If necessary, write a default constructor or `SetUp()` function to prepare
+    the objects for each test. A common mistake is to spell `SetUp()` as
+    **`Setup()`** with a small `u` - Use `override` in C++11 to make sure you
+    spelled it correctly.
+4.  If necessary, write a destructor or `TearDown()` function to release any
+    resources you allocated in `SetUp()` . To learn when you should use the
+    constructor/destructor and when you should use `SetUp()/TearDown()`, read
+    the [FAQ](faq.md#CtorVsSetUp).
+5.  If needed, define subroutines for your tests to share.
+
+When using a fixture, use `TEST_F()` instead of `TEST()` as it allows you to
+access objects and subroutines in the test fixture:
+
+```c++
+TEST_F(TestFixtureClassName, TestName) {
+  ... test body ...
+}
+```
+
+Unlike `TEST()`, in `TEST_F()` the first argument must be the name of the test
+fixture class. (`_F` stands for "Fixture"). No test suite name is specified for
+this macro.
+
+Unfortunately, the C++ macro system does not allow us to create a single macro
+that can handle both types of tests. Using the wrong macro causes a compiler
+error.
+
+Also, you must first define a test fixture class before using it in a
+`TEST_F()`, or you'll get the compiler error "`virtual outside class
+declaration`".
+
+For each test defined with `TEST_F()`, GoogleTest will create a *fresh* test
+fixture at runtime, immediately initialize it via `SetUp()`, run the test, clean
+up by calling `TearDown()`, and then delete the test fixture. Note that
+different tests in the same test suite have different test fixture objects, and
+GoogleTest always deletes a test fixture before it creates the next one.
+GoogleTest does **not** reuse the same test fixture for multiple tests. Any
+changes one test makes to the fixture do not affect other tests.
+
+As an example, let's write tests for a FIFO queue class named `Queue`, which has
+the following interface:
+
+```c++
+template <typename E>  // E is the element type.
+class Queue {
+ public:
+  Queue();
+  void Enqueue(const E& element);
+  E* Dequeue();  // Returns NULL if the queue is empty.
+  size_t size() const;
+  ...
+};
+```
+
+First, define a fixture class. By convention, you should give it the name
+`FooTest` where `Foo` is the class being tested.
+
+```c++
+class QueueTest : public ::testing::Test {
+ protected:
+  void SetUp() override {
+     // q0_ remains empty
+     q1_.Enqueue(1);
+     q2_.Enqueue(2);
+     q2_.Enqueue(3);
+  }
+
+  // void TearDown() override {}
+
+  Queue<int> q0_;
+  Queue<int> q1_;
+  Queue<int> q2_;
+};
+```
+
+In this case, `TearDown()` is not needed since we don't have to clean up after
+each test, other than what's already done by the destructor.
+
+Now we'll write tests using `TEST_F()` and this fixture.
+
+```c++
+TEST_F(QueueTest, IsEmptyInitially) {
+  EXPECT_EQ(q0_.size(), 0);
+}
+
+TEST_F(QueueTest, DequeueWorks) {
+  int* n = q0_.Dequeue();
+  EXPECT_EQ(n, nullptr);
+
+  n = q1_.Dequeue();
+  ASSERT_NE(n, nullptr);
+  EXPECT_EQ(*n, 1);
+  EXPECT_EQ(q1_.size(), 0);
+  delete n;
+
+  n = q2_.Dequeue();
+  ASSERT_NE(n, nullptr);
+  EXPECT_EQ(*n, 2);
+  EXPECT_EQ(q2_.size(), 1);
+  delete n;
+}
+```
+
+The above uses both `ASSERT_*` and `EXPECT_*` assertions. The rule of thumb is
+to use `EXPECT_*` when you want the test to continue to reveal more errors after
+the assertion failure, and use `ASSERT_*` when continuing after failure doesn't
+make sense. For example, the second assertion in the `Dequeue` test is
+`ASSERT_NE(n, nullptr)`, as we need to dereference the pointer `n` later, which
+would lead to a segfault when `n` is `NULL`.
+
+When these tests run, the following happens:
+
+1.  GoogleTest constructs a `QueueTest` object (let's call it `t1`).
+2.  `t1.SetUp()` initializes `t1`.
+3.  The first test (`IsEmptyInitially`) runs on `t1`.
+4.  `t1.TearDown()` cleans up after the test finishes.
+5.  `t1` is destructed.
+6.  The above steps are repeated on another `QueueTest` object, this time
+    running the `DequeueWorks` test.
+
+**Availability**: Linux, Windows, Mac.
+
+## Invoking the Tests
+
+`TEST()` and `TEST_F()` implicitly register their tests with GoogleTest. So,
+unlike with many other C++ testing frameworks, you don't have to re-list all
+your defined tests in order to run them.
+
+After defining your tests, you can run them with `RUN_ALL_TESTS()`, which
+returns `0` if all the tests are successful, or `1` otherwise. Note that
+`RUN_ALL_TESTS()` runs *all tests* in your link unit--they can be from different
+test suites, or even different source files.
+
+When invoked, the `RUN_ALL_TESTS()` macro:
+
+*   Saves the state of all GoogleTest flags.
+
+*   Creates a test fixture object for the first test.
+
+*   Initializes it via `SetUp()`.
+
+*   Runs the test on the fixture object.
+
+*   Cleans up the fixture via `TearDown()`.
+
+*   Deletes the fixture.
+
+*   Restores the state of all GoogleTest flags.
+
+*   Repeats the above steps for the next test, until all tests have run.
+
+If a fatal failure happens the subsequent steps will be skipped.
+
+{: .callout .important}
+> IMPORTANT: You must **not** ignore the return value of `RUN_ALL_TESTS()`, or
+> you will get a compiler error. The rationale for this design is that the
+> automated testing service determines whether a test has passed based on its
+> exit code, not on its stdout/stderr output; thus your `main()` function must
+> return the value of `RUN_ALL_TESTS()`.
+>
+> Also, you should call `RUN_ALL_TESTS()` only **once**. Calling it more than
+> once conflicts with some advanced GoogleTest features (e.g., thread-safe
+> [death tests](advanced.md#death-tests)) and thus is not supported.
+
+**Availability**: Linux, Windows, Mac.
+
+## Writing the main() Function
+
+Most users should *not* need to write their own `main` function and instead link
+with `gtest_main` (as opposed to with `gtest`), which defines a suitable entry
+point. See the end of this section for details. The remainder of this section
+should only apply when you need to do something custom before the tests run that
+cannot be expressed within the framework of fixtures and test suites.
+
+If you write your own `main` function, it should return the value of
+`RUN_ALL_TESTS()`.
+
+You can start from this boilerplate:
+
+```c++
+#include "this/package/foo.h"
+
+#include <gtest/gtest.h>
+
+namespace my {
+namespace project {
+namespace {
+
+// The fixture for testing class Foo.
+class FooTest : public ::testing::Test {
+ protected:
+  // You can remove any or all of the following functions if their bodies would
+  // be empty.
+
+  FooTest() {
+     // You can do set-up work for each test here.
+  }
+
+  ~FooTest() override {
+     // You can do clean-up work that doesn't throw exceptions here.
+  }
+
+  // If the constructor and destructor are not enough for setting up
+  // and cleaning up each test, you can define the following methods:
+
+  void SetUp() override {
+     // Code here will be called immediately after the constructor (right
+     // before each test).
+  }
+
+  void TearDown() override {
+     // Code here will be called immediately after each test (right
+     // before the destructor).
+  }
+
+  // Class members declared here can be used by all tests in the test suite
+  // for Foo.
+};
+
+// Tests that the Foo::Bar() method does Abc.
+TEST_F(FooTest, MethodBarDoesAbc) {
+  const std::string input_filepath = "this/package/testdata/myinputfile.dat";
+  const std::string output_filepath = "this/package/testdata/myoutputfile.dat";
+  Foo f;
+  EXPECT_EQ(f.Bar(input_filepath, output_filepath), 0);
+}
+
+// Tests that Foo does Xyz.
+TEST_F(FooTest, DoesXyz) {
+  // Exercises the Xyz feature of Foo.
+}
+
+}  // namespace
+}  // namespace project
+}  // namespace my
+
+int main(int argc, char **argv) {
+  ::testing::InitGoogleTest(&argc, argv);
+  return RUN_ALL_TESTS();
+}
+```
+
+The `::testing::InitGoogleTest()` function parses the command line for
+GoogleTest flags, and removes all recognized flags. This allows the user to
+control a test program's behavior via various flags, which we'll cover in the
+[AdvancedGuide](advanced.md). You **must** call this function before calling
+`RUN_ALL_TESTS()`, or the flags won't be properly initialized.
+
+On Windows, `InitGoogleTest()` also works with wide strings, so it can be used
+in programs compiled in `UNICODE` mode as well.
+
+But maybe you think that writing all those `main` functions is too much work? We
+agree with you completely, and that's why Google Test provides a basic
+implementation of main(). If it fits your needs, then just link your test with
+the `gtest_main` library and you are good to go.
+
+{: .callout .note}
+NOTE: `ParseGUnitFlags()` is deprecated in favor of `InitGoogleTest()`.
+
+## Known Limitations
+
+*   Google Test is designed to be thread-safe. The implementation is thread-safe
+    on systems where the `pthreads` library is available. It is currently
+    *unsafe* to use Google Test assertions from two threads concurrently on
+    other systems (e.g. Windows). In most tests this is not an issue as usually
+    the assertions are done in the main thread. If you want to help, you can
+    volunteer to implement the necessary synchronization primitives in
+    `gtest-port.h` for your platform.
diff --git a/third_party/googletest/docs/quickstart-bazel.md b/third_party/googletest/docs/quickstart-bazel.md
new file mode 100644
index 0000000..4f693db
--- /dev/null
+++ b/third_party/googletest/docs/quickstart-bazel.md
@@ -0,0 +1,153 @@
+# Quickstart: Building with Bazel
+
+This tutorial aims to get you up and running with GoogleTest using the Bazel
+build system. If you're using GoogleTest for the first time or need a refresher,
+we recommend this tutorial as a starting point.
+
+## Prerequisites
+
+To complete this tutorial, you'll need:
+
+*   A compatible operating system (e.g. Linux, macOS, Windows).
+*   A compatible C++ compiler that supports at least C++14.
+*   [Bazel](https://bazel.build/), the preferred build system used by the
+    GoogleTest team.
+
+See [Supported Platforms](platforms.md) for more information about platforms
+compatible with GoogleTest.
+
+If you don't already have Bazel installed, see the
+[Bazel installation guide](https://bazel.build/install).
+
+{: .callout .note} Note: The terminal commands in this tutorial show a Unix
+shell prompt, but the commands work on the Windows command line as well.
+
+## Set up a Bazel workspace
+
+A
+[Bazel workspace](https://docs.bazel.build/versions/main/build-ref.html#workspace)
+is a directory on your filesystem that you use to manage source files for the
+software you want to build. Each workspace directory has a text file named
+`WORKSPACE` which may be empty, or may contain references to external
+dependencies required to build the outputs.
+
+First, create a directory for your workspace:
+
+```
+$ mkdir my_workspace && cd my_workspace
+```
+
+Next, you’ll create the `WORKSPACE` file to specify dependencies. A common and
+recommended way to depend on GoogleTest is to use a
+[Bazel external dependency](https://docs.bazel.build/versions/main/external.html)
+via the
+[`http_archive` rule](https://docs.bazel.build/versions/main/repo/http.html#http_archive).
+To do this, in the root directory of your workspace (`my_workspace/`), create a
+file named `WORKSPACE` with the following contents:
+
+```
+load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
+
+http_archive(
+  name = "com_google_googletest",
+  urls = ["https://github.com/google/googletest/archive/5ab508a01f9eb089207ee87fd547d290da39d015.zip"],
+  strip_prefix = "googletest-5ab508a01f9eb089207ee87fd547d290da39d015",
+)
+```
+
+The above configuration declares a dependency on GoogleTest which is downloaded
+as a ZIP archive from GitHub. In the above example,
+`5ab508a01f9eb089207ee87fd547d290da39d015` is the Git commit hash of the
+GoogleTest version to use; we recommend updating the hash often to point to the
+latest version. Use a recent hash on the `main` branch.
+
+Now you're ready to build C++ code that uses GoogleTest.
+
+## Create and run a binary
+
+With your Bazel workspace set up, you can now use GoogleTest code within your
+own project.
+
+As an example, create a file named `hello_test.cc` in your `my_workspace`
+directory with the following contents:
+
+```cpp
+#include <gtest/gtest.h>
+
+// Demonstrate some basic assertions.
+TEST(HelloTest, BasicAssertions) {
+  // Expect two strings not to be equal.
+  EXPECT_STRNE("hello", "world");
+  // Expect equality.
+  EXPECT_EQ(7 * 6, 42);
+}
+```
+
+GoogleTest provides [assertions](primer.md#assertions) that you use to test the
+behavior of your code. The above sample includes the main GoogleTest header file
+and demonstrates some basic assertions.
+
+To build the code, create a file named `BUILD` in the same directory with the
+following contents:
+
+```
+cc_test(
+  name = "hello_test",
+  size = "small",
+  srcs = ["hello_test.cc"],
+  deps = ["@com_google_googletest//:gtest_main"],
+)
+```
+
+This `cc_test` rule declares the C++ test binary you want to build, and links to
+GoogleTest (`//:gtest_main`) using the prefix you specified in the `WORKSPACE`
+file (`@com_google_googletest`). For more information about Bazel `BUILD` files,
+see the
+[Bazel C++ Tutorial](https://docs.bazel.build/versions/main/tutorial/cpp.html).
+
+{: .callout .note}
+NOTE: In the example below, we assume Clang or GCC and set `--cxxopt=-std=c++14`
+to ensure that GoogleTest is compiled as C++14 instead of the compiler's default
+setting (which could be C++11). For MSVC, the equivalent would be
+`--cxxopt=/std:c++14`. See [Supported Platforms](platforms.md) for more details
+on supported language versions.
+
+Now you can build and run your test:
+
+<pre>
+<strong>my_workspace$ bazel test --cxxopt=-std=c++14 --test_output=all //:hello_test</strong>
+INFO: Analyzed target //:hello_test (26 packages loaded, 362 targets configured).
+INFO: Found 1 test target...
+INFO: From Testing //:hello_test:
+==================== Test output for //:hello_test:
+Running main() from gmock_main.cc
+[==========] Running 1 test from 1 test suite.
+[----------] Global test environment set-up.
+[----------] 1 test from HelloTest
+[ RUN      ] HelloTest.BasicAssertions
+[       OK ] HelloTest.BasicAssertions (0 ms)
+[----------] 1 test from HelloTest (0 ms total)
+
+[----------] Global test environment tear-down
+[==========] 1 test from 1 test suite ran. (0 ms total)
+[  PASSED  ] 1 test.
+================================================================================
+Target //:hello_test up-to-date:
+  bazel-bin/hello_test
+INFO: Elapsed time: 4.190s, Critical Path: 3.05s
+INFO: 27 processes: 8 internal, 19 linux-sandbox.
+INFO: Build completed successfully, 27 total actions
+//:hello_test                                                     PASSED in 0.1s
+
+INFO: Build completed successfully, 27 total actions
+</pre>
+
+Congratulations! You've successfully built and run a test binary using
+GoogleTest.
+
+## Next steps
+
+*   [Check out the Primer](primer.md) to start learning how to write simple
+    tests.
+*   [See the code samples](samples.md) for more examples showing how to use a
+    variety of GoogleTest features.
diff --git a/third_party/googletest/docs/quickstart-cmake.md b/third_party/googletest/docs/quickstart-cmake.md
new file mode 100644
index 0000000..4e422b7
--- /dev/null
+++ b/third_party/googletest/docs/quickstart-cmake.md
@@ -0,0 +1,157 @@
+# Quickstart: Building with CMake
+
+This tutorial aims to get you up and running with GoogleTest using CMake. If
+you're using GoogleTest for the first time or need a refresher, we recommend
+this tutorial as a starting point. If your project uses Bazel, see the
+[Quickstart for Bazel](quickstart-bazel.md) instead.
+
+## Prerequisites
+
+To complete this tutorial, you'll need:
+
+*   A compatible operating system (e.g. Linux, macOS, Windows).
+*   A compatible C++ compiler that supports at least C++14.
+*   [CMake](https://cmake.org/) and a compatible build tool for building the
+    project.
+    *   Compatible build tools include
+        [Make](https://www.gnu.org/software/make/),
+        [Ninja](https://ninja-build.org/), and others - see
+        [CMake Generators](https://cmake.org/cmake/help/latest/manual/cmake-generators.7.html)
+        for more information.
+
+See [Supported Platforms](platforms.md) for more information about platforms
+compatible with GoogleTest.
+
+If you don't already have CMake installed, see the
+[CMake installation guide](https://cmake.org/install).
+
+{: .callout .note}
+Note: The terminal commands in this tutorial show a Unix shell prompt, but the
+commands work on the Windows command line as well.
+
+## Set up a project
+
+CMake uses a file named `CMakeLists.txt` to configure the build system for a
+project. You'll use this file to set up your project and declare a dependency on
+GoogleTest.
+
+First, create a directory for your project:
+
+```
+$ mkdir my_project && cd my_project
+```
+
+Next, you'll create the `CMakeLists.txt` file and declare a dependency on
+GoogleTest. There are many ways to express dependencies in the CMake ecosystem;
+in this quickstart, you'll use the
+[`FetchContent` CMake module](https://cmake.org/cmake/help/latest/module/FetchContent.html).
+To do this, in your project directory (`my_project`), create a file named
+`CMakeLists.txt` with the following contents:
+
+```cmake
+cmake_minimum_required(VERSION 3.14)
+project(my_project)
+
+# GoogleTest requires at least C++14
+set(CMAKE_CXX_STANDARD 14)
+set(CMAKE_CXX_STANDARD_REQUIRED ON)
+
+include(FetchContent)
+FetchContent_Declare(
+  googletest
+  URL https://github.com/google/googletest/archive/03597a01ee50ed33e9dfd640b249b4be3799d395.zip
+)
+# For Windows: Prevent overriding the parent project's compiler/linker settings
+set(gtest_force_shared_crt ON CACHE BOOL "" FORCE)
+FetchContent_MakeAvailable(googletest)
+```
+
+The above configuration declares a dependency on GoogleTest which is downloaded
+from GitHub. In the above example, `03597a01ee50ed33e9dfd640b249b4be3799d395` is
+the Git commit hash of the GoogleTest version to use; we recommend updating the
+hash often to point to the latest version.
+
+For more information about how to create `CMakeLists.txt` files, see the
+[CMake Tutorial](https://cmake.org/cmake/help/latest/guide/tutorial/index.html).
+
+## Create and run a binary
+
+With GoogleTest declared as a dependency, you can use GoogleTest code within
+your own project.
+
+As an example, create a file named `hello_test.cc` in your `my_project`
+directory with the following contents:
+
+```cpp
+#include <gtest/gtest.h>
+
+// Demonstrate some basic assertions.
+TEST(HelloTest, BasicAssertions) {
+  // Expect two strings not to be equal.
+  EXPECT_STRNE("hello", "world");
+  // Expect equality.
+  EXPECT_EQ(7 * 6, 42);
+}
+```
+
+GoogleTest provides [assertions](primer.md#assertions) that you use to test the
+behavior of your code. The above sample includes the main GoogleTest header file
+and demonstrates some basic assertions.
+
+To build the code, add the following to the end of your `CMakeLists.txt` file:
+
+```cmake
+enable_testing()
+
+add_executable(
+  hello_test
+  hello_test.cc
+)
+target_link_libraries(
+  hello_test
+  GTest::gtest_main
+)
+
+include(GoogleTest)
+gtest_discover_tests(hello_test)
+```
+
+The above configuration enables testing in CMake, declares the C++ test binary
+you want to build (`hello_test`), and links it to GoogleTest (`gtest_main`). The
+last two lines enable CMake's test runner to discover the tests included in the
+binary, using the
+[`GoogleTest` CMake module](https://cmake.org/cmake/help/git-stage/module/GoogleTest.html).
+
+Now you can build and run your test:
+
+<pre>
+<strong>my_project$ cmake -S . -B build</strong>
+-- The C compiler identification is GNU 10.2.1
+-- The CXX compiler identification is GNU 10.2.1
+...
+-- Build files have been written to: .../my_project/build
+
+<strong>my_project$ cmake --build build</strong>
+Scanning dependencies of target gtest
+...
+[100%] Built target gmock_main
+
+<strong>my_project$ cd build && ctest</strong>
+Test project .../my_project/build
+    Start 1: HelloTest.BasicAssertions
+1/1 Test #1: HelloTest.BasicAssertions ........   Passed    0.00 sec
+
+100% tests passed, 0 tests failed out of 1
+
+Total Test time (real) =   0.01 sec
+</pre>
+
+Congratulations! You've successfully built and run a test binary using
+GoogleTest.
+
+## Next steps
+
+*   [Check out the Primer](primer.md) to start learning how to write simple
+    tests.
+*   [See the code samples](samples.md) for more examples showing how to use a
+    variety of GoogleTest features.
diff --git a/third_party/googletest/docs/reference/actions.md b/third_party/googletest/docs/reference/actions.md
new file mode 100644
index 0000000..ab81a12
--- /dev/null
+++ b/third_party/googletest/docs/reference/actions.md
@@ -0,0 +1,115 @@
+# Actions Reference
+
+[**Actions**](../gmock_for_dummies.md#actions-what-should-it-do) specify what a
+mock function should do when invoked. This page lists the built-in actions
+provided by GoogleTest. All actions are defined in the `::testing` namespace.
+
+## Returning a Value
+
+| Action                            | Description                                   |
+| :-------------------------------- | :-------------------------------------------- |
+| `Return()`                        | Return from a `void` mock function.           |
+| `Return(value)`                   | Return `value`. If the type of `value` is     different to the mock function's return type, `value` is converted to the latter type <i>at the time the expectation is set</i>, not when the action is executed. |
+| `ReturnArg<N>()`                  | Return the `N`-th (0-based) argument.         |
+| `ReturnNew<T>(a1, ..., ak)`       | Return `new T(a1, ..., ak)`; a different      object is created each time. |
+| `ReturnNull()`                    | Return a null pointer.                        |
+| `ReturnPointee(ptr)`              | Return the value pointed to by `ptr`.         |
+| `ReturnRef(variable)`             | Return a reference to `variable`.             |
+| `ReturnRefOfCopy(value)`          | Return a reference to a copy of `value`; the  copy lives as long as the action. |
+| `ReturnRoundRobin({a1, ..., ak})` | Each call will return the next `ai` in the list, starting at the beginning when the end of the list is reached. |
+
+## Side Effects
+
+| Action                             | Description                             |
+| :--------------------------------- | :-------------------------------------- |
+| `Assign(&variable, value)` | Assign `value` to variable. |
+| `DeleteArg<N>()` | Delete the `N`-th (0-based) argument, which must be a pointer. |
+| `SaveArg<N>(pointer)` | Save the `N`-th (0-based) argument to `*pointer`. |
+| `SaveArgPointee<N>(pointer)` | Save the value pointed to by the `N`-th (0-based) argument to `*pointer`. |
+| `SetArgReferee<N>(value)` | Assign `value` to the variable referenced by the `N`-th (0-based) argument. |
+| `SetArgPointee<N>(value)` | Assign `value` to the variable pointed by the `N`-th (0-based) argument. |
+| `SetArgumentPointee<N>(value)` | Same as `SetArgPointee<N>(value)`. Deprecated. Will be removed in v1.7.0. |
+| `SetArrayArgument<N>(first, last)` | Copies the elements in source range [`first`, `last`) to the array pointed to by the `N`-th (0-based) argument, which can be either a pointer or an iterator. The action does not take ownership of the elements in the source range. |
+| `SetErrnoAndReturn(error, value)` | Set `errno` to `error` and return `value`. |
+| `Throw(exception)` | Throws the given exception, which can be any copyable value. Available since v1.1.0. |
+
+## Using a Function, Functor, or Lambda as an Action
+
+In the following, by "callable" we mean a free function, `std::function`,
+functor, or lambda.
+
+| Action                              | Description                            |
+| :---------------------------------- | :------------------------------------- |
+| `f` | Invoke `f` with the arguments passed to the mock function, where `f` is a callable. |
+| `Invoke(f)` | Invoke `f` with the arguments passed to the mock function, where `f` can be a global/static function or a functor. |
+| `Invoke(object_pointer, &class::method)` | Invoke the method on the object with the arguments passed to the mock function. |
+| `InvokeWithoutArgs(f)` | Invoke `f`, which can be a global/static function or a functor. `f` must take no arguments. |
+| `InvokeWithoutArgs(object_pointer, &class::method)` | Invoke the method on the object, which takes no arguments. |
+| `InvokeArgument<N>(arg1, arg2, ..., argk)` | Invoke the mock function's `N`-th (0-based) argument, which must be a function or a functor, with the `k` arguments. |
+
+The return value of the invoked function is used as the return value of the
+action.
+
+When defining a callable to be used with `Invoke*()`, you can declare any unused
+parameters as `Unused`:
+
+```cpp
+using ::testing::Invoke;
+double Distance(Unused, double x, double y) { return sqrt(x*x + y*y); }
+...
+EXPECT_CALL(mock, Foo("Hi", _, _)).WillOnce(Invoke(Distance));
+```
+
+`Invoke(callback)` and `InvokeWithoutArgs(callback)` take ownership of
+`callback`, which must be permanent. The type of `callback` must be a base
+callback type instead of a derived one, e.g.
+
+```cpp
+  BlockingClosure* done = new BlockingClosure;
+  ... Invoke(done) ...;  // This won't compile!
+
+  Closure* done2 = new BlockingClosure;
+  ... Invoke(done2) ...;  // This works.
+```
+
+In `InvokeArgument<N>(...)`, if an argument needs to be passed by reference,
+wrap it inside `std::ref()`. For example,
+
+```cpp
+using ::testing::InvokeArgument;
+...
+InvokeArgument<2>(5, string("Hi"), std::ref(foo))
+```
+
+calls the mock function's #2 argument, passing to it `5` and `string("Hi")` by
+value, and `foo` by reference.
+
+## Default Action
+
+| Action        | Description                                            |
+| :------------ | :----------------------------------------------------- |
+| `DoDefault()` | Do the default action (specified by `ON_CALL()` or the built-in one). |
+
+{: .callout .note}
+**Note:** due to technical reasons, `DoDefault()` cannot be used inside a
+composite action - trying to do so will result in a run-time error.
+
+## Composite Actions
+
+| Action                         | Description                                 |
+| :----------------------------- | :------------------------------------------ |
+| `DoAll(a1, a2, ..., an)`       | Do all actions `a1` to `an` and return the result of `an` in each invocation. The first `n - 1` sub-actions must return void and will receive a  readonly view of the arguments. |
+| `IgnoreResult(a)`              | Perform action `a` and ignore its result. `a` must not return void. |
+| `WithArg<N>(a)`                | Pass the `N`-th (0-based) argument of the mock function to action `a` and perform it. |
+| `WithArgs<N1, N2, ..., Nk>(a)` | Pass the selected (0-based) arguments of the mock function to action `a` and perform it. |
+| `WithoutArgs(a)`               | Perform action `a` without any arguments. |
+
+## Defining Actions
+
+| Macro                              | Description                             |
+| :--------------------------------- | :-------------------------------------- |
+| `ACTION(Sum) { return arg0 + arg1; }` | Defines an action `Sum()` to return the sum of the mock function's argument #0 and #1. |
+| `ACTION_P(Plus, n) { return arg0 + n; }` | Defines an action `Plus(n)` to return the sum of the mock function's argument #0 and `n`. |
+| `ACTION_Pk(Foo, p1, ..., pk) { statements; }` | Defines a parameterized action `Foo(p1, ..., pk)` to execute the given `statements`. |
+
+The `ACTION*` macros cannot be used inside a function or class.
diff --git a/third_party/googletest/docs/reference/assertions.md b/third_party/googletest/docs/reference/assertions.md
new file mode 100644
index 0000000..492ff5e
--- /dev/null
+++ b/third_party/googletest/docs/reference/assertions.md
@@ -0,0 +1,633 @@
+# Assertions Reference
+
+This page lists the assertion macros provided by GoogleTest for verifying code
+behavior. To use them, add `#include <gtest/gtest.h>`.
+
+The majority of the macros listed below come as a pair with an `EXPECT_` variant
+and an `ASSERT_` variant. Upon failure, `EXPECT_` macros generate nonfatal
+failures and allow the current function to continue running, while `ASSERT_`
+macros generate fatal failures and abort the current function.
+
+All assertion macros support streaming a custom failure message into them with
+the `<<` operator, for example:
+
+```cpp
+EXPECT_TRUE(my_condition) << "My condition is not true";
+```
+
+Anything that can be streamed to an `ostream` can be streamed to an assertion
+macro—in particular, C strings and string objects. If a wide string (`wchar_t*`,
+`TCHAR*` in `UNICODE` mode on Windows, or `std::wstring`) is streamed to an
+assertion, it will be translated to UTF-8 when printed.
+
+## Explicit Success and Failure {#success-failure}
+
+The assertions in this section generate a success or failure directly instead of
+testing a value or expression. These are useful when control flow, rather than a
+Boolean expression, determines the test's success or failure, as shown by the
+following example:
+
+```c++
+switch(expression) {
+  case 1:
+    ... some checks ...
+  case 2:
+    ... some other checks ...
+  default:
+    FAIL() << "We shouldn't get here.";
+}
+```
+
+### SUCCEED {#SUCCEED}
+
+`SUCCEED()`
+
+Generates a success. This *does not* make the overall test succeed. A test is
+considered successful only if none of its assertions fail during its execution.
+
+The `SUCCEED` assertion is purely documentary and currently doesn't generate any
+user-visible output. However, we may add `SUCCEED` messages to GoogleTest output
+in the future.
+
+### FAIL {#FAIL}
+
+`FAIL()`
+
+Generates a fatal failure, which returns from the current function.
+
+Can only be used in functions that return `void`. See
+[Assertion Placement](../advanced.md#assertion-placement) for more information.
+
+### ADD_FAILURE {#ADD_FAILURE}
+
+`ADD_FAILURE()`
+
+Generates a nonfatal failure, which allows the current function to continue
+running.
+
+### ADD_FAILURE_AT {#ADD_FAILURE_AT}
+
+`ADD_FAILURE_AT(`*`file_path`*`,`*`line_number`*`)`
+
+Generates a nonfatal failure at the file and line number specified.
+
+## Generalized Assertion {#generalized}
+
+The following assertion allows [matchers](matchers.md) to be used to verify
+values.
+
+### EXPECT_THAT {#EXPECT_THAT}
+
+`EXPECT_THAT(`*`value`*`,`*`matcher`*`)` \
+`ASSERT_THAT(`*`value`*`,`*`matcher`*`)`
+
+Verifies that *`value`* matches the [matcher](matchers.md) *`matcher`*.
+
+For example, the following code verifies that the string `value1` starts with
+`"Hello"`, `value2` matches a regular expression, and `value3` is between 5 and
+10:
+
+```cpp
+#include <gmock/gmock.h>
+
+using ::testing::AllOf;
+using ::testing::Gt;
+using ::testing::Lt;
+using ::testing::MatchesRegex;
+using ::testing::StartsWith;
+
+...
+EXPECT_THAT(value1, StartsWith("Hello"));
+EXPECT_THAT(value2, MatchesRegex("Line \\d+"));
+ASSERT_THAT(value3, AllOf(Gt(5), Lt(10)));
+```
+
+Matchers enable assertions of this form to read like English and generate
+informative failure messages. For example, if the above assertion on `value1`
+fails, the resulting message will be similar to the following:
+
+```
+Value of: value1
+  Actual: "Hi, world!"
+Expected: starts with "Hello"
+```
+
+GoogleTest provides a built-in library of matchers—see the
+[Matchers Reference](matchers.md). It is also possible to write your own
+matchers—see [Writing New Matchers Quickly](../gmock_cook_book.md#NewMatchers).
+The use of matchers makes `EXPECT_THAT` a powerful, extensible assertion.
+
+*The idea for this assertion was borrowed from Joe Walnes' Hamcrest project,
+which adds `assertThat()` to JUnit.*
+
+## Boolean Conditions {#boolean}
+
+The following assertions test Boolean conditions.
+
+### EXPECT_TRUE {#EXPECT_TRUE}
+
+`EXPECT_TRUE(`*`condition`*`)` \
+`ASSERT_TRUE(`*`condition`*`)`
+
+Verifies that *`condition`* is true.
+
+### EXPECT_FALSE {#EXPECT_FALSE}
+
+`EXPECT_FALSE(`*`condition`*`)` \
+`ASSERT_FALSE(`*`condition`*`)`
+
+Verifies that *`condition`* is false.
+
+## Binary Comparison {#binary-comparison}
+
+The following assertions compare two values. The value arguments must be
+comparable by the assertion's comparison operator, otherwise a compiler error
+will result.
+
+If an argument supports the `<<` operator, it will be called to print the
+argument when the assertion fails. Otherwise, GoogleTest will attempt to print
+them in the best way it can—see
+[Teaching GoogleTest How to Print Your Values](../advanced.md#teaching-googletest-how-to-print-your-values).
+
+Arguments are always evaluated exactly once, so it's OK for the arguments to
+have side effects. However, the argument evaluation order is undefined and
+programs should not depend on any particular argument evaluation order.
+
+These assertions work with both narrow and wide string objects (`string` and
+`wstring`).
+
+See also the [Floating-Point Comparison](#floating-point) assertions to compare
+floating-point numbers and avoid problems caused by rounding.
+
+### EXPECT_EQ {#EXPECT_EQ}
+
+`EXPECT_EQ(`*`val1`*`,`*`val2`*`)` \
+`ASSERT_EQ(`*`val1`*`,`*`val2`*`)`
+
+Verifies that *`val1`*`==`*`val2`*.
+
+Does pointer equality on pointers. If used on two C strings, it tests if they
+are in the same memory location, not if they have the same value. Use
+[`EXPECT_STREQ`](#EXPECT_STREQ) to compare C strings (e.g. `const char*`) by
+value.
+
+When comparing a pointer to `NULL`, use `EXPECT_EQ(`*`ptr`*`, nullptr)` instead
+of `EXPECT_EQ(`*`ptr`*`, NULL)`.
+
+### EXPECT_NE {#EXPECT_NE}
+
+`EXPECT_NE(`*`val1`*`,`*`val2`*`)` \
+`ASSERT_NE(`*`val1`*`,`*`val2`*`)`
+
+Verifies that *`val1`*`!=`*`val2`*.
+
+Does pointer equality on pointers. If used on two C strings, it tests if they
+are in different memory locations, not if they have different values. Use
+[`EXPECT_STRNE`](#EXPECT_STRNE) to compare C strings (e.g. `const char*`) by
+value.
+
+When comparing a pointer to `NULL`, use `EXPECT_NE(`*`ptr`*`, nullptr)` instead
+of `EXPECT_NE(`*`ptr`*`, NULL)`.
+
+### EXPECT_LT {#EXPECT_LT}
+
+`EXPECT_LT(`*`val1`*`,`*`val2`*`)` \
+`ASSERT_LT(`*`val1`*`,`*`val2`*`)`
+
+Verifies that *`val1`*`<`*`val2`*.
+
+### EXPECT_LE {#EXPECT_LE}
+
+`EXPECT_LE(`*`val1`*`,`*`val2`*`)` \
+`ASSERT_LE(`*`val1`*`,`*`val2`*`)`
+
+Verifies that *`val1`*`<=`*`val2`*.
+
+### EXPECT_GT {#EXPECT_GT}
+
+`EXPECT_GT(`*`val1`*`,`*`val2`*`)` \
+`ASSERT_GT(`*`val1`*`,`*`val2`*`)`
+
+Verifies that *`val1`*`>`*`val2`*.
+
+### EXPECT_GE {#EXPECT_GE}
+
+`EXPECT_GE(`*`val1`*`,`*`val2`*`)` \
+`ASSERT_GE(`*`val1`*`,`*`val2`*`)`
+
+Verifies that *`val1`*`>=`*`val2`*.
+
+## String Comparison {#c-strings}
+
+The following assertions compare two **C strings**. To compare two `string`
+objects, use [`EXPECT_EQ`](#EXPECT_EQ) or [`EXPECT_NE`](#EXPECT_NE) instead.
+
+These assertions also accept wide C strings (`wchar_t*`). If a comparison of two
+wide strings fails, their values will be printed as UTF-8 narrow strings.
+
+To compare a C string with `NULL`, use `EXPECT_EQ(`*`c_string`*`, nullptr)` or
+`EXPECT_NE(`*`c_string`*`, nullptr)`.
+
+### EXPECT_STREQ {#EXPECT_STREQ}
+
+`EXPECT_STREQ(`*`str1`*`,`*`str2`*`)` \
+`ASSERT_STREQ(`*`str1`*`,`*`str2`*`)`
+
+Verifies that the two C strings *`str1`* and *`str2`* have the same contents.
+
+### EXPECT_STRNE {#EXPECT_STRNE}
+
+`EXPECT_STRNE(`*`str1`*`,`*`str2`*`)` \
+`ASSERT_STRNE(`*`str1`*`,`*`str2`*`)`
+
+Verifies that the two C strings *`str1`* and *`str2`* have different contents.
+
+### EXPECT_STRCASEEQ {#EXPECT_STRCASEEQ}
+
+`EXPECT_STRCASEEQ(`*`str1`*`,`*`str2`*`)` \
+`ASSERT_STRCASEEQ(`*`str1`*`,`*`str2`*`)`
+
+Verifies that the two C strings *`str1`* and *`str2`* have the same contents,
+ignoring case.
+
+### EXPECT_STRCASENE {#EXPECT_STRCASENE}
+
+`EXPECT_STRCASENE(`*`str1`*`,`*`str2`*`)` \
+`ASSERT_STRCASENE(`*`str1`*`,`*`str2`*`)`
+
+Verifies that the two C strings *`str1`* and *`str2`* have different contents,
+ignoring case.
+
+## Floating-Point Comparison {#floating-point}
+
+The following assertions compare two floating-point values.
+
+Due to rounding errors, it is very unlikely that two floating-point values will
+match exactly, so `EXPECT_EQ` is not suitable. In general, for floating-point
+comparison to make sense, the user needs to carefully choose the error bound.
+
+GoogleTest also provides assertions that use a default error bound based on
+Units in the Last Place (ULPs). To learn more about ULPs, see the article
+[Comparing Floating Point Numbers](https://randomascii.wordpress.com/2012/02/25/comparing-floating-point-numbers-2012-edition/).
+
+### EXPECT_FLOAT_EQ {#EXPECT_FLOAT_EQ}
+
+`EXPECT_FLOAT_EQ(`*`val1`*`,`*`val2`*`)` \
+`ASSERT_FLOAT_EQ(`*`val1`*`,`*`val2`*`)`
+
+Verifies that the two `float` values *`val1`* and *`val2`* are approximately
+equal, to within 4 ULPs from each other.
+
+### EXPECT_DOUBLE_EQ {#EXPECT_DOUBLE_EQ}
+
+`EXPECT_DOUBLE_EQ(`*`val1`*`,`*`val2`*`)` \
+`ASSERT_DOUBLE_EQ(`*`val1`*`,`*`val2`*`)`
+
+Verifies that the two `double` values *`val1`* and *`val2`* are approximately
+equal, to within 4 ULPs from each other.
+
+### EXPECT_NEAR {#EXPECT_NEAR}
+
+`EXPECT_NEAR(`*`val1`*`,`*`val2`*`,`*`abs_error`*`)` \
+`ASSERT_NEAR(`*`val1`*`,`*`val2`*`,`*`abs_error`*`)`
+
+Verifies that the difference between *`val1`* and *`val2`* does not exceed the
+absolute error bound *`abs_error`*.
+
+## Exception Assertions {#exceptions}
+
+The following assertions verify that a piece of code throws, or does not throw,
+an exception. Usage requires exceptions to be enabled in the build environment.
+
+Note that the piece of code under test can be a compound statement, for example:
+
+```cpp
+EXPECT_NO_THROW({
+  int n = 5;
+  DoSomething(&n);
+});
+```
+
+### EXPECT_THROW {#EXPECT_THROW}
+
+`EXPECT_THROW(`*`statement`*`,`*`exception_type`*`)` \
+`ASSERT_THROW(`*`statement`*`,`*`exception_type`*`)`
+
+Verifies that *`statement`* throws an exception of type *`exception_type`*.
+
+### EXPECT_ANY_THROW {#EXPECT_ANY_THROW}
+
+`EXPECT_ANY_THROW(`*`statement`*`)` \
+`ASSERT_ANY_THROW(`*`statement`*`)`
+
+Verifies that *`statement`* throws an exception of any type.
+
+### EXPECT_NO_THROW {#EXPECT_NO_THROW}
+
+`EXPECT_NO_THROW(`*`statement`*`)` \
+`ASSERT_NO_THROW(`*`statement`*`)`
+
+Verifies that *`statement`* does not throw any exception.
+
+## Predicate Assertions {#predicates}
+
+The following assertions enable more complex predicates to be verified while
+printing a more clear failure message than if `EXPECT_TRUE` were used alone.
+
+### EXPECT_PRED* {#EXPECT_PRED}
+
+`EXPECT_PRED1(`*`pred`*`,`*`val1`*`)` \
+`EXPECT_PRED2(`*`pred`*`,`*`val1`*`,`*`val2`*`)` \
+`EXPECT_PRED3(`*`pred`*`,`*`val1`*`,`*`val2`*`,`*`val3`*`)` \
+`EXPECT_PRED4(`*`pred`*`,`*`val1`*`,`*`val2`*`,`*`val3`*`,`*`val4`*`)` \
+`EXPECT_PRED5(`*`pred`*`,`*`val1`*`,`*`val2`*`,`*`val3`*`,`*`val4`*`,`*`val5`*`)`
+
+`ASSERT_PRED1(`*`pred`*`,`*`val1`*`)` \
+`ASSERT_PRED2(`*`pred`*`,`*`val1`*`,`*`val2`*`)` \
+`ASSERT_PRED3(`*`pred`*`,`*`val1`*`,`*`val2`*`,`*`val3`*`)` \
+`ASSERT_PRED4(`*`pred`*`,`*`val1`*`,`*`val2`*`,`*`val3`*`,`*`val4`*`)` \
+`ASSERT_PRED5(`*`pred`*`,`*`val1`*`,`*`val2`*`,`*`val3`*`,`*`val4`*`,`*`val5`*`)`
+
+Verifies that the predicate *`pred`* returns `true` when passed the given values
+as arguments.
+
+The parameter *`pred`* is a function or functor that accepts as many arguments
+as the corresponding macro accepts values. If *`pred`* returns `true` for the
+given arguments, the assertion succeeds, otherwise the assertion fails.
+
+When the assertion fails, it prints the value of each argument. Arguments are
+always evaluated exactly once.
+
+As an example, see the following code:
+
+```cpp
+// Returns true if m and n have no common divisors except 1.
+bool MutuallyPrime(int m, int n) { ... }
+...
+const int a = 3;
+const int b = 4;
+const int c = 10;
+...
+EXPECT_PRED2(MutuallyPrime, a, b);  // Succeeds
+EXPECT_PRED2(MutuallyPrime, b, c);  // Fails
+```
+
+In the above example, the first assertion succeeds, and the second fails with
+the following message:
+
+```
+MutuallyPrime(b, c) is false, where
+b is 4
+c is 10
+```
+
+Note that if the given predicate is an overloaded function or a function
+template, the assertion macro might not be able to determine which version to
+use, and it might be necessary to explicitly specify the type of the function.
+For example, for a Boolean function `IsPositive()` overloaded to take either a
+single `int` or `double` argument, it would be necessary to write one of the
+following:
+
+```cpp
+EXPECT_PRED1(static_cast<bool (*)(int)>(IsPositive), 5);
+EXPECT_PRED1(static_cast<bool (*)(double)>(IsPositive), 3.14);
+```
+
+Writing simply `EXPECT_PRED1(IsPositive, 5);` would result in a compiler error.
+Similarly, to use a template function, specify the template arguments:
+
+```cpp
+template <typename T>
+bool IsNegative(T x) {
+  return x < 0;
+}
+...
+EXPECT_PRED1(IsNegative<int>, -5);  // Must specify type for IsNegative
+```
+
+If a template has multiple parameters, wrap the predicate in parentheses so the
+macro arguments are parsed correctly:
+
+```cpp
+ASSERT_PRED2((MyPredicate<int, int>), 5, 0);
+```
+
+### EXPECT_PRED_FORMAT* {#EXPECT_PRED_FORMAT}
+
+`EXPECT_PRED_FORMAT1(`*`pred_formatter`*`,`*`val1`*`)` \
+`EXPECT_PRED_FORMAT2(`*`pred_formatter`*`,`*`val1`*`,`*`val2`*`)` \
+`EXPECT_PRED_FORMAT3(`*`pred_formatter`*`,`*`val1`*`,`*`val2`*`,`*`val3`*`)` \
+`EXPECT_PRED_FORMAT4(`*`pred_formatter`*`,`*`val1`*`,`*`val2`*`,`*`val3`*`,`*`val4`*`)`
+\
+`EXPECT_PRED_FORMAT5(`*`pred_formatter`*`,`*`val1`*`,`*`val2`*`,`*`val3`*`,`*`val4`*`,`*`val5`*`)`
+
+`ASSERT_PRED_FORMAT1(`*`pred_formatter`*`,`*`val1`*`)` \
+`ASSERT_PRED_FORMAT2(`*`pred_formatter`*`,`*`val1`*`,`*`val2`*`)` \
+`ASSERT_PRED_FORMAT3(`*`pred_formatter`*`,`*`val1`*`,`*`val2`*`,`*`val3`*`)` \
+`ASSERT_PRED_FORMAT4(`*`pred_formatter`*`,`*`val1`*`,`*`val2`*`,`*`val3`*`,`*`val4`*`)`
+\
+`ASSERT_PRED_FORMAT5(`*`pred_formatter`*`,`*`val1`*`,`*`val2`*`,`*`val3`*`,`*`val4`*`,`*`val5`*`)`
+
+Verifies that the predicate *`pred_formatter`* succeeds when passed the given
+values as arguments.
+
+The parameter *`pred_formatter`* is a *predicate-formatter*, which is a function
+or functor with the signature:
+
+```cpp
+testing::AssertionResult PredicateFormatter(const char* expr1,
+                                            const char* expr2,
+                                            ...
+                                            const char* exprn,
+                                            T1 val1,
+                                            T2 val2,
+                                            ...
+                                            Tn valn);
+```
+
+where *`val1`*, *`val2`*, ..., *`valn`* are the values of the predicate
+arguments, and *`expr1`*, *`expr2`*, ..., *`exprn`* are the corresponding
+expressions as they appear in the source code. The types `T1`, `T2`, ..., `Tn`
+can be either value types or reference types; if an argument has type `T`, it
+can be declared as either `T` or `const T&`, whichever is appropriate. For more
+about the return type `testing::AssertionResult`, see
+[Using a Function That Returns an AssertionResult](../advanced.md#using-a-function-that-returns-an-assertionresult).
+
+As an example, see the following code:
+
+```cpp
+// Returns the smallest prime common divisor of m and n,
+// or 1 when m and n are mutually prime.
+int SmallestPrimeCommonDivisor(int m, int n) { ... }
+
+// Returns true if m and n have no common divisors except 1.
+bool MutuallyPrime(int m, int n) { ... }
+
+// A predicate-formatter for asserting that two integers are mutually prime.
+testing::AssertionResult AssertMutuallyPrime(const char* m_expr,
+                                             const char* n_expr,
+                                             int m,
+                                             int n) {
+  if (MutuallyPrime(m, n)) return testing::AssertionSuccess();
+
+  return testing::AssertionFailure() << m_expr << " and " << n_expr
+      << " (" << m << " and " << n << ") are not mutually prime, "
+      << "as they have a common divisor " << SmallestPrimeCommonDivisor(m, n);
+}
+
+...
+const int a = 3;
+const int b = 4;
+const int c = 10;
+...
+EXPECT_PRED_FORMAT2(AssertMutuallyPrime, a, b);  // Succeeds
+EXPECT_PRED_FORMAT2(AssertMutuallyPrime, b, c);  // Fails
+```
+
+In the above example, the final assertion fails and the predicate-formatter
+produces the following failure message:
+
+```
+b and c (4 and 10) are not mutually prime, as they have a common divisor 2
+```
+
+## Windows HRESULT Assertions {#HRESULT}
+
+The following assertions test for `HRESULT` success or failure. For example:
+
+```cpp
+CComPtr<IShellDispatch2> shell;
+ASSERT_HRESULT_SUCCEEDED(shell.CoCreateInstance(L"Shell.Application"));
+CComVariant empty;
+ASSERT_HRESULT_SUCCEEDED(shell->ShellExecute(CComBSTR(url), empty, empty, empty, empty));
+```
+
+The generated output contains the human-readable error message associated with
+the returned `HRESULT` code.
+
+### EXPECT_HRESULT_SUCCEEDED {#EXPECT_HRESULT_SUCCEEDED}
+
+`EXPECT_HRESULT_SUCCEEDED(`*`expression`*`)` \
+`ASSERT_HRESULT_SUCCEEDED(`*`expression`*`)`
+
+Verifies that *`expression`* is a success `HRESULT`.
+
+### EXPECT_HRESULT_FAILED {#EXPECT_HRESULT_FAILED}
+
+`EXPECT_HRESULT_FAILED(`*`expression`*`)` \
+`ASSERT_HRESULT_FAILED(`*`expression`*`)`
+
+Verifies that *`expression`* is a failure `HRESULT`.
+
+## Death Assertions {#death}
+
+The following assertions verify that a piece of code causes the process to
+terminate. For context, see [Death Tests](../advanced.md#death-tests).
+
+These assertions spawn a new process and execute the code under test in that
+process. How that happens depends on the platform and the variable
+`::testing::GTEST_FLAG(death_test_style)`, which is initialized from the
+command-line flag `--gtest_death_test_style`.
+
+*   On POSIX systems, `fork()` (or `clone()` on Linux) is used to spawn the
+    child, after which:
+    *   If the variable's value is `"fast"`, the death test statement is
+        immediately executed.
+    *   If the variable's value is `"threadsafe"`, the child process re-executes
+        the unit test binary just as it was originally invoked, but with some
+        extra flags to cause just the single death test under consideration to
+        be run.
+*   On Windows, the child is spawned using the `CreateProcess()` API, and
+    re-executes the binary to cause just the single death test under
+    consideration to be run - much like the `"threadsafe"` mode on POSIX.
+
+Other values for the variable are illegal and will cause the death test to fail.
+Currently, the flag's default value is
+**`"fast"`**.
+
+If the death test statement runs to completion without dying, the child process
+will nonetheless terminate, and the assertion fails.
+
+Note that the piece of code under test can be a compound statement, for example:
+
+```cpp
+EXPECT_DEATH({
+  int n = 5;
+  DoSomething(&n);
+}, "Error on line .* of DoSomething()");
+```
+
+### EXPECT_DEATH {#EXPECT_DEATH}
+
+`EXPECT_DEATH(`*`statement`*`,`*`matcher`*`)` \
+`ASSERT_DEATH(`*`statement`*`,`*`matcher`*`)`
+
+Verifies that *`statement`* causes the process to terminate with a nonzero exit
+status and produces `stderr` output that matches *`matcher`*.
+
+The parameter *`matcher`* is either a [matcher](matchers.md) for a `const
+std::string&`, or a regular expression (see
+[Regular Expression Syntax](../advanced.md#regular-expression-syntax))—a bare
+string *`s`* (with no matcher) is treated as
+[`ContainsRegex(s)`](matchers.md#string-matchers), **not**
+[`Eq(s)`](matchers.md#generic-comparison).
+
+For example, the following code verifies that calling `DoSomething(42)` causes
+the process to die with an error message that contains the text `My error`:
+
+```cpp
+EXPECT_DEATH(DoSomething(42), "My error");
+```
+
+### EXPECT_DEATH_IF_SUPPORTED {#EXPECT_DEATH_IF_SUPPORTED}
+
+`EXPECT_DEATH_IF_SUPPORTED(`*`statement`*`,`*`matcher`*`)` \
+`ASSERT_DEATH_IF_SUPPORTED(`*`statement`*`,`*`matcher`*`)`
+
+If death tests are supported, behaves the same as
+[`EXPECT_DEATH`](#EXPECT_DEATH). Otherwise, verifies nothing.
+
+### EXPECT_DEBUG_DEATH {#EXPECT_DEBUG_DEATH}
+
+`EXPECT_DEBUG_DEATH(`*`statement`*`,`*`matcher`*`)` \
+`ASSERT_DEBUG_DEATH(`*`statement`*`,`*`matcher`*`)`
+
+In debug mode, behaves the same as [`EXPECT_DEATH`](#EXPECT_DEATH). When not in
+debug mode (i.e. `NDEBUG` is defined), just executes *`statement`*.
+
+### EXPECT_EXIT {#EXPECT_EXIT}
+
+`EXPECT_EXIT(`*`statement`*`,`*`predicate`*`,`*`matcher`*`)` \
+`ASSERT_EXIT(`*`statement`*`,`*`predicate`*`,`*`matcher`*`)`
+
+Verifies that *`statement`* causes the process to terminate with an exit status
+that satisfies *`predicate`*, and produces `stderr` output that matches
+*`matcher`*.
+
+The parameter *`predicate`* is a function or functor that accepts an `int` exit
+status and returns a `bool`. GoogleTest provides two predicates to handle common
+cases:
+
+```cpp
+// Returns true if the program exited normally with the given exit status code.
+::testing::ExitedWithCode(exit_code);
+
+// Returns true if the program was killed by the given signal.
+// Not available on Windows.
+::testing::KilledBySignal(signal_number);
+```
+
+The parameter *`matcher`* is either a [matcher](matchers.md) for a `const
+std::string&`, or a regular expression (see
+[Regular Expression Syntax](../advanced.md#regular-expression-syntax))—a bare
+string *`s`* (with no matcher) is treated as
+[`ContainsRegex(s)`](matchers.md#string-matchers), **not**
+[`Eq(s)`](matchers.md#generic-comparison).
+
+For example, the following code verifies that calling `NormalExit()` causes the
+process to print a message containing the text `Success` to `stderr` and exit
+with exit status code 0:
+
+```cpp
+EXPECT_EXIT(NormalExit(), testing::ExitedWithCode(0), "Success");
+```
diff --git a/third_party/googletest/docs/reference/matchers.md b/third_party/googletest/docs/reference/matchers.md
new file mode 100644
index 0000000..243e3f9
--- /dev/null
+++ b/third_party/googletest/docs/reference/matchers.md
@@ -0,0 +1,302 @@
+# Matchers Reference
+
+A **matcher** matches a *single* argument. You can use it inside `ON_CALL()` or
+`EXPECT_CALL()`, or use it to validate a value directly using two macros:
+
+| Macro                                | Description                           |
+| :----------------------------------- | :------------------------------------ |
+| `EXPECT_THAT(actual_value, matcher)` | Asserts that `actual_value` matches `matcher`. |
+| `ASSERT_THAT(actual_value, matcher)` | The same as `EXPECT_THAT(actual_value, matcher)`, except that it generates a **fatal** failure. |
+
+{: .callout .warning}
+**WARNING:** Equality matching via `EXPECT_THAT(actual_value, expected_value)`
+is supported, however note that implicit conversions can cause surprising
+results. For example, `EXPECT_THAT(some_bool, "some string")` will compile and
+may pass unintentionally.
+
+**BEST PRACTICE:** Prefer to make the comparison explicit via
+`EXPECT_THAT(actual_value, Eq(expected_value))` or `EXPECT_EQ(actual_value,
+expected_value)`.
+
+Built-in matchers (where `argument` is the function argument, e.g.
+`actual_value` in the example above, or when used in the context of
+`EXPECT_CALL(mock_object, method(matchers))`, the arguments of `method`) are
+divided into several categories. All matchers are defined in the `::testing`
+namespace unless otherwise noted.
+
+## Wildcard
+
+Matcher                     | Description
+:-------------------------- | :-----------------------------------------------
+`_`                         | `argument` can be any value of the correct type.
+`A<type>()` or `An<type>()` | `argument` can be any value of type `type`.
+
+## Generic Comparison
+
+| Matcher                | Description                                         |
+| :--------------------- | :-------------------------------------------------- |
+| `Eq(value)` or `value` | `argument == value`                                 |
+| `Ge(value)`            | `argument >= value`                                 |
+| `Gt(value)`            | `argument > value`                                  |
+| `Le(value)`            | `argument <= value`                                 |
+| `Lt(value)`            | `argument < value`                                  |
+| `Ne(value)`            | `argument != value`                                 |
+| `IsFalse()`            | `argument` evaluates to `false` in a Boolean context. |
+| `IsTrue()`             | `argument` evaluates to `true` in a Boolean context. |
+| `IsNull()`             | `argument` is a `NULL` pointer (raw or smart).      |
+| `NotNull()`            | `argument` is a non-null pointer (raw or smart).    |
+| `Optional(m)`          | `argument` is `optional<>` that contains a value matching `m`. (For testing whether an `optional<>` is set, check for equality with `nullopt`. You may need to use `Eq(nullopt)` if the inner type doesn't have `==`.)|
+| `VariantWith<T>(m)`    | `argument` is `variant<>` that holds the alternative of type T with a value matching `m`. |
+| `Ref(variable)`        | `argument` is a reference to `variable`.            |
+| `TypedEq<type>(value)` | `argument` has type `type` and is equal to `value`. You may need to use this instead of `Eq(value)` when the mock function is overloaded. |
+
+Except `Ref()`, these matchers make a *copy* of `value` in case it's modified or
+destructed later. If the compiler complains that `value` doesn't have a public
+copy constructor, try wrap it in `std::ref()`, e.g.
+`Eq(std::ref(non_copyable_value))`. If you do that, make sure
+`non_copyable_value` is not changed afterwards, or the meaning of your matcher
+will be changed.
+
+`IsTrue` and `IsFalse` are useful when you need to use a matcher, or for types
+that can be explicitly converted to Boolean, but are not implicitly converted to
+Boolean. In other cases, you can use the basic
+[`EXPECT_TRUE` and `EXPECT_FALSE`](assertions.md#boolean) assertions.
+
+## Floating-Point Matchers {#FpMatchers}
+
+| Matcher                          | Description                        |
+| :------------------------------- | :--------------------------------- |
+| `DoubleEq(a_double)`             | `argument` is a `double` value approximately equal to `a_double`, treating two NaNs as unequal. |
+| `FloatEq(a_float)`               | `argument` is a `float` value approximately equal to `a_float`, treating two NaNs as unequal. |
+| `NanSensitiveDoubleEq(a_double)` | `argument` is a `double` value approximately equal to `a_double`, treating two NaNs as equal. |
+| `NanSensitiveFloatEq(a_float)`   | `argument` is a `float` value approximately equal to `a_float`, treating two NaNs as equal. |
+| `IsNan()`   | `argument` is any floating-point type with a NaN value. |
+
+The above matchers use ULP-based comparison (the same as used in googletest).
+They automatically pick a reasonable error bound based on the absolute value of
+the expected value. `DoubleEq()` and `FloatEq()` conform to the IEEE standard,
+which requires comparing two NaNs for equality to return false. The
+`NanSensitive*` version instead treats two NaNs as equal, which is often what a
+user wants.
+
+| Matcher                                           | Description              |
+| :------------------------------------------------ | :----------------------- |
+| `DoubleNear(a_double, max_abs_error)`             | `argument` is a `double` value close to `a_double` (absolute error <= `max_abs_error`), treating two NaNs as unequal. |
+| `FloatNear(a_float, max_abs_error)`               | `argument` is a `float` value close to `a_float` (absolute error <= `max_abs_error`), treating two NaNs as unequal. |
+| `NanSensitiveDoubleNear(a_double, max_abs_error)` | `argument` is a `double` value close to `a_double` (absolute error <= `max_abs_error`), treating two NaNs as equal. |
+| `NanSensitiveFloatNear(a_float, max_abs_error)`   | `argument` is a `float` value close to `a_float` (absolute error <= `max_abs_error`), treating two NaNs as equal. |
+
+## String Matchers
+
+The `argument` can be either a C string or a C++ string object:
+
+| Matcher                 | Description                                        |
+| :---------------------- | :------------------------------------------------- |
+| `ContainsRegex(string)`  | `argument` matches the given regular expression.  |
+| `EndsWith(suffix)`       | `argument` ends with string `suffix`.             |
+| `HasSubstr(string)`      | `argument` contains `string` as a sub-string.     |
+| `IsEmpty()`              | `argument` is an empty string.                    |
+| `MatchesRegex(string)`   | `argument` matches the given regular expression with the match starting at the first character and ending at the last character. |
+| `StartsWith(prefix)`     | `argument` starts with string `prefix`.           |
+| `StrCaseEq(string)`      | `argument` is equal to `string`, ignoring case.   |
+| `StrCaseNe(string)`      | `argument` is not equal to `string`, ignoring case. |
+| `StrEq(string)`          | `argument` is equal to `string`.                  |
+| `StrNe(string)`          | `argument` is not equal to `string`.              |
+| `WhenBase64Unescaped(m)` | `argument` is a base-64 escaped string whose unescaped string matches `m`.  The web-safe format from [RFC 4648](https://www.rfc-editor.org/rfc/rfc4648#section-5) is supported. |
+
+`ContainsRegex()` and `MatchesRegex()` take ownership of the `RE` object. They
+use the regular expression syntax defined
+[here](../advanced.md#regular-expression-syntax). All of these matchers, except
+`ContainsRegex()` and `MatchesRegex()` work for wide strings as well.
+
+## Container Matchers
+
+Most STL-style containers support `==`, so you can use `Eq(expected_container)`
+or simply `expected_container` to match a container exactly. If you want to
+write the elements in-line, match them more flexibly, or get more informative
+messages, you can use:
+
+| Matcher                                   | Description                      |
+| :---------------------------------------- | :------------------------------- |
+| `BeginEndDistanceIs(m)` | `argument` is a container whose `begin()` and `end()` iterators are separated by a number of increments matching `m`. E.g. `BeginEndDistanceIs(2)` or `BeginEndDistanceIs(Lt(2))`. For containers that define a `size()` method, `SizeIs(m)` may be more efficient. |
+| `ContainerEq(container)` | The same as `Eq(container)` except that the failure message also includes which elements are in one container but not the other. |
+| `Contains(e)` | `argument` contains an element that matches `e`, which can be either a value or a matcher. |
+| `Contains(e).Times(n)` | `argument` contains elements that match `e`, which can be either a value or a matcher, and the number of matches is `n`, which can be either a value or a matcher. Unlike the plain `Contains` and `Each` this allows to check for arbitrary occurrences including testing for absence with `Contains(e).Times(0)`. |
+| `Each(e)` | `argument` is a container where *every* element matches `e`, which can be either a value or a matcher. |
+| `ElementsAre(e0, e1, ..., en)` | `argument` has `n + 1` elements, where the *i*-th element matches `ei`, which can be a value or a matcher. |
+| `ElementsAreArray({e0, e1, ..., en})`, `ElementsAreArray(a_container)`, `ElementsAreArray(begin, end)`, `ElementsAreArray(array)`, or `ElementsAreArray(array, count)` | The same as `ElementsAre()` except that the expected element values/matchers come from an initializer list, STL-style container, iterator range, or C-style array. |
+| `IsEmpty()` | `argument` is an empty container (`container.empty()`). |
+| `IsSubsetOf({e0, e1, ..., en})`, `IsSubsetOf(a_container)`, `IsSubsetOf(begin, end)`, `IsSubsetOf(array)`, or `IsSubsetOf(array, count)` | `argument` matches `UnorderedElementsAre(x0, x1, ..., xk)` for some subset `{x0, x1, ..., xk}` of the expected matchers. |
+| `IsSupersetOf({e0, e1, ..., en})`, `IsSupersetOf(a_container)`, `IsSupersetOf(begin, end)`, `IsSupersetOf(array)`, or `IsSupersetOf(array, count)` | Some subset of `argument` matches `UnorderedElementsAre(`expected matchers`)`. |
+| `Pointwise(m, container)`, `Pointwise(m, {e0, e1, ..., en})` | `argument` contains the same number of elements as in `container`, and for all i, (the i-th element in `argument`, the i-th element in `container`) match `m`, which is a matcher on 2-tuples. E.g. `Pointwise(Le(), upper_bounds)` verifies that each element in `argument` doesn't exceed the corresponding element in `upper_bounds`. See more detail below. |
+| `SizeIs(m)` | `argument` is a container whose size matches `m`. E.g. `SizeIs(2)` or `SizeIs(Lt(2))`. |
+| `UnorderedElementsAre(e0, e1, ..., en)` | `argument` has `n + 1` elements, and under *some* permutation of the elements, each element matches an `ei` (for a different `i`), which can be a value or a matcher. |
+| `UnorderedElementsAreArray({e0, e1, ..., en})`, `UnorderedElementsAreArray(a_container)`, `UnorderedElementsAreArray(begin, end)`, `UnorderedElementsAreArray(array)`, or `UnorderedElementsAreArray(array, count)` | The same as `UnorderedElementsAre()` except that the expected element values/matchers come from an initializer list, STL-style container, iterator range, or C-style array. |
+| `UnorderedPointwise(m, container)`, `UnorderedPointwise(m, {e0, e1, ..., en})` | Like `Pointwise(m, container)`, but ignores the order of elements. |
+| `WhenSorted(m)` | When `argument` is sorted using the `<` operator, it matches container matcher `m`. E.g. `WhenSorted(ElementsAre(1, 2, 3))` verifies that `argument` contains elements 1, 2, and 3, ignoring order. |
+| `WhenSortedBy(comparator, m)` | The same as `WhenSorted(m)`, except that the given comparator instead of `<` is used to sort `argument`. E.g. `WhenSortedBy(std::greater(), ElementsAre(3, 2, 1))`. |
+
+**Notes:**
+
+*   These matchers can also match:
+    1.  a native array passed by reference (e.g. in `Foo(const int (&a)[5])`),
+        and
+    2.  an array passed as a pointer and a count (e.g. in `Bar(const T* buffer,
+        int len)` -- see [Multi-argument Matchers](#MultiArgMatchers)).
+*   The array being matched may be multi-dimensional (i.e. its elements can be
+    arrays).
+*   `m` in `Pointwise(m, ...)` and `UnorderedPointwise(m, ...)` should be a
+    matcher for `::std::tuple<T, U>` where `T` and `U` are the element type of
+    the actual container and the expected container, respectively. For example,
+    to compare two `Foo` containers where `Foo` doesn't support `operator==`,
+    one might write:
+
+    ```cpp
+    MATCHER(FooEq, "") {
+      return std::get<0>(arg).Equals(std::get<1>(arg));
+    }
+    ...
+    EXPECT_THAT(actual_foos, Pointwise(FooEq(), expected_foos));
+    ```
+
+## Member Matchers
+
+| Matcher                         | Description                                |
+| :------------------------------ | :----------------------------------------- |
+| `Field(&class::field, m)`       | `argument.field` (or `argument->field` when `argument` is a plain pointer) matches matcher `m`, where `argument` is an object of type _class_. |
+| `Field(field_name, &class::field, m)` | The same as the two-parameter version, but provides a better error message. |
+| `Key(e)`                        | `argument.first` matches `e`, which can be either a value or a matcher. E.g. `Contains(Key(Le(5)))` can verify that a `map` contains a key `<= 5`. |
+| `Pair(m1, m2)`                  | `argument` is an `std::pair` whose `first` field matches `m1` and `second` field matches `m2`. |
+| `FieldsAre(m...)`                   | `argument` is a compatible object where each field matches piecewise with the matchers `m...`. A compatible object is any that supports the `std::tuple_size<Obj>`+`get<I>(obj)` protocol. In C++17 and up this also supports types compatible with structured bindings, like aggregates. |
+| `Property(&class::property, m)` | `argument.property()` (or `argument->property()` when `argument` is a plain pointer) matches matcher `m`, where `argument` is an object of type _class_. The method `property()` must take no argument and be declared as `const`. |
+| `Property(property_name, &class::property, m)` | The same as the two-parameter version, but provides a better error message.
+
+**Notes:**
+
+*   You can use `FieldsAre()` to match any type that supports structured
+    bindings, such as `std::tuple`, `std::pair`, `std::array`, and aggregate
+    types. For example:
+
+    ```cpp
+    std::tuple<int, std::string> my_tuple{7, "hello world"};
+    EXPECT_THAT(my_tuple, FieldsAre(Ge(0), HasSubstr("hello")));
+
+    struct MyStruct {
+      int value = 42;
+      std::string greeting = "aloha";
+    };
+    MyStruct s;
+    EXPECT_THAT(s, FieldsAre(42, "aloha"));
+    ```
+
+*   Don't use `Property()` against member functions that you do not own, because
+    taking addresses of functions is fragile and generally not part of the
+    contract of the function.
+
+## Matching the Result of a Function, Functor, or Callback
+
+| Matcher          | Description                                       |
+| :--------------- | :------------------------------------------------ |
+| `ResultOf(f, m)` | `f(argument)` matches matcher `m`, where `f` is a function or functor. |
+| `ResultOf(result_description, f, m)` | The same as the two-parameter version, but provides a better error message.
+
+## Pointer Matchers
+
+| Matcher                   | Description                                     |
+| :------------------------ | :---------------------------------------------- |
+| `Address(m)`              | the result of `std::addressof(argument)` matches `m`. |
+| `Pointee(m)`              | `argument` (either a smart pointer or a raw pointer) points to a value that matches matcher `m`. |
+| `Pointer(m)`              | `argument` (either a smart pointer or a raw pointer) contains a pointer that matches `m`. `m` will match against the raw pointer regardless of the type of `argument`. |
+| `WhenDynamicCastTo<T>(m)` | when `argument` is passed through `dynamic_cast<T>()`, it matches matcher `m`. |
+
+## Multi-argument Matchers {#MultiArgMatchers}
+
+Technically, all matchers match a *single* value. A "multi-argument" matcher is
+just one that matches a *tuple*. The following matchers can be used to match a
+tuple `(x, y)`:
+
+Matcher | Description
+:------ | :----------
+`Eq()`  | `x == y`
+`Ge()`  | `x >= y`
+`Gt()`  | `x > y`
+`Le()`  | `x <= y`
+`Lt()`  | `x < y`
+`Ne()`  | `x != y`
+
+You can use the following selectors to pick a subset of the arguments (or
+reorder them) to participate in the matching:
+
+| Matcher                    | Description                                     |
+| :------------------------- | :---------------------------------------------- |
+| `AllArgs(m)`               | Equivalent to `m`. Useful as syntactic sugar in `.With(AllArgs(m))`. |
+| `Args<N1, N2, ..., Nk>(m)` | The tuple of the `k` selected (using 0-based indices) arguments matches `m`, e.g. `Args<1, 2>(Eq())`. |
+
+## Composite Matchers
+
+You can make a matcher from one or more other matchers:
+
+| Matcher                          | Description                             |
+| :------------------------------- | :-------------------------------------- |
+| `AllOf(m1, m2, ..., mn)` | `argument` matches all of the matchers `m1` to `mn`. |
+| `AllOfArray({m0, m1, ..., mn})`, `AllOfArray(a_container)`, `AllOfArray(begin, end)`, `AllOfArray(array)`, or `AllOfArray(array, count)` | The same as `AllOf()` except that the matchers come from an initializer list, STL-style container, iterator range, or C-style array. |
+| `AnyOf(m1, m2, ..., mn)` | `argument` matches at least one of the matchers `m1` to `mn`. |
+| `AnyOfArray({m0, m1, ..., mn})`, `AnyOfArray(a_container)`, `AnyOfArray(begin, end)`, `AnyOfArray(array)`, or `AnyOfArray(array, count)` | The same as `AnyOf()` except that the matchers come from an initializer list, STL-style container, iterator range, or C-style array. |
+| `Not(m)` | `argument` doesn't match matcher `m`. |
+| `Conditional(cond, m1, m2)` | Matches matcher `m1` if `cond` evaluates to true, else matches `m2`.|
+
+## Adapters for Matchers
+
+| Matcher                 | Description                           |
+| :---------------------- | :------------------------------------ |
+| `MatcherCast<T>(m)`     | casts matcher `m` to type `Matcher<T>`. |
+| `SafeMatcherCast<T>(m)` | [safely casts](../gmock_cook_book.md#SafeMatcherCast) matcher `m` to type `Matcher<T>`. |
+| `Truly(predicate)`      | `predicate(argument)` returns something considered by C++ to be true, where `predicate` is a function or functor. |
+
+`AddressSatisfies(callback)` and `Truly(callback)` take ownership of `callback`,
+which must be a permanent callback.
+
+## Using Matchers as Predicates {#MatchersAsPredicatesCheat}
+
+| Matcher                       | Description                                 |
+| :---------------------------- | :------------------------------------------ |
+| `Matches(m)(value)` | evaluates to `true` if `value` matches `m`. You can use `Matches(m)` alone as a unary functor. |
+| `ExplainMatchResult(m, value, result_listener)` | evaluates to `true` if `value` matches `m`, explaining the result to `result_listener`. |
+| `Value(value, m)` | evaluates to `true` if `value` matches `m`. |
+
+## Defining Matchers
+
+| Macro                                | Description                           |
+| :----------------------------------- | :------------------------------------ |
+| `MATCHER(IsEven, "") { return (arg % 2) == 0; }` | Defines a matcher `IsEven()` to match an even number. |
+| `MATCHER_P(IsDivisibleBy, n, "") { *result_listener << "where the remainder is " << (arg % n); return (arg % n) == 0; }` | Defines a matcher `IsDivisibleBy(n)` to match a number divisible by `n`. |
+| `MATCHER_P2(IsBetween, a, b, absl::StrCat(negation ? "isn't" : "is", " between ", PrintToString(a), " and ", PrintToString(b))) { return a <= arg && arg <= b; }` | Defines a matcher `IsBetween(a, b)` to match a value in the range [`a`, `b`]. |
+
+**Notes:**
+
+1.  The `MATCHER*` macros cannot be used inside a function or class.
+2.  The matcher body must be *purely functional* (i.e. it cannot have any side
+    effect, and the result must not depend on anything other than the value
+    being matched and the matcher parameters).
+3.  You can use `PrintToString(x)` to convert a value `x` of any type to a
+    string.
+4.  You can use `ExplainMatchResult()` in a custom matcher to wrap another
+    matcher, for example:
+
+    ```cpp
+    MATCHER_P(NestedPropertyMatches, matcher, "") {
+      return ExplainMatchResult(matcher, arg.nested().property(), result_listener);
+    }
+    ```
+
+5.  You can use `DescribeMatcher<>` to describe another matcher. For example:
+
+    ```cpp
+    MATCHER_P(XAndYThat, matcher,
+              "X that " + DescribeMatcher<int>(matcher, negation) +
+                  (negation ? " or" : " and") + " Y that " +
+                  DescribeMatcher<double>(matcher, negation)) {
+      return ExplainMatchResult(matcher, arg.x(), result_listener) &&
+             ExplainMatchResult(matcher, arg.y(), result_listener);
+    }
+    ```
diff --git a/third_party/googletest/docs/reference/mocking.md b/third_party/googletest/docs/reference/mocking.md
new file mode 100644
index 0000000..ab37ebf
--- /dev/null
+++ b/third_party/googletest/docs/reference/mocking.md
@@ -0,0 +1,588 @@
+# Mocking Reference
+
+This page lists the facilities provided by GoogleTest for creating and working
+with mock objects. To use them, add `#include <gmock/gmock.h>`.
+
+## Macros {#macros}
+
+GoogleTest defines the following macros for working with mocks.
+
+### MOCK_METHOD {#MOCK_METHOD}
+
+`MOCK_METHOD(`*`return_type`*`,`*`method_name`*`, (`*`args...`*`));` \
+`MOCK_METHOD(`*`return_type`*`,`*`method_name`*`, (`*`args...`*`),
+(`*`specs...`*`));`
+
+Defines a mock method *`method_name`* with arguments `(`*`args...`*`)` and
+return type *`return_type`* within a mock class.
+
+The parameters of `MOCK_METHOD` mirror the method declaration. The optional
+fourth parameter *`specs...`* is a comma-separated list of qualifiers. The
+following qualifiers are accepted:
+
+| Qualifier                  | Meaning                                      |
+| -------------------------- | -------------------------------------------- |
+| `const`                    | Makes the mocked method a `const` method. Required if overriding a `const` method. |
+| `override`                 | Marks the method with `override`. Recommended if overriding a `virtual` method. |
+| `noexcept`                 | Marks the method with `noexcept`. Required if overriding a `noexcept` method. |
+| `Calltype(`*`calltype`*`)` | Sets the call type for the method, for example `Calltype(STDMETHODCALLTYPE)`. Useful on Windows. |
+| `ref(`*`qualifier`*`)`     | Marks the method with the given reference qualifier, for example `ref(&)` or `ref(&&)`. Required if overriding a method that has a reference qualifier. |
+
+Note that commas in arguments prevent `MOCK_METHOD` from parsing the arguments
+correctly if they are not appropriately surrounded by parentheses. See the
+following example:
+
+```cpp
+class MyMock {
+ public:
+  // The following 2 lines will not compile due to commas in the arguments:
+  MOCK_METHOD(std::pair<bool, int>, GetPair, ());              // Error!
+  MOCK_METHOD(bool, CheckMap, (std::map<int, double>, bool));  // Error!
+
+  // One solution - wrap arguments that contain commas in parentheses:
+  MOCK_METHOD((std::pair<bool, int>), GetPair, ());
+  MOCK_METHOD(bool, CheckMap, ((std::map<int, double>), bool));
+
+  // Another solution - use type aliases:
+  using BoolAndInt = std::pair<bool, int>;
+  MOCK_METHOD(BoolAndInt, GetPair, ());
+  using MapIntDouble = std::map<int, double>;
+  MOCK_METHOD(bool, CheckMap, (MapIntDouble, bool));
+};
+```
+
+`MOCK_METHOD` must be used in the `public:` section of a mock class definition,
+regardless of whether the method being mocked is `public`, `protected`, or
+`private` in the base class.
+
+### EXPECT_CALL {#EXPECT_CALL}
+
+`EXPECT_CALL(`*`mock_object`*`,`*`method_name`*`(`*`matchers...`*`))`
+
+Creates an [expectation](../gmock_for_dummies.md#setting-expectations) that the
+method *`method_name`* of the object *`mock_object`* is called with arguments
+that match the given matchers *`matchers...`*. `EXPECT_CALL` must precede any
+code that exercises the mock object.
+
+The parameter *`matchers...`* is a comma-separated list of
+[matchers](../gmock_for_dummies.md#matchers-what-arguments-do-we-expect) that
+correspond to each argument of the method *`method_name`*. The expectation will
+apply only to calls of *`method_name`* whose arguments match all of the
+matchers. If `(`*`matchers...`*`)` is omitted, the expectation behaves as if
+each argument's matcher were a [wildcard matcher (`_`)](matchers.md#wildcard).
+See the [Matchers Reference](matchers.md) for a list of all built-in matchers.
+
+The following chainable clauses can be used to modify the expectation, and they
+must be used in the following order:
+
+```cpp
+EXPECT_CALL(mock_object, method_name(matchers...))
+    .With(multi_argument_matcher)  // Can be used at most once
+    .Times(cardinality)            // Can be used at most once
+    .InSequence(sequences...)      // Can be used any number of times
+    .After(expectations...)        // Can be used any number of times
+    .WillOnce(action)              // Can be used any number of times
+    .WillRepeatedly(action)        // Can be used at most once
+    .RetiresOnSaturation();        // Can be used at most once
+```
+
+See details for each modifier clause below.
+
+#### With {#EXPECT_CALL.With}
+
+`.With(`*`multi_argument_matcher`*`)`
+
+Restricts the expectation to apply only to mock function calls whose arguments
+as a whole match the multi-argument matcher *`multi_argument_matcher`*.
+
+GoogleTest passes all of the arguments as one tuple into the matcher. The
+parameter *`multi_argument_matcher`* must thus be a matcher of type
+`Matcher<std::tuple<A1, ..., An>>`, where `A1, ..., An` are the types of the
+function arguments.
+
+For example, the following code sets the expectation that
+`my_mock.SetPosition()` is called with any two arguments, the first argument
+being less than the second:
+
+```cpp
+using ::testing::_;
+using ::testing::Lt;
+...
+EXPECT_CALL(my_mock, SetPosition(_, _))
+    .With(Lt());
+```
+
+GoogleTest provides some built-in matchers for 2-tuples, including the `Lt()`
+matcher above. See [Multi-argument Matchers](matchers.md#MultiArgMatchers).
+
+The `With` clause can be used at most once on an expectation and must be the
+first clause.
+
+#### Times {#EXPECT_CALL.Times}
+
+`.Times(`*`cardinality`*`)`
+
+Specifies how many times the mock function call is expected.
+
+The parameter *`cardinality`* represents the number of expected calls and can be
+one of the following, all defined in the `::testing` namespace:
+
+| Cardinality         | Meaning                                             |
+| ------------------- | --------------------------------------------------- |
+| `AnyNumber()`       | The function can be called any number of times.     |
+| `AtLeast(n)`        | The function call is expected at least *n* times.   |
+| `AtMost(n)`         | The function call is expected at most *n* times.    |
+| `Between(m, n)`     | The function call is expected between *m* and *n* times, inclusive. |
+| `Exactly(n)` or `n` | The function call is expected exactly *n* times. If *n* is 0, the call should never happen. |
+
+If the `Times` clause is omitted, GoogleTest infers the cardinality as follows:
+
+*   If neither [`WillOnce`](#EXPECT_CALL.WillOnce) nor
+    [`WillRepeatedly`](#EXPECT_CALL.WillRepeatedly) are specified, the inferred
+    cardinality is `Times(1)`.
+*   If there are *n* `WillOnce` clauses and no `WillRepeatedly` clause, where
+    *n* >= 1, the inferred cardinality is `Times(n)`.
+*   If there are *n* `WillOnce` clauses and one `WillRepeatedly` clause, where
+    *n* >= 0, the inferred cardinality is `Times(AtLeast(n))`.
+
+The `Times` clause can be used at most once on an expectation.
+
+#### InSequence {#EXPECT_CALL.InSequence}
+
+`.InSequence(`*`sequences...`*`)`
+
+Specifies that the mock function call is expected in a certain sequence.
+
+The parameter *`sequences...`* is any number of [`Sequence`](#Sequence) objects.
+Expected calls assigned to the same sequence are expected to occur in the order
+the expectations are declared.
+
+For example, the following code sets the expectation that the `Reset()` method
+of `my_mock` is called before both `GetSize()` and `Describe()`, and `GetSize()`
+and `Describe()` can occur in any order relative to each other:
+
+```cpp
+using ::testing::Sequence;
+Sequence s1, s2;
+...
+EXPECT_CALL(my_mock, Reset())
+    .InSequence(s1, s2);
+EXPECT_CALL(my_mock, GetSize())
+    .InSequence(s1);
+EXPECT_CALL(my_mock, Describe())
+    .InSequence(s2);
+```
+
+The `InSequence` clause can be used any number of times on an expectation.
+
+See also the [`InSequence` class](#InSequence).
+
+#### After {#EXPECT_CALL.After}
+
+`.After(`*`expectations...`*`)`
+
+Specifies that the mock function call is expected to occur after one or more
+other calls.
+
+The parameter *`expectations...`* can be up to five
+[`Expectation`](#Expectation) or [`ExpectationSet`](#ExpectationSet) objects.
+The mock function call is expected to occur after all of the given expectations.
+
+For example, the following code sets the expectation that the `Describe()`
+method of `my_mock` is called only after both `InitX()` and `InitY()` have been
+called.
+
+```cpp
+using ::testing::Expectation;
+...
+Expectation init_x = EXPECT_CALL(my_mock, InitX());
+Expectation init_y = EXPECT_CALL(my_mock, InitY());
+EXPECT_CALL(my_mock, Describe())
+    .After(init_x, init_y);
+```
+
+The `ExpectationSet` object is helpful when the number of prerequisites for an
+expectation is large or variable, for example:
+
+```cpp
+using ::testing::ExpectationSet;
+...
+ExpectationSet all_inits;
+// Collect all expectations of InitElement() calls
+for (int i = 0; i < element_count; i++) {
+  all_inits += EXPECT_CALL(my_mock, InitElement(i));
+}
+EXPECT_CALL(my_mock, Describe())
+    .After(all_inits);  // Expect Describe() call after all InitElement() calls
+```
+
+The `After` clause can be used any number of times on an expectation.
+
+#### WillOnce {#EXPECT_CALL.WillOnce}
+
+`.WillOnce(`*`action`*`)`
+
+Specifies the mock function's actual behavior when invoked, for a single
+matching function call.
+
+The parameter *`action`* represents the
+[action](../gmock_for_dummies.md#actions-what-should-it-do) that the function
+call will perform. See the [Actions Reference](actions.md) for a list of
+built-in actions.
+
+The use of `WillOnce` implicitly sets a cardinality on the expectation when
+`Times` is not specified. See [`Times`](#EXPECT_CALL.Times).
+
+Each matching function call will perform the next action in the order declared.
+For example, the following code specifies that `my_mock.GetNumber()` is expected
+to be called exactly 3 times and will return `1`, `2`, and `3` respectively on
+the first, second, and third calls:
+
+```cpp
+using ::testing::Return;
+...
+EXPECT_CALL(my_mock, GetNumber())
+    .WillOnce(Return(1))
+    .WillOnce(Return(2))
+    .WillOnce(Return(3));
+```
+
+The `WillOnce` clause can be used any number of times on an expectation. Unlike
+`WillRepeatedly`, the action fed to each `WillOnce` call will be called at most
+once, so may be a move-only type and/or have an `&&`-qualified call operator.
+
+#### WillRepeatedly {#EXPECT_CALL.WillRepeatedly}
+
+`.WillRepeatedly(`*`action`*`)`
+
+Specifies the mock function's actual behavior when invoked, for all subsequent
+matching function calls. Takes effect after the actions specified in the
+[`WillOnce`](#EXPECT_CALL.WillOnce) clauses, if any, have been performed.
+
+The parameter *`action`* represents the
+[action](../gmock_for_dummies.md#actions-what-should-it-do) that the function
+call will perform. See the [Actions Reference](actions.md) for a list of
+built-in actions.
+
+The use of `WillRepeatedly` implicitly sets a cardinality on the expectation
+when `Times` is not specified. See [`Times`](#EXPECT_CALL.Times).
+
+If any `WillOnce` clauses have been specified, matching function calls will
+perform those actions before the action specified by `WillRepeatedly`. See the
+following example:
+
+```cpp
+using ::testing::Return;
+...
+EXPECT_CALL(my_mock, GetName())
+    .WillRepeatedly(Return("John Doe"));  // Return "John Doe" on all calls
+
+EXPECT_CALL(my_mock, GetNumber())
+    .WillOnce(Return(42))        // Return 42 on the first call
+    .WillRepeatedly(Return(7));  // Return 7 on all subsequent calls
+```
+
+The `WillRepeatedly` clause can be used at most once on an expectation.
+
+#### RetiresOnSaturation {#EXPECT_CALL.RetiresOnSaturation}
+
+`.RetiresOnSaturation()`
+
+Indicates that the expectation will no longer be active after the expected
+number of matching function calls has been reached.
+
+The `RetiresOnSaturation` clause is only meaningful for expectations with an
+upper-bounded cardinality. The expectation will *retire* (no longer match any
+function calls) after it has been *saturated* (the upper bound has been
+reached). See the following example:
+
+```cpp
+using ::testing::_;
+using ::testing::AnyNumber;
+...
+EXPECT_CALL(my_mock, SetNumber(_))  // Expectation 1
+    .Times(AnyNumber());
+EXPECT_CALL(my_mock, SetNumber(7))  // Expectation 2
+    .Times(2)
+    .RetiresOnSaturation();
+```
+
+In the above example, the first two calls to `my_mock.SetNumber(7)` match
+expectation 2, which then becomes inactive and no longer matches any calls. A
+third call to `my_mock.SetNumber(7)` would then match expectation 1. Without
+`RetiresOnSaturation()` on expectation 2, a third call to `my_mock.SetNumber(7)`
+would match expectation 2 again, producing a failure since the limit of 2 calls
+was exceeded.
+
+The `RetiresOnSaturation` clause can be used at most once on an expectation and
+must be the last clause.
+
+### ON_CALL {#ON_CALL}
+
+`ON_CALL(`*`mock_object`*`,`*`method_name`*`(`*`matchers...`*`))`
+
+Defines what happens when the method *`method_name`* of the object
+*`mock_object`* is called with arguments that match the given matchers
+*`matchers...`*. Requires a modifier clause to specify the method's behavior.
+*Does not* set any expectations that the method will be called.
+
+The parameter *`matchers...`* is a comma-separated list of
+[matchers](../gmock_for_dummies.md#matchers-what-arguments-do-we-expect) that
+correspond to each argument of the method *`method_name`*. The `ON_CALL`
+specification will apply only to calls of *`method_name`* whose arguments match
+all of the matchers. If `(`*`matchers...`*`)` is omitted, the behavior is as if
+each argument's matcher were a [wildcard matcher (`_`)](matchers.md#wildcard).
+See the [Matchers Reference](matchers.md) for a list of all built-in matchers.
+
+The following chainable clauses can be used to set the method's behavior, and
+they must be used in the following order:
+
+```cpp
+ON_CALL(mock_object, method_name(matchers...))
+    .With(multi_argument_matcher)  // Can be used at most once
+    .WillByDefault(action);        // Required
+```
+
+See details for each modifier clause below.
+
+#### With {#ON_CALL.With}
+
+`.With(`*`multi_argument_matcher`*`)`
+
+Restricts the specification to only mock function calls whose arguments as a
+whole match the multi-argument matcher *`multi_argument_matcher`*.
+
+GoogleTest passes all of the arguments as one tuple into the matcher. The
+parameter *`multi_argument_matcher`* must thus be a matcher of type
+`Matcher<std::tuple<A1, ..., An>>`, where `A1, ..., An` are the types of the
+function arguments.
+
+For example, the following code sets the default behavior when
+`my_mock.SetPosition()` is called with any two arguments, the first argument
+being less than the second:
+
+```cpp
+using ::testing::_;
+using ::testing::Lt;
+using ::testing::Return;
+...
+ON_CALL(my_mock, SetPosition(_, _))
+    .With(Lt())
+    .WillByDefault(Return(true));
+```
+
+GoogleTest provides some built-in matchers for 2-tuples, including the `Lt()`
+matcher above. See [Multi-argument Matchers](matchers.md#MultiArgMatchers).
+
+The `With` clause can be used at most once with each `ON_CALL` statement.
+
+#### WillByDefault {#ON_CALL.WillByDefault}
+
+`.WillByDefault(`*`action`*`)`
+
+Specifies the default behavior of a matching mock function call.
+
+The parameter *`action`* represents the
+[action](../gmock_for_dummies.md#actions-what-should-it-do) that the function
+call will perform. See the [Actions Reference](actions.md) for a list of
+built-in actions.
+
+For example, the following code specifies that by default, a call to
+`my_mock.Greet()` will return `"hello"`:
+
+```cpp
+using ::testing::Return;
+...
+ON_CALL(my_mock, Greet())
+    .WillByDefault(Return("hello"));
+```
+
+The action specified by `WillByDefault` is superseded by the actions specified
+on a matching `EXPECT_CALL` statement, if any. See the
+[`WillOnce`](#EXPECT_CALL.WillOnce) and
+[`WillRepeatedly`](#EXPECT_CALL.WillRepeatedly) clauses of `EXPECT_CALL`.
+
+The `WillByDefault` clause must be used exactly once with each `ON_CALL`
+statement.
+
+## Classes {#classes}
+
+GoogleTest defines the following classes for working with mocks.
+
+### DefaultValue {#DefaultValue}
+
+`::testing::DefaultValue<T>`
+
+Allows a user to specify the default value for a type `T` that is both copyable
+and publicly destructible (i.e. anything that can be used as a function return
+type). For mock functions with a return type of `T`, this default value is
+returned from function calls that do not specify an action.
+
+Provides the static methods `Set()`, `SetFactory()`, and `Clear()` to manage the
+default value:
+
+```cpp
+// Sets the default value to be returned. T must be copy constructible.
+DefaultValue<T>::Set(value);
+
+// Sets a factory. Will be invoked on demand. T must be move constructible.
+T MakeT();
+DefaultValue<T>::SetFactory(&MakeT);
+
+// Unsets the default value.
+DefaultValue<T>::Clear();
+```
+
+### NiceMock {#NiceMock}
+
+`::testing::NiceMock<T>`
+
+Represents a mock object that suppresses warnings on
+[uninteresting calls](../gmock_cook_book.md#uninteresting-vs-unexpected). The
+template parameter `T` is any mock class, except for another `NiceMock`,
+`NaggyMock`, or `StrictMock`.
+
+Usage of `NiceMock<T>` is analogous to usage of `T`. `NiceMock<T>` is a subclass
+of `T`, so it can be used wherever an object of type `T` is accepted. In
+addition, `NiceMock<T>` can be constructed with any arguments that a constructor
+of `T` accepts.
+
+For example, the following code suppresses warnings on the mock `my_mock` of
+type `MockClass` if a method other than `DoSomething()` is called:
+
+```cpp
+using ::testing::NiceMock;
+...
+NiceMock<MockClass> my_mock("some", "args");
+EXPECT_CALL(my_mock, DoSomething());
+... code that uses my_mock ...
+```
+
+`NiceMock<T>` only works for mock methods defined using the `MOCK_METHOD` macro
+directly in the definition of class `T`. If a mock method is defined in a base
+class of `T`, a warning might still be generated.
+
+`NiceMock<T>` might not work correctly if the destructor of `T` is not virtual.
+
+### NaggyMock {#NaggyMock}
+
+`::testing::NaggyMock<T>`
+
+Represents a mock object that generates warnings on
+[uninteresting calls](../gmock_cook_book.md#uninteresting-vs-unexpected). The
+template parameter `T` is any mock class, except for another `NiceMock`,
+`NaggyMock`, or `StrictMock`.
+
+Usage of `NaggyMock<T>` is analogous to usage of `T`. `NaggyMock<T>` is a
+subclass of `T`, so it can be used wherever an object of type `T` is accepted.
+In addition, `NaggyMock<T>` can be constructed with any arguments that a
+constructor of `T` accepts.
+
+For example, the following code generates warnings on the mock `my_mock` of type
+`MockClass` if a method other than `DoSomething()` is called:
+
+```cpp
+using ::testing::NaggyMock;
+...
+NaggyMock<MockClass> my_mock("some", "args");
+EXPECT_CALL(my_mock, DoSomething());
+... code that uses my_mock ...
+```
+
+Mock objects of type `T` by default behave the same way as `NaggyMock<T>`.
+
+### StrictMock {#StrictMock}
+
+`::testing::StrictMock<T>`
+
+Represents a mock object that generates test failures on
+[uninteresting calls](../gmock_cook_book.md#uninteresting-vs-unexpected). The
+template parameter `T` is any mock class, except for another `NiceMock`,
+`NaggyMock`, or `StrictMock`.
+
+Usage of `StrictMock<T>` is analogous to usage of `T`. `StrictMock<T>` is a
+subclass of `T`, so it can be used wherever an object of type `T` is accepted.
+In addition, `StrictMock<T>` can be constructed with any arguments that a
+constructor of `T` accepts.
+
+For example, the following code generates a test failure on the mock `my_mock`
+of type `MockClass` if a method other than `DoSomething()` is called:
+
+```cpp
+using ::testing::StrictMock;
+...
+StrictMock<MockClass> my_mock("some", "args");
+EXPECT_CALL(my_mock, DoSomething());
+... code that uses my_mock ...
+```
+
+`StrictMock<T>` only works for mock methods defined using the `MOCK_METHOD`
+macro directly in the definition of class `T`. If a mock method is defined in a
+base class of `T`, a failure might not be generated.
+
+`StrictMock<T>` might not work correctly if the destructor of `T` is not
+virtual.
+
+### Sequence {#Sequence}
+
+`::testing::Sequence`
+
+Represents a chronological sequence of expectations. See the
+[`InSequence`](#EXPECT_CALL.InSequence) clause of `EXPECT_CALL` for usage.
+
+### InSequence {#InSequence}
+
+`::testing::InSequence`
+
+An object of this type causes all expectations encountered in its scope to be
+put in an anonymous sequence.
+
+This allows more convenient expression of multiple expectations in a single
+sequence:
+
+```cpp
+using ::testing::InSequence;
+{
+  InSequence seq;
+
+  // The following are expected to occur in the order declared.
+  EXPECT_CALL(...);
+  EXPECT_CALL(...);
+  ...
+  EXPECT_CALL(...);
+}
+```
+
+The name of the `InSequence` object does not matter.
+
+### Expectation {#Expectation}
+
+`::testing::Expectation`
+
+Represents a mock function call expectation as created by
+[`EXPECT_CALL`](#EXPECT_CALL):
+
+```cpp
+using ::testing::Expectation;
+Expectation my_expectation = EXPECT_CALL(...);
+```
+
+Useful for specifying sequences of expectations; see the
+[`After`](#EXPECT_CALL.After) clause of `EXPECT_CALL`.
+
+### ExpectationSet {#ExpectationSet}
+
+`::testing::ExpectationSet`
+
+Represents a set of mock function call expectations.
+
+Use the `+=` operator to add [`Expectation`](#Expectation) objects to the set:
+
+```cpp
+using ::testing::ExpectationSet;
+ExpectationSet my_expectations;
+my_expectations += EXPECT_CALL(...);
+```
+
+Useful for specifying sequences of expectations; see the
+[`After`](#EXPECT_CALL.After) clause of `EXPECT_CALL`.
diff --git a/third_party/googletest/docs/reference/testing.md b/third_party/googletest/docs/reference/testing.md
new file mode 100644
index 0000000..ead66b3
--- /dev/null
+++ b/third_party/googletest/docs/reference/testing.md
@@ -0,0 +1,1432 @@
+# Testing Reference
+
+<!--* toc_depth: 3 *-->
+
+This page lists the facilities provided by GoogleTest for writing test programs.
+To use them, add `#include <gtest/gtest.h>`.
+
+## Macros
+
+GoogleTest defines the following macros for writing tests.
+
+### TEST {#TEST}
+
+<pre>
+TEST(<em>TestSuiteName</em>, <em>TestName</em>) {
+  ... <em>statements</em> ...
+}
+</pre>
+
+Defines an individual test named *`TestName`* in the test suite
+*`TestSuiteName`*, consisting of the given statements.
+
+Both arguments *`TestSuiteName`* and *`TestName`* must be valid C++ identifiers
+and must not contain underscores (`_`). Tests in different test suites can have
+the same individual name.
+
+The statements within the test body can be any code under test.
+[Assertions](assertions.md) used within the test body determine the outcome of
+the test.
+
+### TEST_F {#TEST_F}
+
+<pre>
+TEST_F(<em>TestFixtureName</em>, <em>TestName</em>) {
+  ... <em>statements</em> ...
+}
+</pre>
+
+Defines an individual test named *`TestName`* that uses the test fixture class
+*`TestFixtureName`*. The test suite name is *`TestFixtureName`*.
+
+Both arguments *`TestFixtureName`* and *`TestName`* must be valid C++
+identifiers and must not contain underscores (`_`). *`TestFixtureName`* must be
+the name of a test fixture class—see
+[Test Fixtures](../primer.md#same-data-multiple-tests).
+
+The statements within the test body can be any code under test.
+[Assertions](assertions.md) used within the test body determine the outcome of
+the test.
+
+### TEST_P {#TEST_P}
+
+<pre>
+TEST_P(<em>TestFixtureName</em>, <em>TestName</em>) {
+  ... <em>statements</em> ...
+}
+</pre>
+
+Defines an individual value-parameterized test named *`TestName`* that uses the
+test fixture class *`TestFixtureName`*. The test suite name is
+*`TestFixtureName`*.
+
+Both arguments *`TestFixtureName`* and *`TestName`* must be valid C++
+identifiers and must not contain underscores (`_`). *`TestFixtureName`* must be
+the name of a value-parameterized test fixture class—see
+[Value-Parameterized Tests](../advanced.md#value-parameterized-tests).
+
+The statements within the test body can be any code under test. Within the test
+body, the test parameter can be accessed with the `GetParam()` function (see
+[`WithParamInterface`](#WithParamInterface)). For example:
+
+```cpp
+TEST_P(MyTestSuite, DoesSomething) {
+  ...
+  EXPECT_TRUE(DoSomething(GetParam()));
+  ...
+}
+```
+
+[Assertions](assertions.md) used within the test body determine the outcome of
+the test.
+
+See also [`INSTANTIATE_TEST_SUITE_P`](#INSTANTIATE_TEST_SUITE_P).
+
+### INSTANTIATE_TEST_SUITE_P {#INSTANTIATE_TEST_SUITE_P}
+
+`INSTANTIATE_TEST_SUITE_P(`*`InstantiationName`*`,`*`TestSuiteName`*`,`*`param_generator`*`)`
+\
+`INSTANTIATE_TEST_SUITE_P(`*`InstantiationName`*`,`*`TestSuiteName`*`,`*`param_generator`*`,`*`name_generator`*`)`
+
+Instantiates the value-parameterized test suite *`TestSuiteName`* (defined with
+[`TEST_P`](#TEST_P)).
+
+The argument *`InstantiationName`* is a unique name for the instantiation of the
+test suite, to distinguish between multiple instantiations. In test output, the
+instantiation name is added as a prefix to the test suite name
+*`TestSuiteName`*.
+
+The argument *`param_generator`* is one of the following GoogleTest-provided
+functions that generate the test parameters, all defined in the `::testing`
+namespace:
+
+<span id="param-generators"></span>
+
+| Parameter Generator | Behavior                                             |
+| ------------------- | ---------------------------------------------------- |
+| `Range(begin, end [, step])` | Yields values `{begin, begin+step, begin+step+step, ...}`. The values do not include `end`. `step` defaults to 1. |
+| `Values(v1, v2, ..., vN)`    | Yields values `{v1, v2, ..., vN}`.          |
+| `ValuesIn(container)` or `ValuesIn(begin,end)` | Yields values from a C-style array, an STL-style container, or an iterator range `[begin, end)`. |
+| `Bool()`                     | Yields sequence `{false, true}`.            |
+| `Combine(g1, g2, ..., gN)`   | Yields as `std::tuple` *n*-tuples all combinations (Cartesian product) of the values generated by the given *n* generators `g1`, `g2`, ..., `gN`. |
+| `ConvertGenerator<T>(g)`     | Yields values generated by generator `g`, `static_cast` to `T`. |
+
+The optional last argument *`name_generator`* is a function or functor that
+generates custom test name suffixes based on the test parameters. The function
+must accept an argument of type
+[`TestParamInfo<class ParamType>`](#TestParamInfo) and return a `std::string`.
+The test name suffix can only contain alphanumeric characters and underscores.
+GoogleTest provides [`PrintToStringParamName`](#PrintToStringParamName), or a
+custom function can be used for more control:
+
+```cpp
+INSTANTIATE_TEST_SUITE_P(
+    MyInstantiation, MyTestSuite,
+    testing::Values(...),
+    [](const testing::TestParamInfo<MyTestSuite::ParamType>& info) {
+      // Can use info.param here to generate the test suffix
+      std::string name = ...
+      return name;
+    });
+```
+
+For more information, see
+[Value-Parameterized Tests](../advanced.md#value-parameterized-tests).
+
+See also
+[`GTEST_ALLOW_UNINSTANTIATED_PARAMETERIZED_TEST`](#GTEST_ALLOW_UNINSTANTIATED_PARAMETERIZED_TEST).
+
+### TYPED_TEST_SUITE {#TYPED_TEST_SUITE}
+
+`TYPED_TEST_SUITE(`*`TestFixtureName`*`,`*`Types`*`)`
+
+Defines a typed test suite based on the test fixture *`TestFixtureName`*. The
+test suite name is *`TestFixtureName`*.
+
+The argument *`TestFixtureName`* is a fixture class template, parameterized by a
+type, for example:
+
+```cpp
+template <typename T>
+class MyFixture : public testing::Test {
+ public:
+  ...
+  using List = std::list<T>;
+  static T shared_;
+  T value_;
+};
+```
+
+The argument *`Types`* is a [`Types`](#Types) object representing the list of
+types to run the tests on, for example:
+
+```cpp
+using MyTypes = ::testing::Types<char, int, unsigned int>;
+TYPED_TEST_SUITE(MyFixture, MyTypes);
+```
+
+The type alias (`using` or `typedef`) is necessary for the `TYPED_TEST_SUITE`
+macro to parse correctly.
+
+See also [`TYPED_TEST`](#TYPED_TEST) and
+[Typed Tests](../advanced.md#typed-tests) for more information.
+
+### TYPED_TEST {#TYPED_TEST}
+
+<pre>
+TYPED_TEST(<em>TestSuiteName</em>, <em>TestName</em>) {
+  ... <em>statements</em> ...
+}
+</pre>
+
+Defines an individual typed test named *`TestName`* in the typed test suite
+*`TestSuiteName`*. The test suite must be defined with
+[`TYPED_TEST_SUITE`](#TYPED_TEST_SUITE).
+
+Within the test body, the special name `TypeParam` refers to the type parameter,
+and `TestFixture` refers to the fixture class. See the following example:
+
+```cpp
+TYPED_TEST(MyFixture, Example) {
+  // Inside a test, refer to the special name TypeParam to get the type
+  // parameter.  Since we are inside a derived class template, C++ requires
+  // us to visit the members of MyFixture via 'this'.
+  TypeParam n = this->value_;
+
+  // To visit static members of the fixture, add the 'TestFixture::'
+  // prefix.
+  n += TestFixture::shared_;
+
+  // To refer to typedefs in the fixture, add the 'typename TestFixture::'
+  // prefix. The 'typename' is required to satisfy the compiler.
+  typename TestFixture::List values;
+
+  values.push_back(n);
+  ...
+}
+```
+
+For more information, see [Typed Tests](../advanced.md#typed-tests).
+
+### TYPED_TEST_SUITE_P {#TYPED_TEST_SUITE_P}
+
+`TYPED_TEST_SUITE_P(`*`TestFixtureName`*`)`
+
+Defines a type-parameterized test suite based on the test fixture
+*`TestFixtureName`*. The test suite name is *`TestFixtureName`*.
+
+The argument *`TestFixtureName`* is a fixture class template, parameterized by a
+type. See [`TYPED_TEST_SUITE`](#TYPED_TEST_SUITE) for an example.
+
+See also [`TYPED_TEST_P`](#TYPED_TEST_P) and
+[Type-Parameterized Tests](../advanced.md#type-parameterized-tests) for more
+information.
+
+### TYPED_TEST_P {#TYPED_TEST_P}
+
+<pre>
+TYPED_TEST_P(<em>TestSuiteName</em>, <em>TestName</em>) {
+  ... <em>statements</em> ...
+}
+</pre>
+
+Defines an individual type-parameterized test named *`TestName`* in the
+type-parameterized test suite *`TestSuiteName`*. The test suite must be defined
+with [`TYPED_TEST_SUITE_P`](#TYPED_TEST_SUITE_P).
+
+Within the test body, the special name `TypeParam` refers to the type parameter,
+and `TestFixture` refers to the fixture class. See [`TYPED_TEST`](#TYPED_TEST)
+for an example.
+
+See also [`REGISTER_TYPED_TEST_SUITE_P`](#REGISTER_TYPED_TEST_SUITE_P) and
+[Type-Parameterized Tests](../advanced.md#type-parameterized-tests) for more
+information.
+
+### REGISTER_TYPED_TEST_SUITE_P {#REGISTER_TYPED_TEST_SUITE_P}
+
+`REGISTER_TYPED_TEST_SUITE_P(`*`TestSuiteName`*`,`*`TestNames...`*`)`
+
+Registers the type-parameterized tests *`TestNames...`* of the test suite
+*`TestSuiteName`*. The test suite and tests must be defined with
+[`TYPED_TEST_SUITE_P`](#TYPED_TEST_SUITE_P) and [`TYPED_TEST_P`](#TYPED_TEST_P).
+
+For example:
+
+```cpp
+// Define the test suite and tests.
+TYPED_TEST_SUITE_P(MyFixture);
+TYPED_TEST_P(MyFixture, HasPropertyA) { ... }
+TYPED_TEST_P(MyFixture, HasPropertyB) { ... }
+
+// Register the tests in the test suite.
+REGISTER_TYPED_TEST_SUITE_P(MyFixture, HasPropertyA, HasPropertyB);
+```
+
+See also [`INSTANTIATE_TYPED_TEST_SUITE_P`](#INSTANTIATE_TYPED_TEST_SUITE_P) and
+[Type-Parameterized Tests](../advanced.md#type-parameterized-tests) for more
+information.
+
+### INSTANTIATE_TYPED_TEST_SUITE_P {#INSTANTIATE_TYPED_TEST_SUITE_P}
+
+`INSTANTIATE_TYPED_TEST_SUITE_P(`*`InstantiationName`*`,`*`TestSuiteName`*`,`*`Types`*`)`
+
+Instantiates the type-parameterized test suite *`TestSuiteName`*. The test suite
+must be registered with
+[`REGISTER_TYPED_TEST_SUITE_P`](#REGISTER_TYPED_TEST_SUITE_P).
+
+The argument *`InstantiationName`* is a unique name for the instantiation of the
+test suite, to distinguish between multiple instantiations. In test output, the
+instantiation name is added as a prefix to the test suite name
+*`TestSuiteName`*.
+
+The argument *`Types`* is a [`Types`](#Types) object representing the list of
+types to run the tests on, for example:
+
+```cpp
+using MyTypes = ::testing::Types<char, int, unsigned int>;
+INSTANTIATE_TYPED_TEST_SUITE_P(MyInstantiation, MyFixture, MyTypes);
+```
+
+The type alias (`using` or `typedef`) is necessary for the
+`INSTANTIATE_TYPED_TEST_SUITE_P` macro to parse correctly.
+
+For more information, see
+[Type-Parameterized Tests](../advanced.md#type-parameterized-tests).
+
+### FRIEND_TEST {#FRIEND_TEST}
+
+`FRIEND_TEST(`*`TestSuiteName`*`,`*`TestName`*`)`
+
+Within a class body, declares an individual test as a friend of the class,
+enabling the test to access private class members.
+
+If the class is defined in a namespace, then in order to be friends of the
+class, test fixtures and tests must be defined in the exact same namespace,
+without inline or anonymous namespaces.
+
+For example, if the class definition looks like the following:
+
+```cpp
+namespace my_namespace {
+
+class MyClass {
+  friend class MyClassTest;
+  FRIEND_TEST(MyClassTest, HasPropertyA);
+  FRIEND_TEST(MyClassTest, HasPropertyB);
+  ... definition of class MyClass ...
+};
+
+}  // namespace my_namespace
+```
+
+Then the test code should look like:
+
+```cpp
+namespace my_namespace {
+
+class MyClassTest : public testing::Test {
+  ...
+};
+
+TEST_F(MyClassTest, HasPropertyA) { ... }
+TEST_F(MyClassTest, HasPropertyB) { ... }
+
+}  // namespace my_namespace
+```
+
+See [Testing Private Code](../advanced.md#testing-private-code) for more
+information.
+
+### SCOPED_TRACE {#SCOPED_TRACE}
+
+`SCOPED_TRACE(`*`message`*`)`
+
+Causes the current file name, line number, and the given message *`message`* to
+be added to the failure message for each assertion failure that occurs in the
+scope.
+
+For more information, see
+[Adding Traces to Assertions](../advanced.md#adding-traces-to-assertions).
+
+See also the [`ScopedTrace` class](#ScopedTrace).
+
+### GTEST_SKIP {#GTEST_SKIP}
+
+`GTEST_SKIP()`
+
+Prevents further test execution at runtime.
+
+Can be used in individual test cases or in the `SetUp()` methods of test
+environments or test fixtures (classes derived from the
+[`Environment`](#Environment) or [`Test`](#Test) classes). If used in a global
+test environment `SetUp()` method, it skips all tests in the test program. If
+used in a test fixture `SetUp()` method, it skips all tests in the corresponding
+test suite.
+
+Similar to assertions, `GTEST_SKIP` allows streaming a custom message into it.
+
+See [Skipping Test Execution](../advanced.md#skipping-test-execution) for more
+information.
+
+### GTEST_ALLOW_UNINSTANTIATED_PARAMETERIZED_TEST {#GTEST_ALLOW_UNINSTANTIATED_PARAMETERIZED_TEST}
+
+`GTEST_ALLOW_UNINSTANTIATED_PARAMETERIZED_TEST(`*`TestSuiteName`*`)`
+
+Allows the value-parameterized test suite *`TestSuiteName`* to be
+uninstantiated.
+
+By default, every [`TEST_P`](#TEST_P) call without a corresponding
+[`INSTANTIATE_TEST_SUITE_P`](#INSTANTIATE_TEST_SUITE_P) call causes a failing
+test in the test suite `GoogleTestVerification`.
+`GTEST_ALLOW_UNINSTANTIATED_PARAMETERIZED_TEST` suppresses this failure for the
+given test suite.
+
+## Classes and types
+
+GoogleTest defines the following classes and types to help with writing tests.
+
+### AssertionResult {#AssertionResult}
+
+`testing::AssertionResult`
+
+A class for indicating whether an assertion was successful.
+
+When the assertion wasn't successful, the `AssertionResult` object stores a
+non-empty failure message that can be retrieved with the object's `message()`
+method.
+
+To create an instance of this class, use one of the factory functions
+[`AssertionSuccess()`](#AssertionSuccess) or
+[`AssertionFailure()`](#AssertionFailure).
+
+### AssertionException {#AssertionException}
+
+`testing::AssertionException`
+
+Exception which can be thrown from
+[`TestEventListener::OnTestPartResult`](#TestEventListener::OnTestPartResult).
+
+### EmptyTestEventListener {#EmptyTestEventListener}
+
+`testing::EmptyTestEventListener`
+
+Provides an empty implementation of all methods in the
+[`TestEventListener`](#TestEventListener) interface, such that a subclass only
+needs to override the methods it cares about.
+
+### Environment {#Environment}
+
+`testing::Environment`
+
+Represents a global test environment. See
+[Global Set-Up and Tear-Down](../advanced.md#global-set-up-and-tear-down).
+
+#### Protected Methods {#Environment-protected}
+
+##### SetUp {#Environment::SetUp}
+
+`virtual void Environment::SetUp()`
+
+Override this to define how to set up the environment.
+
+##### TearDown {#Environment::TearDown}
+
+`virtual void Environment::TearDown()`
+
+Override this to define how to tear down the environment.
+
+### ScopedTrace {#ScopedTrace}
+
+`testing::ScopedTrace`
+
+An instance of this class causes a trace to be included in every test failure
+message generated by code in the scope of the lifetime of the `ScopedTrace`
+instance. The effect is undone with the destruction of the instance.
+
+The `ScopedTrace` constructor has the following form:
+
+```cpp
+template <typename T>
+ScopedTrace(const char* file, int line, const T& message)
+```
+
+Example usage:
+
+```cpp
+testing::ScopedTrace trace("file.cc", 123, "message");
+```
+
+The resulting trace includes the given source file path and line number, and the
+given message. The `message` argument can be anything streamable to
+`std::ostream`.
+
+See also [`SCOPED_TRACE`](#SCOPED_TRACE).
+
+### Test {#Test}
+
+`testing::Test`
+
+The abstract class that all tests inherit from. `Test` is not copyable.
+
+#### Public Methods {#Test-public}
+
+##### SetUpTestSuite {#Test::SetUpTestSuite}
+
+`static void Test::SetUpTestSuite()`
+
+Performs shared setup for all tests in the test suite. GoogleTest calls
+`SetUpTestSuite()` before running the first test in the test suite.
+
+##### TearDownTestSuite {#Test::TearDownTestSuite}
+
+`static void Test::TearDownTestSuite()`
+
+Performs shared teardown for all tests in the test suite. GoogleTest calls
+`TearDownTestSuite()` after running the last test in the test suite.
+
+##### HasFatalFailure {#Test::HasFatalFailure}
+
+`static bool Test::HasFatalFailure()`
+
+Returns true if and only if the current test has a fatal failure.
+
+##### HasNonfatalFailure {#Test::HasNonfatalFailure}
+
+`static bool Test::HasNonfatalFailure()`
+
+Returns true if and only if the current test has a nonfatal failure.
+
+##### HasFailure {#Test::HasFailure}
+
+`static bool Test::HasFailure()`
+
+Returns true if and only if the current test has any failure, either fatal or
+nonfatal.
+
+##### IsSkipped {#Test::IsSkipped}
+
+`static bool Test::IsSkipped()`
+
+Returns true if and only if the current test was skipped.
+
+##### RecordProperty {#Test::RecordProperty}
+
+`static void Test::RecordProperty(const std::string& key, const std::string&
+value)` \
+`static void Test::RecordProperty(const std::string& key, int value)`
+
+Logs a property for the current test, test suite, or entire invocation of the
+test program. Only the last value for a given key is logged.
+
+The key must be a valid XML attribute name, and cannot conflict with the ones
+already used by GoogleTest (`name`, `file`, `line`, `status`, `time`,
+`classname`, `type_param`, and `value_param`).
+
+`RecordProperty` is `public static` so it can be called from utility functions
+that are not members of the test fixture.
+
+Calls to `RecordProperty` made during the lifespan of the test (from the moment
+its constructor starts to the moment its destructor finishes) are output in XML
+as attributes of the `<testcase>` element. Properties recorded from a fixture's
+`SetUpTestSuite` or `TearDownTestSuite` methods are logged as attributes of the
+corresponding `<testsuite>` element. Calls to `RecordProperty` made in the
+global context (before or after invocation of `RUN_ALL_TESTS` or from the
+`SetUp`/`TearDown` methods of registered `Environment` objects) are output as
+attributes of the `<testsuites>` element.
+
+#### Protected Methods {#Test-protected}
+
+##### SetUp {#Test::SetUp}
+
+`virtual void Test::SetUp()`
+
+Override this to perform test fixture setup. GoogleTest calls `SetUp()` before
+running each individual test.
+
+##### TearDown {#Test::TearDown}
+
+`virtual void Test::TearDown()`
+
+Override this to perform test fixture teardown. GoogleTest calls `TearDown()`
+after running each individual test.
+
+### TestWithParam {#TestWithParam}
+
+`testing::TestWithParam<T>`
+
+A convenience class which inherits from both [`Test`](#Test) and
+[`WithParamInterface<T>`](#WithParamInterface).
+
+### TestSuite {#TestSuite}
+
+Represents a test suite. `TestSuite` is not copyable.
+
+#### Public Methods {#TestSuite-public}
+
+##### name {#TestSuite::name}
+
+`const char* TestSuite::name() const`
+
+Gets the name of the test suite.
+
+##### type_param {#TestSuite::type_param}
+
+`const char* TestSuite::type_param() const`
+
+Returns the name of the parameter type, or `NULL` if this is not a typed or
+type-parameterized test suite. See [Typed Tests](../advanced.md#typed-tests) and
+[Type-Parameterized Tests](../advanced.md#type-parameterized-tests).
+
+##### should_run {#TestSuite::should_run}
+
+`bool TestSuite::should_run() const`
+
+Returns true if any test in this test suite should run.
+
+##### successful_test_count {#TestSuite::successful_test_count}
+
+`int TestSuite::successful_test_count() const`
+
+Gets the number of successful tests in this test suite.
+
+##### skipped_test_count {#TestSuite::skipped_test_count}
+
+`int TestSuite::skipped_test_count() const`
+
+Gets the number of skipped tests in this test suite.
+
+##### failed_test_count {#TestSuite::failed_test_count}
+
+`int TestSuite::failed_test_count() const`
+
+Gets the number of failed tests in this test suite.
+
+##### reportable_disabled_test_count {#TestSuite::reportable_disabled_test_count}
+
+`int TestSuite::reportable_disabled_test_count() const`
+
+Gets the number of disabled tests that will be reported in the XML report.
+
+##### disabled_test_count {#TestSuite::disabled_test_count}
+
+`int TestSuite::disabled_test_count() const`
+
+Gets the number of disabled tests in this test suite.
+
+##### reportable_test_count {#TestSuite::reportable_test_count}
+
+`int TestSuite::reportable_test_count() const`
+
+Gets the number of tests to be printed in the XML report.
+
+##### test_to_run_count {#TestSuite::test_to_run_count}
+
+`int TestSuite::test_to_run_count() const`
+
+Get the number of tests in this test suite that should run.
+
+##### total_test_count {#TestSuite::total_test_count}
+
+`int TestSuite::total_test_count() const`
+
+Gets the number of all tests in this test suite.
+
+##### Passed {#TestSuite::Passed}
+
+`bool TestSuite::Passed() const`
+
+Returns true if and only if the test suite passed.
+
+##### Failed {#TestSuite::Failed}
+
+`bool TestSuite::Failed() const`
+
+Returns true if and only if the test suite failed.
+
+##### elapsed_time {#TestSuite::elapsed_time}
+
+`TimeInMillis TestSuite::elapsed_time() const`
+
+Returns the elapsed time, in milliseconds.
+
+##### start_timestamp {#TestSuite::start_timestamp}
+
+`TimeInMillis TestSuite::start_timestamp() const`
+
+Gets the time of the test suite start, in ms from the start of the UNIX epoch.
+
+##### GetTestInfo {#TestSuite::GetTestInfo}
+
+`const TestInfo* TestSuite::GetTestInfo(int i) const`
+
+Returns the [`TestInfo`](#TestInfo) for the `i`-th test among all the tests. `i`
+can range from 0 to `total_test_count() - 1`. If `i` is not in that range,
+returns `NULL`.
+
+##### ad_hoc_test_result {#TestSuite::ad_hoc_test_result}
+
+`const TestResult& TestSuite::ad_hoc_test_result() const`
+
+Returns the [`TestResult`](#TestResult) that holds test properties recorded
+during execution of `SetUpTestSuite` and `TearDownTestSuite`.
+
+### TestInfo {#TestInfo}
+
+`testing::TestInfo`
+
+Stores information about a test.
+
+#### Public Methods {#TestInfo-public}
+
+##### test_suite_name {#TestInfo::test_suite_name}
+
+`const char* TestInfo::test_suite_name() const`
+
+Returns the test suite name.
+
+##### name {#TestInfo::name}
+
+`const char* TestInfo::name() const`
+
+Returns the test name.
+
+##### type_param {#TestInfo::type_param}
+
+`const char* TestInfo::type_param() const`
+
+Returns the name of the parameter type, or `NULL` if this is not a typed or
+type-parameterized test. See [Typed Tests](../advanced.md#typed-tests) and
+[Type-Parameterized Tests](../advanced.md#type-parameterized-tests).
+
+##### value_param {#TestInfo::value_param}
+
+`const char* TestInfo::value_param() const`
+
+Returns the text representation of the value parameter, or `NULL` if this is not
+a value-parameterized test. See
+[Value-Parameterized Tests](../advanced.md#value-parameterized-tests).
+
+##### file {#TestInfo::file}
+
+`const char* TestInfo::file() const`
+
+Returns the file name where this test is defined.
+
+##### line {#TestInfo::line}
+
+`int TestInfo::line() const`
+
+Returns the line where this test is defined.
+
+##### is_in_another_shard {#TestInfo::is_in_another_shard}
+
+`bool TestInfo::is_in_another_shard() const`
+
+Returns true if this test should not be run because it's in another shard.
+
+##### should_run {#TestInfo::should_run}
+
+`bool TestInfo::should_run() const`
+
+Returns true if this test should run, that is if the test is not disabled (or it
+is disabled but the `also_run_disabled_tests` flag has been specified) and its
+full name matches the user-specified filter.
+
+GoogleTest allows the user to filter the tests by their full names. Only the
+tests that match the filter will run. See
+[Running a Subset of the Tests](../advanced.md#running-a-subset-of-the-tests)
+for more information.
+
+##### is_reportable {#TestInfo::is_reportable}
+
+`bool TestInfo::is_reportable() const`
+
+Returns true if and only if this test will appear in the XML report.
+
+##### result {#TestInfo::result}
+
+`const TestResult* TestInfo::result() const`
+
+Returns the result of the test. See [`TestResult`](#TestResult).
+
+### TestParamInfo {#TestParamInfo}
+
+`testing::TestParamInfo<T>`
+
+Describes a parameter to a value-parameterized test. The type `T` is the type of
+the parameter.
+
+Contains the fields `param` and `index` which hold the value of the parameter
+and its integer index respectively.
+
+### UnitTest {#UnitTest}
+
+`testing::UnitTest`
+
+This class contains information about the test program.
+
+`UnitTest` is a singleton class. The only instance is created when
+`UnitTest::GetInstance()` is first called. This instance is never deleted.
+
+`UnitTest` is not copyable.
+
+#### Public Methods {#UnitTest-public}
+
+##### GetInstance {#UnitTest::GetInstance}
+
+`static UnitTest* UnitTest::GetInstance()`
+
+Gets the singleton `UnitTest` object. The first time this method is called, a
+`UnitTest` object is constructed and returned. Consecutive calls will return the
+same object.
+
+##### original_working_dir {#UnitTest::original_working_dir}
+
+`const char* UnitTest::original_working_dir() const`
+
+Returns the working directory when the first [`TEST()`](#TEST) or
+[`TEST_F()`](#TEST_F) was executed. The `UnitTest` object owns the string.
+
+##### current_test_suite {#UnitTest::current_test_suite}
+
+`const TestSuite* UnitTest::current_test_suite() const`
+
+Returns the [`TestSuite`](#TestSuite) object for the test that's currently
+running, or `NULL` if no test is running.
+
+##### current_test_info {#UnitTest::current_test_info}
+
+`const TestInfo* UnitTest::current_test_info() const`
+
+Returns the [`TestInfo`](#TestInfo) object for the test that's currently
+running, or `NULL` if no test is running.
+
+##### random_seed {#UnitTest::random_seed}
+
+`int UnitTest::random_seed() const`
+
+Returns the random seed used at the start of the current test run.
+
+##### successful_test_suite_count {#UnitTest::successful_test_suite_count}
+
+`int UnitTest::successful_test_suite_count() const`
+
+Gets the number of successful test suites.
+
+##### failed_test_suite_count {#UnitTest::failed_test_suite_count}
+
+`int UnitTest::failed_test_suite_count() const`
+
+Gets the number of failed test suites.
+
+##### total_test_suite_count {#UnitTest::total_test_suite_count}
+
+`int UnitTest::total_test_suite_count() const`
+
+Gets the number of all test suites.
+
+##### test_suite_to_run_count {#UnitTest::test_suite_to_run_count}
+
+`int UnitTest::test_suite_to_run_count() const`
+
+Gets the number of all test suites that contain at least one test that should
+run.
+
+##### successful_test_count {#UnitTest::successful_test_count}
+
+`int UnitTest::successful_test_count() const`
+
+Gets the number of successful tests.
+
+##### skipped_test_count {#UnitTest::skipped_test_count}
+
+`int UnitTest::skipped_test_count() const`
+
+Gets the number of skipped tests.
+
+##### failed_test_count {#UnitTest::failed_test_count}
+
+`int UnitTest::failed_test_count() const`
+
+Gets the number of failed tests.
+
+##### reportable_disabled_test_count {#UnitTest::reportable_disabled_test_count}
+
+`int UnitTest::reportable_disabled_test_count() const`
+
+Gets the number of disabled tests that will be reported in the XML report.
+
+##### disabled_test_count {#UnitTest::disabled_test_count}
+
+`int UnitTest::disabled_test_count() const`
+
+Gets the number of disabled tests.
+
+##### reportable_test_count {#UnitTest::reportable_test_count}
+
+`int UnitTest::reportable_test_count() const`
+
+Gets the number of tests to be printed in the XML report.
+
+##### total_test_count {#UnitTest::total_test_count}
+
+`int UnitTest::total_test_count() const`
+
+Gets the number of all tests.
+
+##### test_to_run_count {#UnitTest::test_to_run_count}
+
+`int UnitTest::test_to_run_count() const`
+
+Gets the number of tests that should run.
+
+##### start_timestamp {#UnitTest::start_timestamp}
+
+`TimeInMillis UnitTest::start_timestamp() const`
+
+Gets the time of the test program start, in ms from the start of the UNIX epoch.
+
+##### elapsed_time {#UnitTest::elapsed_time}
+
+`TimeInMillis UnitTest::elapsed_time() const`
+
+Gets the elapsed time, in milliseconds.
+
+##### Passed {#UnitTest::Passed}
+
+`bool UnitTest::Passed() const`
+
+Returns true if and only if the unit test passed (i.e. all test suites passed).
+
+##### Failed {#UnitTest::Failed}
+
+`bool UnitTest::Failed() const`
+
+Returns true if and only if the unit test failed (i.e. some test suite failed or
+something outside of all tests failed).
+
+##### GetTestSuite {#UnitTest::GetTestSuite}
+
+`const TestSuite* UnitTest::GetTestSuite(int i) const`
+
+Gets the [`TestSuite`](#TestSuite) object for the `i`-th test suite among all
+the test suites. `i` can range from 0 to `total_test_suite_count() - 1`. If `i`
+is not in that range, returns `NULL`.
+
+##### ad_hoc_test_result {#UnitTest::ad_hoc_test_result}
+
+`const TestResult& UnitTest::ad_hoc_test_result() const`
+
+Returns the [`TestResult`](#TestResult) containing information on test failures
+and properties logged outside of individual test suites.
+
+##### listeners {#UnitTest::listeners}
+
+`TestEventListeners& UnitTest::listeners()`
+
+Returns the list of event listeners that can be used to track events inside
+GoogleTest. See [`TestEventListeners`](#TestEventListeners).
+
+### TestEventListener {#TestEventListener}
+
+`testing::TestEventListener`
+
+The interface for tracing execution of tests. The methods below are listed in
+the order the corresponding events are fired.
+
+#### Public Methods {#TestEventListener-public}
+
+##### OnTestProgramStart {#TestEventListener::OnTestProgramStart}
+
+`virtual void TestEventListener::OnTestProgramStart(const UnitTest& unit_test)`
+
+Fired before any test activity starts.
+
+##### OnTestIterationStart {#TestEventListener::OnTestIterationStart}
+
+`virtual void TestEventListener::OnTestIterationStart(const UnitTest& unit_test,
+int iteration)`
+
+Fired before each iteration of tests starts. There may be more than one
+iteration if `GTEST_FLAG(repeat)` is set. `iteration` is the iteration index,
+starting from 0.
+
+##### OnEnvironmentsSetUpStart {#TestEventListener::OnEnvironmentsSetUpStart}
+
+`virtual void TestEventListener::OnEnvironmentsSetUpStart(const UnitTest&
+unit_test)`
+
+Fired before environment set-up for each iteration of tests starts.
+
+##### OnEnvironmentsSetUpEnd {#TestEventListener::OnEnvironmentsSetUpEnd}
+
+`virtual void TestEventListener::OnEnvironmentsSetUpEnd(const UnitTest&
+unit_test)`
+
+Fired after environment set-up for each iteration of tests ends.
+
+##### OnTestSuiteStart {#TestEventListener::OnTestSuiteStart}
+
+`virtual void TestEventListener::OnTestSuiteStart(const TestSuite& test_suite)`
+
+Fired before the test suite starts.
+
+##### OnTestStart {#TestEventListener::OnTestStart}
+
+`virtual void TestEventListener::OnTestStart(const TestInfo& test_info)`
+
+Fired before the test starts.
+
+##### OnTestPartResult {#TestEventListener::OnTestPartResult}
+
+`virtual void TestEventListener::OnTestPartResult(const TestPartResult&
+test_part_result)`
+
+Fired after a failed assertion or a `SUCCEED()` invocation. If you want to throw
+an exception from this function to skip to the next test, it must be an
+[`AssertionException`](#AssertionException) or inherited from it.
+
+##### OnTestEnd {#TestEventListener::OnTestEnd}
+
+`virtual void TestEventListener::OnTestEnd(const TestInfo& test_info)`
+
+Fired after the test ends.
+
+##### OnTestSuiteEnd {#TestEventListener::OnTestSuiteEnd}
+
+`virtual void TestEventListener::OnTestSuiteEnd(const TestSuite& test_suite)`
+
+Fired after the test suite ends.
+
+##### OnEnvironmentsTearDownStart {#TestEventListener::OnEnvironmentsTearDownStart}
+
+`virtual void TestEventListener::OnEnvironmentsTearDownStart(const UnitTest&
+unit_test)`
+
+Fired before environment tear-down for each iteration of tests starts.
+
+##### OnEnvironmentsTearDownEnd {#TestEventListener::OnEnvironmentsTearDownEnd}
+
+`virtual void TestEventListener::OnEnvironmentsTearDownEnd(const UnitTest&
+unit_test)`
+
+Fired after environment tear-down for each iteration of tests ends.
+
+##### OnTestIterationEnd {#TestEventListener::OnTestIterationEnd}
+
+`virtual void TestEventListener::OnTestIterationEnd(const UnitTest& unit_test,
+int iteration)`
+
+Fired after each iteration of tests finishes.
+
+##### OnTestProgramEnd {#TestEventListener::OnTestProgramEnd}
+
+`virtual void TestEventListener::OnTestProgramEnd(const UnitTest& unit_test)`
+
+Fired after all test activities have ended.
+
+### TestEventListeners {#TestEventListeners}
+
+`testing::TestEventListeners`
+
+Lets users add listeners to track events in GoogleTest.
+
+#### Public Methods {#TestEventListeners-public}
+
+##### Append {#TestEventListeners::Append}
+
+`void TestEventListeners::Append(TestEventListener* listener)`
+
+Appends an event listener to the end of the list. GoogleTest assumes ownership
+of the listener (i.e. it will delete the listener when the test program
+finishes).
+
+##### Release {#TestEventListeners::Release}
+
+`TestEventListener* TestEventListeners::Release(TestEventListener* listener)`
+
+Removes the given event listener from the list and returns it. It then becomes
+the caller's responsibility to delete the listener. Returns `NULL` if the
+listener is not found in the list.
+
+##### default_result_printer {#TestEventListeners::default_result_printer}
+
+`TestEventListener* TestEventListeners::default_result_printer() const`
+
+Returns the standard listener responsible for the default console output. Can be
+removed from the listeners list to shut down default console output. Note that
+removing this object from the listener list with
+[`Release()`](#TestEventListeners::Release) transfers its ownership to the
+caller and makes this function return `NULL` the next time.
+
+##### default_xml_generator {#TestEventListeners::default_xml_generator}
+
+`TestEventListener* TestEventListeners::default_xml_generator() const`
+
+Returns the standard listener responsible for the default XML output controlled
+by the `--gtest_output=xml` flag. Can be removed from the listeners list by
+users who want to shut down the default XML output controlled by this flag and
+substitute it with custom one. Note that removing this object from the listener
+list with [`Release()`](#TestEventListeners::Release) transfers its ownership to
+the caller and makes this function return `NULL` the next time.
+
+### TestPartResult {#TestPartResult}
+
+`testing::TestPartResult`
+
+A copyable object representing the result of a test part (i.e. an assertion or
+an explicit `FAIL()`, `ADD_FAILURE()`, or `SUCCESS()`).
+
+#### Public Methods {#TestPartResult-public}
+
+##### type {#TestPartResult::type}
+
+`Type TestPartResult::type() const`
+
+Gets the outcome of the test part.
+
+The return type `Type` is an enum defined as follows:
+
+```cpp
+enum Type {
+  kSuccess,          // Succeeded.
+  kNonFatalFailure,  // Failed but the test can continue.
+  kFatalFailure,     // Failed and the test should be terminated.
+  kSkip              // Skipped.
+};
+```
+
+##### file_name {#TestPartResult::file_name}
+
+`const char* TestPartResult::file_name() const`
+
+Gets the name of the source file where the test part took place, or `NULL` if
+it's unknown.
+
+##### line_number {#TestPartResult::line_number}
+
+`int TestPartResult::line_number() const`
+
+Gets the line in the source file where the test part took place, or `-1` if it's
+unknown.
+
+##### summary {#TestPartResult::summary}
+
+`const char* TestPartResult::summary() const`
+
+Gets the summary of the failure message.
+
+##### message {#TestPartResult::message}
+
+`const char* TestPartResult::message() const`
+
+Gets the message associated with the test part.
+
+##### skipped {#TestPartResult::skipped}
+
+`bool TestPartResult::skipped() const`
+
+Returns true if and only if the test part was skipped.
+
+##### passed {#TestPartResult::passed}
+
+`bool TestPartResult::passed() const`
+
+Returns true if and only if the test part passed.
+
+##### nonfatally_failed {#TestPartResult::nonfatally_failed}
+
+`bool TestPartResult::nonfatally_failed() const`
+
+Returns true if and only if the test part non-fatally failed.
+
+##### fatally_failed {#TestPartResult::fatally_failed}
+
+`bool TestPartResult::fatally_failed() const`
+
+Returns true if and only if the test part fatally failed.
+
+##### failed {#TestPartResult::failed}
+
+`bool TestPartResult::failed() const`
+
+Returns true if and only if the test part failed.
+
+### TestProperty {#TestProperty}
+
+`testing::TestProperty`
+
+A copyable object representing a user-specified test property which can be
+output as a key/value string pair.
+
+#### Public Methods {#TestProperty-public}
+
+##### key {#key}
+
+`const char* key() const`
+
+Gets the user-supplied key.
+
+##### value {#value}
+
+`const char* value() const`
+
+Gets the user-supplied value.
+
+##### SetValue {#SetValue}
+
+`void SetValue(const std::string& new_value)`
+
+Sets a new value, overriding the previous one.
+
+### TestResult {#TestResult}
+
+`testing::TestResult`
+
+Contains information about the result of a single test.
+
+`TestResult` is not copyable.
+
+#### Public Methods {#TestResult-public}
+
+##### total_part_count {#TestResult::total_part_count}
+
+`int TestResult::total_part_count() const`
+
+Gets the number of all test parts. This is the sum of the number of successful
+test parts and the number of failed test parts.
+
+##### test_property_count {#TestResult::test_property_count}
+
+`int TestResult::test_property_count() const`
+
+Returns the number of test properties.
+
+##### Passed {#TestResult::Passed}
+
+`bool TestResult::Passed() const`
+
+Returns true if and only if the test passed (i.e. no test part failed).
+
+##### Skipped {#TestResult::Skipped}
+
+`bool TestResult::Skipped() const`
+
+Returns true if and only if the test was skipped.
+
+##### Failed {#TestResult::Failed}
+
+`bool TestResult::Failed() const`
+
+Returns true if and only if the test failed.
+
+##### HasFatalFailure {#TestResult::HasFatalFailure}
+
+`bool TestResult::HasFatalFailure() const`
+
+Returns true if and only if the test fatally failed.
+
+##### HasNonfatalFailure {#TestResult::HasNonfatalFailure}
+
+`bool TestResult::HasNonfatalFailure() const`
+
+Returns true if and only if the test has a non-fatal failure.
+
+##### elapsed_time {#TestResult::elapsed_time}
+
+`TimeInMillis TestResult::elapsed_time() const`
+
+Returns the elapsed time, in milliseconds.
+
+##### start_timestamp {#TestResult::start_timestamp}
+
+`TimeInMillis TestResult::start_timestamp() const`
+
+Gets the time of the test case start, in ms from the start of the UNIX epoch.
+
+##### GetTestPartResult {#TestResult::GetTestPartResult}
+
+`const TestPartResult& TestResult::GetTestPartResult(int i) const`
+
+Returns the [`TestPartResult`](#TestPartResult) for the `i`-th test part result
+among all the results. `i` can range from 0 to `total_part_count() - 1`. If `i`
+is not in that range, aborts the program.
+
+##### GetTestProperty {#TestResult::GetTestProperty}
+
+`const TestProperty& TestResult::GetTestProperty(int i) const`
+
+Returns the [`TestProperty`](#TestProperty) object for the `i`-th test property.
+`i` can range from 0 to `test_property_count() - 1`. If `i` is not in that
+range, aborts the program.
+
+### TimeInMillis {#TimeInMillis}
+
+`testing::TimeInMillis`
+
+An integer type representing time in milliseconds.
+
+### Types {#Types}
+
+`testing::Types<T...>`
+
+Represents a list of types for use in typed tests and type-parameterized tests.
+
+The template argument `T...` can be any number of types, for example:
+
+```
+testing::Types<char, int, unsigned int>
+```
+
+See [Typed Tests](../advanced.md#typed-tests) and
+[Type-Parameterized Tests](../advanced.md#type-parameterized-tests) for more
+information.
+
+### WithParamInterface {#WithParamInterface}
+
+`testing::WithParamInterface<T>`
+
+The pure interface class that all value-parameterized tests inherit from.
+
+A value-parameterized test fixture class must inherit from both [`Test`](#Test)
+and `WithParamInterface`. In most cases that just means inheriting from
+[`TestWithParam`](#TestWithParam), but more complicated test hierarchies may
+need to inherit from `Test` and `WithParamInterface` at different levels.
+
+This interface defines the type alias `ParamType` for the parameter type `T` and
+has support for accessing the test parameter value via the `GetParam()` method:
+
+```
+static const ParamType& GetParam()
+```
+
+For more information, see
+[Value-Parameterized Tests](../advanced.md#value-parameterized-tests).
+
+## Functions
+
+GoogleTest defines the following functions to help with writing and running
+tests.
+
+### InitGoogleTest {#InitGoogleTest}
+
+`void testing::InitGoogleTest(int* argc, char** argv)` \
+`void testing::InitGoogleTest(int* argc, wchar_t** argv)` \
+`void testing::InitGoogleTest()`
+
+Initializes GoogleTest. This must be called before calling
+[`RUN_ALL_TESTS()`](#RUN_ALL_TESTS). In particular, it parses the command line
+for the flags that GoogleTest recognizes. Whenever a GoogleTest flag is seen, it
+is removed from `argv`, and `*argc` is decremented.
+
+No value is returned. Instead, the GoogleTest flag variables are updated.
+
+The `InitGoogleTest(int* argc, wchar_t** argv)` overload can be used in Windows
+programs compiled in `UNICODE` mode.
+
+The argument-less `InitGoogleTest()` overload can be used on Arduino/embedded
+platforms where there is no `argc`/`argv`.
+
+### AddGlobalTestEnvironment {#AddGlobalTestEnvironment}
+
+`Environment* testing::AddGlobalTestEnvironment(Environment* env)`
+
+Adds a test environment to the test program. Must be called before
+[`RUN_ALL_TESTS()`](#RUN_ALL_TESTS) is called. See
+[Global Set-Up and Tear-Down](../advanced.md#global-set-up-and-tear-down) for
+more information.
+
+See also [`Environment`](#Environment).
+
+### RegisterTest {#RegisterTest}
+
+```cpp
+template <typename Factory>
+TestInfo* testing::RegisterTest(const char* test_suite_name, const char* test_name,
+                                  const char* type_param, const char* value_param,
+                                  const char* file, int line, Factory factory)
+```
+
+Dynamically registers a test with the framework.
+
+The `factory` argument is a factory callable (move-constructible) object or
+function pointer that creates a new instance of the `Test` object. It handles
+ownership to the caller. The signature of the callable is `Fixture*()`, where
+`Fixture` is the test fixture class for the test. All tests registered with the
+same `test_suite_name` must return the same fixture type. This is checked at
+runtime.
+
+The framework will infer the fixture class from the factory and will call the
+`SetUpTestSuite` and `TearDownTestSuite` methods for it.
+
+Must be called before [`RUN_ALL_TESTS()`](#RUN_ALL_TESTS) is invoked, otherwise
+behavior is undefined.
+
+See
+[Registering tests programmatically](../advanced.md#registering-tests-programmatically)
+for more information.
+
+### RUN_ALL_TESTS {#RUN_ALL_TESTS}
+
+`int RUN_ALL_TESTS()`
+
+Use this function in `main()` to run all tests. It returns `0` if all tests are
+successful, or `1` otherwise.
+
+`RUN_ALL_TESTS()` should be invoked after the command line has been parsed by
+[`InitGoogleTest()`](#InitGoogleTest).
+
+This function was formerly a macro; thus, it is in the global namespace and has
+an all-caps name.
+
+### AssertionSuccess {#AssertionSuccess}
+
+`AssertionResult testing::AssertionSuccess()`
+
+Creates a successful assertion result. See
+[`AssertionResult`](#AssertionResult).
+
+### AssertionFailure {#AssertionFailure}
+
+`AssertionResult testing::AssertionFailure()`
+
+Creates a failed assertion result. Use the `<<` operator to store a failure
+message:
+
+```cpp
+testing::AssertionFailure() << "My failure message";
+```
+
+See [`AssertionResult`](#AssertionResult).
+
+### StaticAssertTypeEq {#StaticAssertTypeEq}
+
+`testing::StaticAssertTypeEq<T1, T2>()`
+
+Compile-time assertion for type equality. Compiles if and only if `T1` and `T2`
+are the same type. The value it returns is irrelevant.
+
+See [Type Assertions](../advanced.md#type-assertions) for more information.
+
+### PrintToString {#PrintToString}
+
+`std::string testing::PrintToString(x)`
+
+Prints any value `x` using GoogleTest's value printer.
+
+See
+[Teaching GoogleTest How to Print Your Values](../advanced.md#teaching-googletest-how-to-print-your-values)
+for more information.
+
+### PrintToStringParamName {#PrintToStringParamName}
+
+`std::string testing::PrintToStringParamName(TestParamInfo<T>& info)`
+
+A built-in parameterized test name generator which returns the result of
+[`PrintToString`](#PrintToString) called on `info.param`. Does not work when the
+test parameter is a `std::string` or C string. See
+[Specifying Names for Value-Parameterized Test Parameters](../advanced.md#specifying-names-for-value-parameterized-test-parameters)
+for more information.
+
+See also [`TestParamInfo`](#TestParamInfo) and
+[`INSTANTIATE_TEST_SUITE_P`](#INSTANTIATE_TEST_SUITE_P).
diff --git a/third_party/googletest/docs/samples.md b/third_party/googletest/docs/samples.md
new file mode 100644
index 0000000..dedc590
--- /dev/null
+++ b/third_party/googletest/docs/samples.md
@@ -0,0 +1,22 @@
+# Googletest Samples
+
+If you're like us, you'd like to look at
+[googletest samples.](https://github.com/google/googletest/blob/main/googletest/samples)
+The sample directory has a number of well-commented samples showing how to use a
+variety of googletest features.
+
+*   Sample #1 shows the basic steps of using googletest to test C++ functions.
+*   Sample #2 shows a more complex unit test for a class with multiple member
+    functions.
+*   Sample #3 uses a test fixture.
+*   Sample #4 teaches you how to use googletest and `googletest.h` together to
+    get the best of both libraries.
+*   Sample #5 puts shared testing logic in a base test fixture, and reuses it in
+    derived fixtures.
+*   Sample #6 demonstrates type-parameterized tests.
+*   Sample #7 teaches the basics of value-parameterized tests.
+*   Sample #8 shows using `Combine()` in value-parameterized tests.
+*   Sample #9 shows use of the listener API to modify Google Test's console
+    output and the use of its reflection API to inspect test results.
+*   Sample #10 shows use of the listener API to implement a primitive memory
+    leak checker.
diff --git a/third_party/googletest/googlemock/CMakeLists.txt b/third_party/googletest/googlemock/CMakeLists.txt
new file mode 100644
index 0000000..a9aa072
--- /dev/null
+++ b/third_party/googletest/googlemock/CMakeLists.txt
@@ -0,0 +1,209 @@
+########################################################################
+# Note: CMake support is community-based. The maintainers do not use CMake
+# internally.
+#
+# CMake build script for Google Mock.
+#
+# To run the tests for Google Mock itself on Linux, use 'make test' or
+# ctest.  You can select which tests to run using 'ctest -R regex'.
+# For more options, run 'ctest --help'.
+
+option(gmock_build_tests "Build all of Google Mock's own tests." OFF)
+
+# A directory to find Google Test sources.
+if (EXISTS "${CMAKE_CURRENT_SOURCE_DIR}/gtest/CMakeLists.txt")
+  set(gtest_dir gtest)
+else()
+  set(gtest_dir ../googletest)
+endif()
+
+# Defines pre_project_set_up_hermetic_build() and set_up_hermetic_build().
+include("${gtest_dir}/cmake/hermetic_build.cmake" OPTIONAL)
+
+if (COMMAND pre_project_set_up_hermetic_build)
+  # Google Test also calls hermetic setup functions from add_subdirectory,
+  # although its changes will not affect things at the current scope.
+  pre_project_set_up_hermetic_build()
+endif()
+
+########################################################################
+#
+# Project-wide settings
+
+# Name of the project.
+#
+# CMake files in this project can refer to the root source directory
+# as ${gmock_SOURCE_DIR} and to the root binary directory as
+# ${gmock_BINARY_DIR}.
+# Language "C" is required for find_package(Threads).
+cmake_minimum_required(VERSION 3.13)
+project(gmock VERSION ${GOOGLETEST_VERSION} LANGUAGES CXX C)
+
+if (COMMAND set_up_hermetic_build)
+  set_up_hermetic_build()
+endif()
+
+# Instructs CMake to process Google Test's CMakeLists.txt and add its
+# targets to the current scope.  We are placing Google Test's binary
+# directory in a subdirectory of our own as VC compilation may break
+# if they are the same (the default).
+add_subdirectory("${gtest_dir}" "${gmock_BINARY_DIR}/${gtest_dir}")
+
+
+# These commands only run if this is the main project
+if(CMAKE_PROJECT_NAME STREQUAL "gmock" OR CMAKE_PROJECT_NAME STREQUAL "googletest-distribution")
+  # BUILD_SHARED_LIBS is a standard CMake variable, but we declare it here to
+  # make it prominent in the GUI.
+  option(BUILD_SHARED_LIBS "Build shared libraries (DLLs)." OFF)
+else()
+  mark_as_advanced(gmock_build_tests)
+endif()
+
+# Although Google Test's CMakeLists.txt calls this function, the
+# changes there don't affect the current scope.  Therefore we have to
+# call it again here.
+config_compiler_and_linker()  # from ${gtest_dir}/cmake/internal_utils.cmake
+
+# Adds Google Mock's and Google Test's header directories to the search path.
+set(gmock_build_include_dirs
+  "${gmock_SOURCE_DIR}/include"
+  "${gmock_SOURCE_DIR}"
+  "${gtest_SOURCE_DIR}/include"
+  # This directory is needed to build directly from Google Test sources.
+  "${gtest_SOURCE_DIR}")
+include_directories(${gmock_build_include_dirs})
+
+########################################################################
+#
+# Defines the gmock & gmock_main libraries.  User tests should link
+# with one of them.
+
+# Google Mock libraries.  We build them using more strict warnings than what
+# are used for other targets, to ensure that Google Mock can be compiled by
+# a user aggressive about warnings.
+if (MSVC)
+  cxx_library(gmock
+              "${cxx_strict}"
+              "${gtest_dir}/src/gtest-all.cc"
+              src/gmock-all.cc)
+
+  cxx_library(gmock_main
+              "${cxx_strict}"
+              "${gtest_dir}/src/gtest-all.cc"
+              src/gmock-all.cc
+              src/gmock_main.cc)
+else()
+  cxx_library(gmock "${cxx_strict}" src/gmock-all.cc)
+  target_link_libraries(gmock PUBLIC gtest)
+  set_target_properties(gmock PROPERTIES VERSION ${GOOGLETEST_VERSION})
+  cxx_library(gmock_main "${cxx_strict}" src/gmock_main.cc)
+  target_link_libraries(gmock_main PUBLIC gmock)
+  set_target_properties(gmock_main PROPERTIES VERSION ${GOOGLETEST_VERSION})
+endif()
+
+string(REPLACE ";" "$<SEMICOLON>" dirs "${gmock_build_include_dirs}")
+target_include_directories(gmock SYSTEM INTERFACE
+  "$<BUILD_INTERFACE:${dirs}>"
+  "$<INSTALL_INTERFACE:$<INSTALL_PREFIX>/${CMAKE_INSTALL_INCLUDEDIR}>")
+target_include_directories(gmock_main SYSTEM INTERFACE
+  "$<BUILD_INTERFACE:${dirs}>"
+  "$<INSTALL_INTERFACE:$<INSTALL_PREFIX>/${CMAKE_INSTALL_INCLUDEDIR}>")
+
+########################################################################
+#
+# Install rules
+install_project(gmock gmock_main)
+
+########################################################################
+#
+# Google Mock's own tests.
+#
+# You can skip this section if you aren't interested in testing
+# Google Mock itself.
+#
+# The tests are not built by default.  To build them, set the
+# gmock_build_tests option to ON.  You can do it by running ccmake
+# or specifying the -Dgmock_build_tests=ON flag when running cmake.
+
+if (gmock_build_tests)
+  # This must be set in the root directory for the tests to be run by
+  # 'make test' or ctest.
+  enable_testing()
+
+  if (MINGW OR CYGWIN)
+    add_compile_options("-Wa,-mbig-obj")
+  endif()
+
+  ############################################################
+  # C++ tests built with standard compiler flags.
+
+  cxx_test(gmock-actions_test gmock_main)
+  cxx_test(gmock-cardinalities_test gmock_main)
+  cxx_test(gmock_ex_test gmock_main)
+  cxx_test(gmock-function-mocker_test gmock_main)
+  cxx_test(gmock-internal-utils_test gmock_main)
+  cxx_test(gmock-matchers-arithmetic_test gmock_main)
+  cxx_test(gmock-matchers-comparisons_test gmock_main)
+  cxx_test(gmock-matchers-containers_test gmock_main)
+  cxx_test(gmock-matchers-misc_test gmock_main)
+  cxx_test(gmock-more-actions_test gmock_main)
+  cxx_test(gmock-nice-strict_test gmock_main)
+  cxx_test(gmock-port_test gmock_main)
+  cxx_test(gmock-spec-builders_test gmock_main)
+  cxx_test(gmock_link_test gmock_main test/gmock_link2_test.cc)
+  cxx_test(gmock_test gmock_main)
+
+  if (DEFINED GTEST_HAS_PTHREAD)
+    cxx_test(gmock_stress_test gmock)
+  endif()
+
+  # gmock_all_test is commented to save time building and running tests.
+  # Uncomment if necessary.
+  # cxx_test(gmock_all_test gmock_main)
+
+  ############################################################
+  # C++ tests built with non-standard compiler flags.
+
+  if (MSVC)
+    cxx_library(gmock_main_no_exception "${cxx_no_exception}"
+      "${gtest_dir}/src/gtest-all.cc" src/gmock-all.cc src/gmock_main.cc)
+
+    cxx_library(gmock_main_no_rtti "${cxx_no_rtti}"
+      "${gtest_dir}/src/gtest-all.cc" src/gmock-all.cc src/gmock_main.cc)
+
+  else()
+    cxx_library(gmock_main_no_exception "${cxx_no_exception}" src/gmock_main.cc)
+    target_link_libraries(gmock_main_no_exception PUBLIC gmock)
+
+    cxx_library(gmock_main_no_rtti "${cxx_no_rtti}" src/gmock_main.cc)
+    target_link_libraries(gmock_main_no_rtti PUBLIC gmock)
+  endif()
+  cxx_test_with_flags(gmock-more-actions_no_exception_test "${cxx_no_exception}"
+    gmock_main_no_exception test/gmock-more-actions_test.cc)
+
+  cxx_test_with_flags(gmock_no_rtti_test "${cxx_no_rtti}"
+    gmock_main_no_rtti test/gmock-spec-builders_test.cc)
+
+  cxx_shared_library(shared_gmock_main "${cxx_default}"
+    "${gtest_dir}/src/gtest-all.cc" src/gmock-all.cc src/gmock_main.cc)
+
+  # Tests that a binary can be built with Google Mock as a shared library.  On
+  # some system configurations, it may not possible to run the binary without
+  # knowing more details about the system configurations. We do not try to run
+  # this binary. To get a more robust shared library coverage, configure with
+  # -DBUILD_SHARED_LIBS=ON.
+  cxx_executable_with_flags(shared_gmock_test_ "${cxx_default}"
+    shared_gmock_main test/gmock-spec-builders_test.cc)
+  set_target_properties(shared_gmock_test_
+    PROPERTIES
+    COMPILE_DEFINITIONS "GTEST_LINKED_AS_SHARED_LIBRARY=1")
+
+  ############################################################
+  # Python tests.
+
+  cxx_executable(gmock_leak_test_ test gmock_main)
+  py_test(gmock_leak_test)
+
+  cxx_executable(gmock_output_test_ test gmock)
+  py_test(gmock_output_test)
+endif()
diff --git a/third_party/googletest/googlemock/README.md b/third_party/googletest/googlemock/README.md
new file mode 100644
index 0000000..e1103b1
--- /dev/null
+++ b/third_party/googletest/googlemock/README.md
@@ -0,0 +1,40 @@
+# Googletest Mocking (gMock) Framework
+
+### Overview
+
+Google's framework for writing and using C++ mock classes. It can help you
+derive better designs of your system and write better tests.
+
+It is inspired by:
+
+*   [jMock](http://www.jmock.org/)
+*   [EasyMock](https://easymock.org/)
+*   [Hamcrest](https://code.google.com/p/hamcrest/)
+
+It is designed with C++'s specifics in mind.
+
+gMock:
+
+-   Provides a declarative syntax for defining mocks.
+-   Can define partial (hybrid) mocks, which are a cross of real and mock
+    objects.
+-   Handles functions of arbitrary types and overloaded functions.
+-   Comes with a rich set of matchers for validating function arguments.
+-   Uses an intuitive syntax for controlling the behavior of a mock.
+-   Does automatic verification of expectations (no record-and-replay needed).
+-   Allows arbitrary (partial) ordering constraints on function calls to be
+    expressed.
+-   Lets a user extend it by defining new matchers and actions.
+-   Does not use exceptions.
+-   Is easy to learn and use.
+
+Details and examples can be found here:
+
+*   [gMock for Dummies](https://google.github.io/googletest/gmock_for_dummies.html)
+*   [Legacy gMock FAQ](https://google.github.io/googletest/gmock_faq.html)
+*   [gMock Cookbook](https://google.github.io/googletest/gmock_cook_book.html)
+*   [gMock Cheat Sheet](https://google.github.io/googletest/gmock_cheat_sheet.html)
+
+GoogleMock is a part of
+[GoogleTest C++ testing framework](https://github.com/google/googletest/) and a
+subject to the same requirements.
diff --git a/third_party/googletest/googlemock/cmake/gmock.pc.in b/third_party/googletest/googlemock/cmake/gmock.pc.in
new file mode 100644
index 0000000..23c67b5
--- /dev/null
+++ b/third_party/googletest/googlemock/cmake/gmock.pc.in
@@ -0,0 +1,10 @@
+libdir=@CMAKE_INSTALL_FULL_LIBDIR@
+includedir=@CMAKE_INSTALL_FULL_INCLUDEDIR@
+
+Name: gmock
+Description: GoogleMock (without main() function)
+Version: @PROJECT_VERSION@
+URL: https://github.com/google/googletest
+Requires: gtest = @PROJECT_VERSION@
+Libs: -L${libdir} -lgmock @CMAKE_THREAD_LIBS_INIT@
+Cflags: -I${includedir} @GTEST_HAS_PTHREAD_MACRO@
diff --git a/third_party/googletest/googlemock/cmake/gmock_main.pc.in b/third_party/googletest/googlemock/cmake/gmock_main.pc.in
new file mode 100644
index 0000000..66ffea7
--- /dev/null
+++ b/third_party/googletest/googlemock/cmake/gmock_main.pc.in
@@ -0,0 +1,10 @@
+libdir=@CMAKE_INSTALL_FULL_LIBDIR@
+includedir=@CMAKE_INSTALL_FULL_INCLUDEDIR@
+
+Name: gmock_main
+Description: GoogleMock (with main() function)
+Version: @PROJECT_VERSION@
+URL: https://github.com/google/googletest
+Requires: gmock = @PROJECT_VERSION@
+Libs: -L${libdir} -lgmock_main @CMAKE_THREAD_LIBS_INIT@
+Cflags: -I${includedir} @GTEST_HAS_PTHREAD_MACRO@
diff --git a/third_party/googletest/docs/README.md b/third_party/googletest/googlemock/docs/README.md
index 1bc57b7..1bc57b7 100644
--- a/third_party/googletest/docs/README.md
+++ b/third_party/googletest/googlemock/docs/README.md
diff --git a/third_party/googletest/googlemock/include/gmock/gmock-actions.h b/third_party/googletest/googlemock/include/gmock/gmock-actions.h
new file mode 100644
index 0000000..f20258b
--- /dev/null
+++ b/third_party/googletest/googlemock/include/gmock/gmock-actions.h
@@ -0,0 +1,2303 @@
+// Copyright 2007, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Google Mock - a framework for writing C++ mock classes.
+//
+// The ACTION* family of macros can be used in a namespace scope to
+// define custom actions easily.  The syntax:
+//
+//   ACTION(name) { statements; }
+//
+// will define an action with the given name that executes the
+// statements.  The value returned by the statements will be used as
+// the return value of the action.  Inside the statements, you can
+// refer to the K-th (0-based) argument of the mock function by
+// 'argK', and refer to its type by 'argK_type'.  For example:
+//
+//   ACTION(IncrementArg1) {
+//     arg1_type temp = arg1;
+//     return ++(*temp);
+//   }
+//
+// allows you to write
+//
+//   ...WillOnce(IncrementArg1());
+//
+// You can also refer to the entire argument tuple and its type by
+// 'args' and 'args_type', and refer to the mock function type and its
+// return type by 'function_type' and 'return_type'.
+//
+// Note that you don't need to specify the types of the mock function
+// arguments.  However rest assured that your code is still type-safe:
+// you'll get a compiler error if *arg1 doesn't support the ++
+// operator, or if the type of ++(*arg1) isn't compatible with the
+// mock function's return type, for example.
+//
+// Sometimes you'll want to parameterize the action.   For that you can use
+// another macro:
+//
+//   ACTION_P(name, param_name) { statements; }
+//
+// For example:
+//
+//   ACTION_P(Add, n) { return arg0 + n; }
+//
+// will allow you to write:
+//
+//   ...WillOnce(Add(5));
+//
+// Note that you don't need to provide the type of the parameter
+// either.  If you need to reference the type of a parameter named
+// 'foo', you can write 'foo_type'.  For example, in the body of
+// ACTION_P(Add, n) above, you can write 'n_type' to refer to the type
+// of 'n'.
+//
+// We also provide ACTION_P2, ACTION_P3, ..., up to ACTION_P10 to support
+// multi-parameter actions.
+//
+// For the purpose of typing, you can view
+//
+//   ACTION_Pk(Foo, p1, ..., pk) { ... }
+//
+// as shorthand for
+//
+//   template <typename p1_type, ..., typename pk_type>
+//   FooActionPk<p1_type, ..., pk_type> Foo(p1_type p1, ..., pk_type pk) { ... }
+//
+// In particular, you can provide the template type arguments
+// explicitly when invoking Foo(), as in Foo<long, bool>(5, false);
+// although usually you can rely on the compiler to infer the types
+// for you automatically.  You can assign the result of expression
+// Foo(p1, ..., pk) to a variable of type FooActionPk<p1_type, ...,
+// pk_type>.  This can be useful when composing actions.
+//
+// You can also overload actions with different numbers of parameters:
+//
+//   ACTION_P(Plus, a) { ... }
+//   ACTION_P2(Plus, a, b) { ... }
+//
+// While it's tempting to always use the ACTION* macros when defining
+// a new action, you should also consider implementing ActionInterface
+// or using MakePolymorphicAction() instead, especially if you need to
+// use the action a lot.  While these approaches require more work,
+// they give you more control on the types of the mock function
+// arguments and the action parameters, which in general leads to
+// better compiler error messages that pay off in the long run.  They
+// also allow overloading actions based on parameter types (as opposed
+// to just based on the number of parameters).
+//
+// CAVEAT:
+//
+// ACTION*() can only be used in a namespace scope as templates cannot be
+// declared inside of a local class.
+// Users can, however, define any local functors (e.g. a lambda) that
+// can be used as actions.
+//
+// MORE INFORMATION:
+//
+// To learn more about using these macros, please search for 'ACTION' on
+// https://github.com/google/googletest/blob/main/docs/gmock_cook_book.md
+
+// IWYU pragma: private, include "gmock/gmock.h"
+// IWYU pragma: friend gmock/.*
+
+#ifndef GOOGLEMOCK_INCLUDE_GMOCK_GMOCK_ACTIONS_H_
+#define GOOGLEMOCK_INCLUDE_GMOCK_GMOCK_ACTIONS_H_
+
+#ifndef _WIN32_WCE
+#include <errno.h>
+#endif
+
+#include <algorithm>
+#include <functional>
+#include <memory>
+#include <string>
+#include <tuple>
+#include <type_traits>
+#include <utility>
+
+#include "gmock/internal/gmock-internal-utils.h"
+#include "gmock/internal/gmock-port.h"
+#include "gmock/internal/gmock-pp.h"
+
+GTEST_DISABLE_MSC_WARNINGS_PUSH_(4100)
+
+namespace testing {
+
+// To implement an action Foo, define:
+//   1. a class FooAction that implements the ActionInterface interface, and
+//   2. a factory function that creates an Action object from a
+//      const FooAction*.
+//
+// The two-level delegation design follows that of Matcher, providing
+// consistency for extension developers.  It also eases ownership
+// management as Action objects can now be copied like plain values.
+
+namespace internal {
+
+// BuiltInDefaultValueGetter<T, true>::Get() returns a
+// default-constructed T value.  BuiltInDefaultValueGetter<T,
+// false>::Get() crashes with an error.
+//
+// This primary template is used when kDefaultConstructible is true.
+template <typename T, bool kDefaultConstructible>
+struct BuiltInDefaultValueGetter {
+  static T Get() { return T(); }
+};
+template <typename T>
+struct BuiltInDefaultValueGetter<T, false> {
+  static T Get() {
+    Assert(false, __FILE__, __LINE__,
+           "Default action undefined for the function return type.");
+#if defined(__GNUC__) || defined(__clang__)
+    __builtin_unreachable();
+#elif defined(_MSC_VER)
+    __assume(0);
+#else
+    return Invalid<T>();
+    // The above statement will never be reached, but is required in
+    // order for this function to compile.
+#endif
+  }
+};
+
+// BuiltInDefaultValue<T>::Get() returns the "built-in" default value
+// for type T, which is NULL when T is a raw pointer type, 0 when T is
+// a numeric type, false when T is bool, or "" when T is string or
+// std::string.  In addition, in C++11 and above, it turns a
+// default-constructed T value if T is default constructible.  For any
+// other type T, the built-in default T value is undefined, and the
+// function will abort the process.
+template <typename T>
+class BuiltInDefaultValue {
+ public:
+  // This function returns true if and only if type T has a built-in default
+  // value.
+  static bool Exists() { return ::std::is_default_constructible<T>::value; }
+
+  static T Get() {
+    return BuiltInDefaultValueGetter<
+        T, ::std::is_default_constructible<T>::value>::Get();
+  }
+};
+
+// This partial specialization says that we use the same built-in
+// default value for T and const T.
+template <typename T>
+class BuiltInDefaultValue<const T> {
+ public:
+  static bool Exists() { return BuiltInDefaultValue<T>::Exists(); }
+  static T Get() { return BuiltInDefaultValue<T>::Get(); }
+};
+
+// This partial specialization defines the default values for pointer
+// types.
+template <typename T>
+class BuiltInDefaultValue<T*> {
+ public:
+  static bool Exists() { return true; }
+  static T* Get() { return nullptr; }
+};
+
+// The following specializations define the default values for
+// specific types we care about.
+#define GMOCK_DEFINE_DEFAULT_ACTION_FOR_RETURN_TYPE_(type, value) \
+  template <>                                                     \
+  class BuiltInDefaultValue<type> {                               \
+   public:                                                        \
+    static bool Exists() { return true; }                         \
+    static type Get() { return value; }                           \
+  }
+
+GMOCK_DEFINE_DEFAULT_ACTION_FOR_RETURN_TYPE_(void, );  // NOLINT
+GMOCK_DEFINE_DEFAULT_ACTION_FOR_RETURN_TYPE_(::std::string, "");
+GMOCK_DEFINE_DEFAULT_ACTION_FOR_RETURN_TYPE_(bool, false);
+GMOCK_DEFINE_DEFAULT_ACTION_FOR_RETURN_TYPE_(unsigned char, '\0');
+GMOCK_DEFINE_DEFAULT_ACTION_FOR_RETURN_TYPE_(signed char, '\0');
+GMOCK_DEFINE_DEFAULT_ACTION_FOR_RETURN_TYPE_(char, '\0');
+
+// There's no need for a default action for signed wchar_t, as that
+// type is the same as wchar_t for gcc, and invalid for MSVC.
+//
+// There's also no need for a default action for unsigned wchar_t, as
+// that type is the same as unsigned int for gcc, and invalid for
+// MSVC.
+#if GMOCK_WCHAR_T_IS_NATIVE_
+GMOCK_DEFINE_DEFAULT_ACTION_FOR_RETURN_TYPE_(wchar_t, 0U);  // NOLINT
+#endif
+
+GMOCK_DEFINE_DEFAULT_ACTION_FOR_RETURN_TYPE_(unsigned short, 0U);  // NOLINT
+GMOCK_DEFINE_DEFAULT_ACTION_FOR_RETURN_TYPE_(signed short, 0);     // NOLINT
+GMOCK_DEFINE_DEFAULT_ACTION_FOR_RETURN_TYPE_(unsigned int, 0U);
+GMOCK_DEFINE_DEFAULT_ACTION_FOR_RETURN_TYPE_(signed int, 0);
+GMOCK_DEFINE_DEFAULT_ACTION_FOR_RETURN_TYPE_(unsigned long, 0UL);     // NOLINT
+GMOCK_DEFINE_DEFAULT_ACTION_FOR_RETURN_TYPE_(signed long, 0L);        // NOLINT
+GMOCK_DEFINE_DEFAULT_ACTION_FOR_RETURN_TYPE_(unsigned long long, 0);  // NOLINT
+GMOCK_DEFINE_DEFAULT_ACTION_FOR_RETURN_TYPE_(signed long long, 0);    // NOLINT
+GMOCK_DEFINE_DEFAULT_ACTION_FOR_RETURN_TYPE_(float, 0);
+GMOCK_DEFINE_DEFAULT_ACTION_FOR_RETURN_TYPE_(double, 0);
+
+#undef GMOCK_DEFINE_DEFAULT_ACTION_FOR_RETURN_TYPE_
+
+// Partial implementations of metaprogramming types from the standard library
+// not available in C++11.
+
+template <typename P>
+struct negation
+    // NOLINTNEXTLINE
+    : std::integral_constant<bool, bool(!P::value)> {};
+
+// Base case: with zero predicates the answer is always true.
+template <typename...>
+struct conjunction : std::true_type {};
+
+// With a single predicate, the answer is that predicate.
+template <typename P1>
+struct conjunction<P1> : P1 {};
+
+// With multiple predicates the answer is the first predicate if that is false,
+// and we recurse otherwise.
+template <typename P1, typename... Ps>
+struct conjunction<P1, Ps...>
+    : std::conditional<bool(P1::value), conjunction<Ps...>, P1>::type {};
+
+template <typename...>
+struct disjunction : std::false_type {};
+
+template <typename P1>
+struct disjunction<P1> : P1 {};
+
+template <typename P1, typename... Ps>
+struct disjunction<P1, Ps...>
+    // NOLINTNEXTLINE
+    : std::conditional<!bool(P1::value), disjunction<Ps...>, P1>::type {};
+
+template <typename...>
+using void_t = void;
+
+// Detects whether an expression of type `From` can be implicitly converted to
+// `To` according to [conv]. In C++17, [conv]/3 defines this as follows:
+//
+//     An expression e can be implicitly converted to a type T if and only if
+//     the declaration T t=e; is well-formed, for some invented temporary
+//     variable t ([dcl.init]).
+//
+// [conv]/2 implies we can use function argument passing to detect whether this
+// initialization is valid.
+//
+// Note that this is distinct from is_convertible, which requires this be valid:
+//
+//     To test() {
+//       return declval<From>();
+//     }
+//
+// In particular, is_convertible doesn't give the correct answer when `To` and
+// `From` are the same non-moveable type since `declval<From>` will be an rvalue
+// reference, defeating the guaranteed copy elision that would otherwise make
+// this function work.
+//
+// REQUIRES: `From` is not cv void.
+template <typename From, typename To>
+struct is_implicitly_convertible {
+ private:
+  // A function that accepts a parameter of type T. This can be called with type
+  // U successfully only if U is implicitly convertible to T.
+  template <typename T>
+  static void Accept(T);
+
+  // A function that creates a value of type T.
+  template <typename T>
+  static T Make();
+
+  // An overload be selected when implicit conversion from T to To is possible.
+  template <typename T, typename = decltype(Accept<To>(Make<T>()))>
+  static std::true_type TestImplicitConversion(int);
+
+  // A fallback overload selected in all other cases.
+  template <typename T>
+  static std::false_type TestImplicitConversion(...);
+
+ public:
+  using type = decltype(TestImplicitConversion<From>(0));
+  static constexpr bool value = type::value;
+};
+
+// Like std::invoke_result_t from C++17, but works only for objects with call
+// operators (not e.g. member function pointers, which we don't need specific
+// support for in OnceAction because std::function deals with them).
+template <typename F, typename... Args>
+using call_result_t = decltype(std::declval<F>()(std::declval<Args>()...));
+
+template <typename Void, typename R, typename F, typename... Args>
+struct is_callable_r_impl : std::false_type {};
+
+// Specialize the struct for those template arguments where call_result_t is
+// well-formed. When it's not, the generic template above is chosen, resulting
+// in std::false_type.
+template <typename R, typename F, typename... Args>
+struct is_callable_r_impl<void_t<call_result_t<F, Args...>>, R, F, Args...>
+    : std::conditional<
+          std::is_void<R>::value,  //
+          std::true_type,          //
+          is_implicitly_convertible<call_result_t<F, Args...>, R>>::type {};
+
+// Like std::is_invocable_r from C++17, but works only for objects with call
+// operators. See the note on call_result_t.
+template <typename R, typename F, typename... Args>
+using is_callable_r = is_callable_r_impl<void, R, F, Args...>;
+
+// Like std::as_const from C++17.
+template <typename T>
+typename std::add_const<T>::type& as_const(T& t) {
+  return t;
+}
+
+}  // namespace internal
+
+// Specialized for function types below.
+template <typename F>
+class OnceAction;
+
+// An action that can only be used once.
+//
+// This is accepted by WillOnce, which doesn't require the underlying action to
+// be copy-constructible (only move-constructible), and promises to invoke it as
+// an rvalue reference. This allows the action to work with move-only types like
+// std::move_only_function in a type-safe manner.
+//
+// For example:
+//
+//     // Assume we have some API that needs to accept a unique pointer to some
+//     // non-copyable object Foo.
+//     void AcceptUniquePointer(std::unique_ptr<Foo> foo);
+//
+//     // We can define an action that provides a Foo to that API. Because It
+//     // has to give away its unique pointer, it must not be called more than
+//     // once, so its call operator is &&-qualified.
+//     struct ProvideFoo {
+//       std::unique_ptr<Foo> foo;
+//
+//       void operator()() && {
+//         AcceptUniquePointer(std::move(Foo));
+//       }
+//     };
+//
+//     // This action can be used with WillOnce.
+//     EXPECT_CALL(mock, Call)
+//         .WillOnce(ProvideFoo{std::make_unique<Foo>(...)});
+//
+//     // But a call to WillRepeatedly will fail to compile. This is correct,
+//     // since the action cannot correctly be used repeatedly.
+//     EXPECT_CALL(mock, Call)
+//         .WillRepeatedly(ProvideFoo{std::make_unique<Foo>(...)});
+//
+// A less-contrived example would be an action that returns an arbitrary type,
+// whose &&-qualified call operator is capable of dealing with move-only types.
+template <typename Result, typename... Args>
+class OnceAction<Result(Args...)> final {
+ private:
+  // True iff we can use the given callable type (or lvalue reference) directly
+  // via StdFunctionAdaptor.
+  template <typename Callable>
+  using IsDirectlyCompatible = internal::conjunction<
+      // It must be possible to capture the callable in StdFunctionAdaptor.
+      std::is_constructible<typename std::decay<Callable>::type, Callable>,
+      // The callable must be compatible with our signature.
+      internal::is_callable_r<Result, typename std::decay<Callable>::type,
+                              Args...>>;
+
+  // True iff we can use the given callable type via StdFunctionAdaptor once we
+  // ignore incoming arguments.
+  template <typename Callable>
+  using IsCompatibleAfterIgnoringArguments = internal::conjunction<
+      // It must be possible to capture the callable in a lambda.
+      std::is_constructible<typename std::decay<Callable>::type, Callable>,
+      // The callable must be invocable with zero arguments, returning something
+      // convertible to Result.
+      internal::is_callable_r<Result, typename std::decay<Callable>::type>>;
+
+ public:
+  // Construct from a callable that is directly compatible with our mocked
+  // signature: it accepts our function type's arguments and returns something
+  // convertible to our result type.
+  template <typename Callable,
+            typename std::enable_if<
+                internal::conjunction<
+                    // Teach clang on macOS that we're not talking about a
+                    // copy/move constructor here. Otherwise it gets confused
+                    // when checking the is_constructible requirement of our
+                    // traits above.
+                    internal::negation<std::is_same<
+                        OnceAction, typename std::decay<Callable>::type>>,
+                    IsDirectlyCompatible<Callable>>  //
+                ::value,
+                int>::type = 0>
+  OnceAction(Callable&& callable)  // NOLINT
+      : function_(StdFunctionAdaptor<typename std::decay<Callable>::type>(
+            {}, std::forward<Callable>(callable))) {}
+
+  // As above, but for a callable that ignores the mocked function's arguments.
+  template <typename Callable,
+            typename std::enable_if<
+                internal::conjunction<
+                    // Teach clang on macOS that we're not talking about a
+                    // copy/move constructor here. Otherwise it gets confused
+                    // when checking the is_constructible requirement of our
+                    // traits above.
+                    internal::negation<std::is_same<
+                        OnceAction, typename std::decay<Callable>::type>>,
+                    // Exclude callables for which the overload above works.
+                    // We'd rather provide the arguments if possible.
+                    internal::negation<IsDirectlyCompatible<Callable>>,
+                    IsCompatibleAfterIgnoringArguments<Callable>>::value,
+                int>::type = 0>
+  OnceAction(Callable&& callable)  // NOLINT
+                                   // Call the constructor above with a callable
+                                   // that ignores the input arguments.
+      : OnceAction(IgnoreIncomingArguments<typename std::decay<Callable>::type>{
+            std::forward<Callable>(callable)}) {}
+
+  // We are naturally copyable because we store only an std::function, but
+  // semantically we should not be copyable.
+  OnceAction(const OnceAction&) = delete;
+  OnceAction& operator=(const OnceAction&) = delete;
+  OnceAction(OnceAction&&) = default;
+
+  // Invoke the underlying action callable with which we were constructed,
+  // handing it the supplied arguments.
+  Result Call(Args... args) && {
+    return function_(std::forward<Args>(args)...);
+  }
+
+ private:
+  // An adaptor that wraps a callable that is compatible with our signature and
+  // being invoked as an rvalue reference so that it can be used as an
+  // StdFunctionAdaptor. This throws away type safety, but that's fine because
+  // this is only used by WillOnce, which we know calls at most once.
+  //
+  // Once we have something like std::move_only_function from C++23, we can do
+  // away with this.
+  template <typename Callable>
+  class StdFunctionAdaptor final {
+   public:
+    // A tag indicating that the (otherwise universal) constructor is accepting
+    // the callable itself, instead of e.g. stealing calls for the move
+    // constructor.
+    struct CallableTag final {};
+
+    template <typename F>
+    explicit StdFunctionAdaptor(CallableTag, F&& callable)
+        : callable_(std::make_shared<Callable>(std::forward<F>(callable))) {}
+
+    // Rather than explicitly returning Result, we return whatever the wrapped
+    // callable returns. This allows for compatibility with existing uses like
+    // the following, when the mocked function returns void:
+    //
+    //     EXPECT_CALL(mock_fn_, Call)
+    //         .WillOnce([&] {
+    //            [...]
+    //            return 0;
+    //         });
+    //
+    // Such a callable can be turned into std::function<void()>. If we use an
+    // explicit return type of Result here then it *doesn't* work with
+    // std::function, because we'll get a "void function should not return a
+    // value" error.
+    //
+    // We need not worry about incompatible result types because the SFINAE on
+    // OnceAction already checks this for us. std::is_invocable_r_v itself makes
+    // the same allowance for void result types.
+    template <typename... ArgRefs>
+    internal::call_result_t<Callable, ArgRefs...> operator()(
+        ArgRefs&&... args) const {
+      return std::move(*callable_)(std::forward<ArgRefs>(args)...);
+    }
+
+   private:
+    // We must put the callable on the heap so that we are copyable, which
+    // std::function needs.
+    std::shared_ptr<Callable> callable_;
+  };
+
+  // An adaptor that makes a callable that accepts zero arguments callable with
+  // our mocked arguments.
+  template <typename Callable>
+  struct IgnoreIncomingArguments {
+    internal::call_result_t<Callable> operator()(Args&&...) {
+      return std::move(callable)();
+    }
+
+    Callable callable;
+  };
+
+  std::function<Result(Args...)> function_;
+};
+
+// When an unexpected function call is encountered, Google Mock will
+// let it return a default value if the user has specified one for its
+// return type, or if the return type has a built-in default value;
+// otherwise Google Mock won't know what value to return and will have
+// to abort the process.
+//
+// The DefaultValue<T> class allows a user to specify the
+// default value for a type T that is both copyable and publicly
+// destructible (i.e. anything that can be used as a function return
+// type).  The usage is:
+//
+//   // Sets the default value for type T to be foo.
+//   DefaultValue<T>::Set(foo);
+template <typename T>
+class DefaultValue {
+ public:
+  // Sets the default value for type T; requires T to be
+  // copy-constructable and have a public destructor.
+  static void Set(T x) {
+    delete producer_;
+    producer_ = new FixedValueProducer(x);
+  }
+
+  // Provides a factory function to be called to generate the default value.
+  // This method can be used even if T is only move-constructible, but it is not
+  // limited to that case.
+  typedef T (*FactoryFunction)();
+  static void SetFactory(FactoryFunction factory) {
+    delete producer_;
+    producer_ = new FactoryValueProducer(factory);
+  }
+
+  // Unsets the default value for type T.
+  static void Clear() {
+    delete producer_;
+    producer_ = nullptr;
+  }
+
+  // Returns true if and only if the user has set the default value for type T.
+  static bool IsSet() { return producer_ != nullptr; }
+
+  // Returns true if T has a default return value set by the user or there
+  // exists a built-in default value.
+  static bool Exists() {
+    return IsSet() || internal::BuiltInDefaultValue<T>::Exists();
+  }
+
+  // Returns the default value for type T if the user has set one;
+  // otherwise returns the built-in default value. Requires that Exists()
+  // is true, which ensures that the return value is well-defined.
+  static T Get() {
+    return producer_ == nullptr ? internal::BuiltInDefaultValue<T>::Get()
+                                : producer_->Produce();
+  }
+
+ private:
+  class ValueProducer {
+   public:
+    virtual ~ValueProducer() = default;
+    virtual T Produce() = 0;
+  };
+
+  class FixedValueProducer : public ValueProducer {
+   public:
+    explicit FixedValueProducer(T value) : value_(value) {}
+    T Produce() override { return value_; }
+
+   private:
+    const T value_;
+    FixedValueProducer(const FixedValueProducer&) = delete;
+    FixedValueProducer& operator=(const FixedValueProducer&) = delete;
+  };
+
+  class FactoryValueProducer : public ValueProducer {
+   public:
+    explicit FactoryValueProducer(FactoryFunction factory)
+        : factory_(factory) {}
+    T Produce() override { return factory_(); }
+
+   private:
+    const FactoryFunction factory_;
+    FactoryValueProducer(const FactoryValueProducer&) = delete;
+    FactoryValueProducer& operator=(const FactoryValueProducer&) = delete;
+  };
+
+  static ValueProducer* producer_;
+};
+
+// This partial specialization allows a user to set default values for
+// reference types.
+template <typename T>
+class DefaultValue<T&> {
+ public:
+  // Sets the default value for type T&.
+  static void Set(T& x) {  // NOLINT
+    address_ = &x;
+  }
+
+  // Unsets the default value for type T&.
+  static void Clear() { address_ = nullptr; }
+
+  // Returns true if and only if the user has set the default value for type T&.
+  static bool IsSet() { return address_ != nullptr; }
+
+  // Returns true if T has a default return value set by the user or there
+  // exists a built-in default value.
+  static bool Exists() {
+    return IsSet() || internal::BuiltInDefaultValue<T&>::Exists();
+  }
+
+  // Returns the default value for type T& if the user has set one;
+  // otherwise returns the built-in default value if there is one;
+  // otherwise aborts the process.
+  static T& Get() {
+    return address_ == nullptr ? internal::BuiltInDefaultValue<T&>::Get()
+                               : *address_;
+  }
+
+ private:
+  static T* address_;
+};
+
+// This specialization allows DefaultValue<void>::Get() to
+// compile.
+template <>
+class DefaultValue<void> {
+ public:
+  static bool Exists() { return true; }
+  static void Get() {}
+};
+
+// Points to the user-set default value for type T.
+template <typename T>
+typename DefaultValue<T>::ValueProducer* DefaultValue<T>::producer_ = nullptr;
+
+// Points to the user-set default value for type T&.
+template <typename T>
+T* DefaultValue<T&>::address_ = nullptr;
+
+// Implement this interface to define an action for function type F.
+template <typename F>
+class ActionInterface {
+ public:
+  typedef typename internal::Function<F>::Result Result;
+  typedef typename internal::Function<F>::ArgumentTuple ArgumentTuple;
+
+  ActionInterface() = default;
+  virtual ~ActionInterface() = default;
+
+  // Performs the action.  This method is not const, as in general an
+  // action can have side effects and be stateful.  For example, a
+  // get-the-next-element-from-the-collection action will need to
+  // remember the current element.
+  virtual Result Perform(const ArgumentTuple& args) = 0;
+
+ private:
+  ActionInterface(const ActionInterface&) = delete;
+  ActionInterface& operator=(const ActionInterface&) = delete;
+};
+
+template <typename F>
+class Action;
+
+// An Action<R(Args...)> is a copyable and IMMUTABLE (except by assignment)
+// object that represents an action to be taken when a mock function of type
+// R(Args...) is called. The implementation of Action<T> is just a
+// std::shared_ptr to const ActionInterface<T>. Don't inherit from Action! You
+// can view an object implementing ActionInterface<F> as a concrete action
+// (including its current state), and an Action<F> object as a handle to it.
+template <typename R, typename... Args>
+class Action<R(Args...)> {
+ private:
+  using F = R(Args...);
+
+  // Adapter class to allow constructing Action from a legacy ActionInterface.
+  // New code should create Actions from functors instead.
+  struct ActionAdapter {
+    // Adapter must be copyable to satisfy std::function requirements.
+    ::std::shared_ptr<ActionInterface<F>> impl_;
+
+    template <typename... InArgs>
+    typename internal::Function<F>::Result operator()(InArgs&&... args) {
+      return impl_->Perform(
+          ::std::forward_as_tuple(::std::forward<InArgs>(args)...));
+    }
+  };
+
+  template <typename G>
+  using IsCompatibleFunctor = std::is_constructible<std::function<F>, G>;
+
+ public:
+  typedef typename internal::Function<F>::Result Result;
+  typedef typename internal::Function<F>::ArgumentTuple ArgumentTuple;
+
+  // Constructs a null Action.  Needed for storing Action objects in
+  // STL containers.
+  Action() = default;
+
+  // Construct an Action from a specified callable.
+  // This cannot take std::function directly, because then Action would not be
+  // directly constructible from lambda (it would require two conversions).
+  template <
+      typename G,
+      typename = typename std::enable_if<internal::disjunction<
+          IsCompatibleFunctor<G>, std::is_constructible<std::function<Result()>,
+                                                        G>>::value>::type>
+  Action(G&& fun) {  // NOLINT
+    Init(::std::forward<G>(fun), IsCompatibleFunctor<G>());
+  }
+
+  // Constructs an Action from its implementation.
+  explicit Action(ActionInterface<F>* impl)
+      : fun_(ActionAdapter{::std::shared_ptr<ActionInterface<F>>(impl)}) {}
+
+  // This constructor allows us to turn an Action<Func> object into an
+  // Action<F>, as long as F's arguments can be implicitly converted
+  // to Func's and Func's return type can be implicitly converted to F's.
+  template <typename Func>
+  Action(const Action<Func>& action)  // NOLINT
+      : fun_(action.fun_) {}
+
+  // Returns true if and only if this is the DoDefault() action.
+  bool IsDoDefault() const { return fun_ == nullptr; }
+
+  // Performs the action.  Note that this method is const even though
+  // the corresponding method in ActionInterface is not.  The reason
+  // is that a const Action<F> means that it cannot be re-bound to
+  // another concrete action, not that the concrete action it binds to
+  // cannot change state.  (Think of the difference between a const
+  // pointer and a pointer to const.)
+  Result Perform(ArgumentTuple args) const {
+    if (IsDoDefault()) {
+      internal::IllegalDoDefault(__FILE__, __LINE__);
+    }
+    return internal::Apply(fun_, ::std::move(args));
+  }
+
+  // An action can be used as a OnceAction, since it's obviously safe to call it
+  // once.
+  operator OnceAction<F>() const {  // NOLINT
+    // Return a OnceAction-compatible callable that calls Perform with the
+    // arguments it is provided. We could instead just return fun_, but then
+    // we'd need to handle the IsDoDefault() case separately.
+    struct OA {
+      Action<F> action;
+
+      R operator()(Args... args) && {
+        return action.Perform(
+            std::forward_as_tuple(std::forward<Args>(args)...));
+      }
+    };
+
+    return OA{*this};
+  }
+
+ private:
+  template <typename G>
+  friend class Action;
+
+  template <typename G>
+  void Init(G&& g, ::std::true_type) {
+    fun_ = ::std::forward<G>(g);
+  }
+
+  template <typename G>
+  void Init(G&& g, ::std::false_type) {
+    fun_ = IgnoreArgs<typename ::std::decay<G>::type>{::std::forward<G>(g)};
+  }
+
+  template <typename FunctionImpl>
+  struct IgnoreArgs {
+    template <typename... InArgs>
+    Result operator()(const InArgs&...) const {
+      return function_impl();
+    }
+
+    FunctionImpl function_impl;
+  };
+
+  // fun_ is an empty function if and only if this is the DoDefault() action.
+  ::std::function<F> fun_;
+};
+
+// The PolymorphicAction class template makes it easy to implement a
+// polymorphic action (i.e. an action that can be used in mock
+// functions of than one type, e.g. Return()).
+//
+// To define a polymorphic action, a user first provides a COPYABLE
+// implementation class that has a Perform() method template:
+//
+//   class FooAction {
+//    public:
+//     template <typename Result, typename ArgumentTuple>
+//     Result Perform(const ArgumentTuple& args) const {
+//       // Processes the arguments and returns a result, using
+//       // std::get<N>(args) to get the N-th (0-based) argument in the tuple.
+//     }
+//     ...
+//   };
+//
+// Then the user creates the polymorphic action using
+// MakePolymorphicAction(object) where object has type FooAction.  See
+// the definition of Return(void) and SetArgumentPointee<N>(value) for
+// complete examples.
+template <typename Impl>
+class PolymorphicAction {
+ public:
+  explicit PolymorphicAction(const Impl& impl) : impl_(impl) {}
+
+  template <typename F>
+  operator Action<F>() const {
+    return Action<F>(new MonomorphicImpl<F>(impl_));
+  }
+
+ private:
+  template <typename F>
+  class MonomorphicImpl : public ActionInterface<F> {
+   public:
+    typedef typename internal::Function<F>::Result Result;
+    typedef typename internal::Function<F>::ArgumentTuple ArgumentTuple;
+
+    explicit MonomorphicImpl(const Impl& impl) : impl_(impl) {}
+
+    Result Perform(const ArgumentTuple& args) override {
+      return impl_.template Perform<Result>(args);
+    }
+
+   private:
+    Impl impl_;
+  };
+
+  Impl impl_;
+};
+
+// Creates an Action from its implementation and returns it.  The
+// created Action object owns the implementation.
+template <typename F>
+Action<F> MakeAction(ActionInterface<F>* impl) {
+  return Action<F>(impl);
+}
+
+// Creates a polymorphic action from its implementation.  This is
+// easier to use than the PolymorphicAction<Impl> constructor as it
+// doesn't require you to explicitly write the template argument, e.g.
+//
+//   MakePolymorphicAction(foo);
+// vs
+//   PolymorphicAction<TypeOfFoo>(foo);
+template <typename Impl>
+inline PolymorphicAction<Impl> MakePolymorphicAction(const Impl& impl) {
+  return PolymorphicAction<Impl>(impl);
+}
+
+namespace internal {
+
+// Helper struct to specialize ReturnAction to execute a move instead of a copy
+// on return. Useful for move-only types, but could be used on any type.
+template <typename T>
+struct ByMoveWrapper {
+  explicit ByMoveWrapper(T value) : payload(std::move(value)) {}
+  T payload;
+};
+
+// The general implementation of Return(R). Specializations follow below.
+template <typename R>
+class ReturnAction final {
+ public:
+  explicit ReturnAction(R value) : value_(std::move(value)) {}
+
+  template <typename U, typename... Args,
+            typename = typename std::enable_if<conjunction<
+                // See the requirements documented on Return.
+                negation<std::is_same<void, U>>,  //
+                negation<std::is_reference<U>>,   //
+                std::is_convertible<R, U>,        //
+                std::is_move_constructible<U>>::value>::type>
+  operator OnceAction<U(Args...)>() && {  // NOLINT
+    return Impl<U>(std::move(value_));
+  }
+
+  template <typename U, typename... Args,
+            typename = typename std::enable_if<conjunction<
+                // See the requirements documented on Return.
+                negation<std::is_same<void, U>>,   //
+                negation<std::is_reference<U>>,    //
+                std::is_convertible<const R&, U>,  //
+                std::is_copy_constructible<U>>::value>::type>
+  operator Action<U(Args...)>() const {  // NOLINT
+    return Impl<U>(value_);
+  }
+
+ private:
+  // Implements the Return(x) action for a mock function that returns type U.
+  template <typename U>
+  class Impl final {
+   public:
+    // The constructor used when the return value is allowed to move from the
+    // input value (i.e. we are converting to OnceAction).
+    explicit Impl(R&& input_value)
+        : state_(new State(std::move(input_value))) {}
+
+    // The constructor used when the return value is not allowed to move from
+    // the input value (i.e. we are converting to Action).
+    explicit Impl(const R& input_value) : state_(new State(input_value)) {}
+
+    U operator()() && { return std::move(state_->value); }
+    U operator()() const& { return state_->value; }
+
+   private:
+    // We put our state on the heap so that the compiler-generated copy/move
+    // constructors work correctly even when U is a reference-like type. This is
+    // necessary only because we eagerly create State::value (see the note on
+    // that symbol for details). If we instead had only the input value as a
+    // member then the default constructors would work fine.
+    //
+    // For example, when R is std::string and U is std::string_view, value is a
+    // reference to the string backed by input_value. The copy constructor would
+    // copy both, so that we wind up with a new input_value object (with the
+    // same contents) and a reference to the *old* input_value object rather
+    // than the new one.
+    struct State {
+      explicit State(const R& input_value_in)
+          : input_value(input_value_in),
+            // Make an implicit conversion to Result before initializing the U
+            // object we store, avoiding calling any explicit constructor of U
+            // from R.
+            //
+            // This simulates the language rules: a function with return type U
+            // that does `return R()` requires R to be implicitly convertible to
+            // U, and uses that path for the conversion, even U Result has an
+            // explicit constructor from R.
+            value(ImplicitCast_<U>(internal::as_const(input_value))) {}
+
+      // As above, but for the case where we're moving from the ReturnAction
+      // object because it's being used as a OnceAction.
+      explicit State(R&& input_value_in)
+          : input_value(std::move(input_value_in)),
+            // For the same reason as above we make an implicit conversion to U
+            // before initializing the value.
+            //
+            // Unlike above we provide the input value as an rvalue to the
+            // implicit conversion because this is a OnceAction: it's fine if it
+            // wants to consume the input value.
+            value(ImplicitCast_<U>(std::move(input_value))) {}
+
+      // A copy of the value originally provided by the user. We retain this in
+      // addition to the value of the mock function's result type below in case
+      // the latter is a reference-like type. See the std::string_view example
+      // in the documentation on Return.
+      R input_value;
+
+      // The value we actually return, as the type returned by the mock function
+      // itself.
+      //
+      // We eagerly initialize this here, rather than lazily doing the implicit
+      // conversion automatically each time Perform is called, for historical
+      // reasons: in 2009-11, commit a070cbd91c (Google changelist 13540126)
+      // made the Action<U()> conversion operator eagerly convert the R value to
+      // U, but without keeping the R alive. This broke the use case discussed
+      // in the documentation for Return, making reference-like types such as
+      // std::string_view not safe to use as U where the input type R is a
+      // value-like type such as std::string.
+      //
+      // The example the commit gave was not very clear, nor was the issue
+      // thread (https://github.com/google/googlemock/issues/86), but it seems
+      // the worry was about reference-like input types R that flatten to a
+      // value-like type U when being implicitly converted. An example of this
+      // is std::vector<bool>::reference, which is often a proxy type with an
+      // reference to the underlying vector:
+      //
+      //     // Helper method: have the mock function return bools according
+      //     // to the supplied script.
+      //     void SetActions(MockFunction<bool(size_t)>& mock,
+      //                     const std::vector<bool>& script) {
+      //       for (size_t i = 0; i < script.size(); ++i) {
+      //         EXPECT_CALL(mock, Call(i)).WillOnce(Return(script[i]));
+      //       }
+      //     }
+      //
+      //     TEST(Foo, Bar) {
+      //       // Set actions using a temporary vector, whose operator[]
+      //       // returns proxy objects that references that will be
+      //       // dangling once the call to SetActions finishes and the
+      //       // vector is destroyed.
+      //       MockFunction<bool(size_t)> mock;
+      //       SetActions(mock, {false, true});
+      //
+      //       EXPECT_FALSE(mock.AsStdFunction()(0));
+      //       EXPECT_TRUE(mock.AsStdFunction()(1));
+      //     }
+      //
+      // This eager conversion helps with a simple case like this, but doesn't
+      // fully make these types work in general. For example the following still
+      // uses a dangling reference:
+      //
+      //     TEST(Foo, Baz) {
+      //       MockFunction<std::vector<std::string>()> mock;
+      //
+      //       // Return the same vector twice, and then the empty vector
+      //       // thereafter.
+      //       auto action = Return(std::initializer_list<std::string>{
+      //           "taco", "burrito",
+      //       });
+      //
+      //       EXPECT_CALL(mock, Call)
+      //           .WillOnce(action)
+      //           .WillOnce(action)
+      //           .WillRepeatedly(Return(std::vector<std::string>{}));
+      //
+      //       EXPECT_THAT(mock.AsStdFunction()(),
+      //                   ElementsAre("taco", "burrito"));
+      //       EXPECT_THAT(mock.AsStdFunction()(),
+      //                   ElementsAre("taco", "burrito"));
+      //       EXPECT_THAT(mock.AsStdFunction()(), IsEmpty());
+      //     }
+      //
+      U value;
+    };
+
+    const std::shared_ptr<State> state_;
+  };
+
+  R value_;
+};
+
+// A specialization of ReturnAction<R> when R is ByMoveWrapper<T> for some T.
+//
+// This version applies the type system-defeating hack of moving from T even in
+// the const call operator, checking at runtime that it isn't called more than
+// once, since the user has declared their intent to do so by using ByMove.
+template <typename T>
+class ReturnAction<ByMoveWrapper<T>> final {
+ public:
+  explicit ReturnAction(ByMoveWrapper<T> wrapper)
+      : state_(new State(std::move(wrapper.payload))) {}
+
+  T operator()() const {
+    GTEST_CHECK_(!state_->called)
+        << "A ByMove() action must be performed at most once.";
+
+    state_->called = true;
+    return std::move(state_->value);
+  }
+
+ private:
+  // We store our state on the heap so that we are copyable as required by
+  // Action, despite the fact that we are stateful and T may not be copyable.
+  struct State {
+    explicit State(T&& value_in) : value(std::move(value_in)) {}
+
+    T value;
+    bool called = false;
+  };
+
+  const std::shared_ptr<State> state_;
+};
+
+// Implements the ReturnNull() action.
+class ReturnNullAction {
+ public:
+  // Allows ReturnNull() to be used in any pointer-returning function. In C++11
+  // this is enforced by returning nullptr, and in non-C++11 by asserting a
+  // pointer type on compile time.
+  template <typename Result, typename ArgumentTuple>
+  static Result Perform(const ArgumentTuple&) {
+    return nullptr;
+  }
+};
+
+// Implements the Return() action.
+class ReturnVoidAction {
+ public:
+  // Allows Return() to be used in any void-returning function.
+  template <typename Result, typename ArgumentTuple>
+  static void Perform(const ArgumentTuple&) {
+    static_assert(std::is_void<Result>::value, "Result should be void.");
+  }
+};
+
+// Implements the polymorphic ReturnRef(x) action, which can be used
+// in any function that returns a reference to the type of x,
+// regardless of the argument types.
+template <typename T>
+class ReturnRefAction {
+ public:
+  // Constructs a ReturnRefAction object from the reference to be returned.
+  explicit ReturnRefAction(T& ref) : ref_(ref) {}  // NOLINT
+
+  // This template type conversion operator allows ReturnRef(x) to be
+  // used in ANY function that returns a reference to x's type.
+  template <typename F>
+  operator Action<F>() const {
+    typedef typename Function<F>::Result Result;
+    // Asserts that the function return type is a reference.  This
+    // catches the user error of using ReturnRef(x) when Return(x)
+    // should be used, and generates some helpful error message.
+    static_assert(std::is_reference<Result>::value,
+                  "use Return instead of ReturnRef to return a value");
+    return Action<F>(new Impl<F>(ref_));
+  }
+
+ private:
+  // Implements the ReturnRef(x) action for a particular function type F.
+  template <typename F>
+  class Impl : public ActionInterface<F> {
+   public:
+    typedef typename Function<F>::Result Result;
+    typedef typename Function<F>::ArgumentTuple ArgumentTuple;
+
+    explicit Impl(T& ref) : ref_(ref) {}  // NOLINT
+
+    Result Perform(const ArgumentTuple&) override { return ref_; }
+
+   private:
+    T& ref_;
+  };
+
+  T& ref_;
+};
+
+// Implements the polymorphic ReturnRefOfCopy(x) action, which can be
+// used in any function that returns a reference to the type of x,
+// regardless of the argument types.
+template <typename T>
+class ReturnRefOfCopyAction {
+ public:
+  // Constructs a ReturnRefOfCopyAction object from the reference to
+  // be returned.
+  explicit ReturnRefOfCopyAction(const T& value) : value_(value) {}  // NOLINT
+
+  // This template type conversion operator allows ReturnRefOfCopy(x) to be
+  // used in ANY function that returns a reference to x's type.
+  template <typename F>
+  operator Action<F>() const {
+    typedef typename Function<F>::Result Result;
+    // Asserts that the function return type is a reference.  This
+    // catches the user error of using ReturnRefOfCopy(x) when Return(x)
+    // should be used, and generates some helpful error message.
+    static_assert(std::is_reference<Result>::value,
+                  "use Return instead of ReturnRefOfCopy to return a value");
+    return Action<F>(new Impl<F>(value_));
+  }
+
+ private:
+  // Implements the ReturnRefOfCopy(x) action for a particular function type F.
+  template <typename F>
+  class Impl : public ActionInterface<F> {
+   public:
+    typedef typename Function<F>::Result Result;
+    typedef typename Function<F>::ArgumentTuple ArgumentTuple;
+
+    explicit Impl(const T& value) : value_(value) {}  // NOLINT
+
+    Result Perform(const ArgumentTuple&) override { return value_; }
+
+   private:
+    T value_;
+  };
+
+  const T value_;
+};
+
+// Implements the polymorphic ReturnRoundRobin(v) action, which can be
+// used in any function that returns the element_type of v.
+template <typename T>
+class ReturnRoundRobinAction {
+ public:
+  explicit ReturnRoundRobinAction(std::vector<T> values) {
+    GTEST_CHECK_(!values.empty())
+        << "ReturnRoundRobin requires at least one element.";
+    state_->values = std::move(values);
+  }
+
+  template <typename... Args>
+  T operator()(Args&&...) const {
+    return state_->Next();
+  }
+
+ private:
+  struct State {
+    T Next() {
+      T ret_val = values[i++];
+      if (i == values.size()) i = 0;
+      return ret_val;
+    }
+
+    std::vector<T> values;
+    size_t i = 0;
+  };
+  std::shared_ptr<State> state_ = std::make_shared<State>();
+};
+
+// Implements the polymorphic DoDefault() action.
+class DoDefaultAction {
+ public:
+  // This template type conversion operator allows DoDefault() to be
+  // used in any function.
+  template <typename F>
+  operator Action<F>() const {
+    return Action<F>();
+  }  // NOLINT
+};
+
+// Implements the Assign action to set a given pointer referent to a
+// particular value.
+template <typename T1, typename T2>
+class AssignAction {
+ public:
+  AssignAction(T1* ptr, T2 value) : ptr_(ptr), value_(value) {}
+
+  template <typename Result, typename ArgumentTuple>
+  void Perform(const ArgumentTuple& /* args */) const {
+    *ptr_ = value_;
+  }
+
+ private:
+  T1* const ptr_;
+  const T2 value_;
+};
+
+#ifndef GTEST_OS_WINDOWS_MOBILE
+
+// Implements the SetErrnoAndReturn action to simulate return from
+// various system calls and libc functions.
+template <typename T>
+class SetErrnoAndReturnAction {
+ public:
+  SetErrnoAndReturnAction(int errno_value, T result)
+      : errno_(errno_value), result_(result) {}
+  template <typename Result, typename ArgumentTuple>
+  Result Perform(const ArgumentTuple& /* args */) const {
+    errno = errno_;
+    return result_;
+  }
+
+ private:
+  const int errno_;
+  const T result_;
+};
+
+#endif  // !GTEST_OS_WINDOWS_MOBILE
+
+// Implements the SetArgumentPointee<N>(x) action for any function
+// whose N-th argument (0-based) is a pointer to x's type.
+template <size_t N, typename A, typename = void>
+struct SetArgumentPointeeAction {
+  A value;
+
+  template <typename... Args>
+  void operator()(const Args&... args) const {
+    *::std::get<N>(std::tie(args...)) = value;
+  }
+};
+
+// Implements the Invoke(object_ptr, &Class::Method) action.
+template <class Class, typename MethodPtr>
+struct InvokeMethodAction {
+  Class* const obj_ptr;
+  const MethodPtr method_ptr;
+
+  template <typename... Args>
+  auto operator()(Args&&... args) const
+      -> decltype((obj_ptr->*method_ptr)(std::forward<Args>(args)...)) {
+    return (obj_ptr->*method_ptr)(std::forward<Args>(args)...);
+  }
+};
+
+// Implements the InvokeWithoutArgs(f) action.  The template argument
+// FunctionImpl is the implementation type of f, which can be either a
+// function pointer or a functor.  InvokeWithoutArgs(f) can be used as an
+// Action<F> as long as f's type is compatible with F.
+template <typename FunctionImpl>
+struct InvokeWithoutArgsAction {
+  FunctionImpl function_impl;
+
+  // Allows InvokeWithoutArgs(f) to be used as any action whose type is
+  // compatible with f.
+  template <typename... Args>
+  auto operator()(const Args&...) -> decltype(function_impl()) {
+    return function_impl();
+  }
+};
+
+// Implements the InvokeWithoutArgs(object_ptr, &Class::Method) action.
+template <class Class, typename MethodPtr>
+struct InvokeMethodWithoutArgsAction {
+  Class* const obj_ptr;
+  const MethodPtr method_ptr;
+
+  using ReturnType =
+      decltype((std::declval<Class*>()->*std::declval<MethodPtr>())());
+
+  template <typename... Args>
+  ReturnType operator()(const Args&...) const {
+    return (obj_ptr->*method_ptr)();
+  }
+};
+
+// Implements the IgnoreResult(action) action.
+template <typename A>
+class IgnoreResultAction {
+ public:
+  explicit IgnoreResultAction(const A& action) : action_(action) {}
+
+  template <typename F>
+  operator Action<F>() const {
+    // Assert statement belongs here because this is the best place to verify
+    // conditions on F. It produces the clearest error messages
+    // in most compilers.
+    // Impl really belongs in this scope as a local class but can't
+    // because MSVC produces duplicate symbols in different translation units
+    // in this case. Until MS fixes that bug we put Impl into the class scope
+    // and put the typedef both here (for use in assert statement) and
+    // in the Impl class. But both definitions must be the same.
+    typedef typename internal::Function<F>::Result Result;
+
+    // Asserts at compile time that F returns void.
+    static_assert(std::is_void<Result>::value, "Result type should be void.");
+
+    return Action<F>(new Impl<F>(action_));
+  }
+
+ private:
+  template <typename F>
+  class Impl : public ActionInterface<F> {
+   public:
+    typedef typename internal::Function<F>::Result Result;
+    typedef typename internal::Function<F>::ArgumentTuple ArgumentTuple;
+
+    explicit Impl(const A& action) : action_(action) {}
+
+    void Perform(const ArgumentTuple& args) override {
+      // Performs the action and ignores its result.
+      action_.Perform(args);
+    }
+
+   private:
+    // Type OriginalFunction is the same as F except that its return
+    // type is IgnoredValue.
+    typedef
+        typename internal::Function<F>::MakeResultIgnoredValue OriginalFunction;
+
+    const Action<OriginalFunction> action_;
+  };
+
+  const A action_;
+};
+
+template <typename InnerAction, size_t... I>
+struct WithArgsAction {
+  InnerAction inner_action;
+
+  // The signature of the function as seen by the inner action, given an out
+  // action with the given result and argument types.
+  template <typename R, typename... Args>
+  using InnerSignature =
+      R(typename std::tuple_element<I, std::tuple<Args...>>::type...);
+
+  // Rather than a call operator, we must define conversion operators to
+  // particular action types. This is necessary for embedded actions like
+  // DoDefault(), which rely on an action conversion operators rather than
+  // providing a call operator because even with a particular set of arguments
+  // they don't have a fixed return type.
+
+  template <
+      typename R, typename... Args,
+      typename std::enable_if<
+          std::is_convertible<InnerAction,
+                              // Unfortunately we can't use the InnerSignature
+                              // alias here; MSVC complains about the I
+                              // parameter pack not being expanded (error C3520)
+                              // despite it being expanded in the type alias.
+                              // TupleElement is also an MSVC workaround.
+                              // See its definition for details.
+                              OnceAction<R(internal::TupleElement<
+                                           I, std::tuple<Args...>>...)>>::value,
+          int>::type = 0>
+  operator OnceAction<R(Args...)>() && {  // NOLINT
+    struct OA {
+      OnceAction<InnerSignature<R, Args...>> inner_action;
+
+      R operator()(Args&&... args) && {
+        return std::move(inner_action)
+            .Call(std::get<I>(
+                std::forward_as_tuple(std::forward<Args>(args)...))...);
+      }
+    };
+
+    return OA{std::move(inner_action)};
+  }
+
+  template <
+      typename R, typename... Args,
+      typename std::enable_if<
+          std::is_convertible<const InnerAction&,
+                              // Unfortunately we can't use the InnerSignature
+                              // alias here; MSVC complains about the I
+                              // parameter pack not being expanded (error C3520)
+                              // despite it being expanded in the type alias.
+                              // TupleElement is also an MSVC workaround.
+                              // See its definition for details.
+                              Action<R(internal::TupleElement<
+                                       I, std::tuple<Args...>>...)>>::value,
+          int>::type = 0>
+  operator Action<R(Args...)>() const {  // NOLINT
+    Action<InnerSignature<R, Args...>> converted(inner_action);
+
+    return [converted](Args&&... args) -> R {
+      return converted.Perform(std::forward_as_tuple(
+          std::get<I>(std::forward_as_tuple(std::forward<Args>(args)...))...));
+    };
+  }
+};
+
+template <typename... Actions>
+class DoAllAction;
+
+// Base case: only a single action.
+template <typename FinalAction>
+class DoAllAction<FinalAction> {
+ public:
+  struct UserConstructorTag {};
+
+  template <typename T>
+  explicit DoAllAction(UserConstructorTag, T&& action)
+      : final_action_(std::forward<T>(action)) {}
+
+  // Rather than a call operator, we must define conversion operators to
+  // particular action types. This is necessary for embedded actions like
+  // DoDefault(), which rely on an action conversion operators rather than
+  // providing a call operator because even with a particular set of arguments
+  // they don't have a fixed return type.
+
+  template <typename R, typename... Args,
+            typename std::enable_if<
+                std::is_convertible<FinalAction, OnceAction<R(Args...)>>::value,
+                int>::type = 0>
+  operator OnceAction<R(Args...)>() && {  // NOLINT
+    return std::move(final_action_);
+  }
+
+  template <
+      typename R, typename... Args,
+      typename std::enable_if<
+          std::is_convertible<const FinalAction&, Action<R(Args...)>>::value,
+          int>::type = 0>
+  operator Action<R(Args...)>() const {  // NOLINT
+    return final_action_;
+  }
+
+ private:
+  FinalAction final_action_;
+};
+
+// Recursive case: support N actions by calling the initial action and then
+// calling through to the base class containing N-1 actions.
+template <typename InitialAction, typename... OtherActions>
+class DoAllAction<InitialAction, OtherActions...>
+    : private DoAllAction<OtherActions...> {
+ private:
+  using Base = DoAllAction<OtherActions...>;
+
+  // The type of reference that should be provided to an initial action for a
+  // mocked function parameter of type T.
+  //
+  // There are two quirks here:
+  //
+  //  *  Unlike most forwarding functions, we pass scalars through by value.
+  //     This isn't strictly necessary because an lvalue reference would work
+  //     fine too and be consistent with other non-reference types, but it's
+  //     perhaps less surprising.
+  //
+  //     For example if the mocked function has signature void(int), then it
+  //     might seem surprising for the user's initial action to need to be
+  //     convertible to Action<void(const int&)>. This is perhaps less
+  //     surprising for a non-scalar type where there may be a performance
+  //     impact, or it might even be impossible, to pass by value.
+  //
+  //  *  More surprisingly, `const T&` is often not a const reference type.
+  //     By the reference collapsing rules in C++17 [dcl.ref]/6, if T refers to
+  //     U& or U&& for some non-scalar type U, then InitialActionArgType<T> is
+  //     U&. In other words, we may hand over a non-const reference.
+  //
+  //     So for example, given some non-scalar type Obj we have the following
+  //     mappings:
+  //
+  //            T               InitialActionArgType<T>
+  //         -------            -----------------------
+  //         Obj                const Obj&
+  //         Obj&               Obj&
+  //         Obj&&              Obj&
+  //         const Obj          const Obj&
+  //         const Obj&         const Obj&
+  //         const Obj&&        const Obj&
+  //
+  //     In other words, the initial actions get a mutable view of an non-scalar
+  //     argument if and only if the mock function itself accepts a non-const
+  //     reference type. They are never given an rvalue reference to an
+  //     non-scalar type.
+  //
+  //     This situation makes sense if you imagine use with a matcher that is
+  //     designed to write through a reference. For example, if the caller wants
+  //     to fill in a reference argument and then return a canned value:
+  //
+  //         EXPECT_CALL(mock, Call)
+  //             .WillOnce(DoAll(SetArgReferee<0>(17), Return(19)));
+  //
+  template <typename T>
+  using InitialActionArgType =
+      typename std::conditional<std::is_scalar<T>::value, T, const T&>::type;
+
+ public:
+  struct UserConstructorTag {};
+
+  template <typename T, typename... U>
+  explicit DoAllAction(UserConstructorTag, T&& initial_action,
+                       U&&... other_actions)
+      : Base({}, std::forward<U>(other_actions)...),
+        initial_action_(std::forward<T>(initial_action)) {}
+
+  template <typename R, typename... Args,
+            typename std::enable_if<
+                conjunction<
+                    // Both the initial action and the rest must support
+                    // conversion to OnceAction.
+                    std::is_convertible<
+                        InitialAction,
+                        OnceAction<void(InitialActionArgType<Args>...)>>,
+                    std::is_convertible<Base, OnceAction<R(Args...)>>>::value,
+                int>::type = 0>
+  operator OnceAction<R(Args...)>() && {  // NOLINT
+    // Return an action that first calls the initial action with arguments
+    // filtered through InitialActionArgType, then forwards arguments directly
+    // to the base class to deal with the remaining actions.
+    struct OA {
+      OnceAction<void(InitialActionArgType<Args>...)> initial_action;
+      OnceAction<R(Args...)> remaining_actions;
+
+      R operator()(Args... args) && {
+        std::move(initial_action)
+            .Call(static_cast<InitialActionArgType<Args>>(args)...);
+
+        return std::move(remaining_actions).Call(std::forward<Args>(args)...);
+      }
+    };
+
+    return OA{
+        std::move(initial_action_),
+        std::move(static_cast<Base&>(*this)),
+    };
+  }
+
+  template <
+      typename R, typename... Args,
+      typename std::enable_if<
+          conjunction<
+              // Both the initial action and the rest must support conversion to
+              // Action.
+              std::is_convertible<const InitialAction&,
+                                  Action<void(InitialActionArgType<Args>...)>>,
+              std::is_convertible<const Base&, Action<R(Args...)>>>::value,
+          int>::type = 0>
+  operator Action<R(Args...)>() const {  // NOLINT
+    // Return an action that first calls the initial action with arguments
+    // filtered through InitialActionArgType, then forwards arguments directly
+    // to the base class to deal with the remaining actions.
+    struct OA {
+      Action<void(InitialActionArgType<Args>...)> initial_action;
+      Action<R(Args...)> remaining_actions;
+
+      R operator()(Args... args) const {
+        initial_action.Perform(std::forward_as_tuple(
+            static_cast<InitialActionArgType<Args>>(args)...));
+
+        return remaining_actions.Perform(
+            std::forward_as_tuple(std::forward<Args>(args)...));
+      }
+    };
+
+    return OA{
+        initial_action_,
+        static_cast<const Base&>(*this),
+    };
+  }
+
+ private:
+  InitialAction initial_action_;
+};
+
+template <typename T, typename... Params>
+struct ReturnNewAction {
+  T* operator()() const {
+    return internal::Apply(
+        [](const Params&... unpacked_params) {
+          return new T(unpacked_params...);
+        },
+        params);
+  }
+  std::tuple<Params...> params;
+};
+
+template <size_t k>
+struct ReturnArgAction {
+  template <typename... Args,
+            typename = typename std::enable_if<(k < sizeof...(Args))>::type>
+  auto operator()(Args&&... args) const -> decltype(std::get<k>(
+      std::forward_as_tuple(std::forward<Args>(args)...))) {
+    return std::get<k>(std::forward_as_tuple(std::forward<Args>(args)...));
+  }
+};
+
+template <size_t k, typename Ptr>
+struct SaveArgAction {
+  Ptr pointer;
+
+  template <typename... Args>
+  void operator()(const Args&... args) const {
+    *pointer = std::get<k>(std::tie(args...));
+  }
+};
+
+template <size_t k, typename Ptr>
+struct SaveArgPointeeAction {
+  Ptr pointer;
+
+  template <typename... Args>
+  void operator()(const Args&... args) const {
+    *pointer = *std::get<k>(std::tie(args...));
+  }
+};
+
+template <size_t k, typename T>
+struct SetArgRefereeAction {
+  T value;
+
+  template <typename... Args>
+  void operator()(Args&&... args) const {
+    using argk_type =
+        typename ::std::tuple_element<k, std::tuple<Args...>>::type;
+    static_assert(std::is_lvalue_reference<argk_type>::value,
+                  "Argument must be a reference type.");
+    std::get<k>(std::tie(args...)) = value;
+  }
+};
+
+template <size_t k, typename I1, typename I2>
+struct SetArrayArgumentAction {
+  I1 first;
+  I2 last;
+
+  template <typename... Args>
+  void operator()(const Args&... args) const {
+    auto value = std::get<k>(std::tie(args...));
+    for (auto it = first; it != last; ++it, (void)++value) {
+      *value = *it;
+    }
+  }
+};
+
+template <size_t k>
+struct DeleteArgAction {
+  template <typename... Args>
+  void operator()(const Args&... args) const {
+    delete std::get<k>(std::tie(args...));
+  }
+};
+
+template <typename Ptr>
+struct ReturnPointeeAction {
+  Ptr pointer;
+  template <typename... Args>
+  auto operator()(const Args&...) const -> decltype(*pointer) {
+    return *pointer;
+  }
+};
+
+#if GTEST_HAS_EXCEPTIONS
+template <typename T>
+struct ThrowAction {
+  T exception;
+  // We use a conversion operator to adapt to any return type.
+  template <typename R, typename... Args>
+  operator Action<R(Args...)>() const {  // NOLINT
+    T copy = exception;
+    return [copy](Args...) -> R { throw copy; };
+  }
+};
+#endif  // GTEST_HAS_EXCEPTIONS
+
+}  // namespace internal
+
+// An Unused object can be implicitly constructed from ANY value.
+// This is handy when defining actions that ignore some or all of the
+// mock function arguments.  For example, given
+//
+//   MOCK_METHOD3(Foo, double(const string& label, double x, double y));
+//   MOCK_METHOD3(Bar, double(int index, double x, double y));
+//
+// instead of
+//
+//   double DistanceToOriginWithLabel(const string& label, double x, double y) {
+//     return sqrt(x*x + y*y);
+//   }
+//   double DistanceToOriginWithIndex(int index, double x, double y) {
+//     return sqrt(x*x + y*y);
+//   }
+//   ...
+//   EXPECT_CALL(mock, Foo("abc", _, _))
+//       .WillOnce(Invoke(DistanceToOriginWithLabel));
+//   EXPECT_CALL(mock, Bar(5, _, _))
+//       .WillOnce(Invoke(DistanceToOriginWithIndex));
+//
+// you could write
+//
+//   // We can declare any uninteresting argument as Unused.
+//   double DistanceToOrigin(Unused, double x, double y) {
+//     return sqrt(x*x + y*y);
+//   }
+//   ...
+//   EXPECT_CALL(mock, Foo("abc", _, _)).WillOnce(Invoke(DistanceToOrigin));
+//   EXPECT_CALL(mock, Bar(5, _, _)).WillOnce(Invoke(DistanceToOrigin));
+typedef internal::IgnoredValue Unused;
+
+// Creates an action that does actions a1, a2, ..., sequentially in
+// each invocation. All but the last action will have a readonly view of the
+// arguments.
+template <typename... Action>
+internal::DoAllAction<typename std::decay<Action>::type...> DoAll(
+    Action&&... action) {
+  return internal::DoAllAction<typename std::decay<Action>::type...>(
+      {}, std::forward<Action>(action)...);
+}
+
+// WithArg<k>(an_action) creates an action that passes the k-th
+// (0-based) argument of the mock function to an_action and performs
+// it.  It adapts an action accepting one argument to one that accepts
+// multiple arguments.  For convenience, we also provide
+// WithArgs<k>(an_action) (defined below) as a synonym.
+template <size_t k, typename InnerAction>
+internal::WithArgsAction<typename std::decay<InnerAction>::type, k> WithArg(
+    InnerAction&& action) {
+  return {std::forward<InnerAction>(action)};
+}
+
+// WithArgs<N1, N2, ..., Nk>(an_action) creates an action that passes
+// the selected arguments of the mock function to an_action and
+// performs it.  It serves as an adaptor between actions with
+// different argument lists.
+template <size_t k, size_t... ks, typename InnerAction>
+internal::WithArgsAction<typename std::decay<InnerAction>::type, k, ks...>
+WithArgs(InnerAction&& action) {
+  return {std::forward<InnerAction>(action)};
+}
+
+// WithoutArgs(inner_action) can be used in a mock function with a
+// non-empty argument list to perform inner_action, which takes no
+// argument.  In other words, it adapts an action accepting no
+// argument to one that accepts (and ignores) arguments.
+template <typename InnerAction>
+internal::WithArgsAction<typename std::decay<InnerAction>::type> WithoutArgs(
+    InnerAction&& action) {
+  return {std::forward<InnerAction>(action)};
+}
+
+// Creates an action that returns a value.
+//
+// The returned type can be used with a mock function returning a non-void,
+// non-reference type U as follows:
+//
+//  *  If R is convertible to U and U is move-constructible, then the action can
+//     be used with WillOnce.
+//
+//  *  If const R& is convertible to U and U is copy-constructible, then the
+//     action can be used with both WillOnce and WillRepeatedly.
+//
+// The mock expectation contains the R value from which the U return value is
+// constructed (a move/copy of the argument to Return). This means that the R
+// value will survive at least until the mock object's expectations are cleared
+// or the mock object is destroyed, meaning that U can safely be a
+// reference-like type such as std::string_view:
+//
+//     // The mock function returns a view of a copy of the string fed to
+//     // Return. The view is valid even after the action is performed.
+//     MockFunction<std::string_view()> mock;
+//     EXPECT_CALL(mock, Call).WillOnce(Return(std::string("taco")));
+//     const std::string_view result = mock.AsStdFunction()();
+//     EXPECT_EQ("taco", result);
+//
+template <typename R>
+internal::ReturnAction<R> Return(R value) {
+  return internal::ReturnAction<R>(std::move(value));
+}
+
+// Creates an action that returns NULL.
+inline PolymorphicAction<internal::ReturnNullAction> ReturnNull() {
+  return MakePolymorphicAction(internal::ReturnNullAction());
+}
+
+// Creates an action that returns from a void function.
+inline PolymorphicAction<internal::ReturnVoidAction> Return() {
+  return MakePolymorphicAction(internal::ReturnVoidAction());
+}
+
+// Creates an action that returns the reference to a variable.
+template <typename R>
+inline internal::ReturnRefAction<R> ReturnRef(R& x) {  // NOLINT
+  return internal::ReturnRefAction<R>(x);
+}
+
+// Prevent using ReturnRef on reference to temporary.
+template <typename R, R* = nullptr>
+internal::ReturnRefAction<R> ReturnRef(R&&) = delete;
+
+// Creates an action that returns the reference to a copy of the
+// argument.  The copy is created when the action is constructed and
+// lives as long as the action.
+template <typename R>
+inline internal::ReturnRefOfCopyAction<R> ReturnRefOfCopy(const R& x) {
+  return internal::ReturnRefOfCopyAction<R>(x);
+}
+
+// DEPRECATED: use Return(x) directly with WillOnce.
+//
+// Modifies the parent action (a Return() action) to perform a move of the
+// argument instead of a copy.
+// Return(ByMove()) actions can only be executed once and will assert this
+// invariant.
+template <typename R>
+internal::ByMoveWrapper<R> ByMove(R x) {
+  return internal::ByMoveWrapper<R>(std::move(x));
+}
+
+// Creates an action that returns an element of `vals`. Calling this action will
+// repeatedly return the next value from `vals` until it reaches the end and
+// will restart from the beginning.
+template <typename T>
+internal::ReturnRoundRobinAction<T> ReturnRoundRobin(std::vector<T> vals) {
+  return internal::ReturnRoundRobinAction<T>(std::move(vals));
+}
+
+// Creates an action that returns an element of `vals`. Calling this action will
+// repeatedly return the next value from `vals` until it reaches the end and
+// will restart from the beginning.
+template <typename T>
+internal::ReturnRoundRobinAction<T> ReturnRoundRobin(
+    std::initializer_list<T> vals) {
+  return internal::ReturnRoundRobinAction<T>(std::vector<T>(vals));
+}
+
+// Creates an action that does the default action for the give mock function.
+inline internal::DoDefaultAction DoDefault() {
+  return internal::DoDefaultAction();
+}
+
+// Creates an action that sets the variable pointed by the N-th
+// (0-based) function argument to 'value'.
+template <size_t N, typename T>
+internal::SetArgumentPointeeAction<N, T> SetArgPointee(T value) {
+  return {std::move(value)};
+}
+
+// The following version is DEPRECATED.
+template <size_t N, typename T>
+internal::SetArgumentPointeeAction<N, T> SetArgumentPointee(T value) {
+  return {std::move(value)};
+}
+
+// Creates an action that sets a pointer referent to a given value.
+template <typename T1, typename T2>
+PolymorphicAction<internal::AssignAction<T1, T2>> Assign(T1* ptr, T2 val) {
+  return MakePolymorphicAction(internal::AssignAction<T1, T2>(ptr, val));
+}
+
+#ifndef GTEST_OS_WINDOWS_MOBILE
+
+// Creates an action that sets errno and returns the appropriate error.
+template <typename T>
+PolymorphicAction<internal::SetErrnoAndReturnAction<T>> SetErrnoAndReturn(
+    int errval, T result) {
+  return MakePolymorphicAction(
+      internal::SetErrnoAndReturnAction<T>(errval, result));
+}
+
+#endif  // !GTEST_OS_WINDOWS_MOBILE
+
+// Various overloads for Invoke().
+
+// Legacy function.
+// Actions can now be implicitly constructed from callables. No need to create
+// wrapper objects.
+// This function exists for backwards compatibility.
+template <typename FunctionImpl>
+typename std::decay<FunctionImpl>::type Invoke(FunctionImpl&& function_impl) {
+  return std::forward<FunctionImpl>(function_impl);
+}
+
+// Creates an action that invokes the given method on the given object
+// with the mock function's arguments.
+template <class Class, typename MethodPtr>
+internal::InvokeMethodAction<Class, MethodPtr> Invoke(Class* obj_ptr,
+                                                      MethodPtr method_ptr) {
+  return {obj_ptr, method_ptr};
+}
+
+// Creates an action that invokes 'function_impl' with no argument.
+template <typename FunctionImpl>
+internal::InvokeWithoutArgsAction<typename std::decay<FunctionImpl>::type>
+InvokeWithoutArgs(FunctionImpl function_impl) {
+  return {std::move(function_impl)};
+}
+
+// Creates an action that invokes the given method on the given object
+// with no argument.
+template <class Class, typename MethodPtr>
+internal::InvokeMethodWithoutArgsAction<Class, MethodPtr> InvokeWithoutArgs(
+    Class* obj_ptr, MethodPtr method_ptr) {
+  return {obj_ptr, method_ptr};
+}
+
+// Creates an action that performs an_action and throws away its
+// result.  In other words, it changes the return type of an_action to
+// void.  an_action MUST NOT return void, or the code won't compile.
+template <typename A>
+inline internal::IgnoreResultAction<A> IgnoreResult(const A& an_action) {
+  return internal::IgnoreResultAction<A>(an_action);
+}
+
+// Creates a reference wrapper for the given L-value.  If necessary,
+// you can explicitly specify the type of the reference.  For example,
+// suppose 'derived' is an object of type Derived, ByRef(derived)
+// would wrap a Derived&.  If you want to wrap a const Base& instead,
+// where Base is a base class of Derived, just write:
+//
+//   ByRef<const Base>(derived)
+//
+// N.B. ByRef is redundant with std::ref, std::cref and std::reference_wrapper.
+// However, it may still be used for consistency with ByMove().
+template <typename T>
+inline ::std::reference_wrapper<T> ByRef(T& l_value) {  // NOLINT
+  return ::std::reference_wrapper<T>(l_value);
+}
+
+// The ReturnNew<T>(a1, a2, ..., a_k) action returns a pointer to a new
+// instance of type T, constructed on the heap with constructor arguments
+// a1, a2, ..., and a_k. The caller assumes ownership of the returned value.
+template <typename T, typename... Params>
+internal::ReturnNewAction<T, typename std::decay<Params>::type...> ReturnNew(
+    Params&&... params) {
+  return {std::forward_as_tuple(std::forward<Params>(params)...)};
+}
+
+// Action ReturnArg<k>() returns the k-th argument of the mock function.
+template <size_t k>
+internal::ReturnArgAction<k> ReturnArg() {
+  return {};
+}
+
+// Action SaveArg<k>(pointer) saves the k-th (0-based) argument of the
+// mock function to *pointer.
+template <size_t k, typename Ptr>
+internal::SaveArgAction<k, Ptr> SaveArg(Ptr pointer) {
+  return {pointer};
+}
+
+// Action SaveArgPointee<k>(pointer) saves the value pointed to
+// by the k-th (0-based) argument of the mock function to *pointer.
+template <size_t k, typename Ptr>
+internal::SaveArgPointeeAction<k, Ptr> SaveArgPointee(Ptr pointer) {
+  return {pointer};
+}
+
+// Action SetArgReferee<k>(value) assigns 'value' to the variable
+// referenced by the k-th (0-based) argument of the mock function.
+template <size_t k, typename T>
+internal::SetArgRefereeAction<k, typename std::decay<T>::type> SetArgReferee(
+    T&& value) {
+  return {std::forward<T>(value)};
+}
+
+// Action SetArrayArgument<k>(first, last) copies the elements in
+// source range [first, last) to the array pointed to by the k-th
+// (0-based) argument, which can be either a pointer or an
+// iterator. The action does not take ownership of the elements in the
+// source range.
+template <size_t k, typename I1, typename I2>
+internal::SetArrayArgumentAction<k, I1, I2> SetArrayArgument(I1 first,
+                                                             I2 last) {
+  return {first, last};
+}
+
+// Action DeleteArg<k>() deletes the k-th (0-based) argument of the mock
+// function.
+template <size_t k>
+internal::DeleteArgAction<k> DeleteArg() {
+  return {};
+}
+
+// This action returns the value pointed to by 'pointer'.
+template <typename Ptr>
+internal::ReturnPointeeAction<Ptr> ReturnPointee(Ptr pointer) {
+  return {pointer};
+}
+
+// Action Throw(exception) can be used in a mock function of any type
+// to throw the given exception.  Any copyable value can be thrown.
+#if GTEST_HAS_EXCEPTIONS
+template <typename T>
+internal::ThrowAction<typename std::decay<T>::type> Throw(T&& exception) {
+  return {std::forward<T>(exception)};
+}
+#endif  // GTEST_HAS_EXCEPTIONS
+
+namespace internal {
+
+// A macro from the ACTION* family (defined later in gmock-generated-actions.h)
+// defines an action that can be used in a mock function.  Typically,
+// these actions only care about a subset of the arguments of the mock
+// function.  For example, if such an action only uses the second
+// argument, it can be used in any mock function that takes >= 2
+// arguments where the type of the second argument is compatible.
+//
+// Therefore, the action implementation must be prepared to take more
+// arguments than it needs.  The ExcessiveArg type is used to
+// represent those excessive arguments.  In order to keep the compiler
+// error messages tractable, we define it in the testing namespace
+// instead of testing::internal.  However, this is an INTERNAL TYPE
+// and subject to change without notice, so a user MUST NOT USE THIS
+// TYPE DIRECTLY.
+struct ExcessiveArg {};
+
+// Builds an implementation of an Action<> for some particular signature, using
+// a class defined by an ACTION* macro.
+template <typename F, typename Impl>
+struct ActionImpl;
+
+template <typename Impl>
+struct ImplBase {
+  struct Holder {
+    // Allows each copy of the Action<> to get to the Impl.
+    explicit operator const Impl&() const { return *ptr; }
+    std::shared_ptr<Impl> ptr;
+  };
+  using type = typename std::conditional<std::is_constructible<Impl>::value,
+                                         Impl, Holder>::type;
+};
+
+template <typename R, typename... Args, typename Impl>
+struct ActionImpl<R(Args...), Impl> : ImplBase<Impl>::type {
+  using Base = typename ImplBase<Impl>::type;
+  using function_type = R(Args...);
+  using args_type = std::tuple<Args...>;
+
+  ActionImpl() = default;  // Only defined if appropriate for Base.
+  explicit ActionImpl(std::shared_ptr<Impl> impl) : Base{std::move(impl)} {}
+
+  R operator()(Args&&... arg) const {
+    static constexpr size_t kMaxArgs =
+        sizeof...(Args) <= 10 ? sizeof...(Args) : 10;
+    return Apply(MakeIndexSequence<kMaxArgs>{},
+                 MakeIndexSequence<10 - kMaxArgs>{},
+                 args_type{std::forward<Args>(arg)...});
+  }
+
+  template <std::size_t... arg_id, std::size_t... excess_id>
+  R Apply(IndexSequence<arg_id...>, IndexSequence<excess_id...>,
+          const args_type& args) const {
+    // Impl need not be specific to the signature of action being implemented;
+    // only the implementing function body needs to have all of the specific
+    // types instantiated.  Up to 10 of the args that are provided by the
+    // args_type get passed, followed by a dummy of unspecified type for the
+    // remainder up to 10 explicit args.
+    static constexpr ExcessiveArg kExcessArg{};
+    return static_cast<const Impl&>(*this)
+        .template gmock_PerformImpl<
+            /*function_type=*/function_type, /*return_type=*/R,
+            /*args_type=*/args_type,
+            /*argN_type=*/
+            typename std::tuple_element<arg_id, args_type>::type...>(
+            /*args=*/args, std::get<arg_id>(args)...,
+            ((void)excess_id, kExcessArg)...);
+  }
+};
+
+// Stores a default-constructed Impl as part of the Action<>'s
+// std::function<>. The Impl should be trivial to copy.
+template <typename F, typename Impl>
+::testing::Action<F> MakeAction() {
+  return ::testing::Action<F>(ActionImpl<F, Impl>());
+}
+
+// Stores just the one given instance of Impl.
+template <typename F, typename Impl>
+::testing::Action<F> MakeAction(std::shared_ptr<Impl> impl) {
+  return ::testing::Action<F>(ActionImpl<F, Impl>(std::move(impl)));
+}
+
+#define GMOCK_INTERNAL_ARG_UNUSED(i, data, el) \
+  , const arg##i##_type& arg##i GTEST_ATTRIBUTE_UNUSED_
+#define GMOCK_ACTION_ARG_TYPES_AND_NAMES_UNUSED_                 \
+  const args_type& args GTEST_ATTRIBUTE_UNUSED_ GMOCK_PP_REPEAT( \
+      GMOCK_INTERNAL_ARG_UNUSED, , 10)
+
+#define GMOCK_INTERNAL_ARG(i, data, el) , const arg##i##_type& arg##i
+#define GMOCK_ACTION_ARG_TYPES_AND_NAMES_ \
+  const args_type& args GMOCK_PP_REPEAT(GMOCK_INTERNAL_ARG, , 10)
+
+#define GMOCK_INTERNAL_TEMPLATE_ARG(i, data, el) , typename arg##i##_type
+#define GMOCK_ACTION_TEMPLATE_ARGS_NAMES_ \
+  GMOCK_PP_TAIL(GMOCK_PP_REPEAT(GMOCK_INTERNAL_TEMPLATE_ARG, , 10))
+
+#define GMOCK_INTERNAL_TYPENAME_PARAM(i, data, param) , typename param##_type
+#define GMOCK_ACTION_TYPENAME_PARAMS_(params) \
+  GMOCK_PP_TAIL(GMOCK_PP_FOR_EACH(GMOCK_INTERNAL_TYPENAME_PARAM, , params))
+
+#define GMOCK_INTERNAL_TYPE_PARAM(i, data, param) , param##_type
+#define GMOCK_ACTION_TYPE_PARAMS_(params) \
+  GMOCK_PP_TAIL(GMOCK_PP_FOR_EACH(GMOCK_INTERNAL_TYPE_PARAM, , params))
+
+#define GMOCK_INTERNAL_TYPE_GVALUE_PARAM(i, data, param) \
+  , param##_type gmock_p##i
+#define GMOCK_ACTION_TYPE_GVALUE_PARAMS_(params) \
+  GMOCK_PP_TAIL(GMOCK_PP_FOR_EACH(GMOCK_INTERNAL_TYPE_GVALUE_PARAM, , params))
+
+#define GMOCK_INTERNAL_GVALUE_PARAM(i, data, param) \
+  , std::forward<param##_type>(gmock_p##i)
+#define GMOCK_ACTION_GVALUE_PARAMS_(params) \
+  GMOCK_PP_TAIL(GMOCK_PP_FOR_EACH(GMOCK_INTERNAL_GVALUE_PARAM, , params))
+
+#define GMOCK_INTERNAL_INIT_PARAM(i, data, param) \
+  , param(::std::forward<param##_type>(gmock_p##i))
+#define GMOCK_ACTION_INIT_PARAMS_(params) \
+  GMOCK_PP_TAIL(GMOCK_PP_FOR_EACH(GMOCK_INTERNAL_INIT_PARAM, , params))
+
+#define GMOCK_INTERNAL_FIELD_PARAM(i, data, param) param##_type param;
+#define GMOCK_ACTION_FIELD_PARAMS_(params) \
+  GMOCK_PP_FOR_EACH(GMOCK_INTERNAL_FIELD_PARAM, , params)
+
+#define GMOCK_INTERNAL_ACTION(name, full_name, params)                         \
+  template <GMOCK_ACTION_TYPENAME_PARAMS_(params)>                             \
+  class full_name {                                                            \
+   public:                                                                     \
+    explicit full_name(GMOCK_ACTION_TYPE_GVALUE_PARAMS_(params))               \
+        : impl_(std::make_shared<gmock_Impl>(                                  \
+              GMOCK_ACTION_GVALUE_PARAMS_(params))) {}                         \
+    full_name(const full_name&) = default;                                     \
+    full_name(full_name&&) noexcept = default;                                 \
+    template <typename F>                                                      \
+    operator ::testing::Action<F>() const {                                    \
+      return ::testing::internal::MakeAction<F>(impl_);                        \
+    }                                                                          \
+                                                                               \
+   private:                                                                    \
+    class gmock_Impl {                                                         \
+     public:                                                                   \
+      explicit gmock_Impl(GMOCK_ACTION_TYPE_GVALUE_PARAMS_(params))            \
+          : GMOCK_ACTION_INIT_PARAMS_(params) {}                               \
+      template <typename function_type, typename return_type,                  \
+                typename args_type, GMOCK_ACTION_TEMPLATE_ARGS_NAMES_>         \
+      return_type gmock_PerformImpl(GMOCK_ACTION_ARG_TYPES_AND_NAMES_) const;  \
+      GMOCK_ACTION_FIELD_PARAMS_(params)                                       \
+    };                                                                         \
+    std::shared_ptr<const gmock_Impl> impl_;                                   \
+  };                                                                           \
+  template <GMOCK_ACTION_TYPENAME_PARAMS_(params)>                             \
+  inline full_name<GMOCK_ACTION_TYPE_PARAMS_(params)> name(                    \
+      GMOCK_ACTION_TYPE_GVALUE_PARAMS_(params)) GTEST_MUST_USE_RESULT_;        \
+  template <GMOCK_ACTION_TYPENAME_PARAMS_(params)>                             \
+  inline full_name<GMOCK_ACTION_TYPE_PARAMS_(params)> name(                    \
+      GMOCK_ACTION_TYPE_GVALUE_PARAMS_(params)) {                              \
+    return full_name<GMOCK_ACTION_TYPE_PARAMS_(params)>(                       \
+        GMOCK_ACTION_GVALUE_PARAMS_(params));                                  \
+  }                                                                            \
+  template <GMOCK_ACTION_TYPENAME_PARAMS_(params)>                             \
+  template <typename function_type, typename return_type, typename args_type,  \
+            GMOCK_ACTION_TEMPLATE_ARGS_NAMES_>                                 \
+  return_type                                                                  \
+  full_name<GMOCK_ACTION_TYPE_PARAMS_(params)>::gmock_Impl::gmock_PerformImpl( \
+      GMOCK_ACTION_ARG_TYPES_AND_NAMES_UNUSED_) const
+
+}  // namespace internal
+
+// Similar to GMOCK_INTERNAL_ACTION, but no bound parameters are stored.
+#define ACTION(name)                                                          \
+  class name##Action {                                                        \
+   public:                                                                    \
+    explicit name##Action() noexcept {}                                       \
+    name##Action(const name##Action&) noexcept {}                             \
+    template <typename F>                                                     \
+    operator ::testing::Action<F>() const {                                   \
+      return ::testing::internal::MakeAction<F, gmock_Impl>();                \
+    }                                                                         \
+                                                                              \
+   private:                                                                   \
+    class gmock_Impl {                                                        \
+     public:                                                                  \
+      template <typename function_type, typename return_type,                 \
+                typename args_type, GMOCK_ACTION_TEMPLATE_ARGS_NAMES_>        \
+      return_type gmock_PerformImpl(GMOCK_ACTION_ARG_TYPES_AND_NAMES_) const; \
+    };                                                                        \
+  };                                                                          \
+  inline name##Action name() GTEST_MUST_USE_RESULT_;                          \
+  inline name##Action name() { return name##Action(); }                       \
+  template <typename function_type, typename return_type, typename args_type, \
+            GMOCK_ACTION_TEMPLATE_ARGS_NAMES_>                                \
+  return_type name##Action::gmock_Impl::gmock_PerformImpl(                    \
+      GMOCK_ACTION_ARG_TYPES_AND_NAMES_UNUSED_) const
+
+#define ACTION_P(name, ...) \
+  GMOCK_INTERNAL_ACTION(name, name##ActionP, (__VA_ARGS__))
+
+#define ACTION_P2(name, ...) \
+  GMOCK_INTERNAL_ACTION(name, name##ActionP2, (__VA_ARGS__))
+
+#define ACTION_P3(name, ...) \
+  GMOCK_INTERNAL_ACTION(name, name##ActionP3, (__VA_ARGS__))
+
+#define ACTION_P4(name, ...) \
+  GMOCK_INTERNAL_ACTION(name, name##ActionP4, (__VA_ARGS__))
+
+#define ACTION_P5(name, ...) \
+  GMOCK_INTERNAL_ACTION(name, name##ActionP5, (__VA_ARGS__))
+
+#define ACTION_P6(name, ...) \
+  GMOCK_INTERNAL_ACTION(name, name##ActionP6, (__VA_ARGS__))
+
+#define ACTION_P7(name, ...) \
+  GMOCK_INTERNAL_ACTION(name, name##ActionP7, (__VA_ARGS__))
+
+#define ACTION_P8(name, ...) \
+  GMOCK_INTERNAL_ACTION(name, name##ActionP8, (__VA_ARGS__))
+
+#define ACTION_P9(name, ...) \
+  GMOCK_INTERNAL_ACTION(name, name##ActionP9, (__VA_ARGS__))
+
+#define ACTION_P10(name, ...) \
+  GMOCK_INTERNAL_ACTION(name, name##ActionP10, (__VA_ARGS__))
+
+}  // namespace testing
+
+GTEST_DISABLE_MSC_WARNINGS_POP_()  // 4100
+
+#endif  // GOOGLEMOCK_INCLUDE_GMOCK_GMOCK_ACTIONS_H_
diff --git a/third_party/googletest/googlemock/include/gmock/gmock-cardinalities.h b/third_party/googletest/googlemock/include/gmock/gmock-cardinalities.h
new file mode 100644
index 0000000..533e604
--- /dev/null
+++ b/third_party/googletest/googlemock/include/gmock/gmock-cardinalities.h
@@ -0,0 +1,159 @@
+// Copyright 2007, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Google Mock - a framework for writing C++ mock classes.
+//
+// This file implements some commonly used cardinalities.  More
+// cardinalities can be defined by the user implementing the
+// CardinalityInterface interface if necessary.
+
+// IWYU pragma: private, include "gmock/gmock.h"
+// IWYU pragma: friend gmock/.*
+
+#ifndef GOOGLEMOCK_INCLUDE_GMOCK_GMOCK_CARDINALITIES_H_
+#define GOOGLEMOCK_INCLUDE_GMOCK_GMOCK_CARDINALITIES_H_
+
+#include <limits.h>
+
+#include <memory>
+#include <ostream>  // NOLINT
+
+#include "gmock/internal/gmock-port.h"
+#include "gtest/gtest.h"
+
+GTEST_DISABLE_MSC_WARNINGS_PUSH_(4251 \
+/* class A needs to have dll-interface to be used by clients of class B */)
+
+namespace testing {
+
+// To implement a cardinality Foo, define:
+//   1. a class FooCardinality that implements the
+//      CardinalityInterface interface, and
+//   2. a factory function that creates a Cardinality object from a
+//      const FooCardinality*.
+//
+// The two-level delegation design follows that of Matcher, providing
+// consistency for extension developers.  It also eases ownership
+// management as Cardinality objects can now be copied like plain values.
+
+// The implementation of a cardinality.
+class CardinalityInterface {
+ public:
+  virtual ~CardinalityInterface() = default;
+
+  // Conservative estimate on the lower/upper bound of the number of
+  // calls allowed.
+  virtual int ConservativeLowerBound() const { return 0; }
+  virtual int ConservativeUpperBound() const { return INT_MAX; }
+
+  // Returns true if and only if call_count calls will satisfy this
+  // cardinality.
+  virtual bool IsSatisfiedByCallCount(int call_count) const = 0;
+
+  // Returns true if and only if call_count calls will saturate this
+  // cardinality.
+  virtual bool IsSaturatedByCallCount(int call_count) const = 0;
+
+  // Describes self to an ostream.
+  virtual void DescribeTo(::std::ostream* os) const = 0;
+};
+
+// A Cardinality is a copyable and IMMUTABLE (except by assignment)
+// object that specifies how many times a mock function is expected to
+// be called.  The implementation of Cardinality is just a std::shared_ptr
+// to const CardinalityInterface. Don't inherit from Cardinality!
+class GTEST_API_ Cardinality {
+ public:
+  // Constructs a null cardinality.  Needed for storing Cardinality
+  // objects in STL containers.
+  Cardinality() = default;
+
+  // Constructs a Cardinality from its implementation.
+  explicit Cardinality(const CardinalityInterface* impl) : impl_(impl) {}
+
+  // Conservative estimate on the lower/upper bound of the number of
+  // calls allowed.
+  int ConservativeLowerBound() const { return impl_->ConservativeLowerBound(); }
+  int ConservativeUpperBound() const { return impl_->ConservativeUpperBound(); }
+
+  // Returns true if and only if call_count calls will satisfy this
+  // cardinality.
+  bool IsSatisfiedByCallCount(int call_count) const {
+    return impl_->IsSatisfiedByCallCount(call_count);
+  }
+
+  // Returns true if and only if call_count calls will saturate this
+  // cardinality.
+  bool IsSaturatedByCallCount(int call_count) const {
+    return impl_->IsSaturatedByCallCount(call_count);
+  }
+
+  // Returns true if and only if call_count calls will over-saturate this
+  // cardinality, i.e. exceed the maximum number of allowed calls.
+  bool IsOverSaturatedByCallCount(int call_count) const {
+    return impl_->IsSaturatedByCallCount(call_count) &&
+           !impl_->IsSatisfiedByCallCount(call_count);
+  }
+
+  // Describes self to an ostream
+  void DescribeTo(::std::ostream* os) const { impl_->DescribeTo(os); }
+
+  // Describes the given actual call count to an ostream.
+  static void DescribeActualCallCountTo(int actual_call_count,
+                                        ::std::ostream* os);
+
+ private:
+  std::shared_ptr<const CardinalityInterface> impl_;
+};
+
+// Creates a cardinality that allows at least n calls.
+GTEST_API_ Cardinality AtLeast(int n);
+
+// Creates a cardinality that allows at most n calls.
+GTEST_API_ Cardinality AtMost(int n);
+
+// Creates a cardinality that allows any number of calls.
+GTEST_API_ Cardinality AnyNumber();
+
+// Creates a cardinality that allows between min and max calls.
+GTEST_API_ Cardinality Between(int min, int max);
+
+// Creates a cardinality that allows exactly n calls.
+GTEST_API_ Cardinality Exactly(int n);
+
+// Creates a cardinality from its implementation.
+inline Cardinality MakeCardinality(const CardinalityInterface* c) {
+  return Cardinality(c);
+}
+
+}  // namespace testing
+
+GTEST_DISABLE_MSC_WARNINGS_POP_()  //  4251
+
+#endif  // GOOGLEMOCK_INCLUDE_GMOCK_GMOCK_CARDINALITIES_H_
diff --git a/third_party/googletest/googlemock/include/gmock/gmock-function-mocker.h b/third_party/googletest/googlemock/include/gmock/gmock-function-mocker.h
new file mode 100644
index 0000000..1a1f126
--- /dev/null
+++ b/third_party/googletest/googlemock/include/gmock/gmock-function-mocker.h
@@ -0,0 +1,518 @@
+// Copyright 2007, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Google Mock - a framework for writing C++ mock classes.
+//
+// This file implements MOCK_METHOD.
+
+// IWYU pragma: private, include "gmock/gmock.h"
+// IWYU pragma: friend gmock/.*
+
+#ifndef GOOGLEMOCK_INCLUDE_GMOCK_GMOCK_FUNCTION_MOCKER_H_
+#define GOOGLEMOCK_INCLUDE_GMOCK_GMOCK_FUNCTION_MOCKER_H_
+
+#include <type_traits>  // IWYU pragma: keep
+#include <utility>      // IWYU pragma: keep
+
+#include "gmock/gmock-spec-builders.h"
+#include "gmock/internal/gmock-internal-utils.h"
+#include "gmock/internal/gmock-pp.h"
+
+namespace testing {
+namespace internal {
+template <typename T>
+using identity_t = T;
+
+template <typename Pattern>
+struct ThisRefAdjuster {
+  template <typename T>
+  using AdjustT = typename std::conditional<
+      std::is_const<typename std::remove_reference<Pattern>::type>::value,
+      typename std::conditional<std::is_lvalue_reference<Pattern>::value,
+                                const T&, const T&&>::type,
+      typename std::conditional<std::is_lvalue_reference<Pattern>::value, T&,
+                                T&&>::type>::type;
+
+  template <typename MockType>
+  static AdjustT<MockType> Adjust(const MockType& mock) {
+    return static_cast<AdjustT<MockType>>(const_cast<MockType&>(mock));
+  }
+};
+
+constexpr bool PrefixOf(const char* a, const char* b) {
+  return *a == 0 || (*a == *b && internal::PrefixOf(a + 1, b + 1));
+}
+
+template <int N, int M>
+constexpr bool StartsWith(const char (&prefix)[N], const char (&str)[M]) {
+  return N <= M && internal::PrefixOf(prefix, str);
+}
+
+template <int N, int M>
+constexpr bool EndsWith(const char (&suffix)[N], const char (&str)[M]) {
+  return N <= M && internal::PrefixOf(suffix, str + M - N);
+}
+
+template <int N, int M>
+constexpr bool Equals(const char (&a)[N], const char (&b)[M]) {
+  return N == M && internal::PrefixOf(a, b);
+}
+
+template <int N>
+constexpr bool ValidateSpec(const char (&spec)[N]) {
+  return internal::Equals("const", spec) ||
+         internal::Equals("override", spec) ||
+         internal::Equals("final", spec) ||
+         internal::Equals("noexcept", spec) ||
+         (internal::StartsWith("noexcept(", spec) &&
+          internal::EndsWith(")", spec)) ||
+         internal::Equals("ref(&)", spec) ||
+         internal::Equals("ref(&&)", spec) ||
+         (internal::StartsWith("Calltype(", spec) &&
+          internal::EndsWith(")", spec));
+}
+
+}  // namespace internal
+
+// The style guide prohibits "using" statements in a namespace scope
+// inside a header file.  However, the FunctionMocker class template
+// is meant to be defined in the ::testing namespace.  The following
+// line is just a trick for working around a bug in MSVC 8.0, which
+// cannot handle it if we define FunctionMocker in ::testing.
+using internal::FunctionMocker;
+}  // namespace testing
+
+#define MOCK_METHOD(...)                                               \
+  GMOCK_INTERNAL_WARNING_PUSH()                                        \
+  GMOCK_INTERNAL_WARNING_CLANG(ignored, "-Wunused-member-function")    \
+  GMOCK_PP_VARIADIC_CALL(GMOCK_INTERNAL_MOCK_METHOD_ARG_, __VA_ARGS__) \
+  GMOCK_INTERNAL_WARNING_POP()
+
+#define GMOCK_INTERNAL_MOCK_METHOD_ARG_1(...) \
+  GMOCK_INTERNAL_WRONG_ARITY(__VA_ARGS__)
+
+#define GMOCK_INTERNAL_MOCK_METHOD_ARG_2(...) \
+  GMOCK_INTERNAL_WRONG_ARITY(__VA_ARGS__)
+
+#define GMOCK_INTERNAL_MOCK_METHOD_ARG_3(_Ret, _MethodName, _Args) \
+  GMOCK_INTERNAL_MOCK_METHOD_ARG_4(_Ret, _MethodName, _Args, ())
+
+#define GMOCK_INTERNAL_MOCK_METHOD_ARG_4(_Ret, _MethodName, _Args, _Spec)  \
+  GMOCK_INTERNAL_ASSERT_PARENTHESIS(_Args);                                \
+  GMOCK_INTERNAL_ASSERT_PARENTHESIS(_Spec);                                \
+  GMOCK_INTERNAL_ASSERT_VALID_SIGNATURE(                                   \
+      GMOCK_PP_NARG0 _Args, GMOCK_INTERNAL_SIGNATURE(_Ret, _Args));        \
+  GMOCK_INTERNAL_ASSERT_VALID_SPEC(_Spec)                                  \
+  GMOCK_INTERNAL_MOCK_METHOD_IMPL(                                         \
+      GMOCK_PP_NARG0 _Args, _MethodName, GMOCK_INTERNAL_HAS_CONST(_Spec),  \
+      GMOCK_INTERNAL_HAS_OVERRIDE(_Spec), GMOCK_INTERNAL_HAS_FINAL(_Spec), \
+      GMOCK_INTERNAL_GET_NOEXCEPT_SPEC(_Spec),                             \
+      GMOCK_INTERNAL_GET_CALLTYPE_SPEC(_Spec),                             \
+      GMOCK_INTERNAL_GET_REF_SPEC(_Spec),                                  \
+      (GMOCK_INTERNAL_SIGNATURE(_Ret, _Args)))
+
+#define GMOCK_INTERNAL_MOCK_METHOD_ARG_5(...) \
+  GMOCK_INTERNAL_WRONG_ARITY(__VA_ARGS__)
+
+#define GMOCK_INTERNAL_MOCK_METHOD_ARG_6(...) \
+  GMOCK_INTERNAL_WRONG_ARITY(__VA_ARGS__)
+
+#define GMOCK_INTERNAL_MOCK_METHOD_ARG_7(...) \
+  GMOCK_INTERNAL_WRONG_ARITY(__VA_ARGS__)
+
+#define GMOCK_INTERNAL_WRONG_ARITY(...)                                      \
+  static_assert(                                                             \
+      false,                                                                 \
+      "MOCK_METHOD must be called with 3 or 4 arguments. _Ret, "             \
+      "_MethodName, _Args and optionally _Spec. _Args and _Spec must be "    \
+      "enclosed in parentheses. If _Ret is a type with unprotected commas, " \
+      "it must also be enclosed in parentheses.")
+
+#define GMOCK_INTERNAL_ASSERT_PARENTHESIS(_Tuple) \
+  static_assert(                                  \
+      GMOCK_PP_IS_ENCLOSED_PARENS(_Tuple),        \
+      GMOCK_PP_STRINGIZE(_Tuple) " should be enclosed in parentheses.")
+
+#define GMOCK_INTERNAL_ASSERT_VALID_SIGNATURE(_N, ...)                 \
+  static_assert(                                                       \
+      std::is_function<__VA_ARGS__>::value,                            \
+      "Signature must be a function type, maybe return type contains " \
+      "unprotected comma.");                                           \
+  static_assert(                                                       \
+      ::testing::tuple_size<typename ::testing::internal::Function<    \
+              __VA_ARGS__>::ArgumentTuple>::value == _N,               \
+      "This method does not take " GMOCK_PP_STRINGIZE(                 \
+          _N) " arguments. Parenthesize all types with unprotected commas.")
+
+#define GMOCK_INTERNAL_ASSERT_VALID_SPEC(_Spec) \
+  GMOCK_PP_FOR_EACH(GMOCK_INTERNAL_ASSERT_VALID_SPEC_ELEMENT, ~, _Spec)
+
+#define GMOCK_INTERNAL_MOCK_METHOD_IMPL(_N, _MethodName, _Constness,           \
+                                        _Override, _Final, _NoexceptSpec,      \
+                                        _CallType, _RefSpec, _Signature)       \
+  typename ::testing::internal::Function<GMOCK_PP_REMOVE_PARENS(               \
+      _Signature)>::Result                                                     \
+  GMOCK_INTERNAL_EXPAND(_CallType)                                             \
+      _MethodName(GMOCK_PP_REPEAT(GMOCK_INTERNAL_PARAMETER, _Signature, _N))   \
+          GMOCK_PP_IF(_Constness, const, )                                     \
+              _RefSpec _NoexceptSpec GMOCK_PP_IF(_Override, override, )        \
+                  GMOCK_PP_IF(_Final, final, ) {                               \
+    GMOCK_MOCKER_(_N, _Constness, _MethodName)                                 \
+        .SetOwnerAndName(this, #_MethodName);                                  \
+    return GMOCK_MOCKER_(_N, _Constness, _MethodName)                          \
+        .Invoke(GMOCK_PP_REPEAT(GMOCK_INTERNAL_FORWARD_ARG, _Signature, _N));  \
+  }                                                                            \
+  ::testing::MockSpec<GMOCK_PP_REMOVE_PARENS(_Signature)> gmock_##_MethodName( \
+      GMOCK_PP_REPEAT(GMOCK_INTERNAL_MATCHER_PARAMETER, _Signature, _N))       \
+      GMOCK_PP_IF(_Constness, const, ) _RefSpec {                              \
+    GMOCK_MOCKER_(_N, _Constness, _MethodName).RegisterOwner(this);            \
+    return GMOCK_MOCKER_(_N, _Constness, _MethodName)                          \
+        .With(GMOCK_PP_REPEAT(GMOCK_INTERNAL_MATCHER_ARGUMENT, , _N));         \
+  }                                                                            \
+  ::testing::MockSpec<GMOCK_PP_REMOVE_PARENS(_Signature)> gmock_##_MethodName( \
+      const ::testing::internal::WithoutMatchers&,                             \
+      GMOCK_PP_IF(_Constness, const, )::testing::internal::Function<           \
+          GMOCK_PP_REMOVE_PARENS(_Signature)>*) const _RefSpec _NoexceptSpec { \
+    return ::testing::internal::ThisRefAdjuster<GMOCK_PP_IF(                   \
+        _Constness, const, ) int _RefSpec>::Adjust(*this)                      \
+        .gmock_##_MethodName(GMOCK_PP_REPEAT(                                  \
+            GMOCK_INTERNAL_A_MATCHER_ARGUMENT, _Signature, _N));               \
+  }                                                                            \
+  mutable ::testing::FunctionMocker<GMOCK_PP_REMOVE_PARENS(_Signature)>        \
+  GMOCK_MOCKER_(_N, _Constness, _MethodName)
+
+#define GMOCK_INTERNAL_EXPAND(...) __VA_ARGS__
+
+// Valid modifiers.
+#define GMOCK_INTERNAL_HAS_CONST(_Tuple) \
+  GMOCK_PP_HAS_COMMA(GMOCK_PP_FOR_EACH(GMOCK_INTERNAL_DETECT_CONST, ~, _Tuple))
+
+#define GMOCK_INTERNAL_HAS_OVERRIDE(_Tuple) \
+  GMOCK_PP_HAS_COMMA(                       \
+      GMOCK_PP_FOR_EACH(GMOCK_INTERNAL_DETECT_OVERRIDE, ~, _Tuple))
+
+#define GMOCK_INTERNAL_HAS_FINAL(_Tuple) \
+  GMOCK_PP_HAS_COMMA(GMOCK_PP_FOR_EACH(GMOCK_INTERNAL_DETECT_FINAL, ~, _Tuple))
+
+#define GMOCK_INTERNAL_GET_NOEXCEPT_SPEC(_Tuple) \
+  GMOCK_PP_FOR_EACH(GMOCK_INTERNAL_NOEXCEPT_SPEC_IF_NOEXCEPT, ~, _Tuple)
+
+#define GMOCK_INTERNAL_NOEXCEPT_SPEC_IF_NOEXCEPT(_i, _, _elem)          \
+  GMOCK_PP_IF(                                                          \
+      GMOCK_PP_HAS_COMMA(GMOCK_INTERNAL_DETECT_NOEXCEPT(_i, _, _elem)), \
+      _elem, )
+
+#define GMOCK_INTERNAL_GET_CALLTYPE_SPEC(_Tuple) \
+  GMOCK_PP_FOR_EACH(GMOCK_INTERNAL_CALLTYPE_SPEC_IF_CALLTYPE, ~, _Tuple)
+
+#define GMOCK_INTERNAL_CALLTYPE_SPEC_IF_CALLTYPE(_i, _, _elem)          \
+  GMOCK_PP_IF(                                                          \
+      GMOCK_PP_HAS_COMMA(GMOCK_INTERNAL_DETECT_CALLTYPE(_i, _, _elem)), \
+      GMOCK_PP_CAT(GMOCK_INTERNAL_UNPACK_, _elem), )
+
+#define GMOCK_INTERNAL_GET_REF_SPEC(_Tuple) \
+  GMOCK_PP_FOR_EACH(GMOCK_INTERNAL_REF_SPEC_IF_REF, ~, _Tuple)
+
+#define GMOCK_INTERNAL_REF_SPEC_IF_REF(_i, _, _elem)                       \
+  GMOCK_PP_IF(GMOCK_PP_HAS_COMMA(GMOCK_INTERNAL_DETECT_REF(_i, _, _elem)), \
+              GMOCK_PP_CAT(GMOCK_INTERNAL_UNPACK_, _elem), )
+
+#ifdef GMOCK_INTERNAL_STRICT_SPEC_ASSERT
+#define GMOCK_INTERNAL_ASSERT_VALID_SPEC_ELEMENT(_i, _, _elem) \
+  static_assert(                                                     \
+      ::testing::internal::ValidateSpec(GMOCK_PP_STRINGIZE(_elem)),  \
+      "Token \'" GMOCK_PP_STRINGIZE(                                 \
+          _elem) "\' cannot be recognized as a valid specification " \
+                 "modifier. Is a ',' missing?");
+#else
+#define GMOCK_INTERNAL_ASSERT_VALID_SPEC_ELEMENT(_i, _, _elem)                 \
+  static_assert(                                                               \
+      (GMOCK_PP_HAS_COMMA(GMOCK_INTERNAL_DETECT_CONST(_i, _, _elem)) +         \
+       GMOCK_PP_HAS_COMMA(GMOCK_INTERNAL_DETECT_OVERRIDE(_i, _, _elem)) +      \
+       GMOCK_PP_HAS_COMMA(GMOCK_INTERNAL_DETECT_FINAL(_i, _, _elem)) +         \
+       GMOCK_PP_HAS_COMMA(GMOCK_INTERNAL_DETECT_NOEXCEPT(_i, _, _elem)) +      \
+       GMOCK_PP_HAS_COMMA(GMOCK_INTERNAL_DETECT_REF(_i, _, _elem)) +           \
+       GMOCK_PP_HAS_COMMA(GMOCK_INTERNAL_DETECT_CALLTYPE(_i, _, _elem))) == 1, \
+      GMOCK_PP_STRINGIZE(                                                      \
+          _elem) " cannot be recognized as a valid specification modifier.");
+#endif  // GMOCK_INTERNAL_STRICT_SPEC_ASSERT
+
+// Modifiers implementation.
+#define GMOCK_INTERNAL_DETECT_CONST(_i, _, _elem) \
+  GMOCK_PP_CAT(GMOCK_INTERNAL_DETECT_CONST_I_, _elem)
+
+#define GMOCK_INTERNAL_DETECT_CONST_I_const ,
+
+#define GMOCK_INTERNAL_DETECT_OVERRIDE(_i, _, _elem) \
+  GMOCK_PP_CAT(GMOCK_INTERNAL_DETECT_OVERRIDE_I_, _elem)
+
+#define GMOCK_INTERNAL_DETECT_OVERRIDE_I_override ,
+
+#define GMOCK_INTERNAL_DETECT_FINAL(_i, _, _elem) \
+  GMOCK_PP_CAT(GMOCK_INTERNAL_DETECT_FINAL_I_, _elem)
+
+#define GMOCK_INTERNAL_DETECT_FINAL_I_final ,
+
+#define GMOCK_INTERNAL_DETECT_NOEXCEPT(_i, _, _elem) \
+  GMOCK_PP_CAT(GMOCK_INTERNAL_DETECT_NOEXCEPT_I_, _elem)
+
+#define GMOCK_INTERNAL_DETECT_NOEXCEPT_I_noexcept ,
+
+#define GMOCK_INTERNAL_DETECT_REF(_i, _, _elem) \
+  GMOCK_PP_CAT(GMOCK_INTERNAL_DETECT_REF_I_, _elem)
+
+#define GMOCK_INTERNAL_DETECT_REF_I_ref ,
+
+#define GMOCK_INTERNAL_UNPACK_ref(x) x
+
+#define GMOCK_INTERNAL_DETECT_CALLTYPE(_i, _, _elem) \
+  GMOCK_PP_CAT(GMOCK_INTERNAL_DETECT_CALLTYPE_I_, _elem)
+
+#define GMOCK_INTERNAL_DETECT_CALLTYPE_I_Calltype ,
+
+#define GMOCK_INTERNAL_UNPACK_Calltype(...) __VA_ARGS__
+
+// Note: The use of `identity_t` here allows _Ret to represent return types that
+// would normally need to be specified in a different way. For example, a method
+// returning a function pointer must be written as
+//
+// fn_ptr_return_t (*method(method_args_t...))(fn_ptr_args_t...)
+//
+// But we only support placing the return type at the beginning. To handle this,
+// we wrap all calls in identity_t, so that a declaration will be expanded to
+//
+// identity_t<fn_ptr_return_t (*)(fn_ptr_args_t...)> method(method_args_t...)
+//
+// This allows us to work around the syntactic oddities of function/method
+// types.
+#define GMOCK_INTERNAL_SIGNATURE(_Ret, _Args)                                 \
+  ::testing::internal::identity_t<GMOCK_PP_IF(GMOCK_PP_IS_BEGIN_PARENS(_Ret), \
+                                              GMOCK_PP_REMOVE_PARENS,         \
+                                              GMOCK_PP_IDENTITY)(_Ret)>(      \
+      GMOCK_PP_FOR_EACH(GMOCK_INTERNAL_GET_TYPE, _, _Args))
+
+#define GMOCK_INTERNAL_GET_TYPE(_i, _, _elem)                          \
+  GMOCK_PP_COMMA_IF(_i)                                                \
+  GMOCK_PP_IF(GMOCK_PP_IS_BEGIN_PARENS(_elem), GMOCK_PP_REMOVE_PARENS, \
+              GMOCK_PP_IDENTITY)                                       \
+  (_elem)
+
+#define GMOCK_INTERNAL_PARAMETER(_i, _Signature, _)            \
+  GMOCK_PP_COMMA_IF(_i)                                        \
+  GMOCK_INTERNAL_ARG_O(_i, GMOCK_PP_REMOVE_PARENS(_Signature)) \
+  gmock_a##_i
+
+#define GMOCK_INTERNAL_FORWARD_ARG(_i, _Signature, _) \
+  GMOCK_PP_COMMA_IF(_i)                               \
+  ::std::forward<GMOCK_INTERNAL_ARG_O(                \
+      _i, GMOCK_PP_REMOVE_PARENS(_Signature))>(gmock_a##_i)
+
+#define GMOCK_INTERNAL_MATCHER_PARAMETER(_i, _Signature, _)        \
+  GMOCK_PP_COMMA_IF(_i)                                            \
+  GMOCK_INTERNAL_MATCHER_O(_i, GMOCK_PP_REMOVE_PARENS(_Signature)) \
+  gmock_a##_i
+
+#define GMOCK_INTERNAL_MATCHER_ARGUMENT(_i, _1, _2) \
+  GMOCK_PP_COMMA_IF(_i)                             \
+  gmock_a##_i
+
+#define GMOCK_INTERNAL_A_MATCHER_ARGUMENT(_i, _Signature, _) \
+  GMOCK_PP_COMMA_IF(_i)                                      \
+  ::testing::A<GMOCK_INTERNAL_ARG_O(_i, GMOCK_PP_REMOVE_PARENS(_Signature))>()
+
+#define GMOCK_INTERNAL_ARG_O(_i, ...) \
+  typename ::testing::internal::Function<__VA_ARGS__>::template Arg<_i>::type
+
+#define GMOCK_INTERNAL_MATCHER_O(_i, ...)                          \
+  const ::testing::Matcher<typename ::testing::internal::Function< \
+      __VA_ARGS__>::template Arg<_i>::type>&
+
+#define MOCK_METHOD0(m, ...) GMOCK_INTERNAL_MOCK_METHODN(, , m, 0, __VA_ARGS__)
+#define MOCK_METHOD1(m, ...) GMOCK_INTERNAL_MOCK_METHODN(, , m, 1, __VA_ARGS__)
+#define MOCK_METHOD2(m, ...) GMOCK_INTERNAL_MOCK_METHODN(, , m, 2, __VA_ARGS__)
+#define MOCK_METHOD3(m, ...) GMOCK_INTERNAL_MOCK_METHODN(, , m, 3, __VA_ARGS__)
+#define MOCK_METHOD4(m, ...) GMOCK_INTERNAL_MOCK_METHODN(, , m, 4, __VA_ARGS__)
+#define MOCK_METHOD5(m, ...) GMOCK_INTERNAL_MOCK_METHODN(, , m, 5, __VA_ARGS__)
+#define MOCK_METHOD6(m, ...) GMOCK_INTERNAL_MOCK_METHODN(, , m, 6, __VA_ARGS__)
+#define MOCK_METHOD7(m, ...) GMOCK_INTERNAL_MOCK_METHODN(, , m, 7, __VA_ARGS__)
+#define MOCK_METHOD8(m, ...) GMOCK_INTERNAL_MOCK_METHODN(, , m, 8, __VA_ARGS__)
+#define MOCK_METHOD9(m, ...) GMOCK_INTERNAL_MOCK_METHODN(, , m, 9, __VA_ARGS__)
+#define MOCK_METHOD10(m, ...) \
+  GMOCK_INTERNAL_MOCK_METHODN(, , m, 10, __VA_ARGS__)
+
+#define MOCK_CONST_METHOD0(m, ...) \
+  GMOCK_INTERNAL_MOCK_METHODN(const, , m, 0, __VA_ARGS__)
+#define MOCK_CONST_METHOD1(m, ...) \
+  GMOCK_INTERNAL_MOCK_METHODN(const, , m, 1, __VA_ARGS__)
+#define MOCK_CONST_METHOD2(m, ...) \
+  GMOCK_INTERNAL_MOCK_METHODN(const, , m, 2, __VA_ARGS__)
+#define MOCK_CONST_METHOD3(m, ...) \
+  GMOCK_INTERNAL_MOCK_METHODN(const, , m, 3, __VA_ARGS__)
+#define MOCK_CONST_METHOD4(m, ...) \
+  GMOCK_INTERNAL_MOCK_METHODN(const, , m, 4, __VA_ARGS__)
+#define MOCK_CONST_METHOD5(m, ...) \
+  GMOCK_INTERNAL_MOCK_METHODN(const, , m, 5, __VA_ARGS__)
+#define MOCK_CONST_METHOD6(m, ...) \
+  GMOCK_INTERNAL_MOCK_METHODN(const, , m, 6, __VA_ARGS__)
+#define MOCK_CONST_METHOD7(m, ...) \
+  GMOCK_INTERNAL_MOCK_METHODN(const, , m, 7, __VA_ARGS__)
+#define MOCK_CONST_METHOD8(m, ...) \
+  GMOCK_INTERNAL_MOCK_METHODN(const, , m, 8, __VA_ARGS__)
+#define MOCK_CONST_METHOD9(m, ...) \
+  GMOCK_INTERNAL_MOCK_METHODN(const, , m, 9, __VA_ARGS__)
+#define MOCK_CONST_METHOD10(m, ...) \
+  GMOCK_INTERNAL_MOCK_METHODN(const, , m, 10, __VA_ARGS__)
+
+#define MOCK_METHOD0_T(m, ...) MOCK_METHOD0(m, __VA_ARGS__)
+#define MOCK_METHOD1_T(m, ...) MOCK_METHOD1(m, __VA_ARGS__)
+#define MOCK_METHOD2_T(m, ...) MOCK_METHOD2(m, __VA_ARGS__)
+#define MOCK_METHOD3_T(m, ...) MOCK_METHOD3(m, __VA_ARGS__)
+#define MOCK_METHOD4_T(m, ...) MOCK_METHOD4(m, __VA_ARGS__)
+#define MOCK_METHOD5_T(m, ...) MOCK_METHOD5(m, __VA_ARGS__)
+#define MOCK_METHOD6_T(m, ...) MOCK_METHOD6(m, __VA_ARGS__)
+#define MOCK_METHOD7_T(m, ...) MOCK_METHOD7(m, __VA_ARGS__)
+#define MOCK_METHOD8_T(m, ...) MOCK_METHOD8(m, __VA_ARGS__)
+#define MOCK_METHOD9_T(m, ...) MOCK_METHOD9(m, __VA_ARGS__)
+#define MOCK_METHOD10_T(m, ...) MOCK_METHOD10(m, __VA_ARGS__)
+
+#define MOCK_CONST_METHOD0_T(m, ...) MOCK_CONST_METHOD0(m, __VA_ARGS__)
+#define MOCK_CONST_METHOD1_T(m, ...) MOCK_CONST_METHOD1(m, __VA_ARGS__)
+#define MOCK_CONST_METHOD2_T(m, ...) MOCK_CONST_METHOD2(m, __VA_ARGS__)
+#define MOCK_CONST_METHOD3_T(m, ...) MOCK_CONST_METHOD3(m, __VA_ARGS__)
+#define MOCK_CONST_METHOD4_T(m, ...) MOCK_CONST_METHOD4(m, __VA_ARGS__)
+#define MOCK_CONST_METHOD5_T(m, ...) MOCK_CONST_METHOD5(m, __VA_ARGS__)
+#define MOCK_CONST_METHOD6_T(m, ...) MOCK_CONST_METHOD6(m, __VA_ARGS__)
+#define MOCK_CONST_METHOD7_T(m, ...) MOCK_CONST_METHOD7(m, __VA_ARGS__)
+#define MOCK_CONST_METHOD8_T(m, ...) MOCK_CONST_METHOD8(m, __VA_ARGS__)
+#define MOCK_CONST_METHOD9_T(m, ...) MOCK_CONST_METHOD9(m, __VA_ARGS__)
+#define MOCK_CONST_METHOD10_T(m, ...) MOCK_CONST_METHOD10(m, __VA_ARGS__)
+
+#define MOCK_METHOD0_WITH_CALLTYPE(ct, m, ...) \
+  GMOCK_INTERNAL_MOCK_METHODN(, ct, m, 0, __VA_ARGS__)
+#define MOCK_METHOD1_WITH_CALLTYPE(ct, m, ...) \
+  GMOCK_INTERNAL_MOCK_METHODN(, ct, m, 1, __VA_ARGS__)
+#define MOCK_METHOD2_WITH_CALLTYPE(ct, m, ...) \
+  GMOCK_INTERNAL_MOCK_METHODN(, ct, m, 2, __VA_ARGS__)
+#define MOCK_METHOD3_WITH_CALLTYPE(ct, m, ...) \
+  GMOCK_INTERNAL_MOCK_METHODN(, ct, m, 3, __VA_ARGS__)
+#define MOCK_METHOD4_WITH_CALLTYPE(ct, m, ...) \
+  GMOCK_INTERNAL_MOCK_METHODN(, ct, m, 4, __VA_ARGS__)
+#define MOCK_METHOD5_WITH_CALLTYPE(ct, m, ...) \
+  GMOCK_INTERNAL_MOCK_METHODN(, ct, m, 5, __VA_ARGS__)
+#define MOCK_METHOD6_WITH_CALLTYPE(ct, m, ...) \
+  GMOCK_INTERNAL_MOCK_METHODN(, ct, m, 6, __VA_ARGS__)
+#define MOCK_METHOD7_WITH_CALLTYPE(ct, m, ...) \
+  GMOCK_INTERNAL_MOCK_METHODN(, ct, m, 7, __VA_ARGS__)
+#define MOCK_METHOD8_WITH_CALLTYPE(ct, m, ...) \
+  GMOCK_INTERNAL_MOCK_METHODN(, ct, m, 8, __VA_ARGS__)
+#define MOCK_METHOD9_WITH_CALLTYPE(ct, m, ...) \
+  GMOCK_INTERNAL_MOCK_METHODN(, ct, m, 9, __VA_ARGS__)
+#define MOCK_METHOD10_WITH_CALLTYPE(ct, m, ...) \
+  GMOCK_INTERNAL_MOCK_METHODN(, ct, m, 10, __VA_ARGS__)
+
+#define MOCK_CONST_METHOD0_WITH_CALLTYPE(ct, m, ...) \
+  GMOCK_INTERNAL_MOCK_METHODN(const, ct, m, 0, __VA_ARGS__)
+#define MOCK_CONST_METHOD1_WITH_CALLTYPE(ct, m, ...) \
+  GMOCK_INTERNAL_MOCK_METHODN(const, ct, m, 1, __VA_ARGS__)
+#define MOCK_CONST_METHOD2_WITH_CALLTYPE(ct, m, ...) \
+  GMOCK_INTERNAL_MOCK_METHODN(const, ct, m, 2, __VA_ARGS__)
+#define MOCK_CONST_METHOD3_WITH_CALLTYPE(ct, m, ...) \
+  GMOCK_INTERNAL_MOCK_METHODN(const, ct, m, 3, __VA_ARGS__)
+#define MOCK_CONST_METHOD4_WITH_CALLTYPE(ct, m, ...) \
+  GMOCK_INTERNAL_MOCK_METHODN(const, ct, m, 4, __VA_ARGS__)
+#define MOCK_CONST_METHOD5_WITH_CALLTYPE(ct, m, ...) \
+  GMOCK_INTERNAL_MOCK_METHODN(const, ct, m, 5, __VA_ARGS__)
+#define MOCK_CONST_METHOD6_WITH_CALLTYPE(ct, m, ...) \
+  GMOCK_INTERNAL_MOCK_METHODN(const, ct, m, 6, __VA_ARGS__)
+#define MOCK_CONST_METHOD7_WITH_CALLTYPE(ct, m, ...) \
+  GMOCK_INTERNAL_MOCK_METHODN(const, ct, m, 7, __VA_ARGS__)
+#define MOCK_CONST_METHOD8_WITH_CALLTYPE(ct, m, ...) \
+  GMOCK_INTERNAL_MOCK_METHODN(const, ct, m, 8, __VA_ARGS__)
+#define MOCK_CONST_METHOD9_WITH_CALLTYPE(ct, m, ...) \
+  GMOCK_INTERNAL_MOCK_METHODN(const, ct, m, 9, __VA_ARGS__)
+#define MOCK_CONST_METHOD10_WITH_CALLTYPE(ct, m, ...) \
+  GMOCK_INTERNAL_MOCK_METHODN(const, ct, m, 10, __VA_ARGS__)
+
+#define MOCK_METHOD0_T_WITH_CALLTYPE(ct, m, ...) \
+  MOCK_METHOD0_WITH_CALLTYPE(ct, m, __VA_ARGS__)
+#define MOCK_METHOD1_T_WITH_CALLTYPE(ct, m, ...) \
+  MOCK_METHOD1_WITH_CALLTYPE(ct, m, __VA_ARGS__)
+#define MOCK_METHOD2_T_WITH_CALLTYPE(ct, m, ...) \
+  MOCK_METHOD2_WITH_CALLTYPE(ct, m, __VA_ARGS__)
+#define MOCK_METHOD3_T_WITH_CALLTYPE(ct, m, ...) \
+  MOCK_METHOD3_WITH_CALLTYPE(ct, m, __VA_ARGS__)
+#define MOCK_METHOD4_T_WITH_CALLTYPE(ct, m, ...) \
+  MOCK_METHOD4_WITH_CALLTYPE(ct, m, __VA_ARGS__)
+#define MOCK_METHOD5_T_WITH_CALLTYPE(ct, m, ...) \
+  MOCK_METHOD5_WITH_CALLTYPE(ct, m, __VA_ARGS__)
+#define MOCK_METHOD6_T_WITH_CALLTYPE(ct, m, ...) \
+  MOCK_METHOD6_WITH_CALLTYPE(ct, m, __VA_ARGS__)
+#define MOCK_METHOD7_T_WITH_CALLTYPE(ct, m, ...) \
+  MOCK_METHOD7_WITH_CALLTYPE(ct, m, __VA_ARGS__)
+#define MOCK_METHOD8_T_WITH_CALLTYPE(ct, m, ...) \
+  MOCK_METHOD8_WITH_CALLTYPE(ct, m, __VA_ARGS__)
+#define MOCK_METHOD9_T_WITH_CALLTYPE(ct, m, ...) \
+  MOCK_METHOD9_WITH_CALLTYPE(ct, m, __VA_ARGS__)
+#define MOCK_METHOD10_T_WITH_CALLTYPE(ct, m, ...) \
+  MOCK_METHOD10_WITH_CALLTYPE(ct, m, __VA_ARGS__)
+
+#define MOCK_CONST_METHOD0_T_WITH_CALLTYPE(ct, m, ...) \
+  MOCK_CONST_METHOD0_WITH_CALLTYPE(ct, m, __VA_ARGS__)
+#define MOCK_CONST_METHOD1_T_WITH_CALLTYPE(ct, m, ...) \
+  MOCK_CONST_METHOD1_WITH_CALLTYPE(ct, m, __VA_ARGS__)
+#define MOCK_CONST_METHOD2_T_WITH_CALLTYPE(ct, m, ...) \
+  MOCK_CONST_METHOD2_WITH_CALLTYPE(ct, m, __VA_ARGS__)
+#define MOCK_CONST_METHOD3_T_WITH_CALLTYPE(ct, m, ...) \
+  MOCK_CONST_METHOD3_WITH_CALLTYPE(ct, m, __VA_ARGS__)
+#define MOCK_CONST_METHOD4_T_WITH_CALLTYPE(ct, m, ...) \
+  MOCK_CONST_METHOD4_WITH_CALLTYPE(ct, m, __VA_ARGS__)
+#define MOCK_CONST_METHOD5_T_WITH_CALLTYPE(ct, m, ...) \
+  MOCK_CONST_METHOD5_WITH_CALLTYPE(ct, m, __VA_ARGS__)
+#define MOCK_CONST_METHOD6_T_WITH_CALLTYPE(ct, m, ...) \
+  MOCK_CONST_METHOD6_WITH_CALLTYPE(ct, m, __VA_ARGS__)
+#define MOCK_CONST_METHOD7_T_WITH_CALLTYPE(ct, m, ...) \
+  MOCK_CONST_METHOD7_WITH_CALLTYPE(ct, m, __VA_ARGS__)
+#define MOCK_CONST_METHOD8_T_WITH_CALLTYPE(ct, m, ...) \
+  MOCK_CONST_METHOD8_WITH_CALLTYPE(ct, m, __VA_ARGS__)
+#define MOCK_CONST_METHOD9_T_WITH_CALLTYPE(ct, m, ...) \
+  MOCK_CONST_METHOD9_WITH_CALLTYPE(ct, m, __VA_ARGS__)
+#define MOCK_CONST_METHOD10_T_WITH_CALLTYPE(ct, m, ...) \
+  MOCK_CONST_METHOD10_WITH_CALLTYPE(ct, m, __VA_ARGS__)
+
+#define GMOCK_INTERNAL_MOCK_METHODN(constness, ct, Method, args_num, ...) \
+  GMOCK_INTERNAL_ASSERT_VALID_SIGNATURE(                                  \
+      args_num, ::testing::internal::identity_t<__VA_ARGS__>);            \
+  GMOCK_INTERNAL_MOCK_METHOD_IMPL(                                        \
+      args_num, Method, GMOCK_PP_NARG0(constness), 0, 0, , ct, ,          \
+      (::testing::internal::identity_t<__VA_ARGS__>))
+
+#define GMOCK_MOCKER_(arity, constness, Method) \
+  GTEST_CONCAT_TOKEN_(gmock##constness##arity##_##Method##_, __LINE__)
+
+#endif  // GOOGLEMOCK_INCLUDE_GMOCK_GMOCK_FUNCTION_MOCKER_H_
diff --git a/third_party/googletest/googlemock/include/gmock/gmock-matchers.h b/third_party/googletest/googlemock/include/gmock/gmock-matchers.h
new file mode 100644
index 0000000..0f67713
--- /dev/null
+++ b/third_party/googletest/googlemock/include/gmock/gmock-matchers.h
@@ -0,0 +1,5623 @@
+// Copyright 2007, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Google Mock - a framework for writing C++ mock classes.
+//
+// The MATCHER* family of macros can be used in a namespace scope to
+// define custom matchers easily.
+//
+// Basic Usage
+// ===========
+//
+// The syntax
+//
+//   MATCHER(name, description_string) { statements; }
+//
+// defines a matcher with the given name that executes the statements,
+// which must return a bool to indicate if the match succeeds.  Inside
+// the statements, you can refer to the value being matched by 'arg',
+// and refer to its type by 'arg_type'.
+//
+// The description string documents what the matcher does, and is used
+// to generate the failure message when the match fails.  Since a
+// MATCHER() is usually defined in a header file shared by multiple
+// C++ source files, we require the description to be a C-string
+// literal to avoid possible side effects.  It can be empty, in which
+// case we'll use the sequence of words in the matcher name as the
+// description.
+//
+// For example:
+//
+//   MATCHER(IsEven, "") { return (arg % 2) == 0; }
+//
+// allows you to write
+//
+//   // Expects mock_foo.Bar(n) to be called where n is even.
+//   EXPECT_CALL(mock_foo, Bar(IsEven()));
+//
+// or,
+//
+//   // Verifies that the value of some_expression is even.
+//   EXPECT_THAT(some_expression, IsEven());
+//
+// If the above assertion fails, it will print something like:
+//
+//   Value of: some_expression
+//   Expected: is even
+//     Actual: 7
+//
+// where the description "is even" is automatically calculated from the
+// matcher name IsEven.
+//
+// Argument Type
+// =============
+//
+// Note that the type of the value being matched (arg_type) is
+// determined by the context in which you use the matcher and is
+// supplied to you by the compiler, so you don't need to worry about
+// declaring it (nor can you).  This allows the matcher to be
+// polymorphic.  For example, IsEven() can be used to match any type
+// where the value of "(arg % 2) == 0" can be implicitly converted to
+// a bool.  In the "Bar(IsEven())" example above, if method Bar()
+// takes an int, 'arg_type' will be int; if it takes an unsigned long,
+// 'arg_type' will be unsigned long; and so on.
+//
+// Parameterizing Matchers
+// =======================
+//
+// Sometimes you'll want to parameterize the matcher.  For that you
+// can use another macro:
+//
+//   MATCHER_P(name, param_name, description_string) { statements; }
+//
+// For example:
+//
+//   MATCHER_P(HasAbsoluteValue, value, "") { return abs(arg) == value; }
+//
+// will allow you to write:
+//
+//   EXPECT_THAT(Blah("a"), HasAbsoluteValue(n));
+//
+// which may lead to this message (assuming n is 10):
+//
+//   Value of: Blah("a")
+//   Expected: has absolute value 10
+//     Actual: -9
+//
+// Note that both the matcher description and its parameter are
+// printed, making the message human-friendly.
+//
+// In the matcher definition body, you can write 'foo_type' to
+// reference the type of a parameter named 'foo'.  For example, in the
+// body of MATCHER_P(HasAbsoluteValue, value) above, you can write
+// 'value_type' to refer to the type of 'value'.
+//
+// We also provide MATCHER_P2, MATCHER_P3, ..., up to MATCHER_P$n to
+// support multi-parameter matchers.
+//
+// Describing Parameterized Matchers
+// =================================
+//
+// The last argument to MATCHER*() is a string-typed expression.  The
+// expression can reference all of the matcher's parameters and a
+// special bool-typed variable named 'negation'.  When 'negation' is
+// false, the expression should evaluate to the matcher's description;
+// otherwise it should evaluate to the description of the negation of
+// the matcher.  For example,
+//
+//   using testing::PrintToString;
+//
+//   MATCHER_P2(InClosedRange, low, hi,
+//       std::string(negation ? "is not" : "is") + " in range [" +
+//       PrintToString(low) + ", " + PrintToString(hi) + "]") {
+//     return low <= arg && arg <= hi;
+//   }
+//   ...
+//   EXPECT_THAT(3, InClosedRange(4, 6));
+//   EXPECT_THAT(3, Not(InClosedRange(2, 4)));
+//
+// would generate two failures that contain the text:
+//
+//   Expected: is in range [4, 6]
+//   ...
+//   Expected: is not in range [2, 4]
+//
+// If you specify "" as the description, the failure message will
+// contain the sequence of words in the matcher name followed by the
+// parameter values printed as a tuple.  For example,
+//
+//   MATCHER_P2(InClosedRange, low, hi, "") { ... }
+//   ...
+//   EXPECT_THAT(3, InClosedRange(4, 6));
+//   EXPECT_THAT(3, Not(InClosedRange(2, 4)));
+//
+// would generate two failures that contain the text:
+//
+//   Expected: in closed range (4, 6)
+//   ...
+//   Expected: not (in closed range (2, 4))
+//
+// Types of Matcher Parameters
+// ===========================
+//
+// For the purpose of typing, you can view
+//
+//   MATCHER_Pk(Foo, p1, ..., pk, description_string) { ... }
+//
+// as shorthand for
+//
+//   template <typename p1_type, ..., typename pk_type>
+//   FooMatcherPk<p1_type, ..., pk_type>
+//   Foo(p1_type p1, ..., pk_type pk) { ... }
+//
+// When you write Foo(v1, ..., vk), the compiler infers the types of
+// the parameters v1, ..., and vk for you.  If you are not happy with
+// the result of the type inference, you can specify the types by
+// explicitly instantiating the template, as in Foo<long, bool>(5,
+// false).  As said earlier, you don't get to (or need to) specify
+// 'arg_type' as that's determined by the context in which the matcher
+// is used.  You can assign the result of expression Foo(p1, ..., pk)
+// to a variable of type FooMatcherPk<p1_type, ..., pk_type>.  This
+// can be useful when composing matchers.
+//
+// While you can instantiate a matcher template with reference types,
+// passing the parameters by pointer usually makes your code more
+// readable.  If, however, you still want to pass a parameter by
+// reference, be aware that in the failure message generated by the
+// matcher you will see the value of the referenced object but not its
+// address.
+//
+// Explaining Match Results
+// ========================
+//
+// Sometimes the matcher description alone isn't enough to explain why
+// the match has failed or succeeded.  For example, when expecting a
+// long string, it can be very helpful to also print the diff between
+// the expected string and the actual one.  To achieve that, you can
+// optionally stream additional information to a special variable
+// named result_listener, whose type is a pointer to class
+// MatchResultListener:
+//
+//   MATCHER_P(EqualsLongString, str, "") {
+//     if (arg == str) return true;
+//
+//     *result_listener << "the difference: "
+///                     << DiffStrings(str, arg);
+//     return false;
+//   }
+//
+// Overloading Matchers
+// ====================
+//
+// You can overload matchers with different numbers of parameters:
+//
+//   MATCHER_P(Blah, a, description_string1) { ... }
+//   MATCHER_P2(Blah, a, b, description_string2) { ... }
+//
+// Caveats
+// =======
+//
+// When defining a new matcher, you should also consider implementing
+// MatcherInterface or using MakePolymorphicMatcher().  These
+// approaches require more work than the MATCHER* macros, but also
+// give you more control on the types of the value being matched and
+// the matcher parameters, which may leads to better compiler error
+// messages when the matcher is used wrong.  They also allow
+// overloading matchers based on parameter types (as opposed to just
+// based on the number of parameters).
+//
+// MATCHER*() can only be used in a namespace scope as templates cannot be
+// declared inside of a local class.
+//
+// More Information
+// ================
+//
+// To learn more about using these macros, please search for 'MATCHER'
+// on
+// https://github.com/google/googletest/blob/main/docs/gmock_cook_book.md
+//
+// This file also implements some commonly used argument matchers.  More
+// matchers can be defined by the user implementing the
+// MatcherInterface<T> interface if necessary.
+//
+// See googletest/include/gtest/gtest-matchers.h for the definition of class
+// Matcher, class MatcherInterface, and others.
+
+// IWYU pragma: private, include "gmock/gmock.h"
+// IWYU pragma: friend gmock/.*
+
+#ifndef GOOGLEMOCK_INCLUDE_GMOCK_GMOCK_MATCHERS_H_
+#define GOOGLEMOCK_INCLUDE_GMOCK_GMOCK_MATCHERS_H_
+
+#include <algorithm>
+#include <cmath>
+#include <exception>
+#include <functional>
+#include <initializer_list>
+#include <ios>
+#include <iterator>
+#include <limits>
+#include <memory>
+#include <ostream>  // NOLINT
+#include <sstream>
+#include <string>
+#include <type_traits>
+#include <utility>
+#include <vector>
+
+#include "gmock/internal/gmock-internal-utils.h"
+#include "gmock/internal/gmock-port.h"
+#include "gmock/internal/gmock-pp.h"
+#include "gtest/gtest.h"
+
+// MSVC warning C5046 is new as of VS2017 version 15.8.
+#if defined(_MSC_VER) && _MSC_VER >= 1915
+#define GMOCK_MAYBE_5046_ 5046
+#else
+#define GMOCK_MAYBE_5046_
+#endif
+
+GTEST_DISABLE_MSC_WARNINGS_PUSH_(
+    4251 GMOCK_MAYBE_5046_ /* class A needs to have dll-interface to be used by
+                              clients of class B */
+    /* Symbol involving type with internal linkage not defined */)
+
+namespace testing {
+
+// To implement a matcher Foo for type T, define:
+//   1. a class FooMatcherImpl that implements the
+//      MatcherInterface<T> interface, and
+//   2. a factory function that creates a Matcher<T> object from a
+//      FooMatcherImpl*.
+//
+// The two-level delegation design makes it possible to allow a user
+// to write "v" instead of "Eq(v)" where a Matcher is expected, which
+// is impossible if we pass matchers by pointers.  It also eases
+// ownership management as Matcher objects can now be copied like
+// plain values.
+
+// A match result listener that stores the explanation in a string.
+class StringMatchResultListener : public MatchResultListener {
+ public:
+  StringMatchResultListener() : MatchResultListener(&ss_) {}
+
+  // Returns the explanation accumulated so far.
+  std::string str() const { return ss_.str(); }
+
+  // Clears the explanation accumulated so far.
+  void Clear() { ss_.str(""); }
+
+ private:
+  ::std::stringstream ss_;
+
+  StringMatchResultListener(const StringMatchResultListener&) = delete;
+  StringMatchResultListener& operator=(const StringMatchResultListener&) =
+      delete;
+};
+
+// Anything inside the 'internal' namespace IS INTERNAL IMPLEMENTATION
+// and MUST NOT BE USED IN USER CODE!!!
+namespace internal {
+
+// The MatcherCastImpl class template is a helper for implementing
+// MatcherCast().  We need this helper in order to partially
+// specialize the implementation of MatcherCast() (C++ allows
+// class/struct templates to be partially specialized, but not
+// function templates.).
+
+// This general version is used when MatcherCast()'s argument is a
+// polymorphic matcher (i.e. something that can be converted to a
+// Matcher but is not one yet; for example, Eq(value)) or a value (for
+// example, "hello").
+template <typename T, typename M>
+class MatcherCastImpl {
+ public:
+  static Matcher<T> Cast(const M& polymorphic_matcher_or_value) {
+    // M can be a polymorphic matcher, in which case we want to use
+    // its conversion operator to create Matcher<T>.  Or it can be a value
+    // that should be passed to the Matcher<T>'s constructor.
+    //
+    // We can't call Matcher<T>(polymorphic_matcher_or_value) when M is a
+    // polymorphic matcher because it'll be ambiguous if T has an implicit
+    // constructor from M (this usually happens when T has an implicit
+    // constructor from any type).
+    //
+    // It won't work to unconditionally implicit_cast
+    // polymorphic_matcher_or_value to Matcher<T> because it won't trigger
+    // a user-defined conversion from M to T if one exists (assuming M is
+    // a value).
+    return CastImpl(polymorphic_matcher_or_value,
+                    std::is_convertible<M, Matcher<T>>{},
+                    std::is_convertible<M, T>{});
+  }
+
+ private:
+  template <bool Ignore>
+  static Matcher<T> CastImpl(const M& polymorphic_matcher_or_value,
+                             std::true_type /* convertible_to_matcher */,
+                             std::integral_constant<bool, Ignore>) {
+    // M is implicitly convertible to Matcher<T>, which means that either
+    // M is a polymorphic matcher or Matcher<T> has an implicit constructor
+    // from M.  In both cases using the implicit conversion will produce a
+    // matcher.
+    //
+    // Even if T has an implicit constructor from M, it won't be called because
+    // creating Matcher<T> would require a chain of two user-defined conversions
+    // (first to create T from M and then to create Matcher<T> from T).
+    return polymorphic_matcher_or_value;
+  }
+
+  // M can't be implicitly converted to Matcher<T>, so M isn't a polymorphic
+  // matcher. It's a value of a type implicitly convertible to T. Use direct
+  // initialization to create a matcher.
+  static Matcher<T> CastImpl(const M& value,
+                             std::false_type /* convertible_to_matcher */,
+                             std::true_type /* convertible_to_T */) {
+    return Matcher<T>(ImplicitCast_<T>(value));
+  }
+
+  // M can't be implicitly converted to either Matcher<T> or T. Attempt to use
+  // polymorphic matcher Eq(value) in this case.
+  //
+  // Note that we first attempt to perform an implicit cast on the value and
+  // only fall back to the polymorphic Eq() matcher afterwards because the
+  // latter calls bool operator==(const Lhs& lhs, const Rhs& rhs) in the end
+  // which might be undefined even when Rhs is implicitly convertible to Lhs
+  // (e.g. std::pair<const int, int> vs. std::pair<int, int>).
+  //
+  // We don't define this method inline as we need the declaration of Eq().
+  static Matcher<T> CastImpl(const M& value,
+                             std::false_type /* convertible_to_matcher */,
+                             std::false_type /* convertible_to_T */);
+};
+
+// This more specialized version is used when MatcherCast()'s argument
+// is already a Matcher.  This only compiles when type T can be
+// statically converted to type U.
+template <typename T, typename U>
+class MatcherCastImpl<T, Matcher<U>> {
+ public:
+  static Matcher<T> Cast(const Matcher<U>& source_matcher) {
+    return Matcher<T>(new Impl(source_matcher));
+  }
+
+ private:
+  class Impl : public MatcherInterface<T> {
+   public:
+    explicit Impl(const Matcher<U>& source_matcher)
+        : source_matcher_(source_matcher) {}
+
+    // We delegate the matching logic to the source matcher.
+    bool MatchAndExplain(T x, MatchResultListener* listener) const override {
+      using FromType = typename std::remove_cv<typename std::remove_pointer<
+          typename std::remove_reference<T>::type>::type>::type;
+      using ToType = typename std::remove_cv<typename std::remove_pointer<
+          typename std::remove_reference<U>::type>::type>::type;
+      // Do not allow implicitly converting base*/& to derived*/&.
+      static_assert(
+          // Do not trigger if only one of them is a pointer. That implies a
+          // regular conversion and not a down_cast.
+          (std::is_pointer<typename std::remove_reference<T>::type>::value !=
+           std::is_pointer<typename std::remove_reference<U>::type>::value) ||
+              std::is_same<FromType, ToType>::value ||
+              !std::is_base_of<FromType, ToType>::value,
+          "Can't implicitly convert from <base> to <derived>");
+
+      // Do the cast to `U` explicitly if necessary.
+      // Otherwise, let implicit conversions do the trick.
+      using CastType =
+          typename std::conditional<std::is_convertible<T&, const U&>::value,
+                                    T&, U>::type;
+
+      return source_matcher_.MatchAndExplain(static_cast<CastType>(x),
+                                             listener);
+    }
+
+    void DescribeTo(::std::ostream* os) const override {
+      source_matcher_.DescribeTo(os);
+    }
+
+    void DescribeNegationTo(::std::ostream* os) const override {
+      source_matcher_.DescribeNegationTo(os);
+    }
+
+   private:
+    const Matcher<U> source_matcher_;
+  };
+};
+
+// This even more specialized version is used for efficiently casting
+// a matcher to its own type.
+template <typename T>
+class MatcherCastImpl<T, Matcher<T>> {
+ public:
+  static Matcher<T> Cast(const Matcher<T>& matcher) { return matcher; }
+};
+
+// Template specialization for parameterless Matcher.
+template <typename Derived>
+class MatcherBaseImpl {
+ public:
+  MatcherBaseImpl() = default;
+
+  template <typename T>
+  operator ::testing::Matcher<T>() const {  // NOLINT(runtime/explicit)
+    return ::testing::Matcher<T>(new
+                                 typename Derived::template gmock_Impl<T>());
+  }
+};
+
+// Template specialization for Matcher with parameters.
+template <template <typename...> class Derived, typename... Ts>
+class MatcherBaseImpl<Derived<Ts...>> {
+ public:
+  // Mark the constructor explicit for single argument T to avoid implicit
+  // conversions.
+  template <typename E = std::enable_if<sizeof...(Ts) == 1>,
+            typename E::type* = nullptr>
+  explicit MatcherBaseImpl(Ts... params)
+      : params_(std::forward<Ts>(params)...) {}
+  template <typename E = std::enable_if<sizeof...(Ts) != 1>,
+            typename = typename E::type>
+  MatcherBaseImpl(Ts... params)  // NOLINT
+      : params_(std::forward<Ts>(params)...) {}
+
+  template <typename F>
+  operator ::testing::Matcher<F>() const {  // NOLINT(runtime/explicit)
+    return Apply<F>(MakeIndexSequence<sizeof...(Ts)>{});
+  }
+
+ private:
+  template <typename F, std::size_t... tuple_ids>
+  ::testing::Matcher<F> Apply(IndexSequence<tuple_ids...>) const {
+    return ::testing::Matcher<F>(
+        new typename Derived<Ts...>::template gmock_Impl<F>(
+            std::get<tuple_ids>(params_)...));
+  }
+
+  const std::tuple<Ts...> params_;
+};
+
+}  // namespace internal
+
+// In order to be safe and clear, casting between different matcher
+// types is done explicitly via MatcherCast<T>(m), which takes a
+// matcher m and returns a Matcher<T>.  It compiles only when T can be
+// statically converted to the argument type of m.
+template <typename T, typename M>
+inline Matcher<T> MatcherCast(const M& matcher) {
+  return internal::MatcherCastImpl<T, M>::Cast(matcher);
+}
+
+// This overload handles polymorphic matchers and values only since
+// monomorphic matchers are handled by the next one.
+template <typename T, typename M>
+inline Matcher<T> SafeMatcherCast(const M& polymorphic_matcher_or_value) {
+  return MatcherCast<T>(polymorphic_matcher_or_value);
+}
+
+// This overload handles monomorphic matchers.
+//
+// In general, if type T can be implicitly converted to type U, we can
+// safely convert a Matcher<U> to a Matcher<T> (i.e. Matcher is
+// contravariant): just keep a copy of the original Matcher<U>, convert the
+// argument from type T to U, and then pass it to the underlying Matcher<U>.
+// The only exception is when U is a reference and T is not, as the
+// underlying Matcher<U> may be interested in the argument's address, which
+// is not preserved in the conversion from T to U.
+template <typename T, typename U>
+inline Matcher<T> SafeMatcherCast(const Matcher<U>& matcher) {
+  // Enforce that T can be implicitly converted to U.
+  static_assert(std::is_convertible<const T&, const U&>::value,
+                "T must be implicitly convertible to U");
+  // Enforce that we are not converting a non-reference type T to a reference
+  // type U.
+  static_assert(std::is_reference<T>::value || !std::is_reference<U>::value,
+                "cannot convert non reference arg to reference");
+  // In case both T and U are arithmetic types, enforce that the
+  // conversion is not lossy.
+  typedef GTEST_REMOVE_REFERENCE_AND_CONST_(T) RawT;
+  typedef GTEST_REMOVE_REFERENCE_AND_CONST_(U) RawU;
+  constexpr bool kTIsOther = GMOCK_KIND_OF_(RawT) == internal::kOther;
+  constexpr bool kUIsOther = GMOCK_KIND_OF_(RawU) == internal::kOther;
+  static_assert(
+      kTIsOther || kUIsOther ||
+          (internal::LosslessArithmeticConvertible<RawT, RawU>::value),
+      "conversion of arithmetic types must be lossless");
+  return MatcherCast<T>(matcher);
+}
+
+// A<T>() returns a matcher that matches any value of type T.
+template <typename T>
+Matcher<T> A();
+
+// Anything inside the 'internal' namespace IS INTERNAL IMPLEMENTATION
+// and MUST NOT BE USED IN USER CODE!!!
+namespace internal {
+
+// If the explanation is not empty, prints it to the ostream.
+inline void PrintIfNotEmpty(const std::string& explanation,
+                            ::std::ostream* os) {
+  if (!explanation.empty() && os != nullptr) {
+    *os << ", " << explanation;
+  }
+}
+
+// Returns true if the given type name is easy to read by a human.
+// This is used to decide whether printing the type of a value might
+// be helpful.
+inline bool IsReadableTypeName(const std::string& type_name) {
+  // We consider a type name readable if it's short or doesn't contain
+  // a template or function type.
+  return (type_name.length() <= 20 ||
+          type_name.find_first_of("<(") == std::string::npos);
+}
+
+// Matches the value against the given matcher, prints the value and explains
+// the match result to the listener. Returns the match result.
+// 'listener' must not be NULL.
+// Value cannot be passed by const reference, because some matchers take a
+// non-const argument.
+template <typename Value, typename T>
+bool MatchPrintAndExplain(Value& value, const Matcher<T>& matcher,
+                          MatchResultListener* listener) {
+  if (!listener->IsInterested()) {
+    // If the listener is not interested, we do not need to construct the
+    // inner explanation.
+    return matcher.Matches(value);
+  }
+
+  StringMatchResultListener inner_listener;
+  const bool match = matcher.MatchAndExplain(value, &inner_listener);
+
+  UniversalPrint(value, listener->stream());
+#if GTEST_HAS_RTTI
+  const std::string& type_name = GetTypeName<Value>();
+  if (IsReadableTypeName(type_name))
+    *listener->stream() << " (of type " << type_name << ")";
+#endif
+  PrintIfNotEmpty(inner_listener.str(), listener->stream());
+
+  return match;
+}
+
+// An internal helper class for doing compile-time loop on a tuple's
+// fields.
+template <size_t N>
+class TuplePrefix {
+ public:
+  // TuplePrefix<N>::Matches(matcher_tuple, value_tuple) returns true
+  // if and only if the first N fields of matcher_tuple matches
+  // the first N fields of value_tuple, respectively.
+  template <typename MatcherTuple, typename ValueTuple>
+  static bool Matches(const MatcherTuple& matcher_tuple,
+                      const ValueTuple& value_tuple) {
+    return TuplePrefix<N - 1>::Matches(matcher_tuple, value_tuple) &&
+           std::get<N - 1>(matcher_tuple).Matches(std::get<N - 1>(value_tuple));
+  }
+
+  // TuplePrefix<N>::ExplainMatchFailuresTo(matchers, values, os)
+  // describes failures in matching the first N fields of matchers
+  // against the first N fields of values.  If there is no failure,
+  // nothing will be streamed to os.
+  template <typename MatcherTuple, typename ValueTuple>
+  static void ExplainMatchFailuresTo(const MatcherTuple& matchers,
+                                     const ValueTuple& values,
+                                     ::std::ostream* os) {
+    // First, describes failures in the first N - 1 fields.
+    TuplePrefix<N - 1>::ExplainMatchFailuresTo(matchers, values, os);
+
+    // Then describes the failure (if any) in the (N - 1)-th (0-based)
+    // field.
+    typename std::tuple_element<N - 1, MatcherTuple>::type matcher =
+        std::get<N - 1>(matchers);
+    typedef typename std::tuple_element<N - 1, ValueTuple>::type Value;
+    const Value& value = std::get<N - 1>(values);
+    StringMatchResultListener listener;
+    if (!matcher.MatchAndExplain(value, &listener)) {
+      *os << "  Expected arg #" << N - 1 << ": ";
+      std::get<N - 1>(matchers).DescribeTo(os);
+      *os << "\n           Actual: ";
+      // We remove the reference in type Value to prevent the
+      // universal printer from printing the address of value, which
+      // isn't interesting to the user most of the time.  The
+      // matcher's MatchAndExplain() method handles the case when
+      // the address is interesting.
+      internal::UniversalPrint(value, os);
+      PrintIfNotEmpty(listener.str(), os);
+      *os << "\n";
+    }
+  }
+};
+
+// The base case.
+template <>
+class TuplePrefix<0> {
+ public:
+  template <typename MatcherTuple, typename ValueTuple>
+  static bool Matches(const MatcherTuple& /* matcher_tuple */,
+                      const ValueTuple& /* value_tuple */) {
+    return true;
+  }
+
+  template <typename MatcherTuple, typename ValueTuple>
+  static void ExplainMatchFailuresTo(const MatcherTuple& /* matchers */,
+                                     const ValueTuple& /* values */,
+                                     ::std::ostream* /* os */) {}
+};
+
+// TupleMatches(matcher_tuple, value_tuple) returns true if and only if
+// all matchers in matcher_tuple match the corresponding fields in
+// value_tuple.  It is a compiler error if matcher_tuple and
+// value_tuple have different number of fields or incompatible field
+// types.
+template <typename MatcherTuple, typename ValueTuple>
+bool TupleMatches(const MatcherTuple& matcher_tuple,
+                  const ValueTuple& value_tuple) {
+  // Makes sure that matcher_tuple and value_tuple have the same
+  // number of fields.
+  static_assert(std::tuple_size<MatcherTuple>::value ==
+                    std::tuple_size<ValueTuple>::value,
+                "matcher and value have different numbers of fields");
+  return TuplePrefix<std::tuple_size<ValueTuple>::value>::Matches(matcher_tuple,
+                                                                  value_tuple);
+}
+
+// Describes failures in matching matchers against values.  If there
+// is no failure, nothing will be streamed to os.
+template <typename MatcherTuple, typename ValueTuple>
+void ExplainMatchFailureTupleTo(const MatcherTuple& matchers,
+                                const ValueTuple& values, ::std::ostream* os) {
+  TuplePrefix<std::tuple_size<MatcherTuple>::value>::ExplainMatchFailuresTo(
+      matchers, values, os);
+}
+
+// TransformTupleValues and its helper.
+//
+// TransformTupleValuesHelper hides the internal machinery that
+// TransformTupleValues uses to implement a tuple traversal.
+template <typename Tuple, typename Func, typename OutIter>
+class TransformTupleValuesHelper {
+ private:
+  typedef ::std::tuple_size<Tuple> TupleSize;
+
+ public:
+  // For each member of tuple 't', taken in order, evaluates '*out++ = f(t)'.
+  // Returns the final value of 'out' in case the caller needs it.
+  static OutIter Run(Func f, const Tuple& t, OutIter out) {
+    return IterateOverTuple<Tuple, TupleSize::value>()(f, t, out);
+  }
+
+ private:
+  template <typename Tup, size_t kRemainingSize>
+  struct IterateOverTuple {
+    OutIter operator()(Func f, const Tup& t, OutIter out) const {
+      *out++ = f(::std::get<TupleSize::value - kRemainingSize>(t));
+      return IterateOverTuple<Tup, kRemainingSize - 1>()(f, t, out);
+    }
+  };
+  template <typename Tup>
+  struct IterateOverTuple<Tup, 0> {
+    OutIter operator()(Func /* f */, const Tup& /* t */, OutIter out) const {
+      return out;
+    }
+  };
+};
+
+// Successively invokes 'f(element)' on each element of the tuple 't',
+// appending each result to the 'out' iterator. Returns the final value
+// of 'out'.
+template <typename Tuple, typename Func, typename OutIter>
+OutIter TransformTupleValues(Func f, const Tuple& t, OutIter out) {
+  return TransformTupleValuesHelper<Tuple, Func, OutIter>::Run(f, t, out);
+}
+
+// Implements _, a matcher that matches any value of any
+// type.  This is a polymorphic matcher, so we need a template type
+// conversion operator to make it appearing as a Matcher<T> for any
+// type T.
+class AnythingMatcher {
+ public:
+  using is_gtest_matcher = void;
+
+  template <typename T>
+  bool MatchAndExplain(const T& /* x */, std::ostream* /* listener */) const {
+    return true;
+  }
+  void DescribeTo(std::ostream* os) const { *os << "is anything"; }
+  void DescribeNegationTo(::std::ostream* os) const {
+    // This is mostly for completeness' sake, as it's not very useful
+    // to write Not(A<bool>()).  However we cannot completely rule out
+    // such a possibility, and it doesn't hurt to be prepared.
+    *os << "never matches";
+  }
+};
+
+// Implements the polymorphic IsNull() matcher, which matches any raw or smart
+// pointer that is NULL.
+class IsNullMatcher {
+ public:
+  template <typename Pointer>
+  bool MatchAndExplain(const Pointer& p,
+                       MatchResultListener* /* listener */) const {
+    return p == nullptr;
+  }
+
+  void DescribeTo(::std::ostream* os) const { *os << "is NULL"; }
+  void DescribeNegationTo(::std::ostream* os) const { *os << "isn't NULL"; }
+};
+
+// Implements the polymorphic NotNull() matcher, which matches any raw or smart
+// pointer that is not NULL.
+class NotNullMatcher {
+ public:
+  template <typename Pointer>
+  bool MatchAndExplain(const Pointer& p,
+                       MatchResultListener* /* listener */) const {
+    return p != nullptr;
+  }
+
+  void DescribeTo(::std::ostream* os) const { *os << "isn't NULL"; }
+  void DescribeNegationTo(::std::ostream* os) const { *os << "is NULL"; }
+};
+
+// Ref(variable) matches any argument that is a reference to
+// 'variable'.  This matcher is polymorphic as it can match any
+// super type of the type of 'variable'.
+//
+// The RefMatcher template class implements Ref(variable).  It can
+// only be instantiated with a reference type.  This prevents a user
+// from mistakenly using Ref(x) to match a non-reference function
+// argument.  For example, the following will righteously cause a
+// compiler error:
+//
+//   int n;
+//   Matcher<int> m1 = Ref(n);   // This won't compile.
+//   Matcher<int&> m2 = Ref(n);  // This will compile.
+template <typename T>
+class RefMatcher;
+
+template <typename T>
+class RefMatcher<T&> {
+  // Google Mock is a generic framework and thus needs to support
+  // mocking any function types, including those that take non-const
+  // reference arguments.  Therefore the template parameter T (and
+  // Super below) can be instantiated to either a const type or a
+  // non-const type.
+ public:
+  // RefMatcher() takes a T& instead of const T&, as we want the
+  // compiler to catch using Ref(const_value) as a matcher for a
+  // non-const reference.
+  explicit RefMatcher(T& x) : object_(x) {}  // NOLINT
+
+  template <typename Super>
+  operator Matcher<Super&>() const {
+    // By passing object_ (type T&) to Impl(), which expects a Super&,
+    // we make sure that Super is a super type of T.  In particular,
+    // this catches using Ref(const_value) as a matcher for a
+    // non-const reference, as you cannot implicitly convert a const
+    // reference to a non-const reference.
+    return MakeMatcher(new Impl<Super>(object_));
+  }
+
+ private:
+  template <typename Super>
+  class Impl : public MatcherInterface<Super&> {
+   public:
+    explicit Impl(Super& x) : object_(x) {}  // NOLINT
+
+    // MatchAndExplain() takes a Super& (as opposed to const Super&)
+    // in order to match the interface MatcherInterface<Super&>.
+    bool MatchAndExplain(Super& x,
+                         MatchResultListener* listener) const override {
+      *listener << "which is located @" << static_cast<const void*>(&x);
+      return &x == &object_;
+    }
+
+    void DescribeTo(::std::ostream* os) const override {
+      *os << "references the variable ";
+      UniversalPrinter<Super&>::Print(object_, os);
+    }
+
+    void DescribeNegationTo(::std::ostream* os) const override {
+      *os << "does not reference the variable ";
+      UniversalPrinter<Super&>::Print(object_, os);
+    }
+
+   private:
+    const Super& object_;
+  };
+
+  T& object_;
+};
+
+// Polymorphic helper functions for narrow and wide string matchers.
+inline bool CaseInsensitiveCStringEquals(const char* lhs, const char* rhs) {
+  return String::CaseInsensitiveCStringEquals(lhs, rhs);
+}
+
+inline bool CaseInsensitiveCStringEquals(const wchar_t* lhs,
+                                         const wchar_t* rhs) {
+  return String::CaseInsensitiveWideCStringEquals(lhs, rhs);
+}
+
+// String comparison for narrow or wide strings that can have embedded NUL
+// characters.
+template <typename StringType>
+bool CaseInsensitiveStringEquals(const StringType& s1, const StringType& s2) {
+  // Are the heads equal?
+  if (!CaseInsensitiveCStringEquals(s1.c_str(), s2.c_str())) {
+    return false;
+  }
+
+  // Skip the equal heads.
+  const typename StringType::value_type nul = 0;
+  const size_t i1 = s1.find(nul), i2 = s2.find(nul);
+
+  // Are we at the end of either s1 or s2?
+  if (i1 == StringType::npos || i2 == StringType::npos) {
+    return i1 == i2;
+  }
+
+  // Are the tails equal?
+  return CaseInsensitiveStringEquals(s1.substr(i1 + 1), s2.substr(i2 + 1));
+}
+
+// String matchers.
+
+// Implements equality-based string matchers like StrEq, StrCaseNe, and etc.
+template <typename StringType>
+class StrEqualityMatcher {
+ public:
+  StrEqualityMatcher(StringType str, bool expect_eq, bool case_sensitive)
+      : string_(std::move(str)),
+        expect_eq_(expect_eq),
+        case_sensitive_(case_sensitive) {}
+
+#if GTEST_INTERNAL_HAS_STRING_VIEW
+  bool MatchAndExplain(const internal::StringView& s,
+                       MatchResultListener* listener) const {
+    // This should fail to compile if StringView is used with wide
+    // strings.
+    const StringType& str = std::string(s);
+    return MatchAndExplain(str, listener);
+  }
+#endif  // GTEST_INTERNAL_HAS_STRING_VIEW
+
+  // Accepts pointer types, particularly:
+  //   const char*
+  //   char*
+  //   const wchar_t*
+  //   wchar_t*
+  template <typename CharType>
+  bool MatchAndExplain(CharType* s, MatchResultListener* listener) const {
+    if (s == nullptr) {
+      return !expect_eq_;
+    }
+    return MatchAndExplain(StringType(s), listener);
+  }
+
+  // Matches anything that can convert to StringType.
+  //
+  // This is a template, not just a plain function with const StringType&,
+  // because StringView has some interfering non-explicit constructors.
+  template <typename MatcheeStringType>
+  bool MatchAndExplain(const MatcheeStringType& s,
+                       MatchResultListener* /* listener */) const {
+    const StringType s2(s);
+    const bool eq = case_sensitive_ ? s2 == string_
+                                    : CaseInsensitiveStringEquals(s2, string_);
+    return expect_eq_ == eq;
+  }
+
+  void DescribeTo(::std::ostream* os) const {
+    DescribeToHelper(expect_eq_, os);
+  }
+
+  void DescribeNegationTo(::std::ostream* os) const {
+    DescribeToHelper(!expect_eq_, os);
+  }
+
+ private:
+  void DescribeToHelper(bool expect_eq, ::std::ostream* os) const {
+    *os << (expect_eq ? "is " : "isn't ");
+    *os << "equal to ";
+    if (!case_sensitive_) {
+      *os << "(ignoring case) ";
+    }
+    UniversalPrint(string_, os);
+  }
+
+  const StringType string_;
+  const bool expect_eq_;
+  const bool case_sensitive_;
+};
+
+// Implements the polymorphic HasSubstr(substring) matcher, which
+// can be used as a Matcher<T> as long as T can be converted to a
+// string.
+template <typename StringType>
+class HasSubstrMatcher {
+ public:
+  explicit HasSubstrMatcher(const StringType& substring)
+      : substring_(substring) {}
+
+#if GTEST_INTERNAL_HAS_STRING_VIEW
+  bool MatchAndExplain(const internal::StringView& s,
+                       MatchResultListener* listener) const {
+    // This should fail to compile if StringView is used with wide
+    // strings.
+    const StringType& str = std::string(s);
+    return MatchAndExplain(str, listener);
+  }
+#endif  // GTEST_INTERNAL_HAS_STRING_VIEW
+
+  // Accepts pointer types, particularly:
+  //   const char*
+  //   char*
+  //   const wchar_t*
+  //   wchar_t*
+  template <typename CharType>
+  bool MatchAndExplain(CharType* s, MatchResultListener* listener) const {
+    return s != nullptr && MatchAndExplain(StringType(s), listener);
+  }
+
+  // Matches anything that can convert to StringType.
+  //
+  // This is a template, not just a plain function with const StringType&,
+  // because StringView has some interfering non-explicit constructors.
+  template <typename MatcheeStringType>
+  bool MatchAndExplain(const MatcheeStringType& s,
+                       MatchResultListener* /* listener */) const {
+    return StringType(s).find(substring_) != StringType::npos;
+  }
+
+  // Describes what this matcher matches.
+  void DescribeTo(::std::ostream* os) const {
+    *os << "has substring ";
+    UniversalPrint(substring_, os);
+  }
+
+  void DescribeNegationTo(::std::ostream* os) const {
+    *os << "has no substring ";
+    UniversalPrint(substring_, os);
+  }
+
+ private:
+  const StringType substring_;
+};
+
+// Implements the polymorphic StartsWith(substring) matcher, which
+// can be used as a Matcher<T> as long as T can be converted to a
+// string.
+template <typename StringType>
+class StartsWithMatcher {
+ public:
+  explicit StartsWithMatcher(const StringType& prefix) : prefix_(prefix) {}
+
+#if GTEST_INTERNAL_HAS_STRING_VIEW
+  bool MatchAndExplain(const internal::StringView& s,
+                       MatchResultListener* listener) const {
+    // This should fail to compile if StringView is used with wide
+    // strings.
+    const StringType& str = std::string(s);
+    return MatchAndExplain(str, listener);
+  }
+#endif  // GTEST_INTERNAL_HAS_STRING_VIEW
+
+  // Accepts pointer types, particularly:
+  //   const char*
+  //   char*
+  //   const wchar_t*
+  //   wchar_t*
+  template <typename CharType>
+  bool MatchAndExplain(CharType* s, MatchResultListener* listener) const {
+    return s != nullptr && MatchAndExplain(StringType(s), listener);
+  }
+
+  // Matches anything that can convert to StringType.
+  //
+  // This is a template, not just a plain function with const StringType&,
+  // because StringView has some interfering non-explicit constructors.
+  template <typename MatcheeStringType>
+  bool MatchAndExplain(const MatcheeStringType& s,
+                       MatchResultListener* /* listener */) const {
+    const StringType& s2(s);
+    return s2.length() >= prefix_.length() &&
+           s2.substr(0, prefix_.length()) == prefix_;
+  }
+
+  void DescribeTo(::std::ostream* os) const {
+    *os << "starts with ";
+    UniversalPrint(prefix_, os);
+  }
+
+  void DescribeNegationTo(::std::ostream* os) const {
+    *os << "doesn't start with ";
+    UniversalPrint(prefix_, os);
+  }
+
+ private:
+  const StringType prefix_;
+};
+
+// Implements the polymorphic EndsWith(substring) matcher, which
+// can be used as a Matcher<T> as long as T can be converted to a
+// string.
+template <typename StringType>
+class EndsWithMatcher {
+ public:
+  explicit EndsWithMatcher(const StringType& suffix) : suffix_(suffix) {}
+
+#if GTEST_INTERNAL_HAS_STRING_VIEW
+  bool MatchAndExplain(const internal::StringView& s,
+                       MatchResultListener* listener) const {
+    // This should fail to compile if StringView is used with wide
+    // strings.
+    const StringType& str = std::string(s);
+    return MatchAndExplain(str, listener);
+  }
+#endif  // GTEST_INTERNAL_HAS_STRING_VIEW
+
+  // Accepts pointer types, particularly:
+  //   const char*
+  //   char*
+  //   const wchar_t*
+  //   wchar_t*
+  template <typename CharType>
+  bool MatchAndExplain(CharType* s, MatchResultListener* listener) const {
+    return s != nullptr && MatchAndExplain(StringType(s), listener);
+  }
+
+  // Matches anything that can convert to StringType.
+  //
+  // This is a template, not just a plain function with const StringType&,
+  // because StringView has some interfering non-explicit constructors.
+  template <typename MatcheeStringType>
+  bool MatchAndExplain(const MatcheeStringType& s,
+                       MatchResultListener* /* listener */) const {
+    const StringType& s2(s);
+    return s2.length() >= suffix_.length() &&
+           s2.substr(s2.length() - suffix_.length()) == suffix_;
+  }
+
+  void DescribeTo(::std::ostream* os) const {
+    *os << "ends with ";
+    UniversalPrint(suffix_, os);
+  }
+
+  void DescribeNegationTo(::std::ostream* os) const {
+    *os << "doesn't end with ";
+    UniversalPrint(suffix_, os);
+  }
+
+ private:
+  const StringType suffix_;
+};
+
+// Implements the polymorphic WhenBase64Unescaped(matcher) matcher, which can be
+// used as a Matcher<T> as long as T can be converted to a string.
+class WhenBase64UnescapedMatcher {
+ public:
+  using is_gtest_matcher = void;
+
+  explicit WhenBase64UnescapedMatcher(
+      const Matcher<const std::string&>& internal_matcher)
+      : internal_matcher_(internal_matcher) {}
+
+  // Matches anything that can convert to std::string.
+  template <typename MatcheeStringType>
+  bool MatchAndExplain(const MatcheeStringType& s,
+                       MatchResultListener* listener) const {
+    const std::string s2(s);  // NOLINT (needed for working with string_view).
+    std::string unescaped;
+    if (!internal::Base64Unescape(s2, &unescaped)) {
+      if (listener != nullptr) {
+        *listener << "is not a valid base64 escaped string";
+      }
+      return false;
+    }
+    return MatchPrintAndExplain(unescaped, internal_matcher_, listener);
+  }
+
+  void DescribeTo(::std::ostream* os) const {
+    *os << "matches after Base64Unescape ";
+    internal_matcher_.DescribeTo(os);
+  }
+
+  void DescribeNegationTo(::std::ostream* os) const {
+    *os << "does not match after Base64Unescape ";
+    internal_matcher_.DescribeTo(os);
+  }
+
+ private:
+  const Matcher<const std::string&> internal_matcher_;
+};
+
+// Implements a matcher that compares the two fields of a 2-tuple
+// using one of the ==, <=, <, etc, operators.  The two fields being
+// compared don't have to have the same type.
+//
+// The matcher defined here is polymorphic (for example, Eq() can be
+// used to match a std::tuple<int, short>, a std::tuple<const long&, double>,
+// etc).  Therefore we use a template type conversion operator in the
+// implementation.
+template <typename D, typename Op>
+class PairMatchBase {
+ public:
+  template <typename T1, typename T2>
+  operator Matcher<::std::tuple<T1, T2>>() const {
+    return Matcher<::std::tuple<T1, T2>>(new Impl<const ::std::tuple<T1, T2>&>);
+  }
+  template <typename T1, typename T2>
+  operator Matcher<const ::std::tuple<T1, T2>&>() const {
+    return MakeMatcher(new Impl<const ::std::tuple<T1, T2>&>);
+  }
+
+ private:
+  static ::std::ostream& GetDesc(::std::ostream& os) {  // NOLINT
+    return os << D::Desc();
+  }
+
+  template <typename Tuple>
+  class Impl : public MatcherInterface<Tuple> {
+   public:
+    bool MatchAndExplain(Tuple args,
+                         MatchResultListener* /* listener */) const override {
+      return Op()(::std::get<0>(args), ::std::get<1>(args));
+    }
+    void DescribeTo(::std::ostream* os) const override {
+      *os << "are " << GetDesc;
+    }
+    void DescribeNegationTo(::std::ostream* os) const override {
+      *os << "aren't " << GetDesc;
+    }
+  };
+};
+
+class Eq2Matcher : public PairMatchBase<Eq2Matcher, std::equal_to<>> {
+ public:
+  static const char* Desc() { return "an equal pair"; }
+};
+class Ne2Matcher : public PairMatchBase<Ne2Matcher, std::not_equal_to<>> {
+ public:
+  static const char* Desc() { return "an unequal pair"; }
+};
+class Lt2Matcher : public PairMatchBase<Lt2Matcher, std::less<>> {
+ public:
+  static const char* Desc() { return "a pair where the first < the second"; }
+};
+class Gt2Matcher : public PairMatchBase<Gt2Matcher, std::greater<>> {
+ public:
+  static const char* Desc() { return "a pair where the first > the second"; }
+};
+class Le2Matcher : public PairMatchBase<Le2Matcher, std::less_equal<>> {
+ public:
+  static const char* Desc() { return "a pair where the first <= the second"; }
+};
+class Ge2Matcher : public PairMatchBase<Ge2Matcher, std::greater_equal<>> {
+ public:
+  static const char* Desc() { return "a pair where the first >= the second"; }
+};
+
+// Implements the Not(...) matcher for a particular argument type T.
+// We do not nest it inside the NotMatcher class template, as that
+// will prevent different instantiations of NotMatcher from sharing
+// the same NotMatcherImpl<T> class.
+template <typename T>
+class NotMatcherImpl : public MatcherInterface<const T&> {
+ public:
+  explicit NotMatcherImpl(const Matcher<T>& matcher) : matcher_(matcher) {}
+
+  bool MatchAndExplain(const T& x,
+                       MatchResultListener* listener) const override {
+    return !matcher_.MatchAndExplain(x, listener);
+  }
+
+  void DescribeTo(::std::ostream* os) const override {
+    matcher_.DescribeNegationTo(os);
+  }
+
+  void DescribeNegationTo(::std::ostream* os) const override {
+    matcher_.DescribeTo(os);
+  }
+
+ private:
+  const Matcher<T> matcher_;
+};
+
+// Implements the Not(m) matcher, which matches a value that doesn't
+// match matcher m.
+template <typename InnerMatcher>
+class NotMatcher {
+ public:
+  explicit NotMatcher(InnerMatcher matcher) : matcher_(matcher) {}
+
+  // This template type conversion operator allows Not(m) to be used
+  // to match any type m can match.
+  template <typename T>
+  operator Matcher<T>() const {
+    return Matcher<T>(new NotMatcherImpl<T>(SafeMatcherCast<T>(matcher_)));
+  }
+
+ private:
+  InnerMatcher matcher_;
+};
+
+// Implements the AllOf(m1, m2) matcher for a particular argument type
+// T. We do not nest it inside the BothOfMatcher class template, as
+// that will prevent different instantiations of BothOfMatcher from
+// sharing the same BothOfMatcherImpl<T> class.
+template <typename T>
+class AllOfMatcherImpl : public MatcherInterface<const T&> {
+ public:
+  explicit AllOfMatcherImpl(std::vector<Matcher<T>> matchers)
+      : matchers_(std::move(matchers)) {}
+
+  void DescribeTo(::std::ostream* os) const override {
+    *os << "(";
+    for (size_t i = 0; i < matchers_.size(); ++i) {
+      if (i != 0) *os << ") and (";
+      matchers_[i].DescribeTo(os);
+    }
+    *os << ")";
+  }
+
+  void DescribeNegationTo(::std::ostream* os) const override {
+    *os << "(";
+    for (size_t i = 0; i < matchers_.size(); ++i) {
+      if (i != 0) *os << ") or (";
+      matchers_[i].DescribeNegationTo(os);
+    }
+    *os << ")";
+  }
+
+  bool MatchAndExplain(const T& x,
+                       MatchResultListener* listener) const override {
+    // If either matcher1_ or matcher2_ doesn't match x, we only need
+    // to explain why one of them fails.
+    std::string all_match_result;
+
+    for (size_t i = 0; i < matchers_.size(); ++i) {
+      StringMatchResultListener slistener;
+      if (matchers_[i].MatchAndExplain(x, &slistener)) {
+        if (all_match_result.empty()) {
+          all_match_result = slistener.str();
+        } else {
+          std::string result = slistener.str();
+          if (!result.empty()) {
+            all_match_result += ", and ";
+            all_match_result += result;
+          }
+        }
+      } else {
+        *listener << slistener.str();
+        return false;
+      }
+    }
+
+    // Otherwise we need to explain why *both* of them match.
+    *listener << all_match_result;
+    return true;
+  }
+
+ private:
+  const std::vector<Matcher<T>> matchers_;
+};
+
+// VariadicMatcher is used for the variadic implementation of
+// AllOf(m_1, m_2, ...) and AnyOf(m_1, m_2, ...).
+// CombiningMatcher<T> is used to recursively combine the provided matchers
+// (of type Args...).
+template <template <typename T> class CombiningMatcher, typename... Args>
+class VariadicMatcher {
+ public:
+  VariadicMatcher(const Args&... matchers)  // NOLINT
+      : matchers_(matchers...) {
+    static_assert(sizeof...(Args) > 0, "Must have at least one matcher.");
+  }
+
+  VariadicMatcher(const VariadicMatcher&) = default;
+  VariadicMatcher& operator=(const VariadicMatcher&) = delete;
+
+  // This template type conversion operator allows an
+  // VariadicMatcher<Matcher1, Matcher2...> object to match any type that
+  // all of the provided matchers (Matcher1, Matcher2, ...) can match.
+  template <typename T>
+  operator Matcher<T>() const {
+    std::vector<Matcher<T>> values;
+    CreateVariadicMatcher<T>(&values, std::integral_constant<size_t, 0>());
+    return Matcher<T>(new CombiningMatcher<T>(std::move(values)));
+  }
+
+ private:
+  template <typename T, size_t I>
+  void CreateVariadicMatcher(std::vector<Matcher<T>>* values,
+                             std::integral_constant<size_t, I>) const {
+    values->push_back(SafeMatcherCast<T>(std::get<I>(matchers_)));
+    CreateVariadicMatcher<T>(values, std::integral_constant<size_t, I + 1>());
+  }
+
+  template <typename T>
+  void CreateVariadicMatcher(
+      std::vector<Matcher<T>>*,
+      std::integral_constant<size_t, sizeof...(Args)>) const {}
+
+  std::tuple<Args...> matchers_;
+};
+
+template <typename... Args>
+using AllOfMatcher = VariadicMatcher<AllOfMatcherImpl, Args...>;
+
+// Implements the AnyOf(m1, m2) matcher for a particular argument type
+// T.  We do not nest it inside the AnyOfMatcher class template, as
+// that will prevent different instantiations of AnyOfMatcher from
+// sharing the same EitherOfMatcherImpl<T> class.
+template <typename T>
+class AnyOfMatcherImpl : public MatcherInterface<const T&> {
+ public:
+  explicit AnyOfMatcherImpl(std::vector<Matcher<T>> matchers)
+      : matchers_(std::move(matchers)) {}
+
+  void DescribeTo(::std::ostream* os) const override {
+    *os << "(";
+    for (size_t i = 0; i < matchers_.size(); ++i) {
+      if (i != 0) *os << ") or (";
+      matchers_[i].DescribeTo(os);
+    }
+    *os << ")";
+  }
+
+  void DescribeNegationTo(::std::ostream* os) const override {
+    *os << "(";
+    for (size_t i = 0; i < matchers_.size(); ++i) {
+      if (i != 0) *os << ") and (";
+      matchers_[i].DescribeNegationTo(os);
+    }
+    *os << ")";
+  }
+
+  bool MatchAndExplain(const T& x,
+                       MatchResultListener* listener) const override {
+    std::string no_match_result;
+
+    // If either matcher1_ or matcher2_ matches x, we just need to
+    // explain why *one* of them matches.
+    for (size_t i = 0; i < matchers_.size(); ++i) {
+      StringMatchResultListener slistener;
+      if (matchers_[i].MatchAndExplain(x, &slistener)) {
+        *listener << slistener.str();
+        return true;
+      } else {
+        if (no_match_result.empty()) {
+          no_match_result = slistener.str();
+        } else {
+          std::string result = slistener.str();
+          if (!result.empty()) {
+            no_match_result += ", and ";
+            no_match_result += result;
+          }
+        }
+      }
+    }
+
+    // Otherwise we need to explain why *both* of them fail.
+    *listener << no_match_result;
+    return false;
+  }
+
+ private:
+  const std::vector<Matcher<T>> matchers_;
+};
+
+// AnyOfMatcher is used for the variadic implementation of AnyOf(m_1, m_2, ...).
+template <typename... Args>
+using AnyOfMatcher = VariadicMatcher<AnyOfMatcherImpl, Args...>;
+
+// ConditionalMatcher is the implementation of Conditional(cond, m1, m2)
+template <typename MatcherTrue, typename MatcherFalse>
+class ConditionalMatcher {
+ public:
+  ConditionalMatcher(bool condition, MatcherTrue matcher_true,
+                     MatcherFalse matcher_false)
+      : condition_(condition),
+        matcher_true_(std::move(matcher_true)),
+        matcher_false_(std::move(matcher_false)) {}
+
+  template <typename T>
+  operator Matcher<T>() const {  // NOLINT(runtime/explicit)
+    return condition_ ? SafeMatcherCast<T>(matcher_true_)
+                      : SafeMatcherCast<T>(matcher_false_);
+  }
+
+ private:
+  bool condition_;
+  MatcherTrue matcher_true_;
+  MatcherFalse matcher_false_;
+};
+
+// Wrapper for implementation of Any/AllOfArray().
+template <template <class> class MatcherImpl, typename T>
+class SomeOfArrayMatcher {
+ public:
+  // Constructs the matcher from a sequence of element values or
+  // element matchers.
+  template <typename Iter>
+  SomeOfArrayMatcher(Iter first, Iter last) : matchers_(first, last) {}
+
+  template <typename U>
+  operator Matcher<U>() const {  // NOLINT
+    using RawU = typename std::decay<U>::type;
+    std::vector<Matcher<RawU>> matchers;
+    matchers.reserve(matchers_.size());
+    for (const auto& matcher : matchers_) {
+      matchers.push_back(MatcherCast<RawU>(matcher));
+    }
+    return Matcher<U>(new MatcherImpl<RawU>(std::move(matchers)));
+  }
+
+ private:
+  const ::std::vector<T> matchers_;
+};
+
+template <typename T>
+using AllOfArrayMatcher = SomeOfArrayMatcher<AllOfMatcherImpl, T>;
+
+template <typename T>
+using AnyOfArrayMatcher = SomeOfArrayMatcher<AnyOfMatcherImpl, T>;
+
+// Used for implementing Truly(pred), which turns a predicate into a
+// matcher.
+template <typename Predicate>
+class TrulyMatcher {
+ public:
+  explicit TrulyMatcher(Predicate pred) : predicate_(pred) {}
+
+  // This method template allows Truly(pred) to be used as a matcher
+  // for type T where T is the argument type of predicate 'pred'.  The
+  // argument is passed by reference as the predicate may be
+  // interested in the address of the argument.
+  template <typename T>
+  bool MatchAndExplain(T& x,  // NOLINT
+                       MatchResultListener* listener) const {
+    // Without the if-statement, MSVC sometimes warns about converting
+    // a value to bool (warning 4800).
+    //
+    // We cannot write 'return !!predicate_(x);' as that doesn't work
+    // when predicate_(x) returns a class convertible to bool but
+    // having no operator!().
+    if (predicate_(x)) return true;
+    *listener << "didn't satisfy the given predicate";
+    return false;
+  }
+
+  void DescribeTo(::std::ostream* os) const {
+    *os << "satisfies the given predicate";
+  }
+
+  void DescribeNegationTo(::std::ostream* os) const {
+    *os << "doesn't satisfy the given predicate";
+  }
+
+ private:
+  Predicate predicate_;
+};
+
+// Used for implementing Matches(matcher), which turns a matcher into
+// a predicate.
+template <typename M>
+class MatcherAsPredicate {
+ public:
+  explicit MatcherAsPredicate(M matcher) : matcher_(matcher) {}
+
+  // This template operator() allows Matches(m) to be used as a
+  // predicate on type T where m is a matcher on type T.
+  //
+  // The argument x is passed by reference instead of by value, as
+  // some matcher may be interested in its address (e.g. as in
+  // Matches(Ref(n))(x)).
+  template <typename T>
+  bool operator()(const T& x) const {
+    // We let matcher_ commit to a particular type here instead of
+    // when the MatcherAsPredicate object was constructed.  This
+    // allows us to write Matches(m) where m is a polymorphic matcher
+    // (e.g. Eq(5)).
+    //
+    // If we write Matcher<T>(matcher_).Matches(x) here, it won't
+    // compile when matcher_ has type Matcher<const T&>; if we write
+    // Matcher<const T&>(matcher_).Matches(x) here, it won't compile
+    // when matcher_ has type Matcher<T>; if we just write
+    // matcher_.Matches(x), it won't compile when matcher_ is
+    // polymorphic, e.g. Eq(5).
+    //
+    // MatcherCast<const T&>() is necessary for making the code work
+    // in all of the above situations.
+    return MatcherCast<const T&>(matcher_).Matches(x);
+  }
+
+ private:
+  M matcher_;
+};
+
+// For implementing ASSERT_THAT() and EXPECT_THAT().  The template
+// argument M must be a type that can be converted to a matcher.
+template <typename M>
+class PredicateFormatterFromMatcher {
+ public:
+  explicit PredicateFormatterFromMatcher(M m) : matcher_(std::move(m)) {}
+
+  // This template () operator allows a PredicateFormatterFromMatcher
+  // object to act as a predicate-formatter suitable for using with
+  // Google Test's EXPECT_PRED_FORMAT1() macro.
+  template <typename T>
+  AssertionResult operator()(const char* value_text, const T& x) const {
+    // We convert matcher_ to a Matcher<const T&> *now* instead of
+    // when the PredicateFormatterFromMatcher object was constructed,
+    // as matcher_ may be polymorphic (e.g. NotNull()) and we won't
+    // know which type to instantiate it to until we actually see the
+    // type of x here.
+    //
+    // We write SafeMatcherCast<const T&>(matcher_) instead of
+    // Matcher<const T&>(matcher_), as the latter won't compile when
+    // matcher_ has type Matcher<T> (e.g. An<int>()).
+    // We don't write MatcherCast<const T&> either, as that allows
+    // potentially unsafe downcasting of the matcher argument.
+    const Matcher<const T&> matcher = SafeMatcherCast<const T&>(matcher_);
+
+    // The expected path here is that the matcher should match (i.e. that most
+    // tests pass) so optimize for this case.
+    if (matcher.Matches(x)) {
+      return AssertionSuccess();
+    }
+
+    ::std::stringstream ss;
+    ss << "Value of: " << value_text << "\n"
+       << "Expected: ";
+    matcher.DescribeTo(&ss);
+
+    // Rerun the matcher to "PrintAndExplain" the failure.
+    StringMatchResultListener listener;
+    if (MatchPrintAndExplain(x, matcher, &listener)) {
+      ss << "\n  The matcher failed on the initial attempt; but passed when "
+            "rerun to generate the explanation.";
+    }
+    ss << "\n  Actual: " << listener.str();
+    return AssertionFailure() << ss.str();
+  }
+
+ private:
+  const M matcher_;
+};
+
+// A helper function for converting a matcher to a predicate-formatter
+// without the user needing to explicitly write the type.  This is
+// used for implementing ASSERT_THAT() and EXPECT_THAT().
+// Implementation detail: 'matcher' is received by-value to force decaying.
+template <typename M>
+inline PredicateFormatterFromMatcher<M> MakePredicateFormatterFromMatcher(
+    M matcher) {
+  return PredicateFormatterFromMatcher<M>(std::move(matcher));
+}
+
+// Implements the polymorphic IsNan() matcher, which matches any floating type
+// value that is Nan.
+class IsNanMatcher {
+ public:
+  template <typename FloatType>
+  bool MatchAndExplain(const FloatType& f,
+                       MatchResultListener* /* listener */) const {
+    return (::std::isnan)(f);
+  }
+
+  void DescribeTo(::std::ostream* os) const { *os << "is NaN"; }
+  void DescribeNegationTo(::std::ostream* os) const { *os << "isn't NaN"; }
+};
+
+// Implements the polymorphic floating point equality matcher, which matches
+// two float values using ULP-based approximation or, optionally, a
+// user-specified epsilon.  The template is meant to be instantiated with
+// FloatType being either float or double.
+template <typename FloatType>
+class FloatingEqMatcher {
+ public:
+  // Constructor for FloatingEqMatcher.
+  // The matcher's input will be compared with expected.  The matcher treats two
+  // NANs as equal if nan_eq_nan is true.  Otherwise, under IEEE standards,
+  // equality comparisons between NANs will always return false.  We specify a
+  // negative max_abs_error_ term to indicate that ULP-based approximation will
+  // be used for comparison.
+  FloatingEqMatcher(FloatType expected, bool nan_eq_nan)
+      : expected_(expected), nan_eq_nan_(nan_eq_nan), max_abs_error_(-1) {}
+
+  // Constructor that supports a user-specified max_abs_error that will be used
+  // for comparison instead of ULP-based approximation.  The max absolute
+  // should be non-negative.
+  FloatingEqMatcher(FloatType expected, bool nan_eq_nan,
+                    FloatType max_abs_error)
+      : expected_(expected),
+        nan_eq_nan_(nan_eq_nan),
+        max_abs_error_(max_abs_error) {
+    GTEST_CHECK_(max_abs_error >= 0)
+        << ", where max_abs_error is" << max_abs_error;
+  }
+
+  // Implements floating point equality matcher as a Matcher<T>.
+  template <typename T>
+  class Impl : public MatcherInterface<T> {
+   public:
+    Impl(FloatType expected, bool nan_eq_nan, FloatType max_abs_error)
+        : expected_(expected),
+          nan_eq_nan_(nan_eq_nan),
+          max_abs_error_(max_abs_error) {}
+
+    bool MatchAndExplain(T value,
+                         MatchResultListener* listener) const override {
+      const FloatingPoint<FloatType> actual(value), expected(expected_);
+
+      // Compares NaNs first, if nan_eq_nan_ is true.
+      if (actual.is_nan() || expected.is_nan()) {
+        if (actual.is_nan() && expected.is_nan()) {
+          return nan_eq_nan_;
+        }
+        // One is nan; the other is not nan.
+        return false;
+      }
+      if (HasMaxAbsError()) {
+        // We perform an equality check so that inf will match inf, regardless
+        // of error bounds.  If the result of value - expected_ would result in
+        // overflow or if either value is inf, the default result is infinity,
+        // which should only match if max_abs_error_ is also infinity.
+        if (value == expected_) {
+          return true;
+        }
+
+        const FloatType diff = value - expected_;
+        if (::std::fabs(diff) <= max_abs_error_) {
+          return true;
+        }
+
+        if (listener->IsInterested()) {
+          *listener << "which is " << diff << " from " << expected_;
+        }
+        return false;
+      } else {
+        return actual.AlmostEquals(expected);
+      }
+    }
+
+    void DescribeTo(::std::ostream* os) const override {
+      // os->precision() returns the previously set precision, which we
+      // store to restore the ostream to its original configuration
+      // after outputting.
+      const ::std::streamsize old_precision =
+          os->precision(::std::numeric_limits<FloatType>::digits10 + 2);
+      if (FloatingPoint<FloatType>(expected_).is_nan()) {
+        if (nan_eq_nan_) {
+          *os << "is NaN";
+        } else {
+          *os << "never matches";
+        }
+      } else {
+        *os << "is approximately " << expected_;
+        if (HasMaxAbsError()) {
+          *os << " (absolute error <= " << max_abs_error_ << ")";
+        }
+      }
+      os->precision(old_precision);
+    }
+
+    void DescribeNegationTo(::std::ostream* os) const override {
+      // As before, get original precision.
+      const ::std::streamsize old_precision =
+          os->precision(::std::numeric_limits<FloatType>::digits10 + 2);
+      if (FloatingPoint<FloatType>(expected_).is_nan()) {
+        if (nan_eq_nan_) {
+          *os << "isn't NaN";
+        } else {
+          *os << "is anything";
+        }
+      } else {
+        *os << "isn't approximately " << expected_;
+        if (HasMaxAbsError()) {
+          *os << " (absolute error > " << max_abs_error_ << ")";
+        }
+      }
+      // Restore original precision.
+      os->precision(old_precision);
+    }
+
+   private:
+    bool HasMaxAbsError() const { return max_abs_error_ >= 0; }
+
+    const FloatType expected_;
+    const bool nan_eq_nan_;
+    // max_abs_error will be used for value comparison when >= 0.
+    const FloatType max_abs_error_;
+  };
+
+  // The following 3 type conversion operators allow FloatEq(expected) and
+  // NanSensitiveFloatEq(expected) to be used as a Matcher<float>, a
+  // Matcher<const float&>, or a Matcher<float&>, but nothing else.
+  operator Matcher<FloatType>() const {
+    return MakeMatcher(
+        new Impl<FloatType>(expected_, nan_eq_nan_, max_abs_error_));
+  }
+
+  operator Matcher<const FloatType&>() const {
+    return MakeMatcher(
+        new Impl<const FloatType&>(expected_, nan_eq_nan_, max_abs_error_));
+  }
+
+  operator Matcher<FloatType&>() const {
+    return MakeMatcher(
+        new Impl<FloatType&>(expected_, nan_eq_nan_, max_abs_error_));
+  }
+
+ private:
+  const FloatType expected_;
+  const bool nan_eq_nan_;
+  // max_abs_error will be used for value comparison when >= 0.
+  const FloatType max_abs_error_;
+};
+
+// A 2-tuple ("binary") wrapper around FloatingEqMatcher:
+// FloatingEq2Matcher() matches (x, y) by matching FloatingEqMatcher(x, false)
+// against y, and FloatingEq2Matcher(e) matches FloatingEqMatcher(x, false, e)
+// against y. The former implements "Eq", the latter "Near". At present, there
+// is no version that compares NaNs as equal.
+template <typename FloatType>
+class FloatingEq2Matcher {
+ public:
+  FloatingEq2Matcher() { Init(-1, false); }
+
+  explicit FloatingEq2Matcher(bool nan_eq_nan) { Init(-1, nan_eq_nan); }
+
+  explicit FloatingEq2Matcher(FloatType max_abs_error) {
+    Init(max_abs_error, false);
+  }
+
+  FloatingEq2Matcher(FloatType max_abs_error, bool nan_eq_nan) {
+    Init(max_abs_error, nan_eq_nan);
+  }
+
+  template <typename T1, typename T2>
+  operator Matcher<::std::tuple<T1, T2>>() const {
+    return MakeMatcher(
+        new Impl<::std::tuple<T1, T2>>(max_abs_error_, nan_eq_nan_));
+  }
+  template <typename T1, typename T2>
+  operator Matcher<const ::std::tuple<T1, T2>&>() const {
+    return MakeMatcher(
+        new Impl<const ::std::tuple<T1, T2>&>(max_abs_error_, nan_eq_nan_));
+  }
+
+ private:
+  static ::std::ostream& GetDesc(::std::ostream& os) {  // NOLINT
+    return os << "an almost-equal pair";
+  }
+
+  template <typename Tuple>
+  class Impl : public MatcherInterface<Tuple> {
+   public:
+    Impl(FloatType max_abs_error, bool nan_eq_nan)
+        : max_abs_error_(max_abs_error), nan_eq_nan_(nan_eq_nan) {}
+
+    bool MatchAndExplain(Tuple args,
+                         MatchResultListener* listener) const override {
+      if (max_abs_error_ == -1) {
+        FloatingEqMatcher<FloatType> fm(::std::get<0>(args), nan_eq_nan_);
+        return static_cast<Matcher<FloatType>>(fm).MatchAndExplain(
+            ::std::get<1>(args), listener);
+      } else {
+        FloatingEqMatcher<FloatType> fm(::std::get<0>(args), nan_eq_nan_,
+                                        max_abs_error_);
+        return static_cast<Matcher<FloatType>>(fm).MatchAndExplain(
+            ::std::get<1>(args), listener);
+      }
+    }
+    void DescribeTo(::std::ostream* os) const override {
+      *os << "are " << GetDesc;
+    }
+    void DescribeNegationTo(::std::ostream* os) const override {
+      *os << "aren't " << GetDesc;
+    }
+
+   private:
+    FloatType max_abs_error_;
+    const bool nan_eq_nan_;
+  };
+
+  void Init(FloatType max_abs_error_val, bool nan_eq_nan_val) {
+    max_abs_error_ = max_abs_error_val;
+    nan_eq_nan_ = nan_eq_nan_val;
+  }
+  FloatType max_abs_error_;
+  bool nan_eq_nan_;
+};
+
+// Implements the Pointee(m) matcher for matching a pointer whose
+// pointee matches matcher m.  The pointer can be either raw or smart.
+template <typename InnerMatcher>
+class PointeeMatcher {
+ public:
+  explicit PointeeMatcher(const InnerMatcher& matcher) : matcher_(matcher) {}
+
+  // This type conversion operator template allows Pointee(m) to be
+  // used as a matcher for any pointer type whose pointee type is
+  // compatible with the inner matcher, where type Pointer can be
+  // either a raw pointer or a smart pointer.
+  //
+  // The reason we do this instead of relying on
+  // MakePolymorphicMatcher() is that the latter is not flexible
+  // enough for implementing the DescribeTo() method of Pointee().
+  template <typename Pointer>
+  operator Matcher<Pointer>() const {
+    return Matcher<Pointer>(new Impl<const Pointer&>(matcher_));
+  }
+
+ private:
+  // The monomorphic implementation that works for a particular pointer type.
+  template <typename Pointer>
+  class Impl : public MatcherInterface<Pointer> {
+   public:
+    using Pointee =
+        typename std::pointer_traits<GTEST_REMOVE_REFERENCE_AND_CONST_(
+            Pointer)>::element_type;
+
+    explicit Impl(const InnerMatcher& matcher)
+        : matcher_(MatcherCast<const Pointee&>(matcher)) {}
+
+    void DescribeTo(::std::ostream* os) const override {
+      *os << "points to a value that ";
+      matcher_.DescribeTo(os);
+    }
+
+    void DescribeNegationTo(::std::ostream* os) const override {
+      *os << "does not point to a value that ";
+      matcher_.DescribeTo(os);
+    }
+
+    bool MatchAndExplain(Pointer pointer,
+                         MatchResultListener* listener) const override {
+      if (GetRawPointer(pointer) == nullptr) return false;
+
+      *listener << "which points to ";
+      return MatchPrintAndExplain(*pointer, matcher_, listener);
+    }
+
+   private:
+    const Matcher<const Pointee&> matcher_;
+  };
+
+  const InnerMatcher matcher_;
+};
+
+// Implements the Pointer(m) matcher
+// Implements the Pointer(m) matcher for matching a pointer that matches matcher
+// m.  The pointer can be either raw or smart, and will match `m` against the
+// raw pointer.
+template <typename InnerMatcher>
+class PointerMatcher {
+ public:
+  explicit PointerMatcher(const InnerMatcher& matcher) : matcher_(matcher) {}
+
+  // This type conversion operator template allows Pointer(m) to be
+  // used as a matcher for any pointer type whose pointer type is
+  // compatible with the inner matcher, where type PointerType can be
+  // either a raw pointer or a smart pointer.
+  //
+  // The reason we do this instead of relying on
+  // MakePolymorphicMatcher() is that the latter is not flexible
+  // enough for implementing the DescribeTo() method of Pointer().
+  template <typename PointerType>
+  operator Matcher<PointerType>() const {  // NOLINT
+    return Matcher<PointerType>(new Impl<const PointerType&>(matcher_));
+  }
+
+ private:
+  // The monomorphic implementation that works for a particular pointer type.
+  template <typename PointerType>
+  class Impl : public MatcherInterface<PointerType> {
+   public:
+    using Pointer =
+        const typename std::pointer_traits<GTEST_REMOVE_REFERENCE_AND_CONST_(
+            PointerType)>::element_type*;
+
+    explicit Impl(const InnerMatcher& matcher)
+        : matcher_(MatcherCast<Pointer>(matcher)) {}
+
+    void DescribeTo(::std::ostream* os) const override {
+      *os << "is a pointer that ";
+      matcher_.DescribeTo(os);
+    }
+
+    void DescribeNegationTo(::std::ostream* os) const override {
+      *os << "is not a pointer that ";
+      matcher_.DescribeTo(os);
+    }
+
+    bool MatchAndExplain(PointerType pointer,
+                         MatchResultListener* listener) const override {
+      *listener << "which is a pointer that ";
+      Pointer p = GetRawPointer(pointer);
+      return MatchPrintAndExplain(p, matcher_, listener);
+    }
+
+   private:
+    Matcher<Pointer> matcher_;
+  };
+
+  const InnerMatcher matcher_;
+};
+
+#if GTEST_HAS_RTTI
+// Implements the WhenDynamicCastTo<T>(m) matcher that matches a pointer or
+// reference that matches inner_matcher when dynamic_cast<T> is applied.
+// The result of dynamic_cast<To> is forwarded to the inner matcher.
+// If To is a pointer and the cast fails, the inner matcher will receive NULL.
+// If To is a reference and the cast fails, this matcher returns false
+// immediately.
+template <typename To>
+class WhenDynamicCastToMatcherBase {
+ public:
+  explicit WhenDynamicCastToMatcherBase(const Matcher<To>& matcher)
+      : matcher_(matcher) {}
+
+  void DescribeTo(::std::ostream* os) const {
+    GetCastTypeDescription(os);
+    matcher_.DescribeTo(os);
+  }
+
+  void DescribeNegationTo(::std::ostream* os) const {
+    GetCastTypeDescription(os);
+    matcher_.DescribeNegationTo(os);
+  }
+
+ protected:
+  const Matcher<To> matcher_;
+
+  static std::string GetToName() { return GetTypeName<To>(); }
+
+ private:
+  static void GetCastTypeDescription(::std::ostream* os) {
+    *os << "when dynamic_cast to " << GetToName() << ", ";
+  }
+};
+
+// Primary template.
+// To is a pointer. Cast and forward the result.
+template <typename To>
+class WhenDynamicCastToMatcher : public WhenDynamicCastToMatcherBase<To> {
+ public:
+  explicit WhenDynamicCastToMatcher(const Matcher<To>& matcher)
+      : WhenDynamicCastToMatcherBase<To>(matcher) {}
+
+  template <typename From>
+  bool MatchAndExplain(From from, MatchResultListener* listener) const {
+    To to = dynamic_cast<To>(from);
+    return MatchPrintAndExplain(to, this->matcher_, listener);
+  }
+};
+
+// Specialize for references.
+// In this case we return false if the dynamic_cast fails.
+template <typename To>
+class WhenDynamicCastToMatcher<To&> : public WhenDynamicCastToMatcherBase<To&> {
+ public:
+  explicit WhenDynamicCastToMatcher(const Matcher<To&>& matcher)
+      : WhenDynamicCastToMatcherBase<To&>(matcher) {}
+
+  template <typename From>
+  bool MatchAndExplain(From& from, MatchResultListener* listener) const {
+    // We don't want an std::bad_cast here, so do the cast with pointers.
+    To* to = dynamic_cast<To*>(&from);
+    if (to == nullptr) {
+      *listener << "which cannot be dynamic_cast to " << this->GetToName();
+      return false;
+    }
+    return MatchPrintAndExplain(*to, this->matcher_, listener);
+  }
+};
+#endif  // GTEST_HAS_RTTI
+
+// Implements the Field() matcher for matching a field (i.e. member
+// variable) of an object.
+template <typename Class, typename FieldType>
+class FieldMatcher {
+ public:
+  FieldMatcher(FieldType Class::*field,
+               const Matcher<const FieldType&>& matcher)
+      : field_(field), matcher_(matcher), whose_field_("whose given field ") {}
+
+  FieldMatcher(const std::string& field_name, FieldType Class::*field,
+               const Matcher<const FieldType&>& matcher)
+      : field_(field),
+        matcher_(matcher),
+        whose_field_("whose field `" + field_name + "` ") {}
+
+  void DescribeTo(::std::ostream* os) const {
+    *os << "is an object " << whose_field_;
+    matcher_.DescribeTo(os);
+  }
+
+  void DescribeNegationTo(::std::ostream* os) const {
+    *os << "is an object " << whose_field_;
+    matcher_.DescribeNegationTo(os);
+  }
+
+  template <typename T>
+  bool MatchAndExplain(const T& value, MatchResultListener* listener) const {
+    // FIXME: The dispatch on std::is_pointer was introduced as a workaround for
+    // a compiler bug, and can now be removed.
+    return MatchAndExplainImpl(
+        typename std::is_pointer<typename std::remove_const<T>::type>::type(),
+        value, listener);
+  }
+
+ private:
+  bool MatchAndExplainImpl(std::false_type /* is_not_pointer */,
+                           const Class& obj,
+                           MatchResultListener* listener) const {
+    *listener << whose_field_ << "is ";
+    return MatchPrintAndExplain(obj.*field_, matcher_, listener);
+  }
+
+  bool MatchAndExplainImpl(std::true_type /* is_pointer */, const Class* p,
+                           MatchResultListener* listener) const {
+    if (p == nullptr) return false;
+
+    *listener << "which points to an object ";
+    // Since *p has a field, it must be a class/struct/union type and
+    // thus cannot be a pointer.  Therefore we pass false_type() as
+    // the first argument.
+    return MatchAndExplainImpl(std::false_type(), *p, listener);
+  }
+
+  const FieldType Class::*field_;
+  const Matcher<const FieldType&> matcher_;
+
+  // Contains either "whose given field " if the name of the field is unknown
+  // or "whose field `name_of_field` " if the name is known.
+  const std::string whose_field_;
+};
+
+// Implements the Property() matcher for matching a property
+// (i.e. return value of a getter method) of an object.
+//
+// Property is a const-qualified member function of Class returning
+// PropertyType.
+template <typename Class, typename PropertyType, typename Property>
+class PropertyMatcher {
+ public:
+  typedef const PropertyType& RefToConstProperty;
+
+  PropertyMatcher(Property property, const Matcher<RefToConstProperty>& matcher)
+      : property_(property),
+        matcher_(matcher),
+        whose_property_("whose given property ") {}
+
+  PropertyMatcher(const std::string& property_name, Property property,
+                  const Matcher<RefToConstProperty>& matcher)
+      : property_(property),
+        matcher_(matcher),
+        whose_property_("whose property `" + property_name + "` ") {}
+
+  void DescribeTo(::std::ostream* os) const {
+    *os << "is an object " << whose_property_;
+    matcher_.DescribeTo(os);
+  }
+
+  void DescribeNegationTo(::std::ostream* os) const {
+    *os << "is an object " << whose_property_;
+    matcher_.DescribeNegationTo(os);
+  }
+
+  template <typename T>
+  bool MatchAndExplain(const T& value, MatchResultListener* listener) const {
+    return MatchAndExplainImpl(
+        typename std::is_pointer<typename std::remove_const<T>::type>::type(),
+        value, listener);
+  }
+
+ private:
+  bool MatchAndExplainImpl(std::false_type /* is_not_pointer */,
+                           const Class& obj,
+                           MatchResultListener* listener) const {
+    *listener << whose_property_ << "is ";
+    // Cannot pass the return value (for example, int) to MatchPrintAndExplain,
+    // which takes a non-const reference as argument.
+    RefToConstProperty result = (obj.*property_)();
+    return MatchPrintAndExplain(result, matcher_, listener);
+  }
+
+  bool MatchAndExplainImpl(std::true_type /* is_pointer */, const Class* p,
+                           MatchResultListener* listener) const {
+    if (p == nullptr) return false;
+
+    *listener << "which points to an object ";
+    // Since *p has a property method, it must be a class/struct/union
+    // type and thus cannot be a pointer.  Therefore we pass
+    // false_type() as the first argument.
+    return MatchAndExplainImpl(std::false_type(), *p, listener);
+  }
+
+  Property property_;
+  const Matcher<RefToConstProperty> matcher_;
+
+  // Contains either "whose given property " if the name of the property is
+  // unknown or "whose property `name_of_property` " if the name is known.
+  const std::string whose_property_;
+};
+
+// Type traits specifying various features of different functors for ResultOf.
+// The default template specifies features for functor objects.
+template <typename Functor>
+struct CallableTraits {
+  typedef Functor StorageType;
+
+  static void CheckIsValid(Functor /* functor */) {}
+
+  template <typename T>
+  static auto Invoke(Functor f, const T& arg) -> decltype(f(arg)) {
+    return f(arg);
+  }
+};
+
+// Specialization for function pointers.
+template <typename ArgType, typename ResType>
+struct CallableTraits<ResType (*)(ArgType)> {
+  typedef ResType ResultType;
+  typedef ResType (*StorageType)(ArgType);
+
+  static void CheckIsValid(ResType (*f)(ArgType)) {
+    GTEST_CHECK_(f != nullptr)
+        << "NULL function pointer is passed into ResultOf().";
+  }
+  template <typename T>
+  static ResType Invoke(ResType (*f)(ArgType), T arg) {
+    return (*f)(arg);
+  }
+};
+
+// Implements the ResultOf() matcher for matching a return value of a
+// unary function of an object.
+template <typename Callable, typename InnerMatcher>
+class ResultOfMatcher {
+ public:
+  ResultOfMatcher(Callable callable, InnerMatcher matcher)
+      : ResultOfMatcher(/*result_description=*/"", std::move(callable),
+                        std::move(matcher)) {}
+
+  ResultOfMatcher(const std::string& result_description, Callable callable,
+                  InnerMatcher matcher)
+      : result_description_(result_description),
+        callable_(std::move(callable)),
+        matcher_(std::move(matcher)) {
+    CallableTraits<Callable>::CheckIsValid(callable_);
+  }
+
+  template <typename T>
+  operator Matcher<T>() const {
+    return Matcher<T>(
+        new Impl<const T&>(result_description_, callable_, matcher_));
+  }
+
+ private:
+  typedef typename CallableTraits<Callable>::StorageType CallableStorageType;
+
+  template <typename T>
+  class Impl : public MatcherInterface<T> {
+    using ResultType = decltype(CallableTraits<Callable>::template Invoke<T>(
+        std::declval<CallableStorageType>(), std::declval<T>()));
+
+   public:
+    template <typename M>
+    Impl(const std::string& result_description,
+         const CallableStorageType& callable, const M& matcher)
+        : result_description_(result_description),
+          callable_(callable),
+          matcher_(MatcherCast<ResultType>(matcher)) {}
+
+    void DescribeTo(::std::ostream* os) const override {
+      if (result_description_.empty()) {
+        *os << "is mapped by the given callable to a value that ";
+      } else {
+        *os << "whose " << result_description_ << " ";
+      }
+      matcher_.DescribeTo(os);
+    }
+
+    void DescribeNegationTo(::std::ostream* os) const override {
+      if (result_description_.empty()) {
+        *os << "is mapped by the given callable to a value that ";
+      } else {
+        *os << "whose " << result_description_ << " ";
+      }
+      matcher_.DescribeNegationTo(os);
+    }
+
+    bool MatchAndExplain(T obj, MatchResultListener* listener) const override {
+      if (result_description_.empty()) {
+        *listener << "which is mapped by the given callable to ";
+      } else {
+        *listener << "whose " << result_description_ << " is ";
+      }
+      // Cannot pass the return value directly to MatchPrintAndExplain, which
+      // takes a non-const reference as argument.
+      // Also, specifying template argument explicitly is needed because T could
+      // be a non-const reference (e.g. Matcher<Uncopyable&>).
+      ResultType result =
+          CallableTraits<Callable>::template Invoke<T>(callable_, obj);
+      return MatchPrintAndExplain(result, matcher_, listener);
+    }
+
+   private:
+    const std::string result_description_;
+    // Functors often define operator() as non-const method even though
+    // they are actually stateless. But we need to use them even when
+    // 'this' is a const pointer. It's the user's responsibility not to
+    // use stateful callables with ResultOf(), which doesn't guarantee
+    // how many times the callable will be invoked.
+    mutable CallableStorageType callable_;
+    const Matcher<ResultType> matcher_;
+  };  // class Impl
+
+  const std::string result_description_;
+  const CallableStorageType callable_;
+  const InnerMatcher matcher_;
+};
+
+// Implements a matcher that checks the size of an STL-style container.
+template <typename SizeMatcher>
+class SizeIsMatcher {
+ public:
+  explicit SizeIsMatcher(const SizeMatcher& size_matcher)
+      : size_matcher_(size_matcher) {}
+
+  template <typename Container>
+  operator Matcher<Container>() const {
+    return Matcher<Container>(new Impl<const Container&>(size_matcher_));
+  }
+
+  template <typename Container>
+  class Impl : public MatcherInterface<Container> {
+   public:
+    using SizeType = decltype(std::declval<Container>().size());
+    explicit Impl(const SizeMatcher& size_matcher)
+        : size_matcher_(MatcherCast<SizeType>(size_matcher)) {}
+
+    void DescribeTo(::std::ostream* os) const override {
+      *os << "has a size that ";
+      size_matcher_.DescribeTo(os);
+    }
+    void DescribeNegationTo(::std::ostream* os) const override {
+      *os << "has a size that ";
+      size_matcher_.DescribeNegationTo(os);
+    }
+
+    bool MatchAndExplain(Container container,
+                         MatchResultListener* listener) const override {
+      SizeType size = container.size();
+      StringMatchResultListener size_listener;
+      const bool result = size_matcher_.MatchAndExplain(size, &size_listener);
+      *listener << "whose size " << size
+                << (result ? " matches" : " doesn't match");
+      PrintIfNotEmpty(size_listener.str(), listener->stream());
+      return result;
+    }
+
+   private:
+    const Matcher<SizeType> size_matcher_;
+  };
+
+ private:
+  const SizeMatcher size_matcher_;
+};
+
+// Implements a matcher that checks the begin()..end() distance of an STL-style
+// container.
+template <typename DistanceMatcher>
+class BeginEndDistanceIsMatcher {
+ public:
+  explicit BeginEndDistanceIsMatcher(const DistanceMatcher& distance_matcher)
+      : distance_matcher_(distance_matcher) {}
+
+  template <typename Container>
+  operator Matcher<Container>() const {
+    return Matcher<Container>(new Impl<const Container&>(distance_matcher_));
+  }
+
+  template <typename Container>
+  class Impl : public MatcherInterface<Container> {
+   public:
+    typedef internal::StlContainerView<GTEST_REMOVE_REFERENCE_AND_CONST_(
+        Container)>
+        ContainerView;
+    typedef typename std::iterator_traits<
+        typename ContainerView::type::const_iterator>::difference_type
+        DistanceType;
+    explicit Impl(const DistanceMatcher& distance_matcher)
+        : distance_matcher_(MatcherCast<DistanceType>(distance_matcher)) {}
+
+    void DescribeTo(::std::ostream* os) const override {
+      *os << "distance between begin() and end() ";
+      distance_matcher_.DescribeTo(os);
+    }
+    void DescribeNegationTo(::std::ostream* os) const override {
+      *os << "distance between begin() and end() ";
+      distance_matcher_.DescribeNegationTo(os);
+    }
+
+    bool MatchAndExplain(Container container,
+                         MatchResultListener* listener) const override {
+      using std::begin;
+      using std::end;
+      DistanceType distance = std::distance(begin(container), end(container));
+      StringMatchResultListener distance_listener;
+      const bool result =
+          distance_matcher_.MatchAndExplain(distance, &distance_listener);
+      *listener << "whose distance between begin() and end() " << distance
+                << (result ? " matches" : " doesn't match");
+      PrintIfNotEmpty(distance_listener.str(), listener->stream());
+      return result;
+    }
+
+   private:
+    const Matcher<DistanceType> distance_matcher_;
+  };
+
+ private:
+  const DistanceMatcher distance_matcher_;
+};
+
+// Implements an equality matcher for any STL-style container whose elements
+// support ==. This matcher is like Eq(), but its failure explanations provide
+// more detailed information that is useful when the container is used as a set.
+// The failure message reports elements that are in one of the operands but not
+// the other. The failure messages do not report duplicate or out-of-order
+// elements in the containers (which don't properly matter to sets, but can
+// occur if the containers are vectors or lists, for example).
+//
+// Uses the container's const_iterator, value_type, operator ==,
+// begin(), and end().
+template <typename Container>
+class ContainerEqMatcher {
+ public:
+  typedef internal::StlContainerView<Container> View;
+  typedef typename View::type StlContainer;
+  typedef typename View::const_reference StlContainerReference;
+
+  static_assert(!std::is_const<Container>::value,
+                "Container type must not be const");
+  static_assert(!std::is_reference<Container>::value,
+                "Container type must not be a reference");
+
+  // We make a copy of expected in case the elements in it are modified
+  // after this matcher is created.
+  explicit ContainerEqMatcher(const Container& expected)
+      : expected_(View::Copy(expected)) {}
+
+  void DescribeTo(::std::ostream* os) const {
+    *os << "equals ";
+    UniversalPrint(expected_, os);
+  }
+  void DescribeNegationTo(::std::ostream* os) const {
+    *os << "does not equal ";
+    UniversalPrint(expected_, os);
+  }
+
+  template <typename LhsContainer>
+  bool MatchAndExplain(const LhsContainer& lhs,
+                       MatchResultListener* listener) const {
+    typedef internal::StlContainerView<
+        typename std::remove_const<LhsContainer>::type>
+        LhsView;
+    StlContainerReference lhs_stl_container = LhsView::ConstReference(lhs);
+    if (lhs_stl_container == expected_) return true;
+
+    ::std::ostream* const os = listener->stream();
+    if (os != nullptr) {
+      // Something is different. Check for extra values first.
+      bool printed_header = false;
+      for (auto it = lhs_stl_container.begin(); it != lhs_stl_container.end();
+           ++it) {
+        if (internal::ArrayAwareFind(expected_.begin(), expected_.end(), *it) ==
+            expected_.end()) {
+          if (printed_header) {
+            *os << ", ";
+          } else {
+            *os << "which has these unexpected elements: ";
+            printed_header = true;
+          }
+          UniversalPrint(*it, os);
+        }
+      }
+
+      // Now check for missing values.
+      bool printed_header2 = false;
+      for (auto it = expected_.begin(); it != expected_.end(); ++it) {
+        if (internal::ArrayAwareFind(lhs_stl_container.begin(),
+                                     lhs_stl_container.end(),
+                                     *it) == lhs_stl_container.end()) {
+          if (printed_header2) {
+            *os << ", ";
+          } else {
+            *os << (printed_header ? ",\nand" : "which")
+                << " doesn't have these expected elements: ";
+            printed_header2 = true;
+          }
+          UniversalPrint(*it, os);
+        }
+      }
+    }
+
+    return false;
+  }
+
+ private:
+  const StlContainer expected_;
+};
+
+// A comparator functor that uses the < operator to compare two values.
+struct LessComparator {
+  template <typename T, typename U>
+  bool operator()(const T& lhs, const U& rhs) const {
+    return lhs < rhs;
+  }
+};
+
+// Implements WhenSortedBy(comparator, container_matcher).
+template <typename Comparator, typename ContainerMatcher>
+class WhenSortedByMatcher {
+ public:
+  WhenSortedByMatcher(const Comparator& comparator,
+                      const ContainerMatcher& matcher)
+      : comparator_(comparator), matcher_(matcher) {}
+
+  template <typename LhsContainer>
+  operator Matcher<LhsContainer>() const {
+    return MakeMatcher(new Impl<LhsContainer>(comparator_, matcher_));
+  }
+
+  template <typename LhsContainer>
+  class Impl : public MatcherInterface<LhsContainer> {
+   public:
+    typedef internal::StlContainerView<GTEST_REMOVE_REFERENCE_AND_CONST_(
+        LhsContainer)>
+        LhsView;
+    typedef typename LhsView::type LhsStlContainer;
+    typedef typename LhsView::const_reference LhsStlContainerReference;
+    // Transforms std::pair<const Key, Value> into std::pair<Key, Value>
+    // so that we can match associative containers.
+    typedef
+        typename RemoveConstFromKey<typename LhsStlContainer::value_type>::type
+            LhsValue;
+
+    Impl(const Comparator& comparator, const ContainerMatcher& matcher)
+        : comparator_(comparator), matcher_(matcher) {}
+
+    void DescribeTo(::std::ostream* os) const override {
+      *os << "(when sorted) ";
+      matcher_.DescribeTo(os);
+    }
+
+    void DescribeNegationTo(::std::ostream* os) const override {
+      *os << "(when sorted) ";
+      matcher_.DescribeNegationTo(os);
+    }
+
+    bool MatchAndExplain(LhsContainer lhs,
+                         MatchResultListener* listener) const override {
+      LhsStlContainerReference lhs_stl_container = LhsView::ConstReference(lhs);
+      ::std::vector<LhsValue> sorted_container(lhs_stl_container.begin(),
+                                               lhs_stl_container.end());
+      ::std::sort(sorted_container.begin(), sorted_container.end(),
+                  comparator_);
+
+      if (!listener->IsInterested()) {
+        // If the listener is not interested, we do not need to
+        // construct the inner explanation.
+        return matcher_.Matches(sorted_container);
+      }
+
+      *listener << "which is ";
+      UniversalPrint(sorted_container, listener->stream());
+      *listener << " when sorted";
+
+      StringMatchResultListener inner_listener;
+      const bool match =
+          matcher_.MatchAndExplain(sorted_container, &inner_listener);
+      PrintIfNotEmpty(inner_listener.str(), listener->stream());
+      return match;
+    }
+
+   private:
+    const Comparator comparator_;
+    const Matcher<const ::std::vector<LhsValue>&> matcher_;
+
+    Impl(const Impl&) = delete;
+    Impl& operator=(const Impl&) = delete;
+  };
+
+ private:
+  const Comparator comparator_;
+  const ContainerMatcher matcher_;
+};
+
+// Implements Pointwise(tuple_matcher, rhs_container).  tuple_matcher
+// must be able to be safely cast to Matcher<std::tuple<const T1&, const
+// T2&> >, where T1 and T2 are the types of elements in the LHS
+// container and the RHS container respectively.
+template <typename TupleMatcher, typename RhsContainer>
+class PointwiseMatcher {
+  static_assert(
+      !IsHashTable<GTEST_REMOVE_REFERENCE_AND_CONST_(RhsContainer)>::value,
+      "use UnorderedPointwise with hash tables");
+
+ public:
+  typedef internal::StlContainerView<RhsContainer> RhsView;
+  typedef typename RhsView::type RhsStlContainer;
+  typedef typename RhsStlContainer::value_type RhsValue;
+
+  static_assert(!std::is_const<RhsContainer>::value,
+                "RhsContainer type must not be const");
+  static_assert(!std::is_reference<RhsContainer>::value,
+                "RhsContainer type must not be a reference");
+
+  // Like ContainerEq, we make a copy of rhs in case the elements in
+  // it are modified after this matcher is created.
+  PointwiseMatcher(const TupleMatcher& tuple_matcher, const RhsContainer& rhs)
+      : tuple_matcher_(tuple_matcher), rhs_(RhsView::Copy(rhs)) {}
+
+  template <typename LhsContainer>
+  operator Matcher<LhsContainer>() const {
+    static_assert(
+        !IsHashTable<GTEST_REMOVE_REFERENCE_AND_CONST_(LhsContainer)>::value,
+        "use UnorderedPointwise with hash tables");
+
+    return Matcher<LhsContainer>(
+        new Impl<const LhsContainer&>(tuple_matcher_, rhs_));
+  }
+
+  template <typename LhsContainer>
+  class Impl : public MatcherInterface<LhsContainer> {
+   public:
+    typedef internal::StlContainerView<GTEST_REMOVE_REFERENCE_AND_CONST_(
+        LhsContainer)>
+        LhsView;
+    typedef typename LhsView::type LhsStlContainer;
+    typedef typename LhsView::const_reference LhsStlContainerReference;
+    typedef typename LhsStlContainer::value_type LhsValue;
+    // We pass the LHS value and the RHS value to the inner matcher by
+    // reference, as they may be expensive to copy.  We must use tuple
+    // instead of pair here, as a pair cannot hold references (C++ 98,
+    // 20.2.2 [lib.pairs]).
+    typedef ::std::tuple<const LhsValue&, const RhsValue&> InnerMatcherArg;
+
+    Impl(const TupleMatcher& tuple_matcher, const RhsStlContainer& rhs)
+        // mono_tuple_matcher_ holds a monomorphic version of the tuple matcher.
+        : mono_tuple_matcher_(SafeMatcherCast<InnerMatcherArg>(tuple_matcher)),
+          rhs_(rhs) {}
+
+    void DescribeTo(::std::ostream* os) const override {
+      *os << "contains " << rhs_.size()
+          << " values, where each value and its corresponding value in ";
+      UniversalPrinter<RhsStlContainer>::Print(rhs_, os);
+      *os << " ";
+      mono_tuple_matcher_.DescribeTo(os);
+    }
+    void DescribeNegationTo(::std::ostream* os) const override {
+      *os << "doesn't contain exactly " << rhs_.size()
+          << " values, or contains a value x at some index i"
+          << " where x and the i-th value of ";
+      UniversalPrint(rhs_, os);
+      *os << " ";
+      mono_tuple_matcher_.DescribeNegationTo(os);
+    }
+
+    bool MatchAndExplain(LhsContainer lhs,
+                         MatchResultListener* listener) const override {
+      LhsStlContainerReference lhs_stl_container = LhsView::ConstReference(lhs);
+      const size_t actual_size = lhs_stl_container.size();
+      if (actual_size != rhs_.size()) {
+        *listener << "which contains " << actual_size << " values";
+        return false;
+      }
+
+      auto left = lhs_stl_container.begin();
+      auto right = rhs_.begin();
+      for (size_t i = 0; i != actual_size; ++i, ++left, ++right) {
+        if (listener->IsInterested()) {
+          StringMatchResultListener inner_listener;
+          // Create InnerMatcherArg as a temporarily object to avoid it outlives
+          // *left and *right. Dereference or the conversion to `const T&` may
+          // return temp objects, e.g. for vector<bool>.
+          if (!mono_tuple_matcher_.MatchAndExplain(
+                  InnerMatcherArg(ImplicitCast_<const LhsValue&>(*left),
+                                  ImplicitCast_<const RhsValue&>(*right)),
+                  &inner_listener)) {
+            *listener << "where the value pair (";
+            UniversalPrint(*left, listener->stream());
+            *listener << ", ";
+            UniversalPrint(*right, listener->stream());
+            *listener << ") at index #" << i << " don't match";
+            PrintIfNotEmpty(inner_listener.str(), listener->stream());
+            return false;
+          }
+        } else {
+          if (!mono_tuple_matcher_.Matches(
+                  InnerMatcherArg(ImplicitCast_<const LhsValue&>(*left),
+                                  ImplicitCast_<const RhsValue&>(*right))))
+            return false;
+        }
+      }
+
+      return true;
+    }
+
+   private:
+    const Matcher<InnerMatcherArg> mono_tuple_matcher_;
+    const RhsStlContainer rhs_;
+  };
+
+ private:
+  const TupleMatcher tuple_matcher_;
+  const RhsStlContainer rhs_;
+};
+
+// Holds the logic common to ContainsMatcherImpl and EachMatcherImpl.
+template <typename Container>
+class QuantifierMatcherImpl : public MatcherInterface<Container> {
+ public:
+  typedef GTEST_REMOVE_REFERENCE_AND_CONST_(Container) RawContainer;
+  typedef StlContainerView<RawContainer> View;
+  typedef typename View::type StlContainer;
+  typedef typename View::const_reference StlContainerReference;
+  typedef typename StlContainer::value_type Element;
+
+  template <typename InnerMatcher>
+  explicit QuantifierMatcherImpl(InnerMatcher inner_matcher)
+      : inner_matcher_(
+            testing::SafeMatcherCast<const Element&>(inner_matcher)) {}
+
+  // Checks whether:
+  // * All elements in the container match, if all_elements_should_match.
+  // * Any element in the container matches, if !all_elements_should_match.
+  bool MatchAndExplainImpl(bool all_elements_should_match, Container container,
+                           MatchResultListener* listener) const {
+    StlContainerReference stl_container = View::ConstReference(container);
+    size_t i = 0;
+    for (auto it = stl_container.begin(); it != stl_container.end();
+         ++it, ++i) {
+      StringMatchResultListener inner_listener;
+      const bool matches = inner_matcher_.MatchAndExplain(*it, &inner_listener);
+
+      if (matches != all_elements_should_match) {
+        *listener << "whose element #" << i
+                  << (matches ? " matches" : " doesn't match");
+        PrintIfNotEmpty(inner_listener.str(), listener->stream());
+        return !all_elements_should_match;
+      }
+    }
+    return all_elements_should_match;
+  }
+
+  bool MatchAndExplainImpl(const Matcher<size_t>& count_matcher,
+                           Container container,
+                           MatchResultListener* listener) const {
+    StlContainerReference stl_container = View::ConstReference(container);
+    size_t i = 0;
+    std::vector<size_t> match_elements;
+    for (auto it = stl_container.begin(); it != stl_container.end();
+         ++it, ++i) {
+      StringMatchResultListener inner_listener;
+      const bool matches = inner_matcher_.MatchAndExplain(*it, &inner_listener);
+      if (matches) {
+        match_elements.push_back(i);
+      }
+    }
+    if (listener->IsInterested()) {
+      if (match_elements.empty()) {
+        *listener << "has no element that matches";
+      } else if (match_elements.size() == 1) {
+        *listener << "whose element #" << match_elements[0] << " matches";
+      } else {
+        *listener << "whose elements (";
+        std::string sep = "";
+        for (size_t e : match_elements) {
+          *listener << sep << e;
+          sep = ", ";
+        }
+        *listener << ") match";
+      }
+    }
+    StringMatchResultListener count_listener;
+    if (count_matcher.MatchAndExplain(match_elements.size(), &count_listener)) {
+      *listener << " and whose match quantity of " << match_elements.size()
+                << " matches";
+      PrintIfNotEmpty(count_listener.str(), listener->stream());
+      return true;
+    } else {
+      if (match_elements.empty()) {
+        *listener << " and";
+      } else {
+        *listener << " but";
+      }
+      *listener << " whose match quantity of " << match_elements.size()
+                << " does not match";
+      PrintIfNotEmpty(count_listener.str(), listener->stream());
+      return false;
+    }
+  }
+
+ protected:
+  const Matcher<const Element&> inner_matcher_;
+};
+
+// Implements Contains(element_matcher) for the given argument type Container.
+// Symmetric to EachMatcherImpl.
+template <typename Container>
+class ContainsMatcherImpl : public QuantifierMatcherImpl<Container> {
+ public:
+  template <typename InnerMatcher>
+  explicit ContainsMatcherImpl(InnerMatcher inner_matcher)
+      : QuantifierMatcherImpl<Container>(inner_matcher) {}
+
+  // Describes what this matcher does.
+  void DescribeTo(::std::ostream* os) const override {
+    *os << "contains at least one element that ";
+    this->inner_matcher_.DescribeTo(os);
+  }
+
+  void DescribeNegationTo(::std::ostream* os) const override {
+    *os << "doesn't contain any element that ";
+    this->inner_matcher_.DescribeTo(os);
+  }
+
+  bool MatchAndExplain(Container container,
+                       MatchResultListener* listener) const override {
+    return this->MatchAndExplainImpl(false, container, listener);
+  }
+};
+
+// Implements Each(element_matcher) for the given argument type Container.
+// Symmetric to ContainsMatcherImpl.
+template <typename Container>
+class EachMatcherImpl : public QuantifierMatcherImpl<Container> {
+ public:
+  template <typename InnerMatcher>
+  explicit EachMatcherImpl(InnerMatcher inner_matcher)
+      : QuantifierMatcherImpl<Container>(inner_matcher) {}
+
+  // Describes what this matcher does.
+  void DescribeTo(::std::ostream* os) const override {
+    *os << "only contains elements that ";
+    this->inner_matcher_.DescribeTo(os);
+  }
+
+  void DescribeNegationTo(::std::ostream* os) const override {
+    *os << "contains some element that ";
+    this->inner_matcher_.DescribeNegationTo(os);
+  }
+
+  bool MatchAndExplain(Container container,
+                       MatchResultListener* listener) const override {
+    return this->MatchAndExplainImpl(true, container, listener);
+  }
+};
+
+// Implements Contains(element_matcher).Times(n) for the given argument type
+// Container.
+template <typename Container>
+class ContainsTimesMatcherImpl : public QuantifierMatcherImpl<Container> {
+ public:
+  template <typename InnerMatcher>
+  explicit ContainsTimesMatcherImpl(InnerMatcher inner_matcher,
+                                    Matcher<size_t> count_matcher)
+      : QuantifierMatcherImpl<Container>(inner_matcher),
+        count_matcher_(std::move(count_matcher)) {}
+
+  void DescribeTo(::std::ostream* os) const override {
+    *os << "quantity of elements that match ";
+    this->inner_matcher_.DescribeTo(os);
+    *os << " ";
+    count_matcher_.DescribeTo(os);
+  }
+
+  void DescribeNegationTo(::std::ostream* os) const override {
+    *os << "quantity of elements that match ";
+    this->inner_matcher_.DescribeTo(os);
+    *os << " ";
+    count_matcher_.DescribeNegationTo(os);
+  }
+
+  bool MatchAndExplain(Container container,
+                       MatchResultListener* listener) const override {
+    return this->MatchAndExplainImpl(count_matcher_, container, listener);
+  }
+
+ private:
+  const Matcher<size_t> count_matcher_;
+};
+
+// Implements polymorphic Contains(element_matcher).Times(n).
+template <typename M>
+class ContainsTimesMatcher {
+ public:
+  explicit ContainsTimesMatcher(M m, Matcher<size_t> count_matcher)
+      : inner_matcher_(m), count_matcher_(std::move(count_matcher)) {}
+
+  template <typename Container>
+  operator Matcher<Container>() const {  // NOLINT
+    return Matcher<Container>(new ContainsTimesMatcherImpl<const Container&>(
+        inner_matcher_, count_matcher_));
+  }
+
+ private:
+  const M inner_matcher_;
+  const Matcher<size_t> count_matcher_;
+};
+
+// Implements polymorphic Contains(element_matcher).
+template <typename M>
+class ContainsMatcher {
+ public:
+  explicit ContainsMatcher(M m) : inner_matcher_(m) {}
+
+  template <typename Container>
+  operator Matcher<Container>() const {  // NOLINT
+    return Matcher<Container>(
+        new ContainsMatcherImpl<const Container&>(inner_matcher_));
+  }
+
+  ContainsTimesMatcher<M> Times(Matcher<size_t> count_matcher) const {
+    return ContainsTimesMatcher<M>(inner_matcher_, std::move(count_matcher));
+  }
+
+ private:
+  const M inner_matcher_;
+};
+
+// Implements polymorphic Each(element_matcher).
+template <typename M>
+class EachMatcher {
+ public:
+  explicit EachMatcher(M m) : inner_matcher_(m) {}
+
+  template <typename Container>
+  operator Matcher<Container>() const {  // NOLINT
+    return Matcher<Container>(
+        new EachMatcherImpl<const Container&>(inner_matcher_));
+  }
+
+ private:
+  const M inner_matcher_;
+};
+
+struct Rank1 {};
+struct Rank0 : Rank1 {};
+
+namespace pair_getters {
+using std::get;
+template <typename T>
+auto First(T& x, Rank1) -> decltype(get<0>(x)) {  // NOLINT
+  return get<0>(x);
+}
+template <typename T>
+auto First(T& x, Rank0) -> decltype((x.first)) {  // NOLINT
+  return x.first;
+}
+
+template <typename T>
+auto Second(T& x, Rank1) -> decltype(get<1>(x)) {  // NOLINT
+  return get<1>(x);
+}
+template <typename T>
+auto Second(T& x, Rank0) -> decltype((x.second)) {  // NOLINT
+  return x.second;
+}
+}  // namespace pair_getters
+
+// Implements Key(inner_matcher) for the given argument pair type.
+// Key(inner_matcher) matches an std::pair whose 'first' field matches
+// inner_matcher.  For example, Contains(Key(Ge(5))) can be used to match an
+// std::map that contains at least one element whose key is >= 5.
+template <typename PairType>
+class KeyMatcherImpl : public MatcherInterface<PairType> {
+ public:
+  typedef GTEST_REMOVE_REFERENCE_AND_CONST_(PairType) RawPairType;
+  typedef typename RawPairType::first_type KeyType;
+
+  template <typename InnerMatcher>
+  explicit KeyMatcherImpl(InnerMatcher inner_matcher)
+      : inner_matcher_(
+            testing::SafeMatcherCast<const KeyType&>(inner_matcher)) {}
+
+  // Returns true if and only if 'key_value.first' (the key) matches the inner
+  // matcher.
+  bool MatchAndExplain(PairType key_value,
+                       MatchResultListener* listener) const override {
+    StringMatchResultListener inner_listener;
+    const bool match = inner_matcher_.MatchAndExplain(
+        pair_getters::First(key_value, Rank0()), &inner_listener);
+    const std::string explanation = inner_listener.str();
+    if (!explanation.empty()) {
+      *listener << "whose first field is a value " << explanation;
+    }
+    return match;
+  }
+
+  // Describes what this matcher does.
+  void DescribeTo(::std::ostream* os) const override {
+    *os << "has a key that ";
+    inner_matcher_.DescribeTo(os);
+  }
+
+  // Describes what the negation of this matcher does.
+  void DescribeNegationTo(::std::ostream* os) const override {
+    *os << "doesn't have a key that ";
+    inner_matcher_.DescribeTo(os);
+  }
+
+ private:
+  const Matcher<const KeyType&> inner_matcher_;
+};
+
+// Implements polymorphic Key(matcher_for_key).
+template <typename M>
+class KeyMatcher {
+ public:
+  explicit KeyMatcher(M m) : matcher_for_key_(m) {}
+
+  template <typename PairType>
+  operator Matcher<PairType>() const {
+    return Matcher<PairType>(
+        new KeyMatcherImpl<const PairType&>(matcher_for_key_));
+  }
+
+ private:
+  const M matcher_for_key_;
+};
+
+// Implements polymorphic Address(matcher_for_address).
+template <typename InnerMatcher>
+class AddressMatcher {
+ public:
+  explicit AddressMatcher(InnerMatcher m) : matcher_(m) {}
+
+  template <typename Type>
+  operator Matcher<Type>() const {  // NOLINT
+    return Matcher<Type>(new Impl<const Type&>(matcher_));
+  }
+
+ private:
+  // The monomorphic implementation that works for a particular object type.
+  template <typename Type>
+  class Impl : public MatcherInterface<Type> {
+   public:
+    using Address = const GTEST_REMOVE_REFERENCE_AND_CONST_(Type) *;
+    explicit Impl(const InnerMatcher& matcher)
+        : matcher_(MatcherCast<Address>(matcher)) {}
+
+    void DescribeTo(::std::ostream* os) const override {
+      *os << "has address that ";
+      matcher_.DescribeTo(os);
+    }
+
+    void DescribeNegationTo(::std::ostream* os) const override {
+      *os << "does not have address that ";
+      matcher_.DescribeTo(os);
+    }
+
+    bool MatchAndExplain(Type object,
+                         MatchResultListener* listener) const override {
+      *listener << "which has address ";
+      Address address = std::addressof(object);
+      return MatchPrintAndExplain(address, matcher_, listener);
+    }
+
+   private:
+    const Matcher<Address> matcher_;
+  };
+  const InnerMatcher matcher_;
+};
+
+// Implements Pair(first_matcher, second_matcher) for the given argument pair
+// type with its two matchers. See Pair() function below.
+template <typename PairType>
+class PairMatcherImpl : public MatcherInterface<PairType> {
+ public:
+  typedef GTEST_REMOVE_REFERENCE_AND_CONST_(PairType) RawPairType;
+  typedef typename RawPairType::first_type FirstType;
+  typedef typename RawPairType::second_type SecondType;
+
+  template <typename FirstMatcher, typename SecondMatcher>
+  PairMatcherImpl(FirstMatcher first_matcher, SecondMatcher second_matcher)
+      : first_matcher_(
+            testing::SafeMatcherCast<const FirstType&>(first_matcher)),
+        second_matcher_(
+            testing::SafeMatcherCast<const SecondType&>(second_matcher)) {}
+
+  // Describes what this matcher does.
+  void DescribeTo(::std::ostream* os) const override {
+    *os << "has a first field that ";
+    first_matcher_.DescribeTo(os);
+    *os << ", and has a second field that ";
+    second_matcher_.DescribeTo(os);
+  }
+
+  // Describes what the negation of this matcher does.
+  void DescribeNegationTo(::std::ostream* os) const override {
+    *os << "has a first field that ";
+    first_matcher_.DescribeNegationTo(os);
+    *os << ", or has a second field that ";
+    second_matcher_.DescribeNegationTo(os);
+  }
+
+  // Returns true if and only if 'a_pair.first' matches first_matcher and
+  // 'a_pair.second' matches second_matcher.
+  bool MatchAndExplain(PairType a_pair,
+                       MatchResultListener* listener) const override {
+    if (!listener->IsInterested()) {
+      // If the listener is not interested, we don't need to construct the
+      // explanation.
+      return first_matcher_.Matches(pair_getters::First(a_pair, Rank0())) &&
+             second_matcher_.Matches(pair_getters::Second(a_pair, Rank0()));
+    }
+    StringMatchResultListener first_inner_listener;
+    if (!first_matcher_.MatchAndExplain(pair_getters::First(a_pair, Rank0()),
+                                        &first_inner_listener)) {
+      *listener << "whose first field does not match";
+      PrintIfNotEmpty(first_inner_listener.str(), listener->stream());
+      return false;
+    }
+    StringMatchResultListener second_inner_listener;
+    if (!second_matcher_.MatchAndExplain(pair_getters::Second(a_pair, Rank0()),
+                                         &second_inner_listener)) {
+      *listener << "whose second field does not match";
+      PrintIfNotEmpty(second_inner_listener.str(), listener->stream());
+      return false;
+    }
+    ExplainSuccess(first_inner_listener.str(), second_inner_listener.str(),
+                   listener);
+    return true;
+  }
+
+ private:
+  void ExplainSuccess(const std::string& first_explanation,
+                      const std::string& second_explanation,
+                      MatchResultListener* listener) const {
+    *listener << "whose both fields match";
+    if (!first_explanation.empty()) {
+      *listener << ", where the first field is a value " << first_explanation;
+    }
+    if (!second_explanation.empty()) {
+      *listener << ", ";
+      if (!first_explanation.empty()) {
+        *listener << "and ";
+      } else {
+        *listener << "where ";
+      }
+      *listener << "the second field is a value " << second_explanation;
+    }
+  }
+
+  const Matcher<const FirstType&> first_matcher_;
+  const Matcher<const SecondType&> second_matcher_;
+};
+
+// Implements polymorphic Pair(first_matcher, second_matcher).
+template <typename FirstMatcher, typename SecondMatcher>
+class PairMatcher {
+ public:
+  PairMatcher(FirstMatcher first_matcher, SecondMatcher second_matcher)
+      : first_matcher_(first_matcher), second_matcher_(second_matcher) {}
+
+  template <typename PairType>
+  operator Matcher<PairType>() const {
+    return Matcher<PairType>(
+        new PairMatcherImpl<const PairType&>(first_matcher_, second_matcher_));
+  }
+
+ private:
+  const FirstMatcher first_matcher_;
+  const SecondMatcher second_matcher_;
+};
+
+template <typename T, size_t... I>
+auto UnpackStructImpl(const T& t, IndexSequence<I...>, int)
+    -> decltype(std::tie(get<I>(t)...)) {
+  static_assert(std::tuple_size<T>::value == sizeof...(I),
+                "Number of arguments doesn't match the number of fields.");
+  return std::tie(get<I>(t)...);
+}
+
+#if defined(__cpp_structured_bindings) && __cpp_structured_bindings >= 201606
+template <typename T>
+auto UnpackStructImpl(const T& t, MakeIndexSequence<1>, char) {
+  const auto& [a] = t;
+  return std::tie(a);
+}
+template <typename T>
+auto UnpackStructImpl(const T& t, MakeIndexSequence<2>, char) {
+  const auto& [a, b] = t;
+  return std::tie(a, b);
+}
+template <typename T>
+auto UnpackStructImpl(const T& t, MakeIndexSequence<3>, char) {
+  const auto& [a, b, c] = t;
+  return std::tie(a, b, c);
+}
+template <typename T>
+auto UnpackStructImpl(const T& t, MakeIndexSequence<4>, char) {
+  const auto& [a, b, c, d] = t;
+  return std::tie(a, b, c, d);
+}
+template <typename T>
+auto UnpackStructImpl(const T& t, MakeIndexSequence<5>, char) {
+  const auto& [a, b, c, d, e] = t;
+  return std::tie(a, b, c, d, e);
+}
+template <typename T>
+auto UnpackStructImpl(const T& t, MakeIndexSequence<6>, char) {
+  const auto& [a, b, c, d, e, f] = t;
+  return std::tie(a, b, c, d, e, f);
+}
+template <typename T>
+auto UnpackStructImpl(const T& t, MakeIndexSequence<7>, char) {
+  const auto& [a, b, c, d, e, f, g] = t;
+  return std::tie(a, b, c, d, e, f, g);
+}
+template <typename T>
+auto UnpackStructImpl(const T& t, MakeIndexSequence<8>, char) {
+  const auto& [a, b, c, d, e, f, g, h] = t;
+  return std::tie(a, b, c, d, e, f, g, h);
+}
+template <typename T>
+auto UnpackStructImpl(const T& t, MakeIndexSequence<9>, char) {
+  const auto& [a, b, c, d, e, f, g, h, i] = t;
+  return std::tie(a, b, c, d, e, f, g, h, i);
+}
+template <typename T>
+auto UnpackStructImpl(const T& t, MakeIndexSequence<10>, char) {
+  const auto& [a, b, c, d, e, f, g, h, i, j] = t;
+  return std::tie(a, b, c, d, e, f, g, h, i, j);
+}
+template <typename T>
+auto UnpackStructImpl(const T& t, MakeIndexSequence<11>, char) {
+  const auto& [a, b, c, d, e, f, g, h, i, j, k] = t;
+  return std::tie(a, b, c, d, e, f, g, h, i, j, k);
+}
+template <typename T>
+auto UnpackStructImpl(const T& t, MakeIndexSequence<12>, char) {
+  const auto& [a, b, c, d, e, f, g, h, i, j, k, l] = t;
+  return std::tie(a, b, c, d, e, f, g, h, i, j, k, l);
+}
+template <typename T>
+auto UnpackStructImpl(const T& t, MakeIndexSequence<13>, char) {
+  const auto& [a, b, c, d, e, f, g, h, i, j, k, l, m] = t;
+  return std::tie(a, b, c, d, e, f, g, h, i, j, k, l, m);
+}
+template <typename T>
+auto UnpackStructImpl(const T& t, MakeIndexSequence<14>, char) {
+  const auto& [a, b, c, d, e, f, g, h, i, j, k, l, m, n] = t;
+  return std::tie(a, b, c, d, e, f, g, h, i, j, k, l, m, n);
+}
+template <typename T>
+auto UnpackStructImpl(const T& t, MakeIndexSequence<15>, char) {
+  const auto& [a, b, c, d, e, f, g, h, i, j, k, l, m, n, o] = t;
+  return std::tie(a, b, c, d, e, f, g, h, i, j, k, l, m, n, o);
+}
+template <typename T>
+auto UnpackStructImpl(const T& t, MakeIndexSequence<16>, char) {
+  const auto& [a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p] = t;
+  return std::tie(a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p);
+}
+template <typename T>
+auto UnpackStructImpl(const T& t, MakeIndexSequence<17>, char) {
+  const auto& [a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p, q] = t;
+  return std::tie(a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p, q);
+}
+template <typename T>
+auto UnpackStructImpl(const T& t, MakeIndexSequence<18>, char) {
+  const auto& [a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p, q, r] = t;
+  return std::tie(a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p, q, r);
+}
+template <typename T>
+auto UnpackStructImpl(const T& t, MakeIndexSequence<19>, char) {
+  const auto& [a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p, q, r, s] = t;
+  return std::tie(a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p, q, r, s);
+}
+#endif  // defined(__cpp_structured_bindings)
+
+template <size_t I, typename T>
+auto UnpackStruct(const T& t)
+    -> decltype((UnpackStructImpl)(t, MakeIndexSequence<I>{}, 0)) {
+  return (UnpackStructImpl)(t, MakeIndexSequence<I>{}, 0);
+}
+
+// Helper function to do comma folding in C++11.
+// The array ensures left-to-right order of evaluation.
+// Usage: VariadicExpand({expr...});
+template <typename T, size_t N>
+void VariadicExpand(const T (&)[N]) {}
+
+template <typename Struct, typename StructSize>
+class FieldsAreMatcherImpl;
+
+template <typename Struct, size_t... I>
+class FieldsAreMatcherImpl<Struct, IndexSequence<I...>>
+    : public MatcherInterface<Struct> {
+  using UnpackedType =
+      decltype(UnpackStruct<sizeof...(I)>(std::declval<const Struct&>()));
+  using MatchersType = std::tuple<
+      Matcher<const typename std::tuple_element<I, UnpackedType>::type&>...>;
+
+ public:
+  template <typename Inner>
+  explicit FieldsAreMatcherImpl(const Inner& matchers)
+      : matchers_(testing::SafeMatcherCast<
+                  const typename std::tuple_element<I, UnpackedType>::type&>(
+            std::get<I>(matchers))...) {}
+
+  void DescribeTo(::std::ostream* os) const override {
+    const char* separator = "";
+    VariadicExpand(
+        {(*os << separator << "has field #" << I << " that ",
+          std::get<I>(matchers_).DescribeTo(os), separator = ", and ")...});
+  }
+
+  void DescribeNegationTo(::std::ostream* os) const override {
+    const char* separator = "";
+    VariadicExpand({(*os << separator << "has field #" << I << " that ",
+                     std::get<I>(matchers_).DescribeNegationTo(os),
+                     separator = ", or ")...});
+  }
+
+  bool MatchAndExplain(Struct t, MatchResultListener* listener) const override {
+    return MatchInternal((UnpackStruct<sizeof...(I)>)(t), listener);
+  }
+
+ private:
+  bool MatchInternal(UnpackedType tuple, MatchResultListener* listener) const {
+    if (!listener->IsInterested()) {
+      // If the listener is not interested, we don't need to construct the
+      // explanation.
+      bool good = true;
+      VariadicExpand({good = good && std::get<I>(matchers_).Matches(
+                                         std::get<I>(tuple))...});
+      return good;
+    }
+
+    size_t failed_pos = ~size_t{};
+
+    std::vector<StringMatchResultListener> inner_listener(sizeof...(I));
+
+    VariadicExpand(
+        {failed_pos == ~size_t{} && !std::get<I>(matchers_).MatchAndExplain(
+                                        std::get<I>(tuple), &inner_listener[I])
+             ? failed_pos = I
+             : 0 ...});
+    if (failed_pos != ~size_t{}) {
+      *listener << "whose field #" << failed_pos << " does not match";
+      PrintIfNotEmpty(inner_listener[failed_pos].str(), listener->stream());
+      return false;
+    }
+
+    *listener << "whose all elements match";
+    const char* separator = ", where";
+    for (size_t index = 0; index < sizeof...(I); ++index) {
+      const std::string str = inner_listener[index].str();
+      if (!str.empty()) {
+        *listener << separator << " field #" << index << " is a value " << str;
+        separator = ", and";
+      }
+    }
+
+    return true;
+  }
+
+  MatchersType matchers_;
+};
+
+template <typename... Inner>
+class FieldsAreMatcher {
+ public:
+  explicit FieldsAreMatcher(Inner... inner) : matchers_(std::move(inner)...) {}
+
+  template <typename Struct>
+  operator Matcher<Struct>() const {  // NOLINT
+    return Matcher<Struct>(
+        new FieldsAreMatcherImpl<const Struct&, IndexSequenceFor<Inner...>>(
+            matchers_));
+  }
+
+ private:
+  std::tuple<Inner...> matchers_;
+};
+
+// Implements ElementsAre() and ElementsAreArray().
+template <typename Container>
+class ElementsAreMatcherImpl : public MatcherInterface<Container> {
+ public:
+  typedef GTEST_REMOVE_REFERENCE_AND_CONST_(Container) RawContainer;
+  typedef internal::StlContainerView<RawContainer> View;
+  typedef typename View::type StlContainer;
+  typedef typename View::const_reference StlContainerReference;
+  typedef typename StlContainer::value_type Element;
+
+  // Constructs the matcher from a sequence of element values or
+  // element matchers.
+  template <typename InputIter>
+  ElementsAreMatcherImpl(InputIter first, InputIter last) {
+    while (first != last) {
+      matchers_.push_back(MatcherCast<const Element&>(*first++));
+    }
+  }
+
+  // Describes what this matcher does.
+  void DescribeTo(::std::ostream* os) const override {
+    if (count() == 0) {
+      *os << "is empty";
+    } else if (count() == 1) {
+      *os << "has 1 element that ";
+      matchers_[0].DescribeTo(os);
+    } else {
+      *os << "has " << Elements(count()) << " where\n";
+      for (size_t i = 0; i != count(); ++i) {
+        *os << "element #" << i << " ";
+        matchers_[i].DescribeTo(os);
+        if (i + 1 < count()) {
+          *os << ",\n";
+        }
+      }
+    }
+  }
+
+  // Describes what the negation of this matcher does.
+  void DescribeNegationTo(::std::ostream* os) const override {
+    if (count() == 0) {
+      *os << "isn't empty";
+      return;
+    }
+
+    *os << "doesn't have " << Elements(count()) << ", or\n";
+    for (size_t i = 0; i != count(); ++i) {
+      *os << "element #" << i << " ";
+      matchers_[i].DescribeNegationTo(os);
+      if (i + 1 < count()) {
+        *os << ", or\n";
+      }
+    }
+  }
+
+  bool MatchAndExplain(Container container,
+                       MatchResultListener* listener) const override {
+    // To work with stream-like "containers", we must only walk
+    // through the elements in one pass.
+
+    const bool listener_interested = listener->IsInterested();
+
+    // explanations[i] is the explanation of the element at index i.
+    ::std::vector<std::string> explanations(count());
+    StlContainerReference stl_container = View::ConstReference(container);
+    auto it = stl_container.begin();
+    size_t exam_pos = 0;
+    bool mismatch_found = false;  // Have we found a mismatched element yet?
+
+    // Go through the elements and matchers in pairs, until we reach
+    // the end of either the elements or the matchers, or until we find a
+    // mismatch.
+    for (; it != stl_container.end() && exam_pos != count(); ++it, ++exam_pos) {
+      bool match;  // Does the current element match the current matcher?
+      if (listener_interested) {
+        StringMatchResultListener s;
+        match = matchers_[exam_pos].MatchAndExplain(*it, &s);
+        explanations[exam_pos] = s.str();
+      } else {
+        match = matchers_[exam_pos].Matches(*it);
+      }
+
+      if (!match) {
+        mismatch_found = true;
+        break;
+      }
+    }
+    // If mismatch_found is true, 'exam_pos' is the index of the mismatch.
+
+    // Find how many elements the actual container has.  We avoid
+    // calling size() s.t. this code works for stream-like "containers"
+    // that don't define size().
+    size_t actual_count = exam_pos;
+    for (; it != stl_container.end(); ++it) {
+      ++actual_count;
+    }
+
+    if (actual_count != count()) {
+      // The element count doesn't match.  If the container is empty,
+      // there's no need to explain anything as Google Mock already
+      // prints the empty container.  Otherwise we just need to show
+      // how many elements there actually are.
+      if (listener_interested && (actual_count != 0)) {
+        *listener << "which has " << Elements(actual_count);
+      }
+      return false;
+    }
+
+    if (mismatch_found) {
+      // The element count matches, but the exam_pos-th element doesn't match.
+      if (listener_interested) {
+        *listener << "whose element #" << exam_pos << " doesn't match";
+        PrintIfNotEmpty(explanations[exam_pos], listener->stream());
+      }
+      return false;
+    }
+
+    // Every element matches its expectation.  We need to explain why
+    // (the obvious ones can be skipped).
+    if (listener_interested) {
+      bool reason_printed = false;
+      for (size_t i = 0; i != count(); ++i) {
+        const std::string& s = explanations[i];
+        if (!s.empty()) {
+          if (reason_printed) {
+            *listener << ",\nand ";
+          }
+          *listener << "whose element #" << i << " matches, " << s;
+          reason_printed = true;
+        }
+      }
+    }
+    return true;
+  }
+
+ private:
+  static Message Elements(size_t count) {
+    return Message() << count << (count == 1 ? " element" : " elements");
+  }
+
+  size_t count() const { return matchers_.size(); }
+
+  ::std::vector<Matcher<const Element&>> matchers_;
+};
+
+// Connectivity matrix of (elements X matchers), in element-major order.
+// Initially, there are no edges.
+// Use NextGraph() to iterate over all possible edge configurations.
+// Use Randomize() to generate a random edge configuration.
+class GTEST_API_ MatchMatrix {
+ public:
+  MatchMatrix(size_t num_elements, size_t num_matchers)
+      : num_elements_(num_elements),
+        num_matchers_(num_matchers),
+        matched_(num_elements_ * num_matchers_, 0) {}
+
+  size_t LhsSize() const { return num_elements_; }
+  size_t RhsSize() const { return num_matchers_; }
+  bool HasEdge(size_t ilhs, size_t irhs) const {
+    return matched_[SpaceIndex(ilhs, irhs)] == 1;
+  }
+  void SetEdge(size_t ilhs, size_t irhs, bool b) {
+    matched_[SpaceIndex(ilhs, irhs)] = b ? 1 : 0;
+  }
+
+  // Treating the connectivity matrix as a (LhsSize()*RhsSize())-bit number,
+  // adds 1 to that number; returns false if incrementing the graph left it
+  // empty.
+  bool NextGraph();
+
+  void Randomize();
+
+  std::string DebugString() const;
+
+ private:
+  size_t SpaceIndex(size_t ilhs, size_t irhs) const {
+    return ilhs * num_matchers_ + irhs;
+  }
+
+  size_t num_elements_;
+  size_t num_matchers_;
+
+  // Each element is a char interpreted as bool. They are stored as a
+  // flattened array in lhs-major order, use 'SpaceIndex()' to translate
+  // a (ilhs, irhs) matrix coordinate into an offset.
+  ::std::vector<char> matched_;
+};
+
+typedef ::std::pair<size_t, size_t> ElementMatcherPair;
+typedef ::std::vector<ElementMatcherPair> ElementMatcherPairs;
+
+// Returns a maximum bipartite matching for the specified graph 'g'.
+// The matching is represented as a vector of {element, matcher} pairs.
+GTEST_API_ ElementMatcherPairs FindMaxBipartiteMatching(const MatchMatrix& g);
+
+struct UnorderedMatcherRequire {
+  enum Flags {
+    Superset = 1 << 0,
+    Subset = 1 << 1,
+    ExactMatch = Superset | Subset,
+  };
+};
+
+// Untyped base class for implementing UnorderedElementsAre.  By
+// putting logic that's not specific to the element type here, we
+// reduce binary bloat and increase compilation speed.
+class GTEST_API_ UnorderedElementsAreMatcherImplBase {
+ protected:
+  explicit UnorderedElementsAreMatcherImplBase(
+      UnorderedMatcherRequire::Flags matcher_flags)
+      : match_flags_(matcher_flags) {}
+
+  // A vector of matcher describers, one for each element matcher.
+  // Does not own the describers (and thus can be used only when the
+  // element matchers are alive).
+  typedef ::std::vector<const MatcherDescriberInterface*> MatcherDescriberVec;
+
+  // Describes this UnorderedElementsAre matcher.
+  void DescribeToImpl(::std::ostream* os) const;
+
+  // Describes the negation of this UnorderedElementsAre matcher.
+  void DescribeNegationToImpl(::std::ostream* os) const;
+
+  bool VerifyMatchMatrix(const ::std::vector<std::string>& element_printouts,
+                         const MatchMatrix& matrix,
+                         MatchResultListener* listener) const;
+
+  bool FindPairing(const MatchMatrix& matrix,
+                   MatchResultListener* listener) const;
+
+  MatcherDescriberVec& matcher_describers() { return matcher_describers_; }
+
+  static Message Elements(size_t n) {
+    return Message() << n << " element" << (n == 1 ? "" : "s");
+  }
+
+  UnorderedMatcherRequire::Flags match_flags() const { return match_flags_; }
+
+ private:
+  UnorderedMatcherRequire::Flags match_flags_;
+  MatcherDescriberVec matcher_describers_;
+};
+
+// Implements UnorderedElementsAre, UnorderedElementsAreArray, IsSubsetOf, and
+// IsSupersetOf.
+template <typename Container>
+class UnorderedElementsAreMatcherImpl
+    : public MatcherInterface<Container>,
+      public UnorderedElementsAreMatcherImplBase {
+ public:
+  typedef GTEST_REMOVE_REFERENCE_AND_CONST_(Container) RawContainer;
+  typedef internal::StlContainerView<RawContainer> View;
+  typedef typename View::type StlContainer;
+  typedef typename View::const_reference StlContainerReference;
+  typedef typename StlContainer::value_type Element;
+
+  template <typename InputIter>
+  UnorderedElementsAreMatcherImpl(UnorderedMatcherRequire::Flags matcher_flags,
+                                  InputIter first, InputIter last)
+      : UnorderedElementsAreMatcherImplBase(matcher_flags) {
+    for (; first != last; ++first) {
+      matchers_.push_back(MatcherCast<const Element&>(*first));
+    }
+    for (const auto& m : matchers_) {
+      matcher_describers().push_back(m.GetDescriber());
+    }
+  }
+
+  // Describes what this matcher does.
+  void DescribeTo(::std::ostream* os) const override {
+    return UnorderedElementsAreMatcherImplBase::DescribeToImpl(os);
+  }
+
+  // Describes what the negation of this matcher does.
+  void DescribeNegationTo(::std::ostream* os) const override {
+    return UnorderedElementsAreMatcherImplBase::DescribeNegationToImpl(os);
+  }
+
+  bool MatchAndExplain(Container container,
+                       MatchResultListener* listener) const override {
+    StlContainerReference stl_container = View::ConstReference(container);
+    ::std::vector<std::string> element_printouts;
+    MatchMatrix matrix =
+        AnalyzeElements(stl_container.begin(), stl_container.end(),
+                        &element_printouts, listener);
+
+    return VerifyMatchMatrix(element_printouts, matrix, listener) &&
+           FindPairing(matrix, listener);
+  }
+
+ private:
+  template <typename ElementIter>
+  MatchMatrix AnalyzeElements(ElementIter elem_first, ElementIter elem_last,
+                              ::std::vector<std::string>* element_printouts,
+                              MatchResultListener* listener) const {
+    element_printouts->clear();
+    ::std::vector<char> did_match;
+    size_t num_elements = 0;
+    DummyMatchResultListener dummy;
+    for (; elem_first != elem_last; ++num_elements, ++elem_first) {
+      if (listener->IsInterested()) {
+        element_printouts->push_back(PrintToString(*elem_first));
+      }
+      for (size_t irhs = 0; irhs != matchers_.size(); ++irhs) {
+        did_match.push_back(
+            matchers_[irhs].MatchAndExplain(*elem_first, &dummy));
+      }
+    }
+
+    MatchMatrix matrix(num_elements, matchers_.size());
+    ::std::vector<char>::const_iterator did_match_iter = did_match.begin();
+    for (size_t ilhs = 0; ilhs != num_elements; ++ilhs) {
+      for (size_t irhs = 0; irhs != matchers_.size(); ++irhs) {
+        matrix.SetEdge(ilhs, irhs, *did_match_iter++ != 0);
+      }
+    }
+    return matrix;
+  }
+
+  ::std::vector<Matcher<const Element&>> matchers_;
+};
+
+// Functor for use in TransformTuple.
+// Performs MatcherCast<Target> on an input argument of any type.
+template <typename Target>
+struct CastAndAppendTransform {
+  template <typename Arg>
+  Matcher<Target> operator()(const Arg& a) const {
+    return MatcherCast<Target>(a);
+  }
+};
+
+// Implements UnorderedElementsAre.
+template <typename MatcherTuple>
+class UnorderedElementsAreMatcher {
+ public:
+  explicit UnorderedElementsAreMatcher(const MatcherTuple& args)
+      : matchers_(args) {}
+
+  template <typename Container>
+  operator Matcher<Container>() const {
+    typedef GTEST_REMOVE_REFERENCE_AND_CONST_(Container) RawContainer;
+    typedef typename internal::StlContainerView<RawContainer>::type View;
+    typedef typename View::value_type Element;
+    typedef ::std::vector<Matcher<const Element&>> MatcherVec;
+    MatcherVec matchers;
+    matchers.reserve(::std::tuple_size<MatcherTuple>::value);
+    TransformTupleValues(CastAndAppendTransform<const Element&>(), matchers_,
+                         ::std::back_inserter(matchers));
+    return Matcher<Container>(
+        new UnorderedElementsAreMatcherImpl<const Container&>(
+            UnorderedMatcherRequire::ExactMatch, matchers.begin(),
+            matchers.end()));
+  }
+
+ private:
+  const MatcherTuple matchers_;
+};
+
+// Implements ElementsAre.
+template <typename MatcherTuple>
+class ElementsAreMatcher {
+ public:
+  explicit ElementsAreMatcher(const MatcherTuple& args) : matchers_(args) {}
+
+  template <typename Container>
+  operator Matcher<Container>() const {
+    static_assert(
+        !IsHashTable<GTEST_REMOVE_REFERENCE_AND_CONST_(Container)>::value ||
+            ::std::tuple_size<MatcherTuple>::value < 2,
+        "use UnorderedElementsAre with hash tables");
+
+    typedef GTEST_REMOVE_REFERENCE_AND_CONST_(Container) RawContainer;
+    typedef typename internal::StlContainerView<RawContainer>::type View;
+    typedef typename View::value_type Element;
+    typedef ::std::vector<Matcher<const Element&>> MatcherVec;
+    MatcherVec matchers;
+    matchers.reserve(::std::tuple_size<MatcherTuple>::value);
+    TransformTupleValues(CastAndAppendTransform<const Element&>(), matchers_,
+                         ::std::back_inserter(matchers));
+    return Matcher<Container>(new ElementsAreMatcherImpl<const Container&>(
+        matchers.begin(), matchers.end()));
+  }
+
+ private:
+  const MatcherTuple matchers_;
+};
+
+// Implements UnorderedElementsAreArray(), IsSubsetOf(), and IsSupersetOf().
+template <typename T>
+class UnorderedElementsAreArrayMatcher {
+ public:
+  template <typename Iter>
+  UnorderedElementsAreArrayMatcher(UnorderedMatcherRequire::Flags match_flags,
+                                   Iter first, Iter last)
+      : match_flags_(match_flags), matchers_(first, last) {}
+
+  template <typename Container>
+  operator Matcher<Container>() const {
+    return Matcher<Container>(
+        new UnorderedElementsAreMatcherImpl<const Container&>(
+            match_flags_, matchers_.begin(), matchers_.end()));
+  }
+
+ private:
+  UnorderedMatcherRequire::Flags match_flags_;
+  ::std::vector<T> matchers_;
+};
+
+// Implements ElementsAreArray().
+template <typename T>
+class ElementsAreArrayMatcher {
+ public:
+  template <typename Iter>
+  ElementsAreArrayMatcher(Iter first, Iter last) : matchers_(first, last) {}
+
+  template <typename Container>
+  operator Matcher<Container>() const {
+    static_assert(
+        !IsHashTable<GTEST_REMOVE_REFERENCE_AND_CONST_(Container)>::value,
+        "use UnorderedElementsAreArray with hash tables");
+
+    return Matcher<Container>(new ElementsAreMatcherImpl<const Container&>(
+        matchers_.begin(), matchers_.end()));
+  }
+
+ private:
+  const ::std::vector<T> matchers_;
+};
+
+// Given a 2-tuple matcher tm of type Tuple2Matcher and a value second
+// of type Second, BoundSecondMatcher<Tuple2Matcher, Second>(tm,
+// second) is a polymorphic matcher that matches a value x if and only if
+// tm matches tuple (x, second).  Useful for implementing
+// UnorderedPointwise() in terms of UnorderedElementsAreArray().
+//
+// BoundSecondMatcher is copyable and assignable, as we need to put
+// instances of this class in a vector when implementing
+// UnorderedPointwise().
+template <typename Tuple2Matcher, typename Second>
+class BoundSecondMatcher {
+ public:
+  BoundSecondMatcher(const Tuple2Matcher& tm, const Second& second)
+      : tuple2_matcher_(tm), second_value_(second) {}
+
+  BoundSecondMatcher(const BoundSecondMatcher& other) = default;
+
+  template <typename T>
+  operator Matcher<T>() const {
+    return MakeMatcher(new Impl<T>(tuple2_matcher_, second_value_));
+  }
+
+  // We have to define this for UnorderedPointwise() to compile in
+  // C++98 mode, as it puts BoundSecondMatcher instances in a vector,
+  // which requires the elements to be assignable in C++98.  The
+  // compiler cannot generate the operator= for us, as Tuple2Matcher
+  // and Second may not be assignable.
+  //
+  // However, this should never be called, so the implementation just
+  // need to assert.
+  void operator=(const BoundSecondMatcher& /*rhs*/) {
+    GTEST_LOG_(FATAL) << "BoundSecondMatcher should never be assigned.";
+  }
+
+ private:
+  template <typename T>
+  class Impl : public MatcherInterface<T> {
+   public:
+    typedef ::std::tuple<T, Second> ArgTuple;
+
+    Impl(const Tuple2Matcher& tm, const Second& second)
+        : mono_tuple2_matcher_(SafeMatcherCast<const ArgTuple&>(tm)),
+          second_value_(second) {}
+
+    void DescribeTo(::std::ostream* os) const override {
+      *os << "and ";
+      UniversalPrint(second_value_, os);
+      *os << " ";
+      mono_tuple2_matcher_.DescribeTo(os);
+    }
+
+    bool MatchAndExplain(T x, MatchResultListener* listener) const override {
+      return mono_tuple2_matcher_.MatchAndExplain(ArgTuple(x, second_value_),
+                                                  listener);
+    }
+
+   private:
+    const Matcher<const ArgTuple&> mono_tuple2_matcher_;
+    const Second second_value_;
+  };
+
+  const Tuple2Matcher tuple2_matcher_;
+  const Second second_value_;
+};
+
+// Given a 2-tuple matcher tm and a value second,
+// MatcherBindSecond(tm, second) returns a matcher that matches a
+// value x if and only if tm matches tuple (x, second).  Useful for
+// implementing UnorderedPointwise() in terms of UnorderedElementsAreArray().
+template <typename Tuple2Matcher, typename Second>
+BoundSecondMatcher<Tuple2Matcher, Second> MatcherBindSecond(
+    const Tuple2Matcher& tm, const Second& second) {
+  return BoundSecondMatcher<Tuple2Matcher, Second>(tm, second);
+}
+
+// Returns the description for a matcher defined using the MATCHER*()
+// macro where the user-supplied description string is "", if
+// 'negation' is false; otherwise returns the description of the
+// negation of the matcher.  'param_values' contains a list of strings
+// that are the print-out of the matcher's parameters.
+GTEST_API_ std::string FormatMatcherDescription(
+    bool negation, const char* matcher_name,
+    const std::vector<const char*>& param_names, const Strings& param_values);
+
+// Implements a matcher that checks the value of a optional<> type variable.
+template <typename ValueMatcher>
+class OptionalMatcher {
+ public:
+  explicit OptionalMatcher(const ValueMatcher& value_matcher)
+      : value_matcher_(value_matcher) {}
+
+  template <typename Optional>
+  operator Matcher<Optional>() const {
+    return Matcher<Optional>(new Impl<const Optional&>(value_matcher_));
+  }
+
+  template <typename Optional>
+  class Impl : public MatcherInterface<Optional> {
+   public:
+    typedef GTEST_REMOVE_REFERENCE_AND_CONST_(Optional) OptionalView;
+    typedef typename OptionalView::value_type ValueType;
+    explicit Impl(const ValueMatcher& value_matcher)
+        : value_matcher_(MatcherCast<ValueType>(value_matcher)) {}
+
+    void DescribeTo(::std::ostream* os) const override {
+      *os << "value ";
+      value_matcher_.DescribeTo(os);
+    }
+
+    void DescribeNegationTo(::std::ostream* os) const override {
+      *os << "value ";
+      value_matcher_.DescribeNegationTo(os);
+    }
+
+    bool MatchAndExplain(Optional optional,
+                         MatchResultListener* listener) const override {
+      if (!optional) {
+        *listener << "which is not engaged";
+        return false;
+      }
+      const ValueType& value = *optional;
+      StringMatchResultListener value_listener;
+      const bool match = value_matcher_.MatchAndExplain(value, &value_listener);
+      *listener << "whose value " << PrintToString(value)
+                << (match ? " matches" : " doesn't match");
+      PrintIfNotEmpty(value_listener.str(), listener->stream());
+      return match;
+    }
+
+   private:
+    const Matcher<ValueType> value_matcher_;
+  };
+
+ private:
+  const ValueMatcher value_matcher_;
+};
+
+namespace variant_matcher {
+// Overloads to allow VariantMatcher to do proper ADL lookup.
+template <typename T>
+void holds_alternative() {}
+template <typename T>
+void get() {}
+
+// Implements a matcher that checks the value of a variant<> type variable.
+template <typename T>
+class VariantMatcher {
+ public:
+  explicit VariantMatcher(::testing::Matcher<const T&> matcher)
+      : matcher_(std::move(matcher)) {}
+
+  template <typename Variant>
+  bool MatchAndExplain(const Variant& value,
+                       ::testing::MatchResultListener* listener) const {
+    using std::get;
+    if (!listener->IsInterested()) {
+      return holds_alternative<T>(value) && matcher_.Matches(get<T>(value));
+    }
+
+    if (!holds_alternative<T>(value)) {
+      *listener << "whose value is not of type '" << GetTypeName() << "'";
+      return false;
+    }
+
+    const T& elem = get<T>(value);
+    StringMatchResultListener elem_listener;
+    const bool match = matcher_.MatchAndExplain(elem, &elem_listener);
+    *listener << "whose value " << PrintToString(elem)
+              << (match ? " matches" : " doesn't match");
+    PrintIfNotEmpty(elem_listener.str(), listener->stream());
+    return match;
+  }
+
+  void DescribeTo(std::ostream* os) const {
+    *os << "is a variant<> with value of type '" << GetTypeName()
+        << "' and the value ";
+    matcher_.DescribeTo(os);
+  }
+
+  void DescribeNegationTo(std::ostream* os) const {
+    *os << "is a variant<> with value of type other than '" << GetTypeName()
+        << "' or the value ";
+    matcher_.DescribeNegationTo(os);
+  }
+
+ private:
+  static std::string GetTypeName() {
+#if GTEST_HAS_RTTI
+    GTEST_SUPPRESS_UNREACHABLE_CODE_WARNING_BELOW_(
+        return internal::GetTypeName<T>());
+#endif
+    return "the element type";
+  }
+
+  const ::testing::Matcher<const T&> matcher_;
+};
+
+}  // namespace variant_matcher
+
+namespace any_cast_matcher {
+
+// Overloads to allow AnyCastMatcher to do proper ADL lookup.
+template <typename T>
+void any_cast() {}
+
+// Implements a matcher that any_casts the value.
+template <typename T>
+class AnyCastMatcher {
+ public:
+  explicit AnyCastMatcher(const ::testing::Matcher<const T&>& matcher)
+      : matcher_(matcher) {}
+
+  template <typename AnyType>
+  bool MatchAndExplain(const AnyType& value,
+                       ::testing::MatchResultListener* listener) const {
+    if (!listener->IsInterested()) {
+      const T* ptr = any_cast<T>(&value);
+      return ptr != nullptr && matcher_.Matches(*ptr);
+    }
+
+    const T* elem = any_cast<T>(&value);
+    if (elem == nullptr) {
+      *listener << "whose value is not of type '" << GetTypeName() << "'";
+      return false;
+    }
+
+    StringMatchResultListener elem_listener;
+    const bool match = matcher_.MatchAndExplain(*elem, &elem_listener);
+    *listener << "whose value " << PrintToString(*elem)
+              << (match ? " matches" : " doesn't match");
+    PrintIfNotEmpty(elem_listener.str(), listener->stream());
+    return match;
+  }
+
+  void DescribeTo(std::ostream* os) const {
+    *os << "is an 'any' type with value of type '" << GetTypeName()
+        << "' and the value ";
+    matcher_.DescribeTo(os);
+  }
+
+  void DescribeNegationTo(std::ostream* os) const {
+    *os << "is an 'any' type with value of type other than '" << GetTypeName()
+        << "' or the value ";
+    matcher_.DescribeNegationTo(os);
+  }
+
+ private:
+  static std::string GetTypeName() {
+#if GTEST_HAS_RTTI
+    GTEST_SUPPRESS_UNREACHABLE_CODE_WARNING_BELOW_(
+        return internal::GetTypeName<T>());
+#endif
+    return "the element type";
+  }
+
+  const ::testing::Matcher<const T&> matcher_;
+};
+
+}  // namespace any_cast_matcher
+
+// Implements the Args() matcher.
+template <class ArgsTuple, size_t... k>
+class ArgsMatcherImpl : public MatcherInterface<ArgsTuple> {
+ public:
+  using RawArgsTuple = typename std::decay<ArgsTuple>::type;
+  using SelectedArgs =
+      std::tuple<typename std::tuple_element<k, RawArgsTuple>::type...>;
+  using MonomorphicInnerMatcher = Matcher<const SelectedArgs&>;
+
+  template <typename InnerMatcher>
+  explicit ArgsMatcherImpl(const InnerMatcher& inner_matcher)
+      : inner_matcher_(SafeMatcherCast<const SelectedArgs&>(inner_matcher)) {}
+
+  bool MatchAndExplain(ArgsTuple args,
+                       MatchResultListener* listener) const override {
+    // Workaround spurious C4100 on MSVC<=15.7 when k is empty.
+    (void)args;
+    const SelectedArgs& selected_args =
+        std::forward_as_tuple(std::get<k>(args)...);
+    if (!listener->IsInterested()) return inner_matcher_.Matches(selected_args);
+
+    PrintIndices(listener->stream());
+    *listener << "are " << PrintToString(selected_args);
+
+    StringMatchResultListener inner_listener;
+    const bool match =
+        inner_matcher_.MatchAndExplain(selected_args, &inner_listener);
+    PrintIfNotEmpty(inner_listener.str(), listener->stream());
+    return match;
+  }
+
+  void DescribeTo(::std::ostream* os) const override {
+    *os << "are a tuple ";
+    PrintIndices(os);
+    inner_matcher_.DescribeTo(os);
+  }
+
+  void DescribeNegationTo(::std::ostream* os) const override {
+    *os << "are a tuple ";
+    PrintIndices(os);
+    inner_matcher_.DescribeNegationTo(os);
+  }
+
+ private:
+  // Prints the indices of the selected fields.
+  static void PrintIndices(::std::ostream* os) {
+    *os << "whose fields (";
+    const char* sep = "";
+    // Workaround spurious C4189 on MSVC<=15.7 when k is empty.
+    (void)sep;
+    // The static_cast to void is needed to silence Clang's -Wcomma warning.
+    // This pattern looks suspiciously like we may have mismatched parentheses
+    // and may have been trying to use the first operation of the comma operator
+    // as a member of the array, so Clang warns that we may have made a mistake.
+    const char* dummy[] = {
+        "", (static_cast<void>(*os << sep << "#" << k), sep = ", ")...};
+    (void)dummy;
+    *os << ") ";
+  }
+
+  MonomorphicInnerMatcher inner_matcher_;
+};
+
+template <class InnerMatcher, size_t... k>
+class ArgsMatcher {
+ public:
+  explicit ArgsMatcher(InnerMatcher inner_matcher)
+      : inner_matcher_(std::move(inner_matcher)) {}
+
+  template <typename ArgsTuple>
+  operator Matcher<ArgsTuple>() const {  // NOLINT
+    return MakeMatcher(new ArgsMatcherImpl<ArgsTuple, k...>(inner_matcher_));
+  }
+
+ private:
+  InnerMatcher inner_matcher_;
+};
+
+}  // namespace internal
+
+// ElementsAreArray(iterator_first, iterator_last)
+// ElementsAreArray(pointer, count)
+// ElementsAreArray(array)
+// ElementsAreArray(container)
+// ElementsAreArray({ e1, e2, ..., en })
+//
+// The ElementsAreArray() functions are like ElementsAre(...), except
+// that they are given a homogeneous sequence rather than taking each
+// element as a function argument. The sequence can be specified as an
+// array, a pointer and count, a vector, an initializer list, or an
+// STL iterator range. In each of these cases, the underlying sequence
+// can be either a sequence of values or a sequence of matchers.
+//
+// All forms of ElementsAreArray() make a copy of the input matcher sequence.
+
+template <typename Iter>
+inline internal::ElementsAreArrayMatcher<
+    typename ::std::iterator_traits<Iter>::value_type>
+ElementsAreArray(Iter first, Iter last) {
+  typedef typename ::std::iterator_traits<Iter>::value_type T;
+  return internal::ElementsAreArrayMatcher<T>(first, last);
+}
+
+template <typename T>
+inline auto ElementsAreArray(const T* pointer, size_t count)
+    -> decltype(ElementsAreArray(pointer, pointer + count)) {
+  return ElementsAreArray(pointer, pointer + count);
+}
+
+template <typename T, size_t N>
+inline auto ElementsAreArray(const T (&array)[N])
+    -> decltype(ElementsAreArray(array, N)) {
+  return ElementsAreArray(array, N);
+}
+
+template <typename Container>
+inline auto ElementsAreArray(const Container& container)
+    -> decltype(ElementsAreArray(container.begin(), container.end())) {
+  return ElementsAreArray(container.begin(), container.end());
+}
+
+template <typename T>
+inline auto ElementsAreArray(::std::initializer_list<T> xs)
+    -> decltype(ElementsAreArray(xs.begin(), xs.end())) {
+  return ElementsAreArray(xs.begin(), xs.end());
+}
+
+// UnorderedElementsAreArray(iterator_first, iterator_last)
+// UnorderedElementsAreArray(pointer, count)
+// UnorderedElementsAreArray(array)
+// UnorderedElementsAreArray(container)
+// UnorderedElementsAreArray({ e1, e2, ..., en })
+//
+// UnorderedElementsAreArray() verifies that a bijective mapping onto a
+// collection of matchers exists.
+//
+// The matchers can be specified as an array, a pointer and count, a container,
+// an initializer list, or an STL iterator range. In each of these cases, the
+// underlying matchers can be either values or matchers.
+
+template <typename Iter>
+inline internal::UnorderedElementsAreArrayMatcher<
+    typename ::std::iterator_traits<Iter>::value_type>
+UnorderedElementsAreArray(Iter first, Iter last) {
+  typedef typename ::std::iterator_traits<Iter>::value_type T;
+  return internal::UnorderedElementsAreArrayMatcher<T>(
+      internal::UnorderedMatcherRequire::ExactMatch, first, last);
+}
+
+template <typename T>
+inline internal::UnorderedElementsAreArrayMatcher<T> UnorderedElementsAreArray(
+    const T* pointer, size_t count) {
+  return UnorderedElementsAreArray(pointer, pointer + count);
+}
+
+template <typename T, size_t N>
+inline internal::UnorderedElementsAreArrayMatcher<T> UnorderedElementsAreArray(
+    const T (&array)[N]) {
+  return UnorderedElementsAreArray(array, N);
+}
+
+template <typename Container>
+inline internal::UnorderedElementsAreArrayMatcher<
+    typename Container::value_type>
+UnorderedElementsAreArray(const Container& container) {
+  return UnorderedElementsAreArray(container.begin(), container.end());
+}
+
+template <typename T>
+inline internal::UnorderedElementsAreArrayMatcher<T> UnorderedElementsAreArray(
+    ::std::initializer_list<T> xs) {
+  return UnorderedElementsAreArray(xs.begin(), xs.end());
+}
+
+// _ is a matcher that matches anything of any type.
+//
+// This definition is fine as:
+//
+//   1. The C++ standard permits using the name _ in a namespace that
+//      is not the global namespace or ::std.
+//   2. The AnythingMatcher class has no data member or constructor,
+//      so it's OK to create global variables of this type.
+//   3. c-style has approved of using _ in this case.
+const internal::AnythingMatcher _ = {};
+// Creates a matcher that matches any value of the given type T.
+template <typename T>
+inline Matcher<T> A() {
+  return _;
+}
+
+// Creates a matcher that matches any value of the given type T.
+template <typename T>
+inline Matcher<T> An() {
+  return _;
+}
+
+template <typename T, typename M>
+Matcher<T> internal::MatcherCastImpl<T, M>::CastImpl(
+    const M& value, std::false_type /* convertible_to_matcher */,
+    std::false_type /* convertible_to_T */) {
+  return Eq(value);
+}
+
+// Creates a polymorphic matcher that matches any NULL pointer.
+inline PolymorphicMatcher<internal::IsNullMatcher> IsNull() {
+  return MakePolymorphicMatcher(internal::IsNullMatcher());
+}
+
+// Creates a polymorphic matcher that matches any non-NULL pointer.
+// This is convenient as Not(NULL) doesn't compile (the compiler
+// thinks that that expression is comparing a pointer with an integer).
+inline PolymorphicMatcher<internal::NotNullMatcher> NotNull() {
+  return MakePolymorphicMatcher(internal::NotNullMatcher());
+}
+
+// Creates a polymorphic matcher that matches any argument that
+// references variable x.
+template <typename T>
+inline internal::RefMatcher<T&> Ref(T& x) {  // NOLINT
+  return internal::RefMatcher<T&>(x);
+}
+
+// Creates a polymorphic matcher that matches any NaN floating point.
+inline PolymorphicMatcher<internal::IsNanMatcher> IsNan() {
+  return MakePolymorphicMatcher(internal::IsNanMatcher());
+}
+
+// Creates a matcher that matches any double argument approximately
+// equal to rhs, where two NANs are considered unequal.
+inline internal::FloatingEqMatcher<double> DoubleEq(double rhs) {
+  return internal::FloatingEqMatcher<double>(rhs, false);
+}
+
+// Creates a matcher that matches any double argument approximately
+// equal to rhs, including NaN values when rhs is NaN.
+inline internal::FloatingEqMatcher<double> NanSensitiveDoubleEq(double rhs) {
+  return internal::FloatingEqMatcher<double>(rhs, true);
+}
+
+// Creates a matcher that matches any double argument approximately equal to
+// rhs, up to the specified max absolute error bound, where two NANs are
+// considered unequal.  The max absolute error bound must be non-negative.
+inline internal::FloatingEqMatcher<double> DoubleNear(double rhs,
+                                                      double max_abs_error) {
+  return internal::FloatingEqMatcher<double>(rhs, false, max_abs_error);
+}
+
+// Creates a matcher that matches any double argument approximately equal to
+// rhs, up to the specified max absolute error bound, including NaN values when
+// rhs is NaN.  The max absolute error bound must be non-negative.
+inline internal::FloatingEqMatcher<double> NanSensitiveDoubleNear(
+    double rhs, double max_abs_error) {
+  return internal::FloatingEqMatcher<double>(rhs, true, max_abs_error);
+}
+
+// Creates a matcher that matches any float argument approximately
+// equal to rhs, where two NANs are considered unequal.
+inline internal::FloatingEqMatcher<float> FloatEq(float rhs) {
+  return internal::FloatingEqMatcher<float>(rhs, false);
+}
+
+// Creates a matcher that matches any float argument approximately
+// equal to rhs, including NaN values when rhs is NaN.
+inline internal::FloatingEqMatcher<float> NanSensitiveFloatEq(float rhs) {
+  return internal::FloatingEqMatcher<float>(rhs, true);
+}
+
+// Creates a matcher that matches any float argument approximately equal to
+// rhs, up to the specified max absolute error bound, where two NANs are
+// considered unequal.  The max absolute error bound must be non-negative.
+inline internal::FloatingEqMatcher<float> FloatNear(float rhs,
+                                                    float max_abs_error) {
+  return internal::FloatingEqMatcher<float>(rhs, false, max_abs_error);
+}
+
+// Creates a matcher that matches any float argument approximately equal to
+// rhs, up to the specified max absolute error bound, including NaN values when
+// rhs is NaN.  The max absolute error bound must be non-negative.
+inline internal::FloatingEqMatcher<float> NanSensitiveFloatNear(
+    float rhs, float max_abs_error) {
+  return internal::FloatingEqMatcher<float>(rhs, true, max_abs_error);
+}
+
+// Creates a matcher that matches a pointer (raw or smart) that points
+// to a value that matches inner_matcher.
+template <typename InnerMatcher>
+inline internal::PointeeMatcher<InnerMatcher> Pointee(
+    const InnerMatcher& inner_matcher) {
+  return internal::PointeeMatcher<InnerMatcher>(inner_matcher);
+}
+
+#if GTEST_HAS_RTTI
+// Creates a matcher that matches a pointer or reference that matches
+// inner_matcher when dynamic_cast<To> is applied.
+// The result of dynamic_cast<To> is forwarded to the inner matcher.
+// If To is a pointer and the cast fails, the inner matcher will receive NULL.
+// If To is a reference and the cast fails, this matcher returns false
+// immediately.
+template <typename To>
+inline PolymorphicMatcher<internal::WhenDynamicCastToMatcher<To>>
+WhenDynamicCastTo(const Matcher<To>& inner_matcher) {
+  return MakePolymorphicMatcher(
+      internal::WhenDynamicCastToMatcher<To>(inner_matcher));
+}
+#endif  // GTEST_HAS_RTTI
+
+// Creates a matcher that matches an object whose given field matches
+// 'matcher'.  For example,
+//   Field(&Foo::number, Ge(5))
+// matches a Foo object x if and only if x.number >= 5.
+template <typename Class, typename FieldType, typename FieldMatcher>
+inline PolymorphicMatcher<internal::FieldMatcher<Class, FieldType>> Field(
+    FieldType Class::*field, const FieldMatcher& matcher) {
+  return MakePolymorphicMatcher(internal::FieldMatcher<Class, FieldType>(
+      field, MatcherCast<const FieldType&>(matcher)));
+  // The call to MatcherCast() is required for supporting inner
+  // matchers of compatible types.  For example, it allows
+  //   Field(&Foo::bar, m)
+  // to compile where bar is an int32 and m is a matcher for int64.
+}
+
+// Same as Field() but also takes the name of the field to provide better error
+// messages.
+template <typename Class, typename FieldType, typename FieldMatcher>
+inline PolymorphicMatcher<internal::FieldMatcher<Class, FieldType>> Field(
+    const std::string& field_name, FieldType Class::*field,
+    const FieldMatcher& matcher) {
+  return MakePolymorphicMatcher(internal::FieldMatcher<Class, FieldType>(
+      field_name, field, MatcherCast<const FieldType&>(matcher)));
+}
+
+// Creates a matcher that matches an object whose given property
+// matches 'matcher'.  For example,
+//   Property(&Foo::str, StartsWith("hi"))
+// matches a Foo object x if and only if x.str() starts with "hi".
+template <typename Class, typename PropertyType, typename PropertyMatcher>
+inline PolymorphicMatcher<internal::PropertyMatcher<
+    Class, PropertyType, PropertyType (Class::*)() const>>
+Property(PropertyType (Class::*property)() const,
+         const PropertyMatcher& matcher) {
+  return MakePolymorphicMatcher(
+      internal::PropertyMatcher<Class, PropertyType,
+                                PropertyType (Class::*)() const>(
+          property, MatcherCast<const PropertyType&>(matcher)));
+  // The call to MatcherCast() is required for supporting inner
+  // matchers of compatible types.  For example, it allows
+  //   Property(&Foo::bar, m)
+  // to compile where bar() returns an int32 and m is a matcher for int64.
+}
+
+// Same as Property() above, but also takes the name of the property to provide
+// better error messages.
+template <typename Class, typename PropertyType, typename PropertyMatcher>
+inline PolymorphicMatcher<internal::PropertyMatcher<
+    Class, PropertyType, PropertyType (Class::*)() const>>
+Property(const std::string& property_name,
+         PropertyType (Class::*property)() const,
+         const PropertyMatcher& matcher) {
+  return MakePolymorphicMatcher(
+      internal::PropertyMatcher<Class, PropertyType,
+                                PropertyType (Class::*)() const>(
+          property_name, property, MatcherCast<const PropertyType&>(matcher)));
+}
+
+// The same as above but for reference-qualified member functions.
+template <typename Class, typename PropertyType, typename PropertyMatcher>
+inline PolymorphicMatcher<internal::PropertyMatcher<
+    Class, PropertyType, PropertyType (Class::*)() const&>>
+Property(PropertyType (Class::*property)() const&,
+         const PropertyMatcher& matcher) {
+  return MakePolymorphicMatcher(
+      internal::PropertyMatcher<Class, PropertyType,
+                                PropertyType (Class::*)() const&>(
+          property, MatcherCast<const PropertyType&>(matcher)));
+}
+
+// Three-argument form for reference-qualified member functions.
+template <typename Class, typename PropertyType, typename PropertyMatcher>
+inline PolymorphicMatcher<internal::PropertyMatcher<
+    Class, PropertyType, PropertyType (Class::*)() const&>>
+Property(const std::string& property_name,
+         PropertyType (Class::*property)() const&,
+         const PropertyMatcher& matcher) {
+  return MakePolymorphicMatcher(
+      internal::PropertyMatcher<Class, PropertyType,
+                                PropertyType (Class::*)() const&>(
+          property_name, property, MatcherCast<const PropertyType&>(matcher)));
+}
+
+// Creates a matcher that matches an object if and only if the result of
+// applying a callable to x matches 'matcher'. For example,
+//   ResultOf(f, StartsWith("hi"))
+// matches a Foo object x if and only if f(x) starts with "hi".
+// `callable` parameter can be a function, function pointer, or a functor. It is
+// required to keep no state affecting the results of the calls on it and make
+// no assumptions about how many calls will be made. Any state it keeps must be
+// protected from the concurrent access.
+template <typename Callable, typename InnerMatcher>
+internal::ResultOfMatcher<Callable, InnerMatcher> ResultOf(
+    Callable callable, InnerMatcher matcher) {
+  return internal::ResultOfMatcher<Callable, InnerMatcher>(std::move(callable),
+                                                           std::move(matcher));
+}
+
+// Same as ResultOf() above, but also takes a description of the `callable`
+// result to provide better error messages.
+template <typename Callable, typename InnerMatcher>
+internal::ResultOfMatcher<Callable, InnerMatcher> ResultOf(
+    const std::string& result_description, Callable callable,
+    InnerMatcher matcher) {
+  return internal::ResultOfMatcher<Callable, InnerMatcher>(
+      result_description, std::move(callable), std::move(matcher));
+}
+
+// String matchers.
+
+// Matches a string equal to str.
+template <typename T = std::string>
+PolymorphicMatcher<internal::StrEqualityMatcher<std::string>> StrEq(
+    const internal::StringLike<T>& str) {
+  return MakePolymorphicMatcher(
+      internal::StrEqualityMatcher<std::string>(std::string(str), true, true));
+}
+
+// Matches a string not equal to str.
+template <typename T = std::string>
+PolymorphicMatcher<internal::StrEqualityMatcher<std::string>> StrNe(
+    const internal::StringLike<T>& str) {
+  return MakePolymorphicMatcher(
+      internal::StrEqualityMatcher<std::string>(std::string(str), false, true));
+}
+
+// Matches a string equal to str, ignoring case.
+template <typename T = std::string>
+PolymorphicMatcher<internal::StrEqualityMatcher<std::string>> StrCaseEq(
+    const internal::StringLike<T>& str) {
+  return MakePolymorphicMatcher(
+      internal::StrEqualityMatcher<std::string>(std::string(str), true, false));
+}
+
+// Matches a string not equal to str, ignoring case.
+template <typename T = std::string>
+PolymorphicMatcher<internal::StrEqualityMatcher<std::string>> StrCaseNe(
+    const internal::StringLike<T>& str) {
+  return MakePolymorphicMatcher(internal::StrEqualityMatcher<std::string>(
+      std::string(str), false, false));
+}
+
+// Creates a matcher that matches any string, std::string, or C string
+// that contains the given substring.
+template <typename T = std::string>
+PolymorphicMatcher<internal::HasSubstrMatcher<std::string>> HasSubstr(
+    const internal::StringLike<T>& substring) {
+  return MakePolymorphicMatcher(
+      internal::HasSubstrMatcher<std::string>(std::string(substring)));
+}
+
+// Matches a string that starts with 'prefix' (case-sensitive).
+template <typename T = std::string>
+PolymorphicMatcher<internal::StartsWithMatcher<std::string>> StartsWith(
+    const internal::StringLike<T>& prefix) {
+  return MakePolymorphicMatcher(
+      internal::StartsWithMatcher<std::string>(std::string(prefix)));
+}
+
+// Matches a string that ends with 'suffix' (case-sensitive).
+template <typename T = std::string>
+PolymorphicMatcher<internal::EndsWithMatcher<std::string>> EndsWith(
+    const internal::StringLike<T>& suffix) {
+  return MakePolymorphicMatcher(
+      internal::EndsWithMatcher<std::string>(std::string(suffix)));
+}
+
+#if GTEST_HAS_STD_WSTRING
+// Wide string matchers.
+
+// Matches a string equal to str.
+inline PolymorphicMatcher<internal::StrEqualityMatcher<std::wstring>> StrEq(
+    const std::wstring& str) {
+  return MakePolymorphicMatcher(
+      internal::StrEqualityMatcher<std::wstring>(str, true, true));
+}
+
+// Matches a string not equal to str.
+inline PolymorphicMatcher<internal::StrEqualityMatcher<std::wstring>> StrNe(
+    const std::wstring& str) {
+  return MakePolymorphicMatcher(
+      internal::StrEqualityMatcher<std::wstring>(str, false, true));
+}
+
+// Matches a string equal to str, ignoring case.
+inline PolymorphicMatcher<internal::StrEqualityMatcher<std::wstring>> StrCaseEq(
+    const std::wstring& str) {
+  return MakePolymorphicMatcher(
+      internal::StrEqualityMatcher<std::wstring>(str, true, false));
+}
+
+// Matches a string not equal to str, ignoring case.
+inline PolymorphicMatcher<internal::StrEqualityMatcher<std::wstring>> StrCaseNe(
+    const std::wstring& str) {
+  return MakePolymorphicMatcher(
+      internal::StrEqualityMatcher<std::wstring>(str, false, false));
+}
+
+// Creates a matcher that matches any ::wstring, std::wstring, or C wide string
+// that contains the given substring.
+inline PolymorphicMatcher<internal::HasSubstrMatcher<std::wstring>> HasSubstr(
+    const std::wstring& substring) {
+  return MakePolymorphicMatcher(
+      internal::HasSubstrMatcher<std::wstring>(substring));
+}
+
+// Matches a string that starts with 'prefix' (case-sensitive).
+inline PolymorphicMatcher<internal::StartsWithMatcher<std::wstring>> StartsWith(
+    const std::wstring& prefix) {
+  return MakePolymorphicMatcher(
+      internal::StartsWithMatcher<std::wstring>(prefix));
+}
+
+// Matches a string that ends with 'suffix' (case-sensitive).
+inline PolymorphicMatcher<internal::EndsWithMatcher<std::wstring>> EndsWith(
+    const std::wstring& suffix) {
+  return MakePolymorphicMatcher(
+      internal::EndsWithMatcher<std::wstring>(suffix));
+}
+
+#endif  // GTEST_HAS_STD_WSTRING
+
+// Creates a polymorphic matcher that matches a 2-tuple where the
+// first field == the second field.
+inline internal::Eq2Matcher Eq() { return internal::Eq2Matcher(); }
+
+// Creates a polymorphic matcher that matches a 2-tuple where the
+// first field >= the second field.
+inline internal::Ge2Matcher Ge() { return internal::Ge2Matcher(); }
+
+// Creates a polymorphic matcher that matches a 2-tuple where the
+// first field > the second field.
+inline internal::Gt2Matcher Gt() { return internal::Gt2Matcher(); }
+
+// Creates a polymorphic matcher that matches a 2-tuple where the
+// first field <= the second field.
+inline internal::Le2Matcher Le() { return internal::Le2Matcher(); }
+
+// Creates a polymorphic matcher that matches a 2-tuple where the
+// first field < the second field.
+inline internal::Lt2Matcher Lt() { return internal::Lt2Matcher(); }
+
+// Creates a polymorphic matcher that matches a 2-tuple where the
+// first field != the second field.
+inline internal::Ne2Matcher Ne() { return internal::Ne2Matcher(); }
+
+// Creates a polymorphic matcher that matches a 2-tuple where
+// FloatEq(first field) matches the second field.
+inline internal::FloatingEq2Matcher<float> FloatEq() {
+  return internal::FloatingEq2Matcher<float>();
+}
+
+// Creates a polymorphic matcher that matches a 2-tuple where
+// DoubleEq(first field) matches the second field.
+inline internal::FloatingEq2Matcher<double> DoubleEq() {
+  return internal::FloatingEq2Matcher<double>();
+}
+
+// Creates a polymorphic matcher that matches a 2-tuple where
+// FloatEq(first field) matches the second field with NaN equality.
+inline internal::FloatingEq2Matcher<float> NanSensitiveFloatEq() {
+  return internal::FloatingEq2Matcher<float>(true);
+}
+
+// Creates a polymorphic matcher that matches a 2-tuple where
+// DoubleEq(first field) matches the second field with NaN equality.
+inline internal::FloatingEq2Matcher<double> NanSensitiveDoubleEq() {
+  return internal::FloatingEq2Matcher<double>(true);
+}
+
+// Creates a polymorphic matcher that matches a 2-tuple where
+// FloatNear(first field, max_abs_error) matches the second field.
+inline internal::FloatingEq2Matcher<float> FloatNear(float max_abs_error) {
+  return internal::FloatingEq2Matcher<float>(max_abs_error);
+}
+
+// Creates a polymorphic matcher that matches a 2-tuple where
+// DoubleNear(first field, max_abs_error) matches the second field.
+inline internal::FloatingEq2Matcher<double> DoubleNear(double max_abs_error) {
+  return internal::FloatingEq2Matcher<double>(max_abs_error);
+}
+
+// Creates a polymorphic matcher that matches a 2-tuple where
+// FloatNear(first field, max_abs_error) matches the second field with NaN
+// equality.
+inline internal::FloatingEq2Matcher<float> NanSensitiveFloatNear(
+    float max_abs_error) {
+  return internal::FloatingEq2Matcher<float>(max_abs_error, true);
+}
+
+// Creates a polymorphic matcher that matches a 2-tuple where
+// DoubleNear(first field, max_abs_error) matches the second field with NaN
+// equality.
+inline internal::FloatingEq2Matcher<double> NanSensitiveDoubleNear(
+    double max_abs_error) {
+  return internal::FloatingEq2Matcher<double>(max_abs_error, true);
+}
+
+// Creates a matcher that matches any value of type T that m doesn't
+// match.
+template <typename InnerMatcher>
+inline internal::NotMatcher<InnerMatcher> Not(InnerMatcher m) {
+  return internal::NotMatcher<InnerMatcher>(m);
+}
+
+// Returns a matcher that matches anything that satisfies the given
+// predicate.  The predicate can be any unary function or functor
+// whose return type can be implicitly converted to bool.
+template <typename Predicate>
+inline PolymorphicMatcher<internal::TrulyMatcher<Predicate>> Truly(
+    Predicate pred) {
+  return MakePolymorphicMatcher(internal::TrulyMatcher<Predicate>(pred));
+}
+
+// Returns a matcher that matches the container size. The container must
+// support both size() and size_type which all STL-like containers provide.
+// Note that the parameter 'size' can be a value of type size_type as well as
+// matcher. For instance:
+//   EXPECT_THAT(container, SizeIs(2));     // Checks container has 2 elements.
+//   EXPECT_THAT(container, SizeIs(Le(2));  // Checks container has at most 2.
+template <typename SizeMatcher>
+inline internal::SizeIsMatcher<SizeMatcher> SizeIs(
+    const SizeMatcher& size_matcher) {
+  return internal::SizeIsMatcher<SizeMatcher>(size_matcher);
+}
+
+// Returns a matcher that matches the distance between the container's begin()
+// iterator and its end() iterator, i.e. the size of the container. This matcher
+// can be used instead of SizeIs with containers such as std::forward_list which
+// do not implement size(). The container must provide const_iterator (with
+// valid iterator_traits), begin() and end().
+template <typename DistanceMatcher>
+inline internal::BeginEndDistanceIsMatcher<DistanceMatcher> BeginEndDistanceIs(
+    const DistanceMatcher& distance_matcher) {
+  return internal::BeginEndDistanceIsMatcher<DistanceMatcher>(distance_matcher);
+}
+
+// Returns a matcher that matches an equal container.
+// This matcher behaves like Eq(), but in the event of mismatch lists the
+// values that are included in one container but not the other. (Duplicate
+// values and order differences are not explained.)
+template <typename Container>
+inline PolymorphicMatcher<
+    internal::ContainerEqMatcher<typename std::remove_const<Container>::type>>
+ContainerEq(const Container& rhs) {
+  return MakePolymorphicMatcher(internal::ContainerEqMatcher<Container>(rhs));
+}
+
+// Returns a matcher that matches a container that, when sorted using
+// the given comparator, matches container_matcher.
+template <typename Comparator, typename ContainerMatcher>
+inline internal::WhenSortedByMatcher<Comparator, ContainerMatcher> WhenSortedBy(
+    const Comparator& comparator, const ContainerMatcher& container_matcher) {
+  return internal::WhenSortedByMatcher<Comparator, ContainerMatcher>(
+      comparator, container_matcher);
+}
+
+// Returns a matcher that matches a container that, when sorted using
+// the < operator, matches container_matcher.
+template <typename ContainerMatcher>
+inline internal::WhenSortedByMatcher<internal::LessComparator, ContainerMatcher>
+WhenSorted(const ContainerMatcher& container_matcher) {
+  return internal::WhenSortedByMatcher<internal::LessComparator,
+                                       ContainerMatcher>(
+      internal::LessComparator(), container_matcher);
+}
+
+// Matches an STL-style container or a native array that contains the
+// same number of elements as in rhs, where its i-th element and rhs's
+// i-th element (as a pair) satisfy the given pair matcher, for all i.
+// TupleMatcher must be able to be safely cast to Matcher<std::tuple<const
+// T1&, const T2&> >, where T1 and T2 are the types of elements in the
+// LHS container and the RHS container respectively.
+template <typename TupleMatcher, typename Container>
+inline internal::PointwiseMatcher<TupleMatcher,
+                                  typename std::remove_const<Container>::type>
+Pointwise(const TupleMatcher& tuple_matcher, const Container& rhs) {
+  return internal::PointwiseMatcher<TupleMatcher, Container>(tuple_matcher,
+                                                             rhs);
+}
+
+// Supports the Pointwise(m, {a, b, c}) syntax.
+template <typename TupleMatcher, typename T>
+inline internal::PointwiseMatcher<TupleMatcher, std::vector<T>> Pointwise(
+    const TupleMatcher& tuple_matcher, std::initializer_list<T> rhs) {
+  return Pointwise(tuple_matcher, std::vector<T>(rhs));
+}
+
+// UnorderedPointwise(pair_matcher, rhs) matches an STL-style
+// container or a native array that contains the same number of
+// elements as in rhs, where in some permutation of the container, its
+// i-th element and rhs's i-th element (as a pair) satisfy the given
+// pair matcher, for all i.  Tuple2Matcher must be able to be safely
+// cast to Matcher<std::tuple<const T1&, const T2&> >, where T1 and T2 are
+// the types of elements in the LHS container and the RHS container
+// respectively.
+//
+// This is like Pointwise(pair_matcher, rhs), except that the element
+// order doesn't matter.
+template <typename Tuple2Matcher, typename RhsContainer>
+inline internal::UnorderedElementsAreArrayMatcher<
+    typename internal::BoundSecondMatcher<
+        Tuple2Matcher,
+        typename internal::StlContainerView<
+            typename std::remove_const<RhsContainer>::type>::type::value_type>>
+UnorderedPointwise(const Tuple2Matcher& tuple2_matcher,
+                   const RhsContainer& rhs_container) {
+  // RhsView allows the same code to handle RhsContainer being a
+  // STL-style container and it being a native C-style array.
+  typedef typename internal::StlContainerView<RhsContainer> RhsView;
+  typedef typename RhsView::type RhsStlContainer;
+  typedef typename RhsStlContainer::value_type Second;
+  const RhsStlContainer& rhs_stl_container =
+      RhsView::ConstReference(rhs_container);
+
+  // Create a matcher for each element in rhs_container.
+  ::std::vector<internal::BoundSecondMatcher<Tuple2Matcher, Second>> matchers;
+  for (auto it = rhs_stl_container.begin(); it != rhs_stl_container.end();
+       ++it) {
+    matchers.push_back(internal::MatcherBindSecond(tuple2_matcher, *it));
+  }
+
+  // Delegate the work to UnorderedElementsAreArray().
+  return UnorderedElementsAreArray(matchers);
+}
+
+// Supports the UnorderedPointwise(m, {a, b, c}) syntax.
+template <typename Tuple2Matcher, typename T>
+inline internal::UnorderedElementsAreArrayMatcher<
+    typename internal::BoundSecondMatcher<Tuple2Matcher, T>>
+UnorderedPointwise(const Tuple2Matcher& tuple2_matcher,
+                   std::initializer_list<T> rhs) {
+  return UnorderedPointwise(tuple2_matcher, std::vector<T>(rhs));
+}
+
+// Matches an STL-style container or a native array that contains at
+// least one element matching the given value or matcher.
+//
+// Examples:
+//   ::std::set<int> page_ids;
+//   page_ids.insert(3);
+//   page_ids.insert(1);
+//   EXPECT_THAT(page_ids, Contains(1));
+//   EXPECT_THAT(page_ids, Contains(Gt(2)));
+//   EXPECT_THAT(page_ids, Not(Contains(4)));  // See below for Times(0)
+//
+//   ::std::map<int, size_t> page_lengths;
+//   page_lengths[1] = 100;
+//   EXPECT_THAT(page_lengths,
+//               Contains(::std::pair<const int, size_t>(1, 100)));
+//
+//   const char* user_ids[] = { "joe", "mike", "tom" };
+//   EXPECT_THAT(user_ids, Contains(Eq(::std::string("tom"))));
+//
+// The matcher supports a modifier `Times` that allows to check for arbitrary
+// occurrences including testing for absence with Times(0).
+//
+// Examples:
+//   ::std::vector<int> ids;
+//   ids.insert(1);
+//   ids.insert(1);
+//   ids.insert(3);
+//   EXPECT_THAT(ids, Contains(1).Times(2));      // 1 occurs 2 times
+//   EXPECT_THAT(ids, Contains(2).Times(0));      // 2 is not present
+//   EXPECT_THAT(ids, Contains(3).Times(Ge(1)));  // 3 occurs at least once
+
+template <typename M>
+inline internal::ContainsMatcher<M> Contains(M matcher) {
+  return internal::ContainsMatcher<M>(matcher);
+}
+
+// IsSupersetOf(iterator_first, iterator_last)
+// IsSupersetOf(pointer, count)
+// IsSupersetOf(array)
+// IsSupersetOf(container)
+// IsSupersetOf({e1, e2, ..., en})
+//
+// IsSupersetOf() verifies that a surjective partial mapping onto a collection
+// of matchers exists. In other words, a container matches
+// IsSupersetOf({e1, ..., en}) if and only if there is a permutation
+// {y1, ..., yn} of some of the container's elements where y1 matches e1,
+// ..., and yn matches en. Obviously, the size of the container must be >= n
+// in order to have a match. Examples:
+//
+// - {1, 2, 3} matches IsSupersetOf({Ge(3), Ne(0)}), as 3 matches Ge(3) and
+//   1 matches Ne(0).
+// - {1, 2} doesn't match IsSupersetOf({Eq(1), Lt(2)}), even though 1 matches
+//   both Eq(1) and Lt(2). The reason is that different matchers must be used
+//   for elements in different slots of the container.
+// - {1, 1, 2} matches IsSupersetOf({Eq(1), Lt(2)}), as (the first) 1 matches
+//   Eq(1) and (the second) 1 matches Lt(2).
+// - {1, 2, 3} matches IsSupersetOf(Gt(1), Gt(1)), as 2 matches (the first)
+//   Gt(1) and 3 matches (the second) Gt(1).
+//
+// The matchers can be specified as an array, a pointer and count, a container,
+// an initializer list, or an STL iterator range. In each of these cases, the
+// underlying matchers can be either values or matchers.
+
+template <typename Iter>
+inline internal::UnorderedElementsAreArrayMatcher<
+    typename ::std::iterator_traits<Iter>::value_type>
+IsSupersetOf(Iter first, Iter last) {
+  typedef typename ::std::iterator_traits<Iter>::value_type T;
+  return internal::UnorderedElementsAreArrayMatcher<T>(
+      internal::UnorderedMatcherRequire::Superset, first, last);
+}
+
+template <typename T>
+inline internal::UnorderedElementsAreArrayMatcher<T> IsSupersetOf(
+    const T* pointer, size_t count) {
+  return IsSupersetOf(pointer, pointer + count);
+}
+
+template <typename T, size_t N>
+inline internal::UnorderedElementsAreArrayMatcher<T> IsSupersetOf(
+    const T (&array)[N]) {
+  return IsSupersetOf(array, N);
+}
+
+template <typename Container>
+inline internal::UnorderedElementsAreArrayMatcher<
+    typename Container::value_type>
+IsSupersetOf(const Container& container) {
+  return IsSupersetOf(container.begin(), container.end());
+}
+
+template <typename T>
+inline internal::UnorderedElementsAreArrayMatcher<T> IsSupersetOf(
+    ::std::initializer_list<T> xs) {
+  return IsSupersetOf(xs.begin(), xs.end());
+}
+
+// IsSubsetOf(iterator_first, iterator_last)
+// IsSubsetOf(pointer, count)
+// IsSubsetOf(array)
+// IsSubsetOf(container)
+// IsSubsetOf({e1, e2, ..., en})
+//
+// IsSubsetOf() verifies that an injective mapping onto a collection of matchers
+// exists.  In other words, a container matches IsSubsetOf({e1, ..., en}) if and
+// only if there is a subset of matchers {m1, ..., mk} which would match the
+// container using UnorderedElementsAre.  Obviously, the size of the container
+// must be <= n in order to have a match. Examples:
+//
+// - {1} matches IsSubsetOf({Gt(0), Lt(0)}), as 1 matches Gt(0).
+// - {1, -1} matches IsSubsetOf({Lt(0), Gt(0)}), as 1 matches Gt(0) and -1
+//   matches Lt(0).
+// - {1, 2} doesn't matches IsSubsetOf({Gt(0), Lt(0)}), even though 1 and 2 both
+//   match Gt(0). The reason is that different matchers must be used for
+//   elements in different slots of the container.
+//
+// The matchers can be specified as an array, a pointer and count, a container,
+// an initializer list, or an STL iterator range. In each of these cases, the
+// underlying matchers can be either values or matchers.
+
+template <typename Iter>
+inline internal::UnorderedElementsAreArrayMatcher<
+    typename ::std::iterator_traits<Iter>::value_type>
+IsSubsetOf(Iter first, Iter last) {
+  typedef typename ::std::iterator_traits<Iter>::value_type T;
+  return internal::UnorderedElementsAreArrayMatcher<T>(
+      internal::UnorderedMatcherRequire::Subset, first, last);
+}
+
+template <typename T>
+inline internal::UnorderedElementsAreArrayMatcher<T> IsSubsetOf(
+    const T* pointer, size_t count) {
+  return IsSubsetOf(pointer, pointer + count);
+}
+
+template <typename T, size_t N>
+inline internal::UnorderedElementsAreArrayMatcher<T> IsSubsetOf(
+    const T (&array)[N]) {
+  return IsSubsetOf(array, N);
+}
+
+template <typename Container>
+inline internal::UnorderedElementsAreArrayMatcher<
+    typename Container::value_type>
+IsSubsetOf(const Container& container) {
+  return IsSubsetOf(container.begin(), container.end());
+}
+
+template <typename T>
+inline internal::UnorderedElementsAreArrayMatcher<T> IsSubsetOf(
+    ::std::initializer_list<T> xs) {
+  return IsSubsetOf(xs.begin(), xs.end());
+}
+
+// Matches an STL-style container or a native array that contains only
+// elements matching the given value or matcher.
+//
+// Each(m) is semantically equivalent to `Not(Contains(Not(m)))`. Only
+// the messages are different.
+//
+// Examples:
+//   ::std::set<int> page_ids;
+//   // Each(m) matches an empty container, regardless of what m is.
+//   EXPECT_THAT(page_ids, Each(Eq(1)));
+//   EXPECT_THAT(page_ids, Each(Eq(77)));
+//
+//   page_ids.insert(3);
+//   EXPECT_THAT(page_ids, Each(Gt(0)));
+//   EXPECT_THAT(page_ids, Not(Each(Gt(4))));
+//   page_ids.insert(1);
+//   EXPECT_THAT(page_ids, Not(Each(Lt(2))));
+//
+//   ::std::map<int, size_t> page_lengths;
+//   page_lengths[1] = 100;
+//   page_lengths[2] = 200;
+//   page_lengths[3] = 300;
+//   EXPECT_THAT(page_lengths, Not(Each(Pair(1, 100))));
+//   EXPECT_THAT(page_lengths, Each(Key(Le(3))));
+//
+//   const char* user_ids[] = { "joe", "mike", "tom" };
+//   EXPECT_THAT(user_ids, Not(Each(Eq(::std::string("tom")))));
+template <typename M>
+inline internal::EachMatcher<M> Each(M matcher) {
+  return internal::EachMatcher<M>(matcher);
+}
+
+// Key(inner_matcher) matches an std::pair whose 'first' field matches
+// inner_matcher.  For example, Contains(Key(Ge(5))) can be used to match an
+// std::map that contains at least one element whose key is >= 5.
+template <typename M>
+inline internal::KeyMatcher<M> Key(M inner_matcher) {
+  return internal::KeyMatcher<M>(inner_matcher);
+}
+
+// Pair(first_matcher, second_matcher) matches a std::pair whose 'first' field
+// matches first_matcher and whose 'second' field matches second_matcher.  For
+// example, EXPECT_THAT(map_type, ElementsAre(Pair(Ge(5), "foo"))) can be used
+// to match a std::map<int, string> that contains exactly one element whose key
+// is >= 5 and whose value equals "foo".
+template <typename FirstMatcher, typename SecondMatcher>
+inline internal::PairMatcher<FirstMatcher, SecondMatcher> Pair(
+    FirstMatcher first_matcher, SecondMatcher second_matcher) {
+  return internal::PairMatcher<FirstMatcher, SecondMatcher>(first_matcher,
+                                                            second_matcher);
+}
+
+namespace no_adl {
+// Conditional() creates a matcher that conditionally uses either the first or
+// second matcher provided. For example, we could create an `equal if, and only
+// if' matcher using the Conditional wrapper as follows:
+//
+//   EXPECT_THAT(result, Conditional(condition, Eq(expected), Ne(expected)));
+template <typename MatcherTrue, typename MatcherFalse>
+internal::ConditionalMatcher<MatcherTrue, MatcherFalse> Conditional(
+    bool condition, MatcherTrue matcher_true, MatcherFalse matcher_false) {
+  return internal::ConditionalMatcher<MatcherTrue, MatcherFalse>(
+      condition, std::move(matcher_true), std::move(matcher_false));
+}
+
+// FieldsAre(matchers...) matches piecewise the fields of compatible structs.
+// These include those that support `get<I>(obj)`, and when structured bindings
+// are enabled any class that supports them.
+// In particular, `std::tuple`, `std::pair`, `std::array` and aggregate types.
+template <typename... M>
+internal::FieldsAreMatcher<typename std::decay<M>::type...> FieldsAre(
+    M&&... matchers) {
+  return internal::FieldsAreMatcher<typename std::decay<M>::type...>(
+      std::forward<M>(matchers)...);
+}
+
+// Creates a matcher that matches a pointer (raw or smart) that matches
+// inner_matcher.
+template <typename InnerMatcher>
+inline internal::PointerMatcher<InnerMatcher> Pointer(
+    const InnerMatcher& inner_matcher) {
+  return internal::PointerMatcher<InnerMatcher>(inner_matcher);
+}
+
+// Creates a matcher that matches an object that has an address that matches
+// inner_matcher.
+template <typename InnerMatcher>
+inline internal::AddressMatcher<InnerMatcher> Address(
+    const InnerMatcher& inner_matcher) {
+  return internal::AddressMatcher<InnerMatcher>(inner_matcher);
+}
+
+// Matches a base64 escaped string, when the unescaped string matches the
+// internal matcher.
+template <typename MatcherType>
+internal::WhenBase64UnescapedMatcher WhenBase64Unescaped(
+    const MatcherType& internal_matcher) {
+  return internal::WhenBase64UnescapedMatcher(internal_matcher);
+}
+}  // namespace no_adl
+
+// Returns a predicate that is satisfied by anything that matches the
+// given matcher.
+template <typename M>
+inline internal::MatcherAsPredicate<M> Matches(M matcher) {
+  return internal::MatcherAsPredicate<M>(matcher);
+}
+
+// Returns true if and only if the value matches the matcher.
+template <typename T, typename M>
+inline bool Value(const T& value, M matcher) {
+  return testing::Matches(matcher)(value);
+}
+
+// Matches the value against the given matcher and explains the match
+// result to listener.
+template <typename T, typename M>
+inline bool ExplainMatchResult(M matcher, const T& value,
+                               MatchResultListener* listener) {
+  return SafeMatcherCast<const T&>(matcher).MatchAndExplain(value, listener);
+}
+
+// Returns a string representation of the given matcher.  Useful for description
+// strings of matchers defined using MATCHER_P* macros that accept matchers as
+// their arguments.  For example:
+//
+// MATCHER_P(XAndYThat, matcher,
+//           "X that " + DescribeMatcher<int>(matcher, negation) +
+//               (negation ? " or" : " and") + " Y that " +
+//               DescribeMatcher<double>(matcher, negation)) {
+//   return ExplainMatchResult(matcher, arg.x(), result_listener) &&
+//          ExplainMatchResult(matcher, arg.y(), result_listener);
+// }
+template <typename T, typename M>
+std::string DescribeMatcher(const M& matcher, bool negation = false) {
+  ::std::stringstream ss;
+  Matcher<T> monomorphic_matcher = SafeMatcherCast<T>(matcher);
+  if (negation) {
+    monomorphic_matcher.DescribeNegationTo(&ss);
+  } else {
+    monomorphic_matcher.DescribeTo(&ss);
+  }
+  return ss.str();
+}
+
+template <typename... Args>
+internal::ElementsAreMatcher<
+    std::tuple<typename std::decay<const Args&>::type...>>
+ElementsAre(const Args&... matchers) {
+  return internal::ElementsAreMatcher<
+      std::tuple<typename std::decay<const Args&>::type...>>(
+      std::make_tuple(matchers...));
+}
+
+template <typename... Args>
+internal::UnorderedElementsAreMatcher<
+    std::tuple<typename std::decay<const Args&>::type...>>
+UnorderedElementsAre(const Args&... matchers) {
+  return internal::UnorderedElementsAreMatcher<
+      std::tuple<typename std::decay<const Args&>::type...>>(
+      std::make_tuple(matchers...));
+}
+
+// Define variadic matcher versions.
+template <typename... Args>
+internal::AllOfMatcher<typename std::decay<const Args&>::type...> AllOf(
+    const Args&... matchers) {
+  return internal::AllOfMatcher<typename std::decay<const Args&>::type...>(
+      matchers...);
+}
+
+template <typename... Args>
+internal::AnyOfMatcher<typename std::decay<const Args&>::type...> AnyOf(
+    const Args&... matchers) {
+  return internal::AnyOfMatcher<typename std::decay<const Args&>::type...>(
+      matchers...);
+}
+
+// AnyOfArray(array)
+// AnyOfArray(pointer, count)
+// AnyOfArray(container)
+// AnyOfArray({ e1, e2, ..., en })
+// AnyOfArray(iterator_first, iterator_last)
+//
+// AnyOfArray() verifies whether a given value matches any member of a
+// collection of matchers.
+//
+// AllOfArray(array)
+// AllOfArray(pointer, count)
+// AllOfArray(container)
+// AllOfArray({ e1, e2, ..., en })
+// AllOfArray(iterator_first, iterator_last)
+//
+// AllOfArray() verifies whether a given value matches all members of a
+// collection of matchers.
+//
+// The matchers can be specified as an array, a pointer and count, a container,
+// an initializer list, or an STL iterator range. In each of these cases, the
+// underlying matchers can be either values or matchers.
+
+template <typename Iter>
+inline internal::AnyOfArrayMatcher<
+    typename ::std::iterator_traits<Iter>::value_type>
+AnyOfArray(Iter first, Iter last) {
+  return internal::AnyOfArrayMatcher<
+      typename ::std::iterator_traits<Iter>::value_type>(first, last);
+}
+
+template <typename Iter>
+inline internal::AllOfArrayMatcher<
+    typename ::std::iterator_traits<Iter>::value_type>
+AllOfArray(Iter first, Iter last) {
+  return internal::AllOfArrayMatcher<
+      typename ::std::iterator_traits<Iter>::value_type>(first, last);
+}
+
+template <typename T>
+inline internal::AnyOfArrayMatcher<T> AnyOfArray(const T* ptr, size_t count) {
+  return AnyOfArray(ptr, ptr + count);
+}
+
+template <typename T>
+inline internal::AllOfArrayMatcher<T> AllOfArray(const T* ptr, size_t count) {
+  return AllOfArray(ptr, ptr + count);
+}
+
+template <typename T, size_t N>
+inline internal::AnyOfArrayMatcher<T> AnyOfArray(const T (&array)[N]) {
+  return AnyOfArray(array, N);
+}
+
+template <typename T, size_t N>
+inline internal::AllOfArrayMatcher<T> AllOfArray(const T (&array)[N]) {
+  return AllOfArray(array, N);
+}
+
+template <typename Container>
+inline internal::AnyOfArrayMatcher<typename Container::value_type> AnyOfArray(
+    const Container& container) {
+  return AnyOfArray(container.begin(), container.end());
+}
+
+template <typename Container>
+inline internal::AllOfArrayMatcher<typename Container::value_type> AllOfArray(
+    const Container& container) {
+  return AllOfArray(container.begin(), container.end());
+}
+
+template <typename T>
+inline internal::AnyOfArrayMatcher<T> AnyOfArray(
+    ::std::initializer_list<T> xs) {
+  return AnyOfArray(xs.begin(), xs.end());
+}
+
+template <typename T>
+inline internal::AllOfArrayMatcher<T> AllOfArray(
+    ::std::initializer_list<T> xs) {
+  return AllOfArray(xs.begin(), xs.end());
+}
+
+// Args<N1, N2, ..., Nk>(a_matcher) matches a tuple if the selected
+// fields of it matches a_matcher.  C++ doesn't support default
+// arguments for function templates, so we have to overload it.
+template <size_t... k, typename InnerMatcher>
+internal::ArgsMatcher<typename std::decay<InnerMatcher>::type, k...> Args(
+    InnerMatcher&& matcher) {
+  return internal::ArgsMatcher<typename std::decay<InnerMatcher>::type, k...>(
+      std::forward<InnerMatcher>(matcher));
+}
+
+// AllArgs(m) is a synonym of m.  This is useful in
+//
+//   EXPECT_CALL(foo, Bar(_, _)).With(AllArgs(Eq()));
+//
+// which is easier to read than
+//
+//   EXPECT_CALL(foo, Bar(_, _)).With(Eq());
+template <typename InnerMatcher>
+inline InnerMatcher AllArgs(const InnerMatcher& matcher) {
+  return matcher;
+}
+
+// Returns a matcher that matches the value of an optional<> type variable.
+// The matcher implementation only uses '!arg' and requires that the optional<>
+// type has a 'value_type' member type and that '*arg' is of type 'value_type'
+// and is printable using 'PrintToString'. It is compatible with
+// std::optional/std::experimental::optional.
+// Note that to compare an optional type variable against nullopt you should
+// use Eq(nullopt) and not Eq(Optional(nullopt)). The latter implies that the
+// optional value contains an optional itself.
+template <typename ValueMatcher>
+inline internal::OptionalMatcher<ValueMatcher> Optional(
+    const ValueMatcher& value_matcher) {
+  return internal::OptionalMatcher<ValueMatcher>(value_matcher);
+}
+
+// Returns a matcher that matches the value of a absl::any type variable.
+template <typename T>
+PolymorphicMatcher<internal::any_cast_matcher::AnyCastMatcher<T>> AnyWith(
+    const Matcher<const T&>& matcher) {
+  return MakePolymorphicMatcher(
+      internal::any_cast_matcher::AnyCastMatcher<T>(matcher));
+}
+
+// Returns a matcher that matches the value of a variant<> type variable.
+// The matcher implementation uses ADL to find the holds_alternative and get
+// functions.
+// It is compatible with std::variant.
+template <typename T>
+PolymorphicMatcher<internal::variant_matcher::VariantMatcher<T>> VariantWith(
+    const Matcher<const T&>& matcher) {
+  return MakePolymorphicMatcher(
+      internal::variant_matcher::VariantMatcher<T>(matcher));
+}
+
+#if GTEST_HAS_EXCEPTIONS
+
+// Anything inside the `internal` namespace is internal to the implementation
+// and must not be used in user code!
+namespace internal {
+
+class WithWhatMatcherImpl {
+ public:
+  WithWhatMatcherImpl(Matcher<std::string> matcher)
+      : matcher_(std::move(matcher)) {}
+
+  void DescribeTo(std::ostream* os) const {
+    *os << "contains .what() that ";
+    matcher_.DescribeTo(os);
+  }
+
+  void DescribeNegationTo(std::ostream* os) const {
+    *os << "contains .what() that does not ";
+    matcher_.DescribeTo(os);
+  }
+
+  template <typename Err>
+  bool MatchAndExplain(const Err& err, MatchResultListener* listener) const {
+    *listener << "which contains .what() (of value = " << err.what()
+              << ") that ";
+    return matcher_.MatchAndExplain(err.what(), listener);
+  }
+
+ private:
+  const Matcher<std::string> matcher_;
+};
+
+inline PolymorphicMatcher<WithWhatMatcherImpl> WithWhat(
+    Matcher<std::string> m) {
+  return MakePolymorphicMatcher(WithWhatMatcherImpl(std::move(m)));
+}
+
+template <typename Err>
+class ExceptionMatcherImpl {
+  class NeverThrown {
+   public:
+    const char* what() const noexcept {
+      return "this exception should never be thrown";
+    }
+  };
+
+  // If the matchee raises an exception of a wrong type, we'd like to
+  // catch it and print its message and type. To do that, we add an additional
+  // catch clause:
+  //
+  //     try { ... }
+  //     catch (const Err&) { /* an expected exception */ }
+  //     catch (const std::exception&) { /* exception of a wrong type */ }
+  //
+  // However, if the `Err` itself is `std::exception`, we'd end up with two
+  // identical `catch` clauses:
+  //
+  //     try { ... }
+  //     catch (const std::exception&) { /* an expected exception */ }
+  //     catch (const std::exception&) { /* exception of a wrong type */ }
+  //
+  // This can cause a warning or an error in some compilers. To resolve
+  // the issue, we use a fake error type whenever `Err` is `std::exception`:
+  //
+  //     try { ... }
+  //     catch (const std::exception&) { /* an expected exception */ }
+  //     catch (const NeverThrown&) { /* exception of a wrong type */ }
+  using DefaultExceptionType = typename std::conditional<
+      std::is_same<typename std::remove_cv<
+                       typename std::remove_reference<Err>::type>::type,
+                   std::exception>::value,
+      const NeverThrown&, const std::exception&>::type;
+
+ public:
+  ExceptionMatcherImpl(Matcher<const Err&> matcher)
+      : matcher_(std::move(matcher)) {}
+
+  void DescribeTo(std::ostream* os) const {
+    *os << "throws an exception which is a " << GetTypeName<Err>();
+    *os << " which ";
+    matcher_.DescribeTo(os);
+  }
+
+  void DescribeNegationTo(std::ostream* os) const {
+    *os << "throws an exception which is not a " << GetTypeName<Err>();
+    *os << " which ";
+    matcher_.DescribeNegationTo(os);
+  }
+
+  template <typename T>
+  bool MatchAndExplain(T&& x, MatchResultListener* listener) const {
+    try {
+      (void)(std::forward<T>(x)());
+    } catch (const Err& err) {
+      *listener << "throws an exception which is a " << GetTypeName<Err>();
+      *listener << " ";
+      return matcher_.MatchAndExplain(err, listener);
+    } catch (DefaultExceptionType err) {
+#if GTEST_HAS_RTTI
+      *listener << "throws an exception of type " << GetTypeName(typeid(err));
+      *listener << " ";
+#else
+      *listener << "throws an std::exception-derived type ";
+#endif
+      *listener << "with description \"" << err.what() << "\"";
+      return false;
+    } catch (...) {
+      *listener << "throws an exception of an unknown type";
+      return false;
+    }
+
+    *listener << "does not throw any exception";
+    return false;
+  }
+
+ private:
+  const Matcher<const Err&> matcher_;
+};
+
+}  // namespace internal
+
+// Throws()
+// Throws(exceptionMatcher)
+// ThrowsMessage(messageMatcher)
+//
+// This matcher accepts a callable and verifies that when invoked, it throws
+// an exception with the given type and properties.
+//
+// Examples:
+//
+//   EXPECT_THAT(
+//       []() { throw std::runtime_error("message"); },
+//       Throws<std::runtime_error>());
+//
+//   EXPECT_THAT(
+//       []() { throw std::runtime_error("message"); },
+//       ThrowsMessage<std::runtime_error>(HasSubstr("message")));
+//
+//   EXPECT_THAT(
+//       []() { throw std::runtime_error("message"); },
+//       Throws<std::runtime_error>(
+//           Property(&std::runtime_error::what, HasSubstr("message"))));
+
+template <typename Err>
+PolymorphicMatcher<internal::ExceptionMatcherImpl<Err>> Throws() {
+  return MakePolymorphicMatcher(
+      internal::ExceptionMatcherImpl<Err>(A<const Err&>()));
+}
+
+template <typename Err, typename ExceptionMatcher>
+PolymorphicMatcher<internal::ExceptionMatcherImpl<Err>> Throws(
+    const ExceptionMatcher& exception_matcher) {
+  // Using matcher cast allows users to pass a matcher of a more broad type.
+  // For example user may want to pass Matcher<std::exception>
+  // to Throws<std::runtime_error>, or Matcher<int64> to Throws<int32>.
+  return MakePolymorphicMatcher(internal::ExceptionMatcherImpl<Err>(
+      SafeMatcherCast<const Err&>(exception_matcher)));
+}
+
+template <typename Err, typename MessageMatcher>
+PolymorphicMatcher<internal::ExceptionMatcherImpl<Err>> ThrowsMessage(
+    MessageMatcher&& message_matcher) {
+  static_assert(std::is_base_of<std::exception, Err>::value,
+                "expected an std::exception-derived type");
+  return Throws<Err>(internal::WithWhat(
+      MatcherCast<std::string>(std::forward<MessageMatcher>(message_matcher))));
+}
+
+#endif  // GTEST_HAS_EXCEPTIONS
+
+// These macros allow using matchers to check values in Google Test
+// tests.  ASSERT_THAT(value, matcher) and EXPECT_THAT(value, matcher)
+// succeed if and only if the value matches the matcher.  If the assertion
+// fails, the value and the description of the matcher will be printed.
+#define ASSERT_THAT(value, matcher) \
+  ASSERT_PRED_FORMAT1(              \
+      ::testing::internal::MakePredicateFormatterFromMatcher(matcher), value)
+#define EXPECT_THAT(value, matcher) \
+  EXPECT_PRED_FORMAT1(              \
+      ::testing::internal::MakePredicateFormatterFromMatcher(matcher), value)
+
+// MATCHER* macros itself are listed below.
+#define MATCHER(name, description)                                             \
+  class name##Matcher                                                          \
+      : public ::testing::internal::MatcherBaseImpl<name##Matcher> {           \
+   public:                                                                     \
+    template <typename arg_type>                                               \
+    class gmock_Impl : public ::testing::MatcherInterface<const arg_type&> {   \
+     public:                                                                   \
+      gmock_Impl() {}                                                          \
+      bool MatchAndExplain(                                                    \
+          const arg_type& arg,                                                 \
+          ::testing::MatchResultListener* result_listener) const override;     \
+      void DescribeTo(::std::ostream* gmock_os) const override {               \
+        *gmock_os << FormatDescription(false);                                 \
+      }                                                                        \
+      void DescribeNegationTo(::std::ostream* gmock_os) const override {       \
+        *gmock_os << FormatDescription(true);                                  \
+      }                                                                        \
+                                                                               \
+     private:                                                                  \
+      ::std::string FormatDescription(bool negation) const {                   \
+        /* NOLINTNEXTLINE readability-redundant-string-init */                 \
+        ::std::string gmock_description = (description);                       \
+        if (!gmock_description.empty()) {                                      \
+          return gmock_description;                                            \
+        }                                                                      \
+        return ::testing::internal::FormatMatcherDescription(negation, #name,  \
+                                                             {}, {});          \
+      }                                                                        \
+    };                                                                         \
+  };                                                                           \
+  inline name##Matcher GMOCK_INTERNAL_WARNING_PUSH()                           \
+      GMOCK_INTERNAL_WARNING_CLANG(ignored, "-Wunused-function")               \
+          GMOCK_INTERNAL_WARNING_CLANG(ignored, "-Wunused-member-function")    \
+              name GMOCK_INTERNAL_WARNING_POP()() {                            \
+    return {};                                                                 \
+  }                                                                            \
+  template <typename arg_type>                                                 \
+  bool name##Matcher::gmock_Impl<arg_type>::MatchAndExplain(                   \
+      const arg_type& arg,                                                     \
+      ::testing::MatchResultListener* result_listener GTEST_ATTRIBUTE_UNUSED_) \
+      const
+
+#define MATCHER_P(name, p0, description) \
+  GMOCK_INTERNAL_MATCHER(name, name##MatcherP, description, (#p0), (p0))
+#define MATCHER_P2(name, p0, p1, description)                            \
+  GMOCK_INTERNAL_MATCHER(name, name##MatcherP2, description, (#p0, #p1), \
+                         (p0, p1))
+#define MATCHER_P3(name, p0, p1, p2, description)                             \
+  GMOCK_INTERNAL_MATCHER(name, name##MatcherP3, description, (#p0, #p1, #p2), \
+                         (p0, p1, p2))
+#define MATCHER_P4(name, p0, p1, p2, p3, description)        \
+  GMOCK_INTERNAL_MATCHER(name, name##MatcherP4, description, \
+                         (#p0, #p1, #p2, #p3), (p0, p1, p2, p3))
+#define MATCHER_P5(name, p0, p1, p2, p3, p4, description)    \
+  GMOCK_INTERNAL_MATCHER(name, name##MatcherP5, description, \
+                         (#p0, #p1, #p2, #p3, #p4), (p0, p1, p2, p3, p4))
+#define MATCHER_P6(name, p0, p1, p2, p3, p4, p5, description) \
+  GMOCK_INTERNAL_MATCHER(name, name##MatcherP6, description,  \
+                         (#p0, #p1, #p2, #p3, #p4, #p5),      \
+                         (p0, p1, p2, p3, p4, p5))
+#define MATCHER_P7(name, p0, p1, p2, p3, p4, p5, p6, description) \
+  GMOCK_INTERNAL_MATCHER(name, name##MatcherP7, description,      \
+                         (#p0, #p1, #p2, #p3, #p4, #p5, #p6),     \
+                         (p0, p1, p2, p3, p4, p5, p6))
+#define MATCHER_P8(name, p0, p1, p2, p3, p4, p5, p6, p7, description) \
+  GMOCK_INTERNAL_MATCHER(name, name##MatcherP8, description,          \
+                         (#p0, #p1, #p2, #p3, #p4, #p5, #p6, #p7),    \
+                         (p0, p1, p2, p3, p4, p5, p6, p7))
+#define MATCHER_P9(name, p0, p1, p2, p3, p4, p5, p6, p7, p8, description) \
+  GMOCK_INTERNAL_MATCHER(name, name##MatcherP9, description,              \
+                         (#p0, #p1, #p2, #p3, #p4, #p5, #p6, #p7, #p8),   \
+                         (p0, p1, p2, p3, p4, p5, p6, p7, p8))
+#define MATCHER_P10(name, p0, p1, p2, p3, p4, p5, p6, p7, p8, p9, description) \
+  GMOCK_INTERNAL_MATCHER(name, name##MatcherP10, description,                  \
+                         (#p0, #p1, #p2, #p3, #p4, #p5, #p6, #p7, #p8, #p9),   \
+                         (p0, p1, p2, p3, p4, p5, p6, p7, p8, p9))
+
+#define GMOCK_INTERNAL_MATCHER(name, full_name, description, arg_names, args)  \
+  template <GMOCK_INTERNAL_MATCHER_TEMPLATE_PARAMS(args)>                      \
+  class full_name : public ::testing::internal::MatcherBaseImpl<               \
+                        full_name<GMOCK_INTERNAL_MATCHER_TYPE_PARAMS(args)>> { \
+   public:                                                                     \
+    using full_name::MatcherBaseImpl::MatcherBaseImpl;                         \
+    template <typename arg_type>                                               \
+    class gmock_Impl : public ::testing::MatcherInterface<const arg_type&> {   \
+     public:                                                                   \
+      explicit gmock_Impl(GMOCK_INTERNAL_MATCHER_FUNCTION_ARGS(args))          \
+          : GMOCK_INTERNAL_MATCHER_FORWARD_ARGS(args) {}                       \
+      bool MatchAndExplain(                                                    \
+          const arg_type& arg,                                                 \
+          ::testing::MatchResultListener* result_listener) const override;     \
+      void DescribeTo(::std::ostream* gmock_os) const override {               \
+        *gmock_os << FormatDescription(false);                                 \
+      }                                                                        \
+      void DescribeNegationTo(::std::ostream* gmock_os) const override {       \
+        *gmock_os << FormatDescription(true);                                  \
+      }                                                                        \
+      GMOCK_INTERNAL_MATCHER_MEMBERS(args)                                     \
+                                                                               \
+     private:                                                                  \
+      ::std::string FormatDescription(bool negation) const {                   \
+        ::std::string gmock_description;                                       \
+        gmock_description = (description);                                     \
+        if (!gmock_description.empty()) {                                      \
+          return gmock_description;                                            \
+        }                                                                      \
+        return ::testing::internal::FormatMatcherDescription(                  \
+            negation, #name, {GMOCK_PP_REMOVE_PARENS(arg_names)},              \
+            ::testing::internal::UniversalTersePrintTupleFieldsToStrings(      \
+                ::std::tuple<GMOCK_INTERNAL_MATCHER_TYPE_PARAMS(args)>(        \
+                    GMOCK_INTERNAL_MATCHER_MEMBERS_USAGE(args))));             \
+      }                                                                        \
+    };                                                                         \
+  };                                                                           \
+  template <GMOCK_INTERNAL_MATCHER_TEMPLATE_PARAMS(args)>                      \
+  inline full_name<GMOCK_INTERNAL_MATCHER_TYPE_PARAMS(args)> name(             \
+      GMOCK_INTERNAL_MATCHER_FUNCTION_ARGS(args)) {                            \
+    return full_name<GMOCK_INTERNAL_MATCHER_TYPE_PARAMS(args)>(                \
+        GMOCK_INTERNAL_MATCHER_ARGS_USAGE(args));                              \
+  }                                                                            \
+  template <GMOCK_INTERNAL_MATCHER_TEMPLATE_PARAMS(args)>                      \
+  template <typename arg_type>                                                 \
+  bool full_name<GMOCK_INTERNAL_MATCHER_TYPE_PARAMS(args)>::gmock_Impl<        \
+      arg_type>::MatchAndExplain(const arg_type& arg,                          \
+                                 ::testing::MatchResultListener*               \
+                                     result_listener GTEST_ATTRIBUTE_UNUSED_)  \
+      const
+
+#define GMOCK_INTERNAL_MATCHER_TEMPLATE_PARAMS(args) \
+  GMOCK_PP_TAIL(                                     \
+      GMOCK_PP_FOR_EACH(GMOCK_INTERNAL_MATCHER_TEMPLATE_PARAM, , args))
+#define GMOCK_INTERNAL_MATCHER_TEMPLATE_PARAM(i_unused, data_unused, arg) \
+  , typename arg##_type
+
+#define GMOCK_INTERNAL_MATCHER_TYPE_PARAMS(args) \
+  GMOCK_PP_TAIL(GMOCK_PP_FOR_EACH(GMOCK_INTERNAL_MATCHER_TYPE_PARAM, , args))
+#define GMOCK_INTERNAL_MATCHER_TYPE_PARAM(i_unused, data_unused, arg) \
+  , arg##_type
+
+#define GMOCK_INTERNAL_MATCHER_FUNCTION_ARGS(args) \
+  GMOCK_PP_TAIL(dummy_first GMOCK_PP_FOR_EACH(     \
+      GMOCK_INTERNAL_MATCHER_FUNCTION_ARG, , args))
+#define GMOCK_INTERNAL_MATCHER_FUNCTION_ARG(i, data_unused, arg) \
+  , arg##_type gmock_p##i
+
+#define GMOCK_INTERNAL_MATCHER_FORWARD_ARGS(args) \
+  GMOCK_PP_TAIL(GMOCK_PP_FOR_EACH(GMOCK_INTERNAL_MATCHER_FORWARD_ARG, , args))
+#define GMOCK_INTERNAL_MATCHER_FORWARD_ARG(i, data_unused, arg) \
+  , arg(::std::forward<arg##_type>(gmock_p##i))
+
+#define GMOCK_INTERNAL_MATCHER_MEMBERS(args) \
+  GMOCK_PP_FOR_EACH(GMOCK_INTERNAL_MATCHER_MEMBER, , args)
+#define GMOCK_INTERNAL_MATCHER_MEMBER(i_unused, data_unused, arg) \
+  const arg##_type arg;
+
+#define GMOCK_INTERNAL_MATCHER_MEMBERS_USAGE(args) \
+  GMOCK_PP_TAIL(GMOCK_PP_FOR_EACH(GMOCK_INTERNAL_MATCHER_MEMBER_USAGE, , args))
+#define GMOCK_INTERNAL_MATCHER_MEMBER_USAGE(i_unused, data_unused, arg) , arg
+
+#define GMOCK_INTERNAL_MATCHER_ARGS_USAGE(args) \
+  GMOCK_PP_TAIL(GMOCK_PP_FOR_EACH(GMOCK_INTERNAL_MATCHER_ARG_USAGE, , args))
+#define GMOCK_INTERNAL_MATCHER_ARG_USAGE(i, data_unused, arg_unused) \
+  , gmock_p##i
+
+// To prevent ADL on certain functions we put them on a separate namespace.
+using namespace no_adl;  // NOLINT
+
+}  // namespace testing
+
+GTEST_DISABLE_MSC_WARNINGS_POP_()  //  4251 5046
+
+// Include any custom callback matchers added by the local installation.
+// We must include this header at the end to make sure it can use the
+// declarations from this file.
+#include "gmock/internal/custom/gmock-matchers.h"
+
+#endif  // GOOGLEMOCK_INCLUDE_GMOCK_GMOCK_MATCHERS_H_
diff --git a/third_party/googletest/googlemock/include/gmock/gmock-more-actions.h b/third_party/googletest/googlemock/include/gmock/gmock-more-actions.h
new file mode 100644
index 0000000..4030076
--- /dev/null
+++ b/third_party/googletest/googlemock/include/gmock/gmock-more-actions.h
@@ -0,0 +1,658 @@
+// Copyright 2007, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Google Mock - a framework for writing C++ mock classes.
+//
+// This file implements some commonly used variadic actions.
+
+// IWYU pragma: private, include "gmock/gmock.h"
+// IWYU pragma: friend gmock/.*
+
+#ifndef GOOGLEMOCK_INCLUDE_GMOCK_GMOCK_MORE_ACTIONS_H_
+#define GOOGLEMOCK_INCLUDE_GMOCK_GMOCK_MORE_ACTIONS_H_
+
+#include <memory>
+#include <utility>
+
+#include "gmock/gmock-actions.h"
+#include "gmock/internal/gmock-port.h"
+
+// Include any custom callback actions added by the local installation.
+#include "gmock/internal/custom/gmock-generated-actions.h"
+
+// Sometimes you want to give an action explicit template parameters
+// that cannot be inferred from its value parameters.  ACTION() and
+// ACTION_P*() don't support that.  ACTION_TEMPLATE() remedies that
+// and can be viewed as an extension to ACTION() and ACTION_P*().
+//
+// The syntax:
+//
+//   ACTION_TEMPLATE(ActionName,
+//                   HAS_m_TEMPLATE_PARAMS(kind1, name1, ..., kind_m, name_m),
+//                   AND_n_VALUE_PARAMS(p1, ..., p_n)) { statements; }
+//
+// defines an action template that takes m explicit template
+// parameters and n value parameters.  name_i is the name of the i-th
+// template parameter, and kind_i specifies whether it's a typename,
+// an integral constant, or a template.  p_i is the name of the i-th
+// value parameter.
+//
+// Example:
+//
+//   // DuplicateArg<k, T>(output) converts the k-th argument of the mock
+//   // function to type T and copies it to *output.
+//   ACTION_TEMPLATE(DuplicateArg,
+//                   HAS_2_TEMPLATE_PARAMS(int, k, typename, T),
+//                   AND_1_VALUE_PARAMS(output)) {
+//     *output = T(::std::get<k>(args));
+//   }
+//   ...
+//     int n;
+//     EXPECT_CALL(mock, Foo(_, _))
+//         .WillOnce(DuplicateArg<1, unsigned char>(&n));
+//
+// To create an instance of an action template, write:
+//
+//   ActionName<t1, ..., t_m>(v1, ..., v_n)
+//
+// where the ts are the template arguments and the vs are the value
+// arguments.  The value argument types are inferred by the compiler.
+// If you want to explicitly specify the value argument types, you can
+// provide additional template arguments:
+//
+//   ActionName<t1, ..., t_m, u1, ..., u_k>(v1, ..., v_n)
+//
+// where u_i is the desired type of v_i.
+//
+// ACTION_TEMPLATE and ACTION/ACTION_P* can be overloaded on the
+// number of value parameters, but not on the number of template
+// parameters.  Without the restriction, the meaning of the following
+// is unclear:
+//
+//   OverloadedAction<int, bool>(x);
+//
+// Are we using a single-template-parameter action where 'bool' refers
+// to the type of x, or are we using a two-template-parameter action
+// where the compiler is asked to infer the type of x?
+//
+// Implementation notes:
+//
+// GMOCK_INTERNAL_*_HAS_m_TEMPLATE_PARAMS and
+// GMOCK_INTERNAL_*_AND_n_VALUE_PARAMS are internal macros for
+// implementing ACTION_TEMPLATE.  The main trick we use is to create
+// new macro invocations when expanding a macro.  For example, we have
+//
+//   #define ACTION_TEMPLATE(name, template_params, value_params)
+//       ... GMOCK_INTERNAL_DECL_##template_params ...
+//
+// which causes ACTION_TEMPLATE(..., HAS_1_TEMPLATE_PARAMS(typename, T), ...)
+// to expand to
+//
+//       ... GMOCK_INTERNAL_DECL_HAS_1_TEMPLATE_PARAMS(typename, T) ...
+//
+// Since GMOCK_INTERNAL_DECL_HAS_1_TEMPLATE_PARAMS is a macro, the
+// preprocessor will continue to expand it to
+//
+//       ... typename T ...
+//
+// This technique conforms to the C++ standard and is portable.  It
+// allows us to implement action templates using O(N) code, where N is
+// the maximum number of template/value parameters supported.  Without
+// using it, we'd have to devote O(N^2) amount of code to implement all
+// combinations of m and n.
+
+// Declares the template parameters.
+#define GMOCK_INTERNAL_DECL_HAS_1_TEMPLATE_PARAMS(kind0, name0) kind0 name0
+#define GMOCK_INTERNAL_DECL_HAS_2_TEMPLATE_PARAMS(kind0, name0, kind1, name1) \
+  kind0 name0, kind1 name1
+#define GMOCK_INTERNAL_DECL_HAS_3_TEMPLATE_PARAMS(kind0, name0, kind1, name1, \
+                                                  kind2, name2)               \
+  kind0 name0, kind1 name1, kind2 name2
+#define GMOCK_INTERNAL_DECL_HAS_4_TEMPLATE_PARAMS(kind0, name0, kind1, name1, \
+                                                  kind2, name2, kind3, name3) \
+  kind0 name0, kind1 name1, kind2 name2, kind3 name3
+#define GMOCK_INTERNAL_DECL_HAS_5_TEMPLATE_PARAMS(                        \
+    kind0, name0, kind1, name1, kind2, name2, kind3, name3, kind4, name4) \
+  kind0 name0, kind1 name1, kind2 name2, kind3 name3, kind4 name4
+#define GMOCK_INTERNAL_DECL_HAS_6_TEMPLATE_PARAMS(kind0, name0, kind1, name1, \
+                                                  kind2, name2, kind3, name3, \
+                                                  kind4, name4, kind5, name5) \
+  kind0 name0, kind1 name1, kind2 name2, kind3 name3, kind4 name4, kind5 name5
+#define GMOCK_INTERNAL_DECL_HAS_7_TEMPLATE_PARAMS(                        \
+    kind0, name0, kind1, name1, kind2, name2, kind3, name3, kind4, name4, \
+    kind5, name5, kind6, name6)                                           \
+  kind0 name0, kind1 name1, kind2 name2, kind3 name3, kind4 name4,        \
+      kind5 name5, kind6 name6
+#define GMOCK_INTERNAL_DECL_HAS_8_TEMPLATE_PARAMS(                        \
+    kind0, name0, kind1, name1, kind2, name2, kind3, name3, kind4, name4, \
+    kind5, name5, kind6, name6, kind7, name7)                             \
+  kind0 name0, kind1 name1, kind2 name2, kind3 name3, kind4 name4,        \
+      kind5 name5, kind6 name6, kind7 name7
+#define GMOCK_INTERNAL_DECL_HAS_9_TEMPLATE_PARAMS(                        \
+    kind0, name0, kind1, name1, kind2, name2, kind3, name3, kind4, name4, \
+    kind5, name5, kind6, name6, kind7, name7, kind8, name8)               \
+  kind0 name0, kind1 name1, kind2 name2, kind3 name3, kind4 name4,        \
+      kind5 name5, kind6 name6, kind7 name7, kind8 name8
+#define GMOCK_INTERNAL_DECL_HAS_10_TEMPLATE_PARAMS(                       \
+    kind0, name0, kind1, name1, kind2, name2, kind3, name3, kind4, name4, \
+    kind5, name5, kind6, name6, kind7, name7, kind8, name8, kind9, name9) \
+  kind0 name0, kind1 name1, kind2 name2, kind3 name3, kind4 name4,        \
+      kind5 name5, kind6 name6, kind7 name7, kind8 name8, kind9 name9
+
+// Lists the template parameters.
+#define GMOCK_INTERNAL_LIST_HAS_1_TEMPLATE_PARAMS(kind0, name0) name0
+#define GMOCK_INTERNAL_LIST_HAS_2_TEMPLATE_PARAMS(kind0, name0, kind1, name1) \
+  name0, name1
+#define GMOCK_INTERNAL_LIST_HAS_3_TEMPLATE_PARAMS(kind0, name0, kind1, name1, \
+                                                  kind2, name2)               \
+  name0, name1, name2
+#define GMOCK_INTERNAL_LIST_HAS_4_TEMPLATE_PARAMS(kind0, name0, kind1, name1, \
+                                                  kind2, name2, kind3, name3) \
+  name0, name1, name2, name3
+#define GMOCK_INTERNAL_LIST_HAS_5_TEMPLATE_PARAMS(                        \
+    kind0, name0, kind1, name1, kind2, name2, kind3, name3, kind4, name4) \
+  name0, name1, name2, name3, name4
+#define GMOCK_INTERNAL_LIST_HAS_6_TEMPLATE_PARAMS(kind0, name0, kind1, name1, \
+                                                  kind2, name2, kind3, name3, \
+                                                  kind4, name4, kind5, name5) \
+  name0, name1, name2, name3, name4, name5
+#define GMOCK_INTERNAL_LIST_HAS_7_TEMPLATE_PARAMS(                        \
+    kind0, name0, kind1, name1, kind2, name2, kind3, name3, kind4, name4, \
+    kind5, name5, kind6, name6)                                           \
+  name0, name1, name2, name3, name4, name5, name6
+#define GMOCK_INTERNAL_LIST_HAS_8_TEMPLATE_PARAMS(                        \
+    kind0, name0, kind1, name1, kind2, name2, kind3, name3, kind4, name4, \
+    kind5, name5, kind6, name6, kind7, name7)                             \
+  name0, name1, name2, name3, name4, name5, name6, name7
+#define GMOCK_INTERNAL_LIST_HAS_9_TEMPLATE_PARAMS(                        \
+    kind0, name0, kind1, name1, kind2, name2, kind3, name3, kind4, name4, \
+    kind5, name5, kind6, name6, kind7, name7, kind8, name8)               \
+  name0, name1, name2, name3, name4, name5, name6, name7, name8
+#define GMOCK_INTERNAL_LIST_HAS_10_TEMPLATE_PARAMS(                       \
+    kind0, name0, kind1, name1, kind2, name2, kind3, name3, kind4, name4, \
+    kind5, name5, kind6, name6, kind7, name7, kind8, name8, kind9, name9) \
+  name0, name1, name2, name3, name4, name5, name6, name7, name8, name9
+
+// Declares the types of value parameters.
+#define GMOCK_INTERNAL_DECL_TYPE_AND_0_VALUE_PARAMS()
+#define GMOCK_INTERNAL_DECL_TYPE_AND_1_VALUE_PARAMS(p0) , typename p0##_type
+#define GMOCK_INTERNAL_DECL_TYPE_AND_2_VALUE_PARAMS(p0, p1) \
+  , typename p0##_type, typename p1##_type
+#define GMOCK_INTERNAL_DECL_TYPE_AND_3_VALUE_PARAMS(p0, p1, p2) \
+  , typename p0##_type, typename p1##_type, typename p2##_type
+#define GMOCK_INTERNAL_DECL_TYPE_AND_4_VALUE_PARAMS(p0, p1, p2, p3) \
+  , typename p0##_type, typename p1##_type, typename p2##_type,     \
+      typename p3##_type
+#define GMOCK_INTERNAL_DECL_TYPE_AND_5_VALUE_PARAMS(p0, p1, p2, p3, p4) \
+  , typename p0##_type, typename p1##_type, typename p2##_type,         \
+      typename p3##_type, typename p4##_type
+#define GMOCK_INTERNAL_DECL_TYPE_AND_6_VALUE_PARAMS(p0, p1, p2, p3, p4, p5) \
+  , typename p0##_type, typename p1##_type, typename p2##_type,             \
+      typename p3##_type, typename p4##_type, typename p5##_type
+#define GMOCK_INTERNAL_DECL_TYPE_AND_7_VALUE_PARAMS(p0, p1, p2, p3, p4, p5, \
+                                                    p6)                     \
+  , typename p0##_type, typename p1##_type, typename p2##_type,             \
+      typename p3##_type, typename p4##_type, typename p5##_type,           \
+      typename p6##_type
+#define GMOCK_INTERNAL_DECL_TYPE_AND_8_VALUE_PARAMS(p0, p1, p2, p3, p4, p5, \
+                                                    p6, p7)                 \
+  , typename p0##_type, typename p1##_type, typename p2##_type,             \
+      typename p3##_type, typename p4##_type, typename p5##_type,           \
+      typename p6##_type, typename p7##_type
+#define GMOCK_INTERNAL_DECL_TYPE_AND_9_VALUE_PARAMS(p0, p1, p2, p3, p4, p5, \
+                                                    p6, p7, p8)             \
+  , typename p0##_type, typename p1##_type, typename p2##_type,             \
+      typename p3##_type, typename p4##_type, typename p5##_type,           \
+      typename p6##_type, typename p7##_type, typename p8##_type
+#define GMOCK_INTERNAL_DECL_TYPE_AND_10_VALUE_PARAMS(p0, p1, p2, p3, p4, p5, \
+                                                     p6, p7, p8, p9)         \
+  , typename p0##_type, typename p1##_type, typename p2##_type,              \
+      typename p3##_type, typename p4##_type, typename p5##_type,            \
+      typename p6##_type, typename p7##_type, typename p8##_type,            \
+      typename p9##_type
+
+// Initializes the value parameters.
+#define GMOCK_INTERNAL_INIT_AND_0_VALUE_PARAMS() ()
+#define GMOCK_INTERNAL_INIT_AND_1_VALUE_PARAMS(p0) \
+  (p0##_type gmock_p0) : p0(::std::move(gmock_p0))
+#define GMOCK_INTERNAL_INIT_AND_2_VALUE_PARAMS(p0, p1) \
+  (p0##_type gmock_p0, p1##_type gmock_p1)             \
+      : p0(::std::move(gmock_p0)), p1(::std::move(gmock_p1))
+#define GMOCK_INTERNAL_INIT_AND_3_VALUE_PARAMS(p0, p1, p2)     \
+  (p0##_type gmock_p0, p1##_type gmock_p1, p2##_type gmock_p2) \
+      : p0(::std::move(gmock_p0)),                             \
+        p1(::std::move(gmock_p1)),                             \
+        p2(::std::move(gmock_p2))
+#define GMOCK_INTERNAL_INIT_AND_4_VALUE_PARAMS(p0, p1, p2, p3) \
+  (p0##_type gmock_p0, p1##_type gmock_p1, p2##_type gmock_p2, \
+   p3##_type gmock_p3)                                         \
+      : p0(::std::move(gmock_p0)),                             \
+        p1(::std::move(gmock_p1)),                             \
+        p2(::std::move(gmock_p2)),                             \
+        p3(::std::move(gmock_p3))
+#define GMOCK_INTERNAL_INIT_AND_5_VALUE_PARAMS(p0, p1, p2, p3, p4) \
+  (p0##_type gmock_p0, p1##_type gmock_p1, p2##_type gmock_p2,     \
+   p3##_type gmock_p3, p4##_type gmock_p4)                         \
+      : p0(::std::move(gmock_p0)),                                 \
+        p1(::std::move(gmock_p1)),                                 \
+        p2(::std::move(gmock_p2)),                                 \
+        p3(::std::move(gmock_p3)),                                 \
+        p4(::std::move(gmock_p4))
+#define GMOCK_INTERNAL_INIT_AND_6_VALUE_PARAMS(p0, p1, p2, p3, p4, p5) \
+  (p0##_type gmock_p0, p1##_type gmock_p1, p2##_type gmock_p2,         \
+   p3##_type gmock_p3, p4##_type gmock_p4, p5##_type gmock_p5)         \
+      : p0(::std::move(gmock_p0)),                                     \
+        p1(::std::move(gmock_p1)),                                     \
+        p2(::std::move(gmock_p2)),                                     \
+        p3(::std::move(gmock_p3)),                                     \
+        p4(::std::move(gmock_p4)),                                     \
+        p5(::std::move(gmock_p5))
+#define GMOCK_INTERNAL_INIT_AND_7_VALUE_PARAMS(p0, p1, p2, p3, p4, p5, p6) \
+  (p0##_type gmock_p0, p1##_type gmock_p1, p2##_type gmock_p2,             \
+   p3##_type gmock_p3, p4##_type gmock_p4, p5##_type gmock_p5,             \
+   p6##_type gmock_p6)                                                     \
+      : p0(::std::move(gmock_p0)),                                         \
+        p1(::std::move(gmock_p1)),                                         \
+        p2(::std::move(gmock_p2)),                                         \
+        p3(::std::move(gmock_p3)),                                         \
+        p4(::std::move(gmock_p4)),                                         \
+        p5(::std::move(gmock_p5)),                                         \
+        p6(::std::move(gmock_p6))
+#define GMOCK_INTERNAL_INIT_AND_8_VALUE_PARAMS(p0, p1, p2, p3, p4, p5, p6, p7) \
+  (p0##_type gmock_p0, p1##_type gmock_p1, p2##_type gmock_p2,                 \
+   p3##_type gmock_p3, p4##_type gmock_p4, p5##_type gmock_p5,                 \
+   p6##_type gmock_p6, p7##_type gmock_p7)                                     \
+      : p0(::std::move(gmock_p0)),                                             \
+        p1(::std::move(gmock_p1)),                                             \
+        p2(::std::move(gmock_p2)),                                             \
+        p3(::std::move(gmock_p3)),                                             \
+        p4(::std::move(gmock_p4)),                                             \
+        p5(::std::move(gmock_p5)),                                             \
+        p6(::std::move(gmock_p6)),                                             \
+        p7(::std::move(gmock_p7))
+#define GMOCK_INTERNAL_INIT_AND_9_VALUE_PARAMS(p0, p1, p2, p3, p4, p5, p6, p7, \
+                                               p8)                             \
+  (p0##_type gmock_p0, p1##_type gmock_p1, p2##_type gmock_p2,                 \
+   p3##_type gmock_p3, p4##_type gmock_p4, p5##_type gmock_p5,                 \
+   p6##_type gmock_p6, p7##_type gmock_p7, p8##_type gmock_p8)                 \
+      : p0(::std::move(gmock_p0)),                                             \
+        p1(::std::move(gmock_p1)),                                             \
+        p2(::std::move(gmock_p2)),                                             \
+        p3(::std::move(gmock_p3)),                                             \
+        p4(::std::move(gmock_p4)),                                             \
+        p5(::std::move(gmock_p5)),                                             \
+        p6(::std::move(gmock_p6)),                                             \
+        p7(::std::move(gmock_p7)),                                             \
+        p8(::std::move(gmock_p8))
+#define GMOCK_INTERNAL_INIT_AND_10_VALUE_PARAMS(p0, p1, p2, p3, p4, p5, p6, \
+                                                p7, p8, p9)                 \
+  (p0##_type gmock_p0, p1##_type gmock_p1, p2##_type gmock_p2,              \
+   p3##_type gmock_p3, p4##_type gmock_p4, p5##_type gmock_p5,              \
+   p6##_type gmock_p6, p7##_type gmock_p7, p8##_type gmock_p8,              \
+   p9##_type gmock_p9)                                                      \
+      : p0(::std::move(gmock_p0)),                                          \
+        p1(::std::move(gmock_p1)),                                          \
+        p2(::std::move(gmock_p2)),                                          \
+        p3(::std::move(gmock_p3)),                                          \
+        p4(::std::move(gmock_p4)),                                          \
+        p5(::std::move(gmock_p5)),                                          \
+        p6(::std::move(gmock_p6)),                                          \
+        p7(::std::move(gmock_p7)),                                          \
+        p8(::std::move(gmock_p8)),                                          \
+        p9(::std::move(gmock_p9))
+
+// Defines the copy constructor
+#define GMOCK_INTERNAL_DEFN_COPY_AND_0_VALUE_PARAMS() \
+  {}  // Avoid https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82134
+#define GMOCK_INTERNAL_DEFN_COPY_AND_1_VALUE_PARAMS(...) = default;
+#define GMOCK_INTERNAL_DEFN_COPY_AND_2_VALUE_PARAMS(...) = default;
+#define GMOCK_INTERNAL_DEFN_COPY_AND_3_VALUE_PARAMS(...) = default;
+#define GMOCK_INTERNAL_DEFN_COPY_AND_4_VALUE_PARAMS(...) = default;
+#define GMOCK_INTERNAL_DEFN_COPY_AND_5_VALUE_PARAMS(...) = default;
+#define GMOCK_INTERNAL_DEFN_COPY_AND_6_VALUE_PARAMS(...) = default;
+#define GMOCK_INTERNAL_DEFN_COPY_AND_7_VALUE_PARAMS(...) = default;
+#define GMOCK_INTERNAL_DEFN_COPY_AND_8_VALUE_PARAMS(...) = default;
+#define GMOCK_INTERNAL_DEFN_COPY_AND_9_VALUE_PARAMS(...) = default;
+#define GMOCK_INTERNAL_DEFN_COPY_AND_10_VALUE_PARAMS(...) = default;
+
+// Declares the fields for storing the value parameters.
+#define GMOCK_INTERNAL_DEFN_AND_0_VALUE_PARAMS()
+#define GMOCK_INTERNAL_DEFN_AND_1_VALUE_PARAMS(p0) p0##_type p0;
+#define GMOCK_INTERNAL_DEFN_AND_2_VALUE_PARAMS(p0, p1) \
+  p0##_type p0;                                        \
+  p1##_type p1;
+#define GMOCK_INTERNAL_DEFN_AND_3_VALUE_PARAMS(p0, p1, p2) \
+  p0##_type p0;                                            \
+  p1##_type p1;                                            \
+  p2##_type p2;
+#define GMOCK_INTERNAL_DEFN_AND_4_VALUE_PARAMS(p0, p1, p2, p3) \
+  p0##_type p0;                                                \
+  p1##_type p1;                                                \
+  p2##_type p2;                                                \
+  p3##_type p3;
+#define GMOCK_INTERNAL_DEFN_AND_5_VALUE_PARAMS(p0, p1, p2, p3, p4) \
+  p0##_type p0;                                                    \
+  p1##_type p1;                                                    \
+  p2##_type p2;                                                    \
+  p3##_type p3;                                                    \
+  p4##_type p4;
+#define GMOCK_INTERNAL_DEFN_AND_6_VALUE_PARAMS(p0, p1, p2, p3, p4, p5) \
+  p0##_type p0;                                                        \
+  p1##_type p1;                                                        \
+  p2##_type p2;                                                        \
+  p3##_type p3;                                                        \
+  p4##_type p4;                                                        \
+  p5##_type p5;
+#define GMOCK_INTERNAL_DEFN_AND_7_VALUE_PARAMS(p0, p1, p2, p3, p4, p5, p6) \
+  p0##_type p0;                                                            \
+  p1##_type p1;                                                            \
+  p2##_type p2;                                                            \
+  p3##_type p3;                                                            \
+  p4##_type p4;                                                            \
+  p5##_type p5;                                                            \
+  p6##_type p6;
+#define GMOCK_INTERNAL_DEFN_AND_8_VALUE_PARAMS(p0, p1, p2, p3, p4, p5, p6, p7) \
+  p0##_type p0;                                                                \
+  p1##_type p1;                                                                \
+  p2##_type p2;                                                                \
+  p3##_type p3;                                                                \
+  p4##_type p4;                                                                \
+  p5##_type p5;                                                                \
+  p6##_type p6;                                                                \
+  p7##_type p7;
+#define GMOCK_INTERNAL_DEFN_AND_9_VALUE_PARAMS(p0, p1, p2, p3, p4, p5, p6, p7, \
+                                               p8)                             \
+  p0##_type p0;                                                                \
+  p1##_type p1;                                                                \
+  p2##_type p2;                                                                \
+  p3##_type p3;                                                                \
+  p4##_type p4;                                                                \
+  p5##_type p5;                                                                \
+  p6##_type p6;                                                                \
+  p7##_type p7;                                                                \
+  p8##_type p8;
+#define GMOCK_INTERNAL_DEFN_AND_10_VALUE_PARAMS(p0, p1, p2, p3, p4, p5, p6, \
+                                                p7, p8, p9)                 \
+  p0##_type p0;                                                             \
+  p1##_type p1;                                                             \
+  p2##_type p2;                                                             \
+  p3##_type p3;                                                             \
+  p4##_type p4;                                                             \
+  p5##_type p5;                                                             \
+  p6##_type p6;                                                             \
+  p7##_type p7;                                                             \
+  p8##_type p8;                                                             \
+  p9##_type p9;
+
+// Lists the value parameters.
+#define GMOCK_INTERNAL_LIST_AND_0_VALUE_PARAMS()
+#define GMOCK_INTERNAL_LIST_AND_1_VALUE_PARAMS(p0) p0
+#define GMOCK_INTERNAL_LIST_AND_2_VALUE_PARAMS(p0, p1) p0, p1
+#define GMOCK_INTERNAL_LIST_AND_3_VALUE_PARAMS(p0, p1, p2) p0, p1, p2
+#define GMOCK_INTERNAL_LIST_AND_4_VALUE_PARAMS(p0, p1, p2, p3) p0, p1, p2, p3
+#define GMOCK_INTERNAL_LIST_AND_5_VALUE_PARAMS(p0, p1, p2, p3, p4) \
+  p0, p1, p2, p3, p4
+#define GMOCK_INTERNAL_LIST_AND_6_VALUE_PARAMS(p0, p1, p2, p3, p4, p5) \
+  p0, p1, p2, p3, p4, p5
+#define GMOCK_INTERNAL_LIST_AND_7_VALUE_PARAMS(p0, p1, p2, p3, p4, p5, p6) \
+  p0, p1, p2, p3, p4, p5, p6
+#define GMOCK_INTERNAL_LIST_AND_8_VALUE_PARAMS(p0, p1, p2, p3, p4, p5, p6, p7) \
+  p0, p1, p2, p3, p4, p5, p6, p7
+#define GMOCK_INTERNAL_LIST_AND_9_VALUE_PARAMS(p0, p1, p2, p3, p4, p5, p6, p7, \
+                                               p8)                             \
+  p0, p1, p2, p3, p4, p5, p6, p7, p8
+#define GMOCK_INTERNAL_LIST_AND_10_VALUE_PARAMS(p0, p1, p2, p3, p4, p5, p6, \
+                                                p7, p8, p9)                 \
+  p0, p1, p2, p3, p4, p5, p6, p7, p8, p9
+
+// Lists the value parameter types.
+#define GMOCK_INTERNAL_LIST_TYPE_AND_0_VALUE_PARAMS()
+#define GMOCK_INTERNAL_LIST_TYPE_AND_1_VALUE_PARAMS(p0) , p0##_type
+#define GMOCK_INTERNAL_LIST_TYPE_AND_2_VALUE_PARAMS(p0, p1) \
+  , p0##_type, p1##_type
+#define GMOCK_INTERNAL_LIST_TYPE_AND_3_VALUE_PARAMS(p0, p1, p2) \
+  , p0##_type, p1##_type, p2##_type
+#define GMOCK_INTERNAL_LIST_TYPE_AND_4_VALUE_PARAMS(p0, p1, p2, p3) \
+  , p0##_type, p1##_type, p2##_type, p3##_type
+#define GMOCK_INTERNAL_LIST_TYPE_AND_5_VALUE_PARAMS(p0, p1, p2, p3, p4) \
+  , p0##_type, p1##_type, p2##_type, p3##_type, p4##_type
+#define GMOCK_INTERNAL_LIST_TYPE_AND_6_VALUE_PARAMS(p0, p1, p2, p3, p4, p5) \
+  , p0##_type, p1##_type, p2##_type, p3##_type, p4##_type, p5##_type
+#define GMOCK_INTERNAL_LIST_TYPE_AND_7_VALUE_PARAMS(p0, p1, p2, p3, p4, p5, \
+                                                    p6)                     \
+  , p0##_type, p1##_type, p2##_type, p3##_type, p4##_type, p5##_type, p6##_type
+#define GMOCK_INTERNAL_LIST_TYPE_AND_8_VALUE_PARAMS(p0, p1, p2, p3, p4, p5, \
+                                                    p6, p7)                 \
+  , p0##_type, p1##_type, p2##_type, p3##_type, p4##_type, p5##_type,       \
+      p6##_type, p7##_type
+#define GMOCK_INTERNAL_LIST_TYPE_AND_9_VALUE_PARAMS(p0, p1, p2, p3, p4, p5, \
+                                                    p6, p7, p8)             \
+  , p0##_type, p1##_type, p2##_type, p3##_type, p4##_type, p5##_type,       \
+      p6##_type, p7##_type, p8##_type
+#define GMOCK_INTERNAL_LIST_TYPE_AND_10_VALUE_PARAMS(p0, p1, p2, p3, p4, p5, \
+                                                     p6, p7, p8, p9)         \
+  , p0##_type, p1##_type, p2##_type, p3##_type, p4##_type, p5##_type,        \
+      p6##_type, p7##_type, p8##_type, p9##_type
+
+// Declares the value parameters.
+#define GMOCK_INTERNAL_DECL_AND_0_VALUE_PARAMS()
+#define GMOCK_INTERNAL_DECL_AND_1_VALUE_PARAMS(p0) p0##_type p0
+#define GMOCK_INTERNAL_DECL_AND_2_VALUE_PARAMS(p0, p1) \
+  p0##_type p0, p1##_type p1
+#define GMOCK_INTERNAL_DECL_AND_3_VALUE_PARAMS(p0, p1, p2) \
+  p0##_type p0, p1##_type p1, p2##_type p2
+#define GMOCK_INTERNAL_DECL_AND_4_VALUE_PARAMS(p0, p1, p2, p3) \
+  p0##_type p0, p1##_type p1, p2##_type p2, p3##_type p3
+#define GMOCK_INTERNAL_DECL_AND_5_VALUE_PARAMS(p0, p1, p2, p3, p4) \
+  p0##_type p0, p1##_type p1, p2##_type p2, p3##_type p3, p4##_type p4
+#define GMOCK_INTERNAL_DECL_AND_6_VALUE_PARAMS(p0, p1, p2, p3, p4, p5)  \
+  p0##_type p0, p1##_type p1, p2##_type p2, p3##_type p3, p4##_type p4, \
+      p5##_type p5
+#define GMOCK_INTERNAL_DECL_AND_7_VALUE_PARAMS(p0, p1, p2, p3, p4, p5, p6) \
+  p0##_type p0, p1##_type p1, p2##_type p2, p3##_type p3, p4##_type p4,    \
+      p5##_type p5, p6##_type p6
+#define GMOCK_INTERNAL_DECL_AND_8_VALUE_PARAMS(p0, p1, p2, p3, p4, p5, p6, p7) \
+  p0##_type p0, p1##_type p1, p2##_type p2, p3##_type p3, p4##_type p4,        \
+      p5##_type p5, p6##_type p6, p7##_type p7
+#define GMOCK_INTERNAL_DECL_AND_9_VALUE_PARAMS(p0, p1, p2, p3, p4, p5, p6, p7, \
+                                               p8)                             \
+  p0##_type p0, p1##_type p1, p2##_type p2, p3##_type p3, p4##_type p4,        \
+      p5##_type p5, p6##_type p6, p7##_type p7, p8##_type p8
+#define GMOCK_INTERNAL_DECL_AND_10_VALUE_PARAMS(p0, p1, p2, p3, p4, p5, p6, \
+                                                p7, p8, p9)                 \
+  p0##_type p0, p1##_type p1, p2##_type p2, p3##_type p3, p4##_type p4,     \
+      p5##_type p5, p6##_type p6, p7##_type p7, p8##_type p8, p9##_type p9
+
+// The suffix of the class template implementing the action template.
+#define GMOCK_INTERNAL_COUNT_AND_0_VALUE_PARAMS()
+#define GMOCK_INTERNAL_COUNT_AND_1_VALUE_PARAMS(p0) P
+#define GMOCK_INTERNAL_COUNT_AND_2_VALUE_PARAMS(p0, p1) P2
+#define GMOCK_INTERNAL_COUNT_AND_3_VALUE_PARAMS(p0, p1, p2) P3
+#define GMOCK_INTERNAL_COUNT_AND_4_VALUE_PARAMS(p0, p1, p2, p3) P4
+#define GMOCK_INTERNAL_COUNT_AND_5_VALUE_PARAMS(p0, p1, p2, p3, p4) P5
+#define GMOCK_INTERNAL_COUNT_AND_6_VALUE_PARAMS(p0, p1, p2, p3, p4, p5) P6
+#define GMOCK_INTERNAL_COUNT_AND_7_VALUE_PARAMS(p0, p1, p2, p3, p4, p5, p6) P7
+#define GMOCK_INTERNAL_COUNT_AND_8_VALUE_PARAMS(p0, p1, p2, p3, p4, p5, p6, \
+                                                p7)                         \
+  P8
+#define GMOCK_INTERNAL_COUNT_AND_9_VALUE_PARAMS(p0, p1, p2, p3, p4, p5, p6, \
+                                                p7, p8)                     \
+  P9
+#define GMOCK_INTERNAL_COUNT_AND_10_VALUE_PARAMS(p0, p1, p2, p3, p4, p5, p6, \
+                                                 p7, p8, p9)                 \
+  P10
+
+// The name of the class template implementing the action template.
+#define GMOCK_ACTION_CLASS_(name, value_params) \
+  GTEST_CONCAT_TOKEN_(name##Action, GMOCK_INTERNAL_COUNT_##value_params)
+
+#define ACTION_TEMPLATE(name, template_params, value_params)                   \
+  template <GMOCK_INTERNAL_DECL_##template_params                              \
+                GMOCK_INTERNAL_DECL_TYPE_##value_params>                       \
+  class GMOCK_ACTION_CLASS_(name, value_params) {                              \
+   public:                                                                     \
+    explicit GMOCK_ACTION_CLASS_(name, value_params)(                          \
+        GMOCK_INTERNAL_DECL_##value_params)                                    \
+        GMOCK_PP_IF(GMOCK_PP_IS_EMPTY(GMOCK_INTERNAL_COUNT_##value_params),    \
+                    = default;                                                 \
+                    ,                                                          \
+                    : impl_(std::make_shared<gmock_Impl>(                      \
+                        GMOCK_INTERNAL_LIST_##value_params)){})                \
+            GMOCK_ACTION_CLASS_(name, value_params)(const GMOCK_ACTION_CLASS_( \
+                name, value_params) &) noexcept GMOCK_INTERNAL_DEFN_COPY_      \
+        ##value_params                                                         \
+        GMOCK_ACTION_CLASS_(name, value_params)(GMOCK_ACTION_CLASS_(           \
+            name, value_params) &&) noexcept GMOCK_INTERNAL_DEFN_COPY_         \
+        ##value_params template <typename F>                                   \
+        operator ::testing::Action<F>() const {                                \
+      return GMOCK_PP_IF(                                                      \
+          GMOCK_PP_IS_EMPTY(GMOCK_INTERNAL_COUNT_##value_params),              \
+          (::testing::internal::MakeAction<F, gmock_Impl>()),                  \
+          (::testing::internal::MakeAction<F>(impl_)));                        \
+    }                                                                          \
+                                                                               \
+   private:                                                                    \
+    class gmock_Impl {                                                         \
+     public:                                                                   \
+      explicit gmock_Impl GMOCK_INTERNAL_INIT_##value_params {}                \
+      template <typename function_type, typename return_type,                  \
+                typename args_type, GMOCK_ACTION_TEMPLATE_ARGS_NAMES_>         \
+      return_type gmock_PerformImpl(GMOCK_ACTION_ARG_TYPES_AND_NAMES_) const;  \
+      GMOCK_INTERNAL_DEFN_##value_params                                       \
+    };                                                                         \
+    GMOCK_PP_IF(GMOCK_PP_IS_EMPTY(GMOCK_INTERNAL_COUNT_##value_params), ,      \
+                std::shared_ptr<const gmock_Impl> impl_;)                      \
+  };                                                                           \
+  template <GMOCK_INTERNAL_DECL_##template_params                              \
+                GMOCK_INTERNAL_DECL_TYPE_##value_params>                       \
+  GMOCK_ACTION_CLASS_(                                                         \
+      name, value_params)<GMOCK_INTERNAL_LIST_##template_params                \
+                              GMOCK_INTERNAL_LIST_TYPE_##value_params>         \
+      name(GMOCK_INTERNAL_DECL_##value_params) GTEST_MUST_USE_RESULT_;         \
+  template <GMOCK_INTERNAL_DECL_##template_params                              \
+                GMOCK_INTERNAL_DECL_TYPE_##value_params>                       \
+  inline GMOCK_ACTION_CLASS_(                                                  \
+      name, value_params)<GMOCK_INTERNAL_LIST_##template_params                \
+                              GMOCK_INTERNAL_LIST_TYPE_##value_params>         \
+  name(GMOCK_INTERNAL_DECL_##value_params) {                                   \
+    return GMOCK_ACTION_CLASS_(                                                \
+        name, value_params)<GMOCK_INTERNAL_LIST_##template_params              \
+                                GMOCK_INTERNAL_LIST_TYPE_##value_params>(      \
+        GMOCK_INTERNAL_LIST_##value_params);                                   \
+  }                                                                            \
+  template <GMOCK_INTERNAL_DECL_##template_params                              \
+                GMOCK_INTERNAL_DECL_TYPE_##value_params>                       \
+  template <typename function_type, typename return_type, typename args_type,  \
+            GMOCK_ACTION_TEMPLATE_ARGS_NAMES_>                                 \
+  return_type GMOCK_ACTION_CLASS_(                                             \
+      name, value_params)<GMOCK_INTERNAL_LIST_##template_params                \
+                              GMOCK_INTERNAL_LIST_TYPE_##value_params>::       \
+      gmock_Impl::gmock_PerformImpl(GMOCK_ACTION_ARG_TYPES_AND_NAMES_UNUSED_)  \
+          const
+
+namespace testing {
+
+// The ACTION*() macros trigger warning C4100 (unreferenced formal
+// parameter) in MSVC with -W4.  Unfortunately they cannot be fixed in
+// the macro definition, as the warnings are generated when the macro
+// is expanded and macro expansion cannot contain #pragma.  Therefore
+// we suppress them here.
+GTEST_DISABLE_MSC_WARNINGS_PUSH_(4100)
+
+namespace internal {
+
+// internal::InvokeArgument - a helper for InvokeArgument action.
+// The basic overloads are provided here for generic functors.
+// Overloads for other custom-callables are provided in the
+// internal/custom/gmock-generated-actions.h header.
+template <typename F, typename... Args>
+auto InvokeArgument(F f, Args... args) -> decltype(f(args...)) {
+  return f(args...);
+}
+
+template <std::size_t index, typename... Params>
+struct InvokeArgumentAction {
+  template <typename... Args,
+            typename = typename std::enable_if<(index < sizeof...(Args))>::type>
+  auto operator()(Args &&...args) const -> decltype(internal::InvokeArgument(
+      std::get<index>(std::forward_as_tuple(std::forward<Args>(args)...)),
+      std::declval<const Params &>()...)) {
+    internal::FlatTuple<Args &&...> args_tuple(FlatTupleConstructTag{},
+                                               std::forward<Args>(args)...);
+    return params.Apply([&](const Params &...unpacked_params) {
+      auto &&callable = args_tuple.template Get<index>();
+      return internal::InvokeArgument(
+          std::forward<decltype(callable)>(callable), unpacked_params...);
+    });
+  }
+
+  internal::FlatTuple<Params...> params;
+};
+
+}  // namespace internal
+
+// The InvokeArgument<N>(a1, a2, ..., a_k) action invokes the N-th
+// (0-based) argument, which must be a k-ary callable, of the mock
+// function, with arguments a1, a2, ..., a_k.
+//
+// Notes:
+//
+//   1. The arguments are passed by value by default.  If you need to
+//   pass an argument by reference, wrap it inside std::ref().  For
+//   example,
+//
+//     InvokeArgument<1>(5, string("Hello"), std::ref(foo))
+//
+//   passes 5 and string("Hello") by value, and passes foo by
+//   reference.
+//
+//   2. If the callable takes an argument by reference but std::ref() is
+//   not used, it will receive the reference to a copy of the value,
+//   instead of the original value.  For example, when the 0-th
+//   argument of the mock function takes a const string&, the action
+//
+//     InvokeArgument<0>(string("Hello"))
+//
+//   makes a copy of the temporary string("Hello") object and passes a
+//   reference of the copy, instead of the original temporary object,
+//   to the callable.  This makes it easy for a user to define an
+//   InvokeArgument action from temporary values and have it performed
+//   later.
+template <std::size_t index, typename... Params>
+internal::InvokeArgumentAction<index, typename std::decay<Params>::type...>
+InvokeArgument(Params &&...params) {
+  return {internal::FlatTuple<typename std::decay<Params>::type...>(
+      internal::FlatTupleConstructTag{}, std::forward<Params>(params)...)};
+}
+
+GTEST_DISABLE_MSC_WARNINGS_POP_()  // 4100
+
+}  // namespace testing
+
+#endif  // GOOGLEMOCK_INCLUDE_GMOCK_GMOCK_MORE_ACTIONS_H_
diff --git a/third_party/googletest/googlemock/include/gmock/gmock-more-matchers.h b/third_party/googletest/googlemock/include/gmock/gmock-more-matchers.h
new file mode 100644
index 0000000..54ea68b
--- /dev/null
+++ b/third_party/googletest/googlemock/include/gmock/gmock-more-matchers.h
@@ -0,0 +1,120 @@
+// Copyright 2013, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Google Mock - a framework for writing C++ mock classes.
+//
+// This file implements some matchers that depend on gmock-matchers.h.
+//
+// Note that tests are implemented in gmock-matchers_test.cc rather than
+// gmock-more-matchers-test.cc.
+
+// IWYU pragma: private, include "gmock/gmock.h"
+// IWYU pragma: friend gmock/.*
+
+#ifndef GOOGLEMOCK_INCLUDE_GMOCK_GMOCK_MORE_MATCHERS_H_
+#define GOOGLEMOCK_INCLUDE_GMOCK_GMOCK_MORE_MATCHERS_H_
+
+#include <ostream>
+#include <string>
+
+#include "gmock/gmock-matchers.h"
+
+namespace testing {
+
+// Silence C4100 (unreferenced formal
+// parameter) for MSVC
+GTEST_DISABLE_MSC_WARNINGS_PUSH_(4100)
+#if defined(_MSC_VER) && (_MSC_VER == 1900)
+// and silence C4800 (C4800: 'int *const ': forcing value
+// to bool 'true' or 'false') for MSVC 14
+GTEST_DISABLE_MSC_WARNINGS_PUSH_(4800)
+#endif
+
+namespace internal {
+
+// Implements the polymorphic IsEmpty matcher, which
+// can be used as a Matcher<T> as long as T is either a container that defines
+// empty() and size() (e.g. std::vector or std::string), or a C-style string.
+class IsEmptyMatcher {
+ public:
+  // Matches anything that defines empty() and size().
+  template <typename MatcheeContainerType>
+  bool MatchAndExplain(const MatcheeContainerType& c,
+                       MatchResultListener* listener) const {
+    if (c.empty()) {
+      return true;
+    }
+    *listener << "whose size is " << c.size();
+    return false;
+  }
+
+  // Matches C-style strings.
+  bool MatchAndExplain(const char* s, MatchResultListener* listener) const {
+    return MatchAndExplain(std::string(s), listener);
+  }
+
+  // Describes what this matcher matches.
+  void DescribeTo(std::ostream* os) const { *os << "is empty"; }
+
+  void DescribeNegationTo(std::ostream* os) const { *os << "isn't empty"; }
+};
+
+}  // namespace internal
+
+// Creates a polymorphic matcher that matches an empty container or C-style
+// string. The container must support both size() and empty(), which all
+// STL-like containers provide.
+inline PolymorphicMatcher<internal::IsEmptyMatcher> IsEmpty() {
+  return MakePolymorphicMatcher(internal::IsEmptyMatcher());
+}
+
+// Define a matcher that matches a value that evaluates in boolean
+// context to true.  Useful for types that define "explicit operator
+// bool" operators and so can't be compared for equality with true
+// and false.
+MATCHER(IsTrue, negation ? "is false" : "is true") {
+  return static_cast<bool>(arg);
+}
+
+// Define a matcher that matches a value that evaluates in boolean
+// context to false.  Useful for types that define "explicit operator
+// bool" operators and so can't be compared for equality with true
+// and false.
+MATCHER(IsFalse, negation ? "is true" : "is false") {
+  return !static_cast<bool>(arg);
+}
+
+#if defined(_MSC_VER) && (_MSC_VER == 1900)
+GTEST_DISABLE_MSC_WARNINGS_POP_()  // 4800
+#endif
+GTEST_DISABLE_MSC_WARNINGS_POP_()  // 4100
+
+}  // namespace testing
+
+#endif  // GOOGLEMOCK_INCLUDE_GMOCK_GMOCK_MORE_MATCHERS_H_
diff --git a/third_party/googletest/googlemock/include/gmock/gmock-nice-strict.h b/third_party/googletest/googlemock/include/gmock/gmock-nice-strict.h
new file mode 100644
index 0000000..056d471
--- /dev/null
+++ b/third_party/googletest/googlemock/include/gmock/gmock-nice-strict.h
@@ -0,0 +1,277 @@
+// Copyright 2008, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Implements class templates NiceMock, NaggyMock, and StrictMock.
+//
+// Given a mock class MockFoo that is created using Google Mock,
+// NiceMock<MockFoo> is a subclass of MockFoo that allows
+// uninteresting calls (i.e. calls to mock methods that have no
+// EXPECT_CALL specs), NaggyMock<MockFoo> is a subclass of MockFoo
+// that prints a warning when an uninteresting call occurs, and
+// StrictMock<MockFoo> is a subclass of MockFoo that treats all
+// uninteresting calls as errors.
+//
+// Currently a mock is naggy by default, so MockFoo and
+// NaggyMock<MockFoo> behave like the same.  However, we will soon
+// switch the default behavior of mocks to be nice, as that in general
+// leads to more maintainable tests.  When that happens, MockFoo will
+// stop behaving like NaggyMock<MockFoo> and start behaving like
+// NiceMock<MockFoo>.
+//
+// NiceMock, NaggyMock, and StrictMock "inherit" the constructors of
+// their respective base class.  Therefore you can write
+// NiceMock<MockFoo>(5, "a") to construct a nice mock where MockFoo
+// has a constructor that accepts (int, const char*), for example.
+//
+// A known limitation is that NiceMock<MockFoo>, NaggyMock<MockFoo>,
+// and StrictMock<MockFoo> only works for mock methods defined using
+// the MOCK_METHOD* family of macros DIRECTLY in the MockFoo class.
+// If a mock method is defined in a base class of MockFoo, the "nice"
+// or "strict" modifier may not affect it, depending on the compiler.
+// In particular, nesting NiceMock, NaggyMock, and StrictMock is NOT
+// supported.
+
+// IWYU pragma: private, include "gmock/gmock.h"
+// IWYU pragma: friend gmock/.*
+
+#ifndef GOOGLEMOCK_INCLUDE_GMOCK_GMOCK_NICE_STRICT_H_
+#define GOOGLEMOCK_INCLUDE_GMOCK_GMOCK_NICE_STRICT_H_
+
+#include <cstdint>
+#include <type_traits>
+
+#include "gmock/gmock-spec-builders.h"
+#include "gmock/internal/gmock-port.h"
+
+namespace testing {
+template <class MockClass>
+class NiceMock;
+template <class MockClass>
+class NaggyMock;
+template <class MockClass>
+class StrictMock;
+
+namespace internal {
+template <typename T>
+std::true_type StrictnessModifierProbe(const NiceMock<T>&);
+template <typename T>
+std::true_type StrictnessModifierProbe(const NaggyMock<T>&);
+template <typename T>
+std::true_type StrictnessModifierProbe(const StrictMock<T>&);
+std::false_type StrictnessModifierProbe(...);
+
+template <typename T>
+constexpr bool HasStrictnessModifier() {
+  return decltype(StrictnessModifierProbe(std::declval<const T&>()))::value;
+}
+
+// Base classes that register and deregister with testing::Mock to alter the
+// default behavior around uninteresting calls. Inheriting from one of these
+// classes first and then MockClass ensures the MockClass constructor is run
+// after registration, and that the MockClass destructor runs before
+// deregistration. This guarantees that MockClass's constructor and destructor
+// run with the same level of strictness as its instance methods.
+
+#if defined(GTEST_OS_WINDOWS) && !defined(GTEST_OS_WINDOWS_MINGW) && \
+    (defined(_MSC_VER) || defined(__clang__))
+// We need to mark these classes with this declspec to ensure that
+// the empty base class optimization is performed.
+#define GTEST_INTERNAL_EMPTY_BASE_CLASS __declspec(empty_bases)
+#else
+#define GTEST_INTERNAL_EMPTY_BASE_CLASS
+#endif
+
+template <typename Base>
+class NiceMockImpl {
+ public:
+  NiceMockImpl() {
+    ::testing::Mock::AllowUninterestingCalls(reinterpret_cast<uintptr_t>(this));
+  }
+
+  ~NiceMockImpl() {
+    ::testing::Mock::UnregisterCallReaction(reinterpret_cast<uintptr_t>(this));
+  }
+};
+
+template <typename Base>
+class NaggyMockImpl {
+ public:
+  NaggyMockImpl() {
+    ::testing::Mock::WarnUninterestingCalls(reinterpret_cast<uintptr_t>(this));
+  }
+
+  ~NaggyMockImpl() {
+    ::testing::Mock::UnregisterCallReaction(reinterpret_cast<uintptr_t>(this));
+  }
+};
+
+template <typename Base>
+class StrictMockImpl {
+ public:
+  StrictMockImpl() {
+    ::testing::Mock::FailUninterestingCalls(reinterpret_cast<uintptr_t>(this));
+  }
+
+  ~StrictMockImpl() {
+    ::testing::Mock::UnregisterCallReaction(reinterpret_cast<uintptr_t>(this));
+  }
+};
+
+}  // namespace internal
+
+template <class MockClass>
+class GTEST_INTERNAL_EMPTY_BASE_CLASS NiceMock
+    : private internal::NiceMockImpl<MockClass>,
+      public MockClass {
+ public:
+  static_assert(!internal::HasStrictnessModifier<MockClass>(),
+                "Can't apply NiceMock to a class hierarchy that already has a "
+                "strictness modifier. See "
+                "https://google.github.io/googletest/"
+                "gmock_cook_book.html#NiceStrictNaggy");
+  NiceMock() : MockClass() {
+    static_assert(sizeof(*this) == sizeof(MockClass),
+                  "The impl subclass shouldn't introduce any padding");
+  }
+
+  // Ideally, we would inherit base class's constructors through a using
+  // declaration, which would preserve their visibility. However, many existing
+  // tests rely on the fact that current implementation reexports protected
+  // constructors as public. These tests would need to be cleaned up first.
+
+  // Single argument constructor is special-cased so that it can be
+  // made explicit.
+  template <typename A>
+  explicit NiceMock(A&& arg) : MockClass(std::forward<A>(arg)) {
+    static_assert(sizeof(*this) == sizeof(MockClass),
+                  "The impl subclass shouldn't introduce any padding");
+  }
+
+  template <typename TArg1, typename TArg2, typename... An>
+  NiceMock(TArg1&& arg1, TArg2&& arg2, An&&... args)
+      : MockClass(std::forward<TArg1>(arg1), std::forward<TArg2>(arg2),
+                  std::forward<An>(args)...) {
+    static_assert(sizeof(*this) == sizeof(MockClass),
+                  "The impl subclass shouldn't introduce any padding");
+  }
+
+ private:
+  NiceMock(const NiceMock&) = delete;
+  NiceMock& operator=(const NiceMock&) = delete;
+};
+
+template <class MockClass>
+class GTEST_INTERNAL_EMPTY_BASE_CLASS NaggyMock
+    : private internal::NaggyMockImpl<MockClass>,
+      public MockClass {
+  static_assert(!internal::HasStrictnessModifier<MockClass>(),
+                "Can't apply NaggyMock to a class hierarchy that already has a "
+                "strictness modifier. See "
+                "https://google.github.io/googletest/"
+                "gmock_cook_book.html#NiceStrictNaggy");
+
+ public:
+  NaggyMock() : MockClass() {
+    static_assert(sizeof(*this) == sizeof(MockClass),
+                  "The impl subclass shouldn't introduce any padding");
+  }
+
+  // Ideally, we would inherit base class's constructors through a using
+  // declaration, which would preserve their visibility. However, many existing
+  // tests rely on the fact that current implementation reexports protected
+  // constructors as public. These tests would need to be cleaned up first.
+
+  // Single argument constructor is special-cased so that it can be
+  // made explicit.
+  template <typename A>
+  explicit NaggyMock(A&& arg) : MockClass(std::forward<A>(arg)) {
+    static_assert(sizeof(*this) == sizeof(MockClass),
+                  "The impl subclass shouldn't introduce any padding");
+  }
+
+  template <typename TArg1, typename TArg2, typename... An>
+  NaggyMock(TArg1&& arg1, TArg2&& arg2, An&&... args)
+      : MockClass(std::forward<TArg1>(arg1), std::forward<TArg2>(arg2),
+                  std::forward<An>(args)...) {
+    static_assert(sizeof(*this) == sizeof(MockClass),
+                  "The impl subclass shouldn't introduce any padding");
+  }
+
+ private:
+  NaggyMock(const NaggyMock&) = delete;
+  NaggyMock& operator=(const NaggyMock&) = delete;
+};
+
+template <class MockClass>
+class GTEST_INTERNAL_EMPTY_BASE_CLASS StrictMock
+    : private internal::StrictMockImpl<MockClass>,
+      public MockClass {
+ public:
+  static_assert(
+      !internal::HasStrictnessModifier<MockClass>(),
+      "Can't apply StrictMock to a class hierarchy that already has a "
+      "strictness modifier. See "
+      "https://google.github.io/googletest/"
+      "gmock_cook_book.html#NiceStrictNaggy");
+  StrictMock() : MockClass() {
+    static_assert(sizeof(*this) == sizeof(MockClass),
+                  "The impl subclass shouldn't introduce any padding");
+  }
+
+  // Ideally, we would inherit base class's constructors through a using
+  // declaration, which would preserve their visibility. However, many existing
+  // tests rely on the fact that current implementation reexports protected
+  // constructors as public. These tests would need to be cleaned up first.
+
+  // Single argument constructor is special-cased so that it can be
+  // made explicit.
+  template <typename A>
+  explicit StrictMock(A&& arg) : MockClass(std::forward<A>(arg)) {
+    static_assert(sizeof(*this) == sizeof(MockClass),
+                  "The impl subclass shouldn't introduce any padding");
+  }
+
+  template <typename TArg1, typename TArg2, typename... An>
+  StrictMock(TArg1&& arg1, TArg2&& arg2, An&&... args)
+      : MockClass(std::forward<TArg1>(arg1), std::forward<TArg2>(arg2),
+                  std::forward<An>(args)...) {
+    static_assert(sizeof(*this) == sizeof(MockClass),
+                  "The impl subclass shouldn't introduce any padding");
+  }
+
+ private:
+  StrictMock(const StrictMock&) = delete;
+  StrictMock& operator=(const StrictMock&) = delete;
+};
+
+#undef GTEST_INTERNAL_EMPTY_BASE_CLASS
+
+}  // namespace testing
+
+#endif  // GOOGLEMOCK_INCLUDE_GMOCK_GMOCK_NICE_STRICT_H_
diff --git a/third_party/googletest/googlemock/include/gmock/gmock-spec-builders.h b/third_party/googletest/googlemock/include/gmock/gmock-spec-builders.h
new file mode 100644
index 0000000..78ca15d
--- /dev/null
+++ b/third_party/googletest/googlemock/include/gmock/gmock-spec-builders.h
@@ -0,0 +1,2148 @@
+// Copyright 2007, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Google Mock - a framework for writing C++ mock classes.
+//
+// This file implements the ON_CALL() and EXPECT_CALL() macros.
+//
+// A user can use the ON_CALL() macro to specify the default action of
+// a mock method.  The syntax is:
+//
+//   ON_CALL(mock_object, Method(argument-matchers))
+//       .With(multi-argument-matcher)
+//       .WillByDefault(action);
+//
+//  where the .With() clause is optional.
+//
+// A user can use the EXPECT_CALL() macro to specify an expectation on
+// a mock method.  The syntax is:
+//
+//   EXPECT_CALL(mock_object, Method(argument-matchers))
+//       .With(multi-argument-matchers)
+//       .Times(cardinality)
+//       .InSequence(sequences)
+//       .After(expectations)
+//       .WillOnce(action)
+//       .WillRepeatedly(action)
+//       .RetiresOnSaturation();
+//
+// where all clauses are optional, and .InSequence()/.After()/
+// .WillOnce() can appear any number of times.
+
+// IWYU pragma: private, include "gmock/gmock.h"
+// IWYU pragma: friend gmock/.*
+
+#ifndef GOOGLEMOCK_INCLUDE_GMOCK_GMOCK_SPEC_BUILDERS_H_
+#define GOOGLEMOCK_INCLUDE_GMOCK_GMOCK_SPEC_BUILDERS_H_
+
+#include <cstdint>
+#include <functional>
+#include <map>
+#include <memory>
+#include <ostream>
+#include <set>
+#include <sstream>
+#include <string>
+#include <type_traits>
+#include <utility>
+#include <vector>
+
+#include "gmock/gmock-actions.h"
+#include "gmock/gmock-cardinalities.h"
+#include "gmock/gmock-matchers.h"
+#include "gmock/internal/gmock-internal-utils.h"
+#include "gmock/internal/gmock-port.h"
+#include "gtest/gtest.h"
+
+#if GTEST_HAS_EXCEPTIONS
+#include <stdexcept>  // NOLINT
+#endif
+
+GTEST_DISABLE_MSC_WARNINGS_PUSH_(4251 \
+/* class A needs to have dll-interface to be used by clients of class B */)
+
+namespace testing {
+
+// An abstract handle of an expectation.
+class Expectation;
+
+// A set of expectation handles.
+class ExpectationSet;
+
+// Anything inside the 'internal' namespace IS INTERNAL IMPLEMENTATION
+// and MUST NOT BE USED IN USER CODE!!!
+namespace internal {
+
+// Implements a mock function.
+template <typename F>
+class FunctionMocker;
+
+// Base class for expectations.
+class ExpectationBase;
+
+// Implements an expectation.
+template <typename F>
+class TypedExpectation;
+
+// Helper class for testing the Expectation class template.
+class ExpectationTester;
+
+// Helper classes for implementing NiceMock, StrictMock, and NaggyMock.
+template <typename MockClass>
+class NiceMockImpl;
+template <typename MockClass>
+class StrictMockImpl;
+template <typename MockClass>
+class NaggyMockImpl;
+
+// Protects the mock object registry (in class Mock), all function
+// mockers, and all expectations.
+//
+// The reason we don't use more fine-grained protection is: when a
+// mock function Foo() is called, it needs to consult its expectations
+// to see which one should be picked.  If another thread is allowed to
+// call a mock function (either Foo() or a different one) at the same
+// time, it could affect the "retired" attributes of Foo()'s
+// expectations when InSequence() is used, and thus affect which
+// expectation gets picked.  Therefore, we sequence all mock function
+// calls to ensure the integrity of the mock objects' states.
+GTEST_API_ GTEST_DECLARE_STATIC_MUTEX_(g_gmock_mutex);
+
+// Abstract base class of FunctionMocker.  This is the
+// type-agnostic part of the function mocker interface.  Its pure
+// virtual methods are implemented by FunctionMocker.
+class GTEST_API_ UntypedFunctionMockerBase {
+ public:
+  UntypedFunctionMockerBase();
+  virtual ~UntypedFunctionMockerBase();
+
+  // Verifies that all expectations on this mock function have been
+  // satisfied.  Reports one or more Google Test non-fatal failures
+  // and returns false if not.
+  bool VerifyAndClearExpectationsLocked()
+      GTEST_EXCLUSIVE_LOCK_REQUIRED_(g_gmock_mutex);
+
+  // Clears the ON_CALL()s set on this mock function.
+  virtual void ClearDefaultActionsLocked()
+      GTEST_EXCLUSIVE_LOCK_REQUIRED_(g_gmock_mutex) = 0;
+
+  // In all of the following Untyped* functions, it's the caller's
+  // responsibility to guarantee the correctness of the arguments'
+  // types.
+
+  // Writes a message that the call is uninteresting (i.e. neither
+  // explicitly expected nor explicitly unexpected) to the given
+  // ostream.
+  virtual void UntypedDescribeUninterestingCall(const void* untyped_args,
+                                                ::std::ostream* os) const
+      GTEST_LOCK_EXCLUDED_(g_gmock_mutex) = 0;
+
+  // Returns the expectation that matches the given function arguments
+  // (or NULL is there's no match); when a match is found,
+  // untyped_action is set to point to the action that should be
+  // performed (or NULL if the action is "do default"), and
+  // is_excessive is modified to indicate whether the call exceeds the
+  // expected number.
+  virtual const ExpectationBase* UntypedFindMatchingExpectation(
+      const void* untyped_args, const void** untyped_action, bool* is_excessive,
+      ::std::ostream* what, ::std::ostream* why)
+      GTEST_LOCK_EXCLUDED_(g_gmock_mutex) = 0;
+
+  // Prints the given function arguments to the ostream.
+  virtual void UntypedPrintArgs(const void* untyped_args,
+                                ::std::ostream* os) const = 0;
+
+  // Sets the mock object this mock method belongs to, and registers
+  // this information in the global mock registry.  Will be called
+  // whenever an EXPECT_CALL() or ON_CALL() is executed on this mock
+  // method.
+  void RegisterOwner(const void* mock_obj) GTEST_LOCK_EXCLUDED_(g_gmock_mutex);
+
+  // Sets the mock object this mock method belongs to, and sets the
+  // name of the mock function.  Will be called upon each invocation
+  // of this mock function.
+  void SetOwnerAndName(const void* mock_obj, const char* name)
+      GTEST_LOCK_EXCLUDED_(g_gmock_mutex);
+
+  // Returns the mock object this mock method belongs to.  Must be
+  // called after RegisterOwner() or SetOwnerAndName() has been
+  // called.
+  const void* MockObject() const GTEST_LOCK_EXCLUDED_(g_gmock_mutex);
+
+  // Returns the name of this mock method.  Must be called after
+  // SetOwnerAndName() has been called.
+  const char* Name() const GTEST_LOCK_EXCLUDED_(g_gmock_mutex);
+
+ protected:
+  typedef std::vector<const void*> UntypedOnCallSpecs;
+
+  using UntypedExpectations = std::vector<std::shared_ptr<ExpectationBase>>;
+
+  struct UninterestingCallCleanupHandler;
+  struct FailureCleanupHandler;
+
+  // Returns an Expectation object that references and co-owns exp,
+  // which must be an expectation on this mock function.
+  Expectation GetHandleOf(ExpectationBase* exp);
+
+  // Address of the mock object this mock method belongs to.  Only
+  // valid after this mock method has been called or
+  // ON_CALL/EXPECT_CALL has been invoked on it.
+  const void* mock_obj_;  // Protected by g_gmock_mutex.
+
+  // Name of the function being mocked.  Only valid after this mock
+  // method has been called.
+  const char* name_;  // Protected by g_gmock_mutex.
+
+  // All default action specs for this function mocker.
+  UntypedOnCallSpecs untyped_on_call_specs_;
+
+  // All expectations for this function mocker.
+  //
+  // It's undefined behavior to interleave expectations (EXPECT_CALLs
+  // or ON_CALLs) and mock function calls.  Also, the order of
+  // expectations is important.  Therefore it's a logic race condition
+  // to read/write untyped_expectations_ concurrently.  In order for
+  // tools like tsan to catch concurrent read/write accesses to
+  // untyped_expectations, we deliberately leave accesses to it
+  // unprotected.
+  UntypedExpectations untyped_expectations_;
+};  // class UntypedFunctionMockerBase
+
+// Untyped base class for OnCallSpec<F>.
+class UntypedOnCallSpecBase {
+ public:
+  // The arguments are the location of the ON_CALL() statement.
+  UntypedOnCallSpecBase(const char* a_file, int a_line)
+      : file_(a_file), line_(a_line), last_clause_(kNone) {}
+
+  // Where in the source file was the default action spec defined?
+  const char* file() const { return file_; }
+  int line() const { return line_; }
+
+ protected:
+  // Gives each clause in the ON_CALL() statement a name.
+  enum Clause {
+    // Do not change the order of the enum members!  The run-time
+    // syntax checking relies on it.
+    kNone,
+    kWith,
+    kWillByDefault
+  };
+
+  // Asserts that the ON_CALL() statement has a certain property.
+  void AssertSpecProperty(bool property,
+                          const std::string& failure_message) const {
+    Assert(property, file_, line_, failure_message);
+  }
+
+  // Expects that the ON_CALL() statement has a certain property.
+  void ExpectSpecProperty(bool property,
+                          const std::string& failure_message) const {
+    Expect(property, file_, line_, failure_message);
+  }
+
+  const char* file_;
+  int line_;
+
+  // The last clause in the ON_CALL() statement as seen so far.
+  // Initially kNone and changes as the statement is parsed.
+  Clause last_clause_;
+};  // class UntypedOnCallSpecBase
+
+// This template class implements an ON_CALL spec.
+template <typename F>
+class OnCallSpec : public UntypedOnCallSpecBase {
+ public:
+  typedef typename Function<F>::ArgumentTuple ArgumentTuple;
+  typedef typename Function<F>::ArgumentMatcherTuple ArgumentMatcherTuple;
+
+  // Constructs an OnCallSpec object from the information inside
+  // the parenthesis of an ON_CALL() statement.
+  OnCallSpec(const char* a_file, int a_line,
+             const ArgumentMatcherTuple& matchers)
+      : UntypedOnCallSpecBase(a_file, a_line),
+        matchers_(matchers),
+        // By default, extra_matcher_ should match anything.  However,
+        // we cannot initialize it with _ as that causes ambiguity between
+        // Matcher's copy and move constructor for some argument types.
+        extra_matcher_(A<const ArgumentTuple&>()) {}
+
+  // Implements the .With() clause.
+  OnCallSpec& With(const Matcher<const ArgumentTuple&>& m) {
+    // Makes sure this is called at most once.
+    ExpectSpecProperty(last_clause_ < kWith,
+                       ".With() cannot appear "
+                       "more than once in an ON_CALL().");
+    last_clause_ = kWith;
+
+    extra_matcher_ = m;
+    return *this;
+  }
+
+  // Implements the .WillByDefault() clause.
+  OnCallSpec& WillByDefault(const Action<F>& action) {
+    ExpectSpecProperty(last_clause_ < kWillByDefault,
+                       ".WillByDefault() must appear "
+                       "exactly once in an ON_CALL().");
+    last_clause_ = kWillByDefault;
+
+    ExpectSpecProperty(!action.IsDoDefault(),
+                       "DoDefault() cannot be used in ON_CALL().");
+    action_ = action;
+    return *this;
+  }
+
+  // Returns true if and only if the given arguments match the matchers.
+  bool Matches(const ArgumentTuple& args) const {
+    return TupleMatches(matchers_, args) && extra_matcher_.Matches(args);
+  }
+
+  // Returns the action specified by the user.
+  const Action<F>& GetAction() const {
+    AssertSpecProperty(last_clause_ == kWillByDefault,
+                       ".WillByDefault() must appear exactly "
+                       "once in an ON_CALL().");
+    return action_;
+  }
+
+ private:
+  // The information in statement
+  //
+  //   ON_CALL(mock_object, Method(matchers))
+  //       .With(multi-argument-matcher)
+  //       .WillByDefault(action);
+  //
+  // is recorded in the data members like this:
+  //
+  //   source file that contains the statement => file_
+  //   line number of the statement            => line_
+  //   matchers                                => matchers_
+  //   multi-argument-matcher                  => extra_matcher_
+  //   action                                  => action_
+  ArgumentMatcherTuple matchers_;
+  Matcher<const ArgumentTuple&> extra_matcher_;
+  Action<F> action_;
+};  // class OnCallSpec
+
+// Possible reactions on uninteresting calls.
+enum CallReaction {
+  kAllow,
+  kWarn,
+  kFail,
+};
+
+}  // namespace internal
+
+// Utilities for manipulating mock objects.
+class GTEST_API_ Mock {
+ public:
+  // The following public methods can be called concurrently.
+
+  // Tells Google Mock to ignore mock_obj when checking for leaked
+  // mock objects.
+  static void AllowLeak(const void* mock_obj)
+      GTEST_LOCK_EXCLUDED_(internal::g_gmock_mutex);
+
+  // Verifies and clears all expectations on the given mock object.
+  // If the expectations aren't satisfied, generates one or more
+  // Google Test non-fatal failures and returns false.
+  static bool VerifyAndClearExpectations(void* mock_obj)
+      GTEST_LOCK_EXCLUDED_(internal::g_gmock_mutex);
+
+  // Verifies all expectations on the given mock object and clears its
+  // default actions and expectations.  Returns true if and only if the
+  // verification was successful.
+  static bool VerifyAndClear(void* mock_obj)
+      GTEST_LOCK_EXCLUDED_(internal::g_gmock_mutex);
+
+  // Returns whether the mock was created as a naggy mock (default)
+  static bool IsNaggy(void* mock_obj)
+      GTEST_LOCK_EXCLUDED_(internal::g_gmock_mutex);
+  // Returns whether the mock was created as a nice mock
+  static bool IsNice(void* mock_obj)
+      GTEST_LOCK_EXCLUDED_(internal::g_gmock_mutex);
+  // Returns whether the mock was created as a strict mock
+  static bool IsStrict(void* mock_obj)
+      GTEST_LOCK_EXCLUDED_(internal::g_gmock_mutex);
+
+ private:
+  friend class internal::UntypedFunctionMockerBase;
+
+  // Needed for a function mocker to register itself (so that we know
+  // how to clear a mock object).
+  template <typename F>
+  friend class internal::FunctionMocker;
+
+  template <typename MockClass>
+  friend class internal::NiceMockImpl;
+  template <typename MockClass>
+  friend class internal::NaggyMockImpl;
+  template <typename MockClass>
+  friend class internal::StrictMockImpl;
+
+  // Tells Google Mock to allow uninteresting calls on the given mock
+  // object.
+  static void AllowUninterestingCalls(uintptr_t mock_obj)
+      GTEST_LOCK_EXCLUDED_(internal::g_gmock_mutex);
+
+  // Tells Google Mock to warn the user about uninteresting calls on
+  // the given mock object.
+  static void WarnUninterestingCalls(uintptr_t mock_obj)
+      GTEST_LOCK_EXCLUDED_(internal::g_gmock_mutex);
+
+  // Tells Google Mock to fail uninteresting calls on the given mock
+  // object.
+  static void FailUninterestingCalls(uintptr_t mock_obj)
+      GTEST_LOCK_EXCLUDED_(internal::g_gmock_mutex);
+
+  // Tells Google Mock the given mock object is being destroyed and
+  // its entry in the call-reaction table should be removed.
+  static void UnregisterCallReaction(uintptr_t mock_obj)
+      GTEST_LOCK_EXCLUDED_(internal::g_gmock_mutex);
+
+  // Returns the reaction Google Mock will have on uninteresting calls
+  // made on the given mock object.
+  static internal::CallReaction GetReactionOnUninterestingCalls(
+      const void* mock_obj) GTEST_LOCK_EXCLUDED_(internal::g_gmock_mutex);
+
+  // Verifies that all expectations on the given mock object have been
+  // satisfied.  Reports one or more Google Test non-fatal failures
+  // and returns false if not.
+  static bool VerifyAndClearExpectationsLocked(void* mock_obj)
+      GTEST_EXCLUSIVE_LOCK_REQUIRED_(internal::g_gmock_mutex);
+
+  // Clears all ON_CALL()s set on the given mock object.
+  static void ClearDefaultActionsLocked(void* mock_obj)
+      GTEST_EXCLUSIVE_LOCK_REQUIRED_(internal::g_gmock_mutex);
+
+  // Registers a mock object and a mock method it owns.
+  static void Register(const void* mock_obj,
+                       internal::UntypedFunctionMockerBase* mocker)
+      GTEST_LOCK_EXCLUDED_(internal::g_gmock_mutex);
+
+  // Tells Google Mock where in the source code mock_obj is used in an
+  // ON_CALL or EXPECT_CALL.  In case mock_obj is leaked, this
+  // information helps the user identify which object it is.
+  static void RegisterUseByOnCallOrExpectCall(const void* mock_obj,
+                                              const char* file, int line)
+      GTEST_LOCK_EXCLUDED_(internal::g_gmock_mutex);
+
+  // Unregisters a mock method; removes the owning mock object from
+  // the registry when the last mock method associated with it has
+  // been unregistered.  This is called only in the destructor of
+  // FunctionMocker.
+  static void UnregisterLocked(internal::UntypedFunctionMockerBase* mocker)
+      GTEST_EXCLUSIVE_LOCK_REQUIRED_(internal::g_gmock_mutex);
+};  // class Mock
+
+// An abstract handle of an expectation.  Useful in the .After()
+// clause of EXPECT_CALL() for setting the (partial) order of
+// expectations.  The syntax:
+//
+//   Expectation e1 = EXPECT_CALL(...)...;
+//   EXPECT_CALL(...).After(e1)...;
+//
+// sets two expectations where the latter can only be matched after
+// the former has been satisfied.
+//
+// Notes:
+//   - This class is copyable and has value semantics.
+//   - Constness is shallow: a const Expectation object itself cannot
+//     be modified, but the mutable methods of the ExpectationBase
+//     object it references can be called via expectation_base().
+
+class GTEST_API_ Expectation {
+ public:
+  // Constructs a null object that doesn't reference any expectation.
+  Expectation();
+  Expectation(Expectation&&) = default;
+  Expectation(const Expectation&) = default;
+  Expectation& operator=(Expectation&&) = default;
+  Expectation& operator=(const Expectation&) = default;
+  ~Expectation();
+
+  // This single-argument ctor must not be explicit, in order to support the
+  //   Expectation e = EXPECT_CALL(...);
+  // syntax.
+  //
+  // A TypedExpectation object stores its pre-requisites as
+  // Expectation objects, and needs to call the non-const Retire()
+  // method on the ExpectationBase objects they reference.  Therefore
+  // Expectation must receive a *non-const* reference to the
+  // ExpectationBase object.
+  Expectation(internal::ExpectationBase& exp);  // NOLINT
+
+  // The compiler-generated copy ctor and operator= work exactly as
+  // intended, so we don't need to define our own.
+
+  // Returns true if and only if rhs references the same expectation as this
+  // object does.
+  bool operator==(const Expectation& rhs) const {
+    return expectation_base_ == rhs.expectation_base_;
+  }
+
+  bool operator!=(const Expectation& rhs) const { return !(*this == rhs); }
+
+ private:
+  friend class ExpectationSet;
+  friend class Sequence;
+  friend class ::testing::internal::ExpectationBase;
+  friend class ::testing::internal::UntypedFunctionMockerBase;
+
+  template <typename F>
+  friend class ::testing::internal::FunctionMocker;
+
+  template <typename F>
+  friend class ::testing::internal::TypedExpectation;
+
+  // This comparator is needed for putting Expectation objects into a set.
+  class Less {
+   public:
+    bool operator()(const Expectation& lhs, const Expectation& rhs) const {
+      return lhs.expectation_base_.get() < rhs.expectation_base_.get();
+    }
+  };
+
+  typedef ::std::set<Expectation, Less> Set;
+
+  Expectation(
+      const std::shared_ptr<internal::ExpectationBase>& expectation_base);
+
+  // Returns the expectation this object references.
+  const std::shared_ptr<internal::ExpectationBase>& expectation_base() const {
+    return expectation_base_;
+  }
+
+  // A shared_ptr that co-owns the expectation this handle references.
+  std::shared_ptr<internal::ExpectationBase> expectation_base_;
+};
+
+// A set of expectation handles.  Useful in the .After() clause of
+// EXPECT_CALL() for setting the (partial) order of expectations.  The
+// syntax:
+//
+//   ExpectationSet es;
+//   es += EXPECT_CALL(...)...;
+//   es += EXPECT_CALL(...)...;
+//   EXPECT_CALL(...).After(es)...;
+//
+// sets three expectations where the last one can only be matched
+// after the first two have both been satisfied.
+//
+// This class is copyable and has value semantics.
+class ExpectationSet {
+ public:
+  // A bidirectional iterator that can read a const element in the set.
+  typedef Expectation::Set::const_iterator const_iterator;
+
+  // An object stored in the set.  This is an alias of Expectation.
+  typedef Expectation::Set::value_type value_type;
+
+  // Constructs an empty set.
+  ExpectationSet() = default;
+
+  // This single-argument ctor must not be explicit, in order to support the
+  //   ExpectationSet es = EXPECT_CALL(...);
+  // syntax.
+  ExpectationSet(internal::ExpectationBase& exp) {  // NOLINT
+    *this += Expectation(exp);
+  }
+
+  // This single-argument ctor implements implicit conversion from
+  // Expectation and thus must not be explicit.  This allows either an
+  // Expectation or an ExpectationSet to be used in .After().
+  ExpectationSet(const Expectation& e) {  // NOLINT
+    *this += e;
+  }
+
+  // The compiler-generator ctor and operator= works exactly as
+  // intended, so we don't need to define our own.
+
+  // Returns true if and only if rhs contains the same set of Expectation
+  // objects as this does.
+  bool operator==(const ExpectationSet& rhs) const {
+    return expectations_ == rhs.expectations_;
+  }
+
+  bool operator!=(const ExpectationSet& rhs) const { return !(*this == rhs); }
+
+  // Implements the syntax
+  //   expectation_set += EXPECT_CALL(...);
+  ExpectationSet& operator+=(const Expectation& e) {
+    expectations_.insert(e);
+    return *this;
+  }
+
+  int size() const { return static_cast<int>(expectations_.size()); }
+
+  const_iterator begin() const { return expectations_.begin(); }
+  const_iterator end() const { return expectations_.end(); }
+
+ private:
+  Expectation::Set expectations_;
+};
+
+// Sequence objects are used by a user to specify the relative order
+// in which the expectations should match.  They are copyable (we rely
+// on the compiler-defined copy constructor and assignment operator).
+class GTEST_API_ Sequence {
+ public:
+  // Constructs an empty sequence.
+  Sequence() : last_expectation_(new Expectation) {}
+
+  // Adds an expectation to this sequence.  The caller must ensure
+  // that no other thread is accessing this Sequence object.
+  void AddExpectation(const Expectation& expectation) const;
+
+ private:
+  // The last expectation in this sequence.
+  std::shared_ptr<Expectation> last_expectation_;
+};  // class Sequence
+
+// An object of this type causes all EXPECT_CALL() statements
+// encountered in its scope to be put in an anonymous sequence.  The
+// work is done in the constructor and destructor.  You should only
+// create an InSequence object on the stack.
+//
+// The sole purpose for this class is to support easy definition of
+// sequential expectations, e.g.
+//
+//   {
+//     InSequence dummy;  // The name of the object doesn't matter.
+//
+//     // The following expectations must match in the order they appear.
+//     EXPECT_CALL(a, Bar())...;
+//     EXPECT_CALL(a, Baz())...;
+//     ...
+//     EXPECT_CALL(b, Xyz())...;
+//   }
+//
+// You can create InSequence objects in multiple threads, as long as
+// they are used to affect different mock objects.  The idea is that
+// each thread can create and set up its own mocks as if it's the only
+// thread.  However, for clarity of your tests we recommend you to set
+// up mocks in the main thread unless you have a good reason not to do
+// so.
+class GTEST_API_ InSequence {
+ public:
+  InSequence();
+  ~InSequence();
+
+ private:
+  bool sequence_created_;
+
+  InSequence(const InSequence&) = delete;
+  InSequence& operator=(const InSequence&) = delete;
+};
+
+namespace internal {
+
+// Points to the implicit sequence introduced by a living InSequence
+// object (if any) in the current thread or NULL.
+GTEST_API_ extern ThreadLocal<Sequence*> g_gmock_implicit_sequence;
+
+// Base class for implementing expectations.
+//
+// There are two reasons for having a type-agnostic base class for
+// Expectation:
+//
+//   1. We need to store collections of expectations of different
+//   types (e.g. all pre-requisites of a particular expectation, all
+//   expectations in a sequence).  Therefore these expectation objects
+//   must share a common base class.
+//
+//   2. We can avoid binary code bloat by moving methods not depending
+//   on the template argument of Expectation to the base class.
+//
+// This class is internal and mustn't be used by user code directly.
+class GTEST_API_ ExpectationBase {
+ public:
+  // source_text is the EXPECT_CALL(...) source that created this Expectation.
+  ExpectationBase(const char* file, int line, const std::string& source_text);
+
+  virtual ~ExpectationBase();
+
+  // Where in the source file was the expectation spec defined?
+  const char* file() const { return file_; }
+  int line() const { return line_; }
+  const char* source_text() const { return source_text_.c_str(); }
+  // Returns the cardinality specified in the expectation spec.
+  const Cardinality& cardinality() const { return cardinality_; }
+
+  // Describes the source file location of this expectation.
+  void DescribeLocationTo(::std::ostream* os) const {
+    *os << FormatFileLocation(file(), line()) << " ";
+  }
+
+  // Describes how many times a function call matching this
+  // expectation has occurred.
+  void DescribeCallCountTo(::std::ostream* os) const
+      GTEST_EXCLUSIVE_LOCK_REQUIRED_(g_gmock_mutex);
+
+  // If this mock method has an extra matcher (i.e. .With(matcher)),
+  // describes it to the ostream.
+  virtual void MaybeDescribeExtraMatcherTo(::std::ostream* os) = 0;
+
+  // Do not rely on this for correctness.
+  // This is only for making human-readable test output easier to understand.
+  void UntypedDescription(std::string description) {
+    description_ = std::move(description);
+  }
+
+ protected:
+  friend class ::testing::Expectation;
+  friend class UntypedFunctionMockerBase;
+
+  enum Clause {
+    // Don't change the order of the enum members!
+    kNone,
+    kWith,
+    kTimes,
+    kInSequence,
+    kAfter,
+    kWillOnce,
+    kWillRepeatedly,
+    kRetiresOnSaturation
+  };
+
+  typedef std::vector<const void*> UntypedActions;
+
+  // Returns an Expectation object that references and co-owns this
+  // expectation.
+  virtual Expectation GetHandle() = 0;
+
+  // Asserts that the EXPECT_CALL() statement has the given property.
+  void AssertSpecProperty(bool property,
+                          const std::string& failure_message) const {
+    Assert(property, file_, line_, failure_message);
+  }
+
+  // Expects that the EXPECT_CALL() statement has the given property.
+  void ExpectSpecProperty(bool property,
+                          const std::string& failure_message) const {
+    Expect(property, file_, line_, failure_message);
+  }
+
+  // Explicitly specifies the cardinality of this expectation.  Used
+  // by the subclasses to implement the .Times() clause.
+  void SpecifyCardinality(const Cardinality& cardinality);
+
+  // Returns true if and only if the user specified the cardinality
+  // explicitly using a .Times().
+  bool cardinality_specified() const { return cardinality_specified_; }
+
+  // Sets the cardinality of this expectation spec.
+  void set_cardinality(const Cardinality& a_cardinality) {
+    cardinality_ = a_cardinality;
+  }
+
+  // The following group of methods should only be called after the
+  // EXPECT_CALL() statement, and only when g_gmock_mutex is held by
+  // the current thread.
+
+  // Retires all pre-requisites of this expectation.
+  void RetireAllPreRequisites() GTEST_EXCLUSIVE_LOCK_REQUIRED_(g_gmock_mutex);
+
+  // Returns true if and only if this expectation is retired.
+  bool is_retired() const GTEST_EXCLUSIVE_LOCK_REQUIRED_(g_gmock_mutex) {
+    g_gmock_mutex.AssertHeld();
+    return retired_;
+  }
+
+  // Retires this expectation.
+  void Retire() GTEST_EXCLUSIVE_LOCK_REQUIRED_(g_gmock_mutex) {
+    g_gmock_mutex.AssertHeld();
+    retired_ = true;
+  }
+
+  // Returns a human-readable description of this expectation.
+  // Do not rely on this for correctness. It is only for human readability.
+  const std::string& GetDescription() const { return description_; }
+
+  // Returns true if and only if this expectation is satisfied.
+  bool IsSatisfied() const GTEST_EXCLUSIVE_LOCK_REQUIRED_(g_gmock_mutex) {
+    g_gmock_mutex.AssertHeld();
+    return cardinality().IsSatisfiedByCallCount(call_count_);
+  }
+
+  // Returns true if and only if this expectation is saturated.
+  bool IsSaturated() const GTEST_EXCLUSIVE_LOCK_REQUIRED_(g_gmock_mutex) {
+    g_gmock_mutex.AssertHeld();
+    return cardinality().IsSaturatedByCallCount(call_count_);
+  }
+
+  // Returns true if and only if this expectation is over-saturated.
+  bool IsOverSaturated() const GTEST_EXCLUSIVE_LOCK_REQUIRED_(g_gmock_mutex) {
+    g_gmock_mutex.AssertHeld();
+    return cardinality().IsOverSaturatedByCallCount(call_count_);
+  }
+
+  // Returns true if and only if all pre-requisites of this expectation are
+  // satisfied.
+  bool AllPrerequisitesAreSatisfied() const
+      GTEST_EXCLUSIVE_LOCK_REQUIRED_(g_gmock_mutex);
+
+  // Adds unsatisfied pre-requisites of this expectation to 'result'.
+  void FindUnsatisfiedPrerequisites(ExpectationSet* result) const
+      GTEST_EXCLUSIVE_LOCK_REQUIRED_(g_gmock_mutex);
+
+  // Returns the number this expectation has been invoked.
+  int call_count() const GTEST_EXCLUSIVE_LOCK_REQUIRED_(g_gmock_mutex) {
+    g_gmock_mutex.AssertHeld();
+    return call_count_;
+  }
+
+  // Increments the number this expectation has been invoked.
+  void IncrementCallCount() GTEST_EXCLUSIVE_LOCK_REQUIRED_(g_gmock_mutex) {
+    g_gmock_mutex.AssertHeld();
+    call_count_++;
+  }
+
+  // Checks the action count (i.e. the number of WillOnce() and
+  // WillRepeatedly() clauses) against the cardinality if this hasn't
+  // been done before.  Prints a warning if there are too many or too
+  // few actions.
+  void CheckActionCountIfNotDone() const GTEST_LOCK_EXCLUDED_(mutex_);
+
+  friend class ::testing::Sequence;
+  friend class ::testing::internal::ExpectationTester;
+
+  template <typename Function>
+  friend class TypedExpectation;
+
+  // Implements the .Times() clause.
+  void UntypedTimes(const Cardinality& a_cardinality);
+
+  // This group of fields are part of the spec and won't change after
+  // an EXPECT_CALL() statement finishes.
+  const char* file_;               // The file that contains the expectation.
+  int line_;                       // The line number of the expectation.
+  const std::string source_text_;  // The EXPECT_CALL(...) source text.
+  std::string description_;        // User-readable name for the expectation.
+  // True if and only if the cardinality is specified explicitly.
+  bool cardinality_specified_;
+  Cardinality cardinality_;  // The cardinality of the expectation.
+  // The immediate pre-requisites (i.e. expectations that must be
+  // satisfied before this expectation can be matched) of this
+  // expectation.  We use std::shared_ptr in the set because we want an
+  // Expectation object to be co-owned by its FunctionMocker and its
+  // successors.  This allows multiple mock objects to be deleted at
+  // different times.
+  ExpectationSet immediate_prerequisites_;
+
+  // This group of fields are the current state of the expectation,
+  // and can change as the mock function is called.
+  int call_count_;  // How many times this expectation has been invoked.
+  bool retired_;    // True if and only if this expectation has retired.
+  UntypedActions untyped_actions_;
+  bool extra_matcher_specified_;
+  bool repeated_action_specified_;  // True if a WillRepeatedly() was specified.
+  bool retires_on_saturation_;
+  Clause last_clause_;
+  mutable bool action_count_checked_;  // Under mutex_.
+  mutable Mutex mutex_;                // Protects action_count_checked_.
+};                                     // class ExpectationBase
+
+template <typename F>
+class TypedExpectation;
+
+// Implements an expectation for the given function type.
+template <typename R, typename... Args>
+class TypedExpectation<R(Args...)> : public ExpectationBase {
+ private:
+  using F = R(Args...);
+
+ public:
+  typedef typename Function<F>::ArgumentTuple ArgumentTuple;
+  typedef typename Function<F>::ArgumentMatcherTuple ArgumentMatcherTuple;
+  typedef typename Function<F>::Result Result;
+
+  TypedExpectation(FunctionMocker<F>* owner, const char* a_file, int a_line,
+                   const std::string& a_source_text,
+                   const ArgumentMatcherTuple& m)
+      : ExpectationBase(a_file, a_line, a_source_text),
+        owner_(owner),
+        matchers_(m),
+        // By default, extra_matcher_ should match anything.  However,
+        // we cannot initialize it with _ as that causes ambiguity between
+        // Matcher's copy and move constructor for some argument types.
+        extra_matcher_(A<const ArgumentTuple&>()),
+        repeated_action_(DoDefault()) {}
+
+  ~TypedExpectation() override {
+    // Check the validity of the action count if it hasn't been done
+    // yet (for example, if the expectation was never used).
+    CheckActionCountIfNotDone();
+    for (UntypedActions::const_iterator it = untyped_actions_.begin();
+         it != untyped_actions_.end(); ++it) {
+      delete static_cast<const Action<F>*>(*it);
+    }
+  }
+
+  // Implements the .With() clause.
+  TypedExpectation& With(const Matcher<const ArgumentTuple&>& m) {
+    if (last_clause_ == kWith) {
+      ExpectSpecProperty(false,
+                         ".With() cannot appear "
+                         "more than once in an EXPECT_CALL().");
+    } else {
+      ExpectSpecProperty(last_clause_ < kWith,
+                         ".With() must be the first "
+                         "clause in an EXPECT_CALL().");
+    }
+    last_clause_ = kWith;
+
+    extra_matcher_ = m;
+    extra_matcher_specified_ = true;
+    return *this;
+  }
+
+  // Do not rely on this for correctness.
+  // This is only for making human-readable test output easier to understand.
+  TypedExpectation& Description(std::string name) {
+    ExpectationBase::UntypedDescription(std::move(name));
+    return *this;
+  }
+
+  // Implements the .Times() clause.
+  TypedExpectation& Times(const Cardinality& a_cardinality) {
+    ExpectationBase::UntypedTimes(a_cardinality);
+    return *this;
+  }
+
+  // Implements the .Times() clause.
+  TypedExpectation& Times(int n) { return Times(Exactly(n)); }
+
+  // Implements the .InSequence() clause.
+  TypedExpectation& InSequence(const Sequence& s) {
+    ExpectSpecProperty(last_clause_ <= kInSequence,
+                       ".InSequence() cannot appear after .After(),"
+                       " .WillOnce(), .WillRepeatedly(), or "
+                       ".RetiresOnSaturation().");
+    last_clause_ = kInSequence;
+
+    s.AddExpectation(GetHandle());
+    return *this;
+  }
+  TypedExpectation& InSequence(const Sequence& s1, const Sequence& s2) {
+    return InSequence(s1).InSequence(s2);
+  }
+  TypedExpectation& InSequence(const Sequence& s1, const Sequence& s2,
+                               const Sequence& s3) {
+    return InSequence(s1, s2).InSequence(s3);
+  }
+  TypedExpectation& InSequence(const Sequence& s1, const Sequence& s2,
+                               const Sequence& s3, const Sequence& s4) {
+    return InSequence(s1, s2, s3).InSequence(s4);
+  }
+  TypedExpectation& InSequence(const Sequence& s1, const Sequence& s2,
+                               const Sequence& s3, const Sequence& s4,
+                               const Sequence& s5) {
+    return InSequence(s1, s2, s3, s4).InSequence(s5);
+  }
+
+  // Implements that .After() clause.
+  TypedExpectation& After(const ExpectationSet& s) {
+    ExpectSpecProperty(last_clause_ <= kAfter,
+                       ".After() cannot appear after .WillOnce(),"
+                       " .WillRepeatedly(), or "
+                       ".RetiresOnSaturation().");
+    last_clause_ = kAfter;
+
+    for (ExpectationSet::const_iterator it = s.begin(); it != s.end(); ++it) {
+      immediate_prerequisites_ += *it;
+    }
+    return *this;
+  }
+  TypedExpectation& After(const ExpectationSet& s1, const ExpectationSet& s2) {
+    return After(s1).After(s2);
+  }
+  TypedExpectation& After(const ExpectationSet& s1, const ExpectationSet& s2,
+                          const ExpectationSet& s3) {
+    return After(s1, s2).After(s3);
+  }
+  TypedExpectation& After(const ExpectationSet& s1, const ExpectationSet& s2,
+                          const ExpectationSet& s3, const ExpectationSet& s4) {
+    return After(s1, s2, s3).After(s4);
+  }
+  TypedExpectation& After(const ExpectationSet& s1, const ExpectationSet& s2,
+                          const ExpectationSet& s3, const ExpectationSet& s4,
+                          const ExpectationSet& s5) {
+    return After(s1, s2, s3, s4).After(s5);
+  }
+
+  // Preferred, type-safe overload: consume anything that can be directly
+  // converted to a OnceAction, except for Action<F> objects themselves.
+  TypedExpectation& WillOnce(OnceAction<F> once_action) {
+    // Call the overload below, smuggling the OnceAction as a copyable callable.
+    // We know this is safe because a WillOnce action will not be called more
+    // than once.
+    return WillOnce(Action<F>(ActionAdaptor{
+        std::make_shared<OnceAction<F>>(std::move(once_action)),
+    }));
+  }
+
+  // Fallback overload: accept Action<F> objects and those actions that define
+  // `operator Action<F>` but not `operator OnceAction<F>`.
+  //
+  // This is templated in order to cause the overload above to be preferred
+  // when the input is convertible to either type.
+  template <int&... ExplicitArgumentBarrier, typename = void>
+  TypedExpectation& WillOnce(Action<F> action) {
+    ExpectSpecProperty(last_clause_ <= kWillOnce,
+                       ".WillOnce() cannot appear after "
+                       ".WillRepeatedly() or .RetiresOnSaturation().");
+    last_clause_ = kWillOnce;
+
+    untyped_actions_.push_back(new Action<F>(std::move(action)));
+
+    if (!cardinality_specified()) {
+      set_cardinality(Exactly(static_cast<int>(untyped_actions_.size())));
+    }
+    return *this;
+  }
+
+  // Implements the .WillRepeatedly() clause.
+  TypedExpectation& WillRepeatedly(const Action<F>& action) {
+    if (last_clause_ == kWillRepeatedly) {
+      ExpectSpecProperty(false,
+                         ".WillRepeatedly() cannot appear "
+                         "more than once in an EXPECT_CALL().");
+    } else {
+      ExpectSpecProperty(last_clause_ < kWillRepeatedly,
+                         ".WillRepeatedly() cannot appear "
+                         "after .RetiresOnSaturation().");
+    }
+    last_clause_ = kWillRepeatedly;
+    repeated_action_specified_ = true;
+
+    repeated_action_ = action;
+    if (!cardinality_specified()) {
+      set_cardinality(AtLeast(static_cast<int>(untyped_actions_.size())));
+    }
+
+    // Now that no more action clauses can be specified, we check
+    // whether their count makes sense.
+    CheckActionCountIfNotDone();
+    return *this;
+  }
+
+  // Implements the .RetiresOnSaturation() clause.
+  TypedExpectation& RetiresOnSaturation() {
+    ExpectSpecProperty(last_clause_ < kRetiresOnSaturation,
+                       ".RetiresOnSaturation() cannot appear "
+                       "more than once.");
+    last_clause_ = kRetiresOnSaturation;
+    retires_on_saturation_ = true;
+
+    // Now that no more action clauses can be specified, we check
+    // whether their count makes sense.
+    CheckActionCountIfNotDone();
+    return *this;
+  }
+
+  // Returns the matchers for the arguments as specified inside the
+  // EXPECT_CALL() macro.
+  const ArgumentMatcherTuple& matchers() const { return matchers_; }
+
+  // Returns the matcher specified by the .With() clause.
+  const Matcher<const ArgumentTuple&>& extra_matcher() const {
+    return extra_matcher_;
+  }
+
+  // Returns the action specified by the .WillRepeatedly() clause.
+  const Action<F>& repeated_action() const { return repeated_action_; }
+
+  // If this mock method has an extra matcher (i.e. .With(matcher)),
+  // describes it to the ostream.
+  void MaybeDescribeExtraMatcherTo(::std::ostream* os) override {
+    if (extra_matcher_specified_) {
+      *os << "    Expected args: ";
+      extra_matcher_.DescribeTo(os);
+      *os << "\n";
+    }
+  }
+
+ private:
+  template <typename Function>
+  friend class FunctionMocker;
+
+  // An adaptor that turns a OneAction<F> into something compatible with
+  // Action<F>. Must be called at most once.
+  struct ActionAdaptor {
+    std::shared_ptr<OnceAction<R(Args...)>> once_action;
+
+    R operator()(Args&&... args) const {
+      return std::move(*once_action).Call(std::forward<Args>(args)...);
+    }
+  };
+
+  // Returns an Expectation object that references and co-owns this
+  // expectation.
+  Expectation GetHandle() override { return owner_->GetHandleOf(this); }
+
+  // The following methods will be called only after the EXPECT_CALL()
+  // statement finishes and when the current thread holds
+  // g_gmock_mutex.
+
+  // Returns true if and only if this expectation matches the given arguments.
+  bool Matches(const ArgumentTuple& args) const
+      GTEST_EXCLUSIVE_LOCK_REQUIRED_(g_gmock_mutex) {
+    g_gmock_mutex.AssertHeld();
+    return TupleMatches(matchers_, args) && extra_matcher_.Matches(args);
+  }
+
+  // Returns true if and only if this expectation should handle the given
+  // arguments.
+  bool ShouldHandleArguments(const ArgumentTuple& args) const
+      GTEST_EXCLUSIVE_LOCK_REQUIRED_(g_gmock_mutex) {
+    g_gmock_mutex.AssertHeld();
+
+    // In case the action count wasn't checked when the expectation
+    // was defined (e.g. if this expectation has no WillRepeatedly()
+    // or RetiresOnSaturation() clause), we check it when the
+    // expectation is used for the first time.
+    CheckActionCountIfNotDone();
+    return !is_retired() && AllPrerequisitesAreSatisfied() && Matches(args);
+  }
+
+  // Describes the result of matching the arguments against this
+  // expectation to the given ostream.
+  void ExplainMatchResultTo(const ArgumentTuple& args, ::std::ostream* os) const
+      GTEST_EXCLUSIVE_LOCK_REQUIRED_(g_gmock_mutex) {
+    g_gmock_mutex.AssertHeld();
+
+    if (is_retired()) {
+      *os << "         Expected: the expectation is active\n"
+          << "           Actual: it is retired\n";
+    } else if (!Matches(args)) {
+      if (!TupleMatches(matchers_, args)) {
+        ExplainMatchFailureTupleTo(matchers_, args, os);
+      }
+      StringMatchResultListener listener;
+      if (!extra_matcher_.MatchAndExplain(args, &listener)) {
+        *os << "    Expected args: ";
+        extra_matcher_.DescribeTo(os);
+        *os << "\n           Actual: don't match";
+
+        internal::PrintIfNotEmpty(listener.str(), os);
+        *os << "\n";
+      }
+    } else if (!AllPrerequisitesAreSatisfied()) {
+      *os << "         Expected: all pre-requisites are satisfied\n"
+          << "           Actual: the following immediate pre-requisites "
+          << "are not satisfied:\n";
+      ExpectationSet unsatisfied_prereqs;
+      FindUnsatisfiedPrerequisites(&unsatisfied_prereqs);
+      int i = 0;
+      for (ExpectationSet::const_iterator it = unsatisfied_prereqs.begin();
+           it != unsatisfied_prereqs.end(); ++it) {
+        it->expectation_base()->DescribeLocationTo(os);
+        *os << "pre-requisite #" << i++ << "\n";
+      }
+      *os << "                   (end of pre-requisites)\n";
+    } else {
+      // This line is here just for completeness' sake.  It will never
+      // be executed as currently the ExplainMatchResultTo() function
+      // is called only when the mock function call does NOT match the
+      // expectation.
+      *os << "The call matches the expectation.\n";
+    }
+  }
+
+  // Returns the action that should be taken for the current invocation.
+  const Action<F>& GetCurrentAction(const FunctionMocker<F>* mocker,
+                                    const ArgumentTuple& args) const
+      GTEST_EXCLUSIVE_LOCK_REQUIRED_(g_gmock_mutex) {
+    g_gmock_mutex.AssertHeld();
+    const int count = call_count();
+    Assert(count >= 1, __FILE__, __LINE__,
+           "call_count() is <= 0 when GetCurrentAction() is "
+           "called - this should never happen.");
+
+    const int action_count = static_cast<int>(untyped_actions_.size());
+    if (action_count > 0 && !repeated_action_specified_ &&
+        count > action_count) {
+      // If there is at least one WillOnce() and no WillRepeatedly(),
+      // we warn the user when the WillOnce() clauses ran out.
+      ::std::stringstream ss;
+      DescribeLocationTo(&ss);
+      ss << "Actions ran out in " << source_text() << "...\n"
+         << "Called " << count << " times, but only " << action_count
+         << " WillOnce()" << (action_count == 1 ? " is" : "s are")
+         << " specified - ";
+      mocker->DescribeDefaultActionTo(args, &ss);
+      Log(kWarning, ss.str(), 1);
+    }
+
+    return count <= action_count
+               ? *static_cast<const Action<F>*>(
+                     untyped_actions_[static_cast<size_t>(count - 1)])
+               : repeated_action();
+  }
+
+  // Given the arguments of a mock function call, if the call will
+  // over-saturate this expectation, returns the default action;
+  // otherwise, returns the next action in this expectation.  Also
+  // describes *what* happened to 'what', and explains *why* Google
+  // Mock does it to 'why'.  This method is not const as it calls
+  // IncrementCallCount().  A return value of NULL means the default
+  // action.
+  const Action<F>* GetActionForArguments(const FunctionMocker<F>* mocker,
+                                         const ArgumentTuple& args,
+                                         ::std::ostream* what,
+                                         ::std::ostream* why)
+      GTEST_EXCLUSIVE_LOCK_REQUIRED_(g_gmock_mutex) {
+    g_gmock_mutex.AssertHeld();
+    const ::std::string& expectation_description = GetDescription();
+    if (IsSaturated()) {
+      // We have an excessive call.
+      IncrementCallCount();
+      *what << "Mock function ";
+      if (!expectation_description.empty()) {
+        *what << "\"" << expectation_description << "\" ";
+      }
+      *what << "called more times than expected - ";
+      mocker->DescribeDefaultActionTo(args, what);
+      DescribeCallCountTo(why);
+
+      return nullptr;
+    }
+
+    IncrementCallCount();
+    RetireAllPreRequisites();
+
+    if (retires_on_saturation_ && IsSaturated()) {
+      Retire();
+    }
+
+    // Must be done after IncrementCount()!
+    *what << "Mock function ";
+    if (!expectation_description.empty()) {
+      *what << "\"" << expectation_description << "\" ";
+    }
+    *what << "call matches " << source_text() << "...\n";
+    return &(GetCurrentAction(mocker, args));
+  }
+
+  // All the fields below won't change once the EXPECT_CALL()
+  // statement finishes.
+  FunctionMocker<F>* const owner_;
+  ArgumentMatcherTuple matchers_;
+  Matcher<const ArgumentTuple&> extra_matcher_;
+  Action<F> repeated_action_;
+
+  TypedExpectation(const TypedExpectation&) = delete;
+  TypedExpectation& operator=(const TypedExpectation&) = delete;
+};  // class TypedExpectation
+
+// A MockSpec object is used by ON_CALL() or EXPECT_CALL() for
+// specifying the default behavior of, or expectation on, a mock
+// function.
+
+// Note: class MockSpec really belongs to the ::testing namespace.
+// However if we define it in ::testing, MSVC will complain when
+// classes in ::testing::internal declare it as a friend class
+// template.  To workaround this compiler bug, we define MockSpec in
+// ::testing::internal and import it into ::testing.
+
+// Logs a message including file and line number information.
+GTEST_API_ void LogWithLocation(testing::internal::LogSeverity severity,
+                                const char* file, int line,
+                                const std::string& message);
+
+template <typename F>
+class MockSpec {
+ public:
+  typedef typename internal::Function<F>::ArgumentTuple ArgumentTuple;
+  typedef
+      typename internal::Function<F>::ArgumentMatcherTuple ArgumentMatcherTuple;
+
+  // Constructs a MockSpec object, given the function mocker object
+  // that the spec is associated with.
+  MockSpec(internal::FunctionMocker<F>* function_mocker,
+           const ArgumentMatcherTuple& matchers)
+      : function_mocker_(function_mocker), matchers_(matchers) {}
+
+  // Adds a new default action spec to the function mocker and returns
+  // the newly created spec.
+  internal::OnCallSpec<F>& InternalDefaultActionSetAt(const char* file,
+                                                      int line, const char* obj,
+                                                      const char* call) {
+    LogWithLocation(internal::kInfo, file, line,
+                    std::string("ON_CALL(") + obj + ", " + call + ") invoked");
+    return function_mocker_->AddNewOnCallSpec(file, line, matchers_);
+  }
+
+  // Adds a new expectation spec to the function mocker and returns
+  // the newly created spec.
+  internal::TypedExpectation<F>& InternalExpectedAt(const char* file, int line,
+                                                    const char* obj,
+                                                    const char* call) {
+    const std::string source_text(std::string("EXPECT_CALL(") + obj + ", " +
+                                  call + ")");
+    LogWithLocation(internal::kInfo, file, line, source_text + " invoked");
+    return function_mocker_->AddNewExpectation(file, line, source_text,
+                                               matchers_);
+  }
+
+  // This operator overload is used to swallow the superfluous parameter list
+  // introduced by the ON/EXPECT_CALL macros. See the macro comments for more
+  // explanation.
+  MockSpec<F>& operator()(const internal::WithoutMatchers&, void* const) {
+    return *this;
+  }
+
+ private:
+  template <typename Function>
+  friend class internal::FunctionMocker;
+
+  // The function mocker that owns this spec.
+  internal::FunctionMocker<F>* const function_mocker_;
+  // The argument matchers specified in the spec.
+  ArgumentMatcherTuple matchers_;
+};  // class MockSpec
+
+// Wrapper type for generically holding an ordinary value or lvalue reference.
+// If T is not a reference type, it must be copyable or movable.
+// ReferenceOrValueWrapper<T> is movable, and will also be copyable unless
+// T is a move-only value type (which means that it will always be copyable
+// if the current platform does not support move semantics).
+//
+// The primary template defines handling for values, but function header
+// comments describe the contract for the whole template (including
+// specializations).
+template <typename T>
+class ReferenceOrValueWrapper {
+ public:
+  // Constructs a wrapper from the given value/reference.
+  explicit ReferenceOrValueWrapper(T value) : value_(std::move(value)) {}
+
+  // Unwraps and returns the underlying value/reference, exactly as
+  // originally passed. The behavior of calling this more than once on
+  // the same object is unspecified.
+  T Unwrap() { return std::move(value_); }
+
+  // Provides nondestructive access to the underlying value/reference.
+  // Always returns a const reference (more precisely,
+  // const std::add_lvalue_reference<T>::type). The behavior of calling this
+  // after calling Unwrap on the same object is unspecified.
+  const T& Peek() const { return value_; }
+
+ private:
+  T value_;
+};
+
+// Specialization for lvalue reference types. See primary template
+// for documentation.
+template <typename T>
+class ReferenceOrValueWrapper<T&> {
+ public:
+  // Workaround for debatable pass-by-reference lint warning (c-library-team
+  // policy precludes NOLINT in this context)
+  typedef T& reference;
+  explicit ReferenceOrValueWrapper(reference ref) : value_ptr_(&ref) {}
+  T& Unwrap() { return *value_ptr_; }
+  const T& Peek() const { return *value_ptr_; }
+
+ private:
+  T* value_ptr_;
+};
+
+// Prints the held value as an action's result to os.
+template <typename T>
+void PrintAsActionResult(const T& result, std::ostream& os) {
+  os << "\n          Returns: ";
+  // T may be a reference type, so we don't use UniversalPrint().
+  UniversalPrinter<T>::Print(result, &os);
+}
+
+// Reports an uninteresting call (whose description is in msg) in the
+// manner specified by 'reaction'.
+GTEST_API_ void ReportUninterestingCall(CallReaction reaction,
+                                        const std::string& msg);
+
+// A generic RAII type that runs a user-provided function in its destructor.
+class Cleanup final {
+ public:
+  explicit Cleanup(std::function<void()> f) : f_(std::move(f)) {}
+  ~Cleanup() { f_(); }
+
+ private:
+  std::function<void()> f_;
+};
+
+struct UntypedFunctionMockerBase::UninterestingCallCleanupHandler {
+  CallReaction reaction;
+  std::stringstream& ss;
+
+  ~UninterestingCallCleanupHandler() {
+    ReportUninterestingCall(reaction, ss.str());
+  }
+};
+
+struct UntypedFunctionMockerBase::FailureCleanupHandler {
+  std::stringstream& ss;
+  std::stringstream& why;
+  std::stringstream& loc;
+  const ExpectationBase* untyped_expectation;
+  bool found;
+  bool is_excessive;
+
+  ~FailureCleanupHandler() {
+    ss << "\n" << why.str();
+
+    if (!found) {
+      // No expectation matches this call - reports a failure.
+      Expect(false, nullptr, -1, ss.str());
+    } else if (is_excessive) {
+      // We had an upper-bound violation and the failure message is in ss.
+      Expect(false, untyped_expectation->file(), untyped_expectation->line(),
+             ss.str());
+    } else {
+      // We had an expected call and the matching expectation is
+      // described in ss.
+      Log(kInfo, loc.str() + ss.str(), 2);
+    }
+  }
+};
+
+template <typename F>
+class FunctionMocker;
+
+template <typename R, typename... Args>
+class FunctionMocker<R(Args...)> final : public UntypedFunctionMockerBase {
+  using F = R(Args...);
+
+ public:
+  using Result = R;
+  using ArgumentTuple = std::tuple<Args...>;
+  using ArgumentMatcherTuple = std::tuple<Matcher<Args>...>;
+
+  FunctionMocker() = default;
+
+  // There is no generally useful and implementable semantics of
+  // copying a mock object, so copying a mock is usually a user error.
+  // Thus we disallow copying function mockers.  If the user really
+  // wants to copy a mock object, they should implement their own copy
+  // operation, for example:
+  //
+  //   class MockFoo : public Foo {
+  //    public:
+  //     // Defines a copy constructor explicitly.
+  //     MockFoo(const MockFoo& src) {}
+  //     ...
+  //   };
+  FunctionMocker(const FunctionMocker&) = delete;
+  FunctionMocker& operator=(const FunctionMocker&) = delete;
+
+  // The destructor verifies that all expectations on this mock
+  // function have been satisfied.  If not, it will report Google Test
+  // non-fatal failures for the violations.
+  ~FunctionMocker() override GTEST_LOCK_EXCLUDED_(g_gmock_mutex) {
+    MutexLock l(&g_gmock_mutex);
+    VerifyAndClearExpectationsLocked();
+    Mock::UnregisterLocked(this);
+    ClearDefaultActionsLocked();
+  }
+
+  // Returns the ON_CALL spec that matches this mock function with the
+  // given arguments; returns NULL if no matching ON_CALL is found.
+  // L = *
+  const OnCallSpec<F>* FindOnCallSpec(const ArgumentTuple& args) const {
+    for (UntypedOnCallSpecs::const_reverse_iterator it =
+             untyped_on_call_specs_.rbegin();
+         it != untyped_on_call_specs_.rend(); ++it) {
+      const OnCallSpec<F>* spec = static_cast<const OnCallSpec<F>*>(*it);
+      if (spec->Matches(args)) return spec;
+    }
+
+    return nullptr;
+  }
+
+  // Performs the default action of this mock function on the given
+  // arguments and returns the result. Asserts (or throws if
+  // exceptions are enabled) with a helpful call description if there
+  // is no valid return value. This method doesn't depend on the
+  // mutable state of this object, and thus can be called concurrently
+  // without locking.
+  // L = *
+  Result PerformDefaultAction(ArgumentTuple&& args,
+                              const std::string& call_description) const {
+    const OnCallSpec<F>* const spec = this->FindOnCallSpec(args);
+    if (spec != nullptr) {
+      return spec->GetAction().Perform(std::move(args));
+    }
+    const std::string message =
+        call_description +
+        "\n    The mock function has no default action "
+        "set, and its return type has no default value set.";
+#if GTEST_HAS_EXCEPTIONS
+    if (!DefaultValue<Result>::Exists()) {
+      throw std::runtime_error(message);
+    }
+#else
+    Assert(DefaultValue<Result>::Exists(), "", -1, message);
+#endif
+    return DefaultValue<Result>::Get();
+  }
+
+  // Implements UntypedFunctionMockerBase::ClearDefaultActionsLocked():
+  // clears the ON_CALL()s set on this mock function.
+  void ClearDefaultActionsLocked() override
+      GTEST_EXCLUSIVE_LOCK_REQUIRED_(g_gmock_mutex) {
+    g_gmock_mutex.AssertHeld();
+
+    // Deleting our default actions may trigger other mock objects to be
+    // deleted, for example if an action contains a reference counted smart
+    // pointer to that mock object, and that is the last reference. So if we
+    // delete our actions within the context of the global mutex we may deadlock
+    // when this method is called again. Instead, make a copy of the set of
+    // actions to delete, clear our set within the mutex, and then delete the
+    // actions outside of the mutex.
+    UntypedOnCallSpecs specs_to_delete;
+    untyped_on_call_specs_.swap(specs_to_delete);
+
+    g_gmock_mutex.Unlock();
+    for (UntypedOnCallSpecs::const_iterator it = specs_to_delete.begin();
+         it != specs_to_delete.end(); ++it) {
+      delete static_cast<const OnCallSpec<F>*>(*it);
+    }
+
+    // Lock the mutex again, since the caller expects it to be locked when we
+    // return.
+    g_gmock_mutex.Lock();
+  }
+
+  // Returns the result of invoking this mock function with the given
+  // arguments.  This function can be safely called from multiple
+  // threads concurrently.
+  Result Invoke(Args... args) GTEST_LOCK_EXCLUDED_(g_gmock_mutex) {
+    return InvokeWith(ArgumentTuple(std::forward<Args>(args)...));
+  }
+
+  MockSpec<F> With(Matcher<Args>... m) {
+    return MockSpec<F>(this, ::std::make_tuple(std::move(m)...));
+  }
+
+ protected:
+  template <typename Function>
+  friend class MockSpec;
+
+  // Adds and returns a default action spec for this mock function.
+  OnCallSpec<F>& AddNewOnCallSpec(const char* file, int line,
+                                  const ArgumentMatcherTuple& m)
+      GTEST_LOCK_EXCLUDED_(g_gmock_mutex) {
+    Mock::RegisterUseByOnCallOrExpectCall(MockObject(), file, line);
+    OnCallSpec<F>* const on_call_spec = new OnCallSpec<F>(file, line, m);
+    untyped_on_call_specs_.push_back(on_call_spec);
+    return *on_call_spec;
+  }
+
+  // Adds and returns an expectation spec for this mock function.
+  TypedExpectation<F>& AddNewExpectation(const char* file, int line,
+                                         const std::string& source_text,
+                                         const ArgumentMatcherTuple& m)
+      GTEST_LOCK_EXCLUDED_(g_gmock_mutex) {
+    Mock::RegisterUseByOnCallOrExpectCall(MockObject(), file, line);
+    TypedExpectation<F>* const expectation =
+        new TypedExpectation<F>(this, file, line, source_text, m);
+    const std::shared_ptr<ExpectationBase> untyped_expectation(expectation);
+    // See the definition of untyped_expectations_ for why access to
+    // it is unprotected here.
+    untyped_expectations_.push_back(untyped_expectation);
+
+    // Adds this expectation into the implicit sequence if there is one.
+    Sequence* const implicit_sequence = g_gmock_implicit_sequence.get();
+    if (implicit_sequence != nullptr) {
+      implicit_sequence->AddExpectation(Expectation(untyped_expectation));
+    }
+
+    return *expectation;
+  }
+
+ private:
+  template <typename Func>
+  friend class TypedExpectation;
+
+  // Some utilities needed for implementing UntypedInvokeWith().
+
+  // Describes what default action will be performed for the given
+  // arguments.
+  // L = *
+  void DescribeDefaultActionTo(const ArgumentTuple& args,
+                               ::std::ostream* os) const {
+    const OnCallSpec<F>* const spec = FindOnCallSpec(args);
+
+    if (spec == nullptr) {
+      *os << (std::is_void<Result>::value ? "returning directly.\n"
+                                          : "returning default value.\n");
+    } else {
+      *os << "taking default action specified at:\n"
+          << FormatFileLocation(spec->file(), spec->line()) << "\n";
+    }
+  }
+
+  // Writes a message that the call is uninteresting (i.e. neither
+  // explicitly expected nor explicitly unexpected) to the given
+  // ostream.
+  void UntypedDescribeUninterestingCall(const void* untyped_args,
+                                        ::std::ostream* os) const override
+      GTEST_LOCK_EXCLUDED_(g_gmock_mutex) {
+    const ArgumentTuple& args =
+        *static_cast<const ArgumentTuple*>(untyped_args);
+    *os << "Uninteresting mock function call - ";
+    DescribeDefaultActionTo(args, os);
+    *os << "    Function call: " << Name();
+    UniversalPrint(args, os);
+  }
+
+  // Returns the expectation that matches the given function arguments
+  // (or NULL is there's no match); when a match is found,
+  // untyped_action is set to point to the action that should be
+  // performed (or NULL if the action is "do default"), and
+  // is_excessive is modified to indicate whether the call exceeds the
+  // expected number.
+  //
+  // Critical section: We must find the matching expectation and the
+  // corresponding action that needs to be taken in an ATOMIC
+  // transaction.  Otherwise another thread may call this mock
+  // method in the middle and mess up the state.
+  //
+  // However, performing the action has to be left out of the critical
+  // section.  The reason is that we have no control on what the
+  // action does (it can invoke an arbitrary user function or even a
+  // mock function) and excessive locking could cause a dead lock.
+  const ExpectationBase* UntypedFindMatchingExpectation(
+      const void* untyped_args, const void** untyped_action, bool* is_excessive,
+      ::std::ostream* what, ::std::ostream* why) override
+      GTEST_LOCK_EXCLUDED_(g_gmock_mutex) {
+    const ArgumentTuple& args =
+        *static_cast<const ArgumentTuple*>(untyped_args);
+    MutexLock l(&g_gmock_mutex);
+    TypedExpectation<F>* exp = this->FindMatchingExpectationLocked(args);
+    if (exp == nullptr) {  // A match wasn't found.
+      this->FormatUnexpectedCallMessageLocked(args, what, why);
+      return nullptr;
+    }
+
+    // This line must be done before calling GetActionForArguments(),
+    // which will increment the call count for *exp and thus affect
+    // its saturation status.
+    *is_excessive = exp->IsSaturated();
+    const Action<F>* action = exp->GetActionForArguments(this, args, what, why);
+    if (action != nullptr && action->IsDoDefault())
+      action = nullptr;  // Normalize "do default" to NULL.
+    *untyped_action = action;
+    return exp;
+  }
+
+  // Prints the given function arguments to the ostream.
+  void UntypedPrintArgs(const void* untyped_args,
+                        ::std::ostream* os) const override {
+    const ArgumentTuple& args =
+        *static_cast<const ArgumentTuple*>(untyped_args);
+    UniversalPrint(args, os);
+  }
+
+  // Returns the expectation that matches the arguments, or NULL if no
+  // expectation matches them.
+  TypedExpectation<F>* FindMatchingExpectationLocked(const ArgumentTuple& args)
+      const GTEST_EXCLUSIVE_LOCK_REQUIRED_(g_gmock_mutex) {
+    g_gmock_mutex.AssertHeld();
+    // See the definition of untyped_expectations_ for why access to
+    // it is unprotected here.
+    for (typename UntypedExpectations::const_reverse_iterator it =
+             untyped_expectations_.rbegin();
+         it != untyped_expectations_.rend(); ++it) {
+      TypedExpectation<F>* const exp =
+          static_cast<TypedExpectation<F>*>(it->get());
+      if (exp->ShouldHandleArguments(args)) {
+        return exp;
+      }
+    }
+    return nullptr;
+  }
+
+  // Returns a message that the arguments don't match any expectation.
+  void FormatUnexpectedCallMessageLocked(const ArgumentTuple& args,
+                                         ::std::ostream* os,
+                                         ::std::ostream* why) const
+      GTEST_EXCLUSIVE_LOCK_REQUIRED_(g_gmock_mutex) {
+    g_gmock_mutex.AssertHeld();
+    *os << "\nUnexpected mock function call - ";
+    DescribeDefaultActionTo(args, os);
+    PrintTriedExpectationsLocked(args, why);
+  }
+
+  // Prints a list of expectations that have been tried against the
+  // current mock function call.
+  void PrintTriedExpectationsLocked(const ArgumentTuple& args,
+                                    ::std::ostream* why) const
+      GTEST_EXCLUSIVE_LOCK_REQUIRED_(g_gmock_mutex) {
+    g_gmock_mutex.AssertHeld();
+    const size_t count = untyped_expectations_.size();
+    *why << "Google Mock tried the following " << count << " "
+         << (count == 1 ? "expectation, but it didn't match"
+                        : "expectations, but none matched")
+         << ":\n";
+    for (size_t i = 0; i < count; i++) {
+      TypedExpectation<F>* const expectation =
+          static_cast<TypedExpectation<F>*>(untyped_expectations_[i].get());
+      *why << "\n";
+      expectation->DescribeLocationTo(why);
+      if (count > 1) {
+        *why << "tried expectation #" << i << ": ";
+      }
+      *why << expectation->source_text() << "...\n";
+      expectation->ExplainMatchResultTo(args, why);
+      expectation->DescribeCallCountTo(why);
+    }
+  }
+
+  // Performs the given action (or the default if it's null) with the given
+  // arguments and returns the action's result.
+  // L = *
+  R PerformAction(const void* untyped_action, ArgumentTuple&& args,
+                  const std::string& call_description) const {
+    if (untyped_action == nullptr) {
+      return PerformDefaultAction(std::move(args), call_description);
+    }
+
+    // Make a copy of the action before performing it, in case the
+    // action deletes the mock object (and thus deletes itself).
+    const Action<F> action = *static_cast<const Action<F>*>(untyped_action);
+    return action.Perform(std::move(args));
+  }
+
+  // Is it possible to store an object of the supplied type in a local variable
+  // for the sake of printing it, then return it on to the caller?
+  template <typename T>
+  using can_print_result = internal::conjunction<
+      // void can't be stored as an object (and we also don't need to print it).
+      internal::negation<std::is_void<T>>,
+      // Non-moveable types can't be returned on to the user, so there's no way
+      // for us to intercept and print them.
+      std::is_move_constructible<T>>;
+
+  // Perform the supplied action, printing the result to os.
+  template <typename T = R,
+            typename std::enable_if<can_print_result<T>::value, int>::type = 0>
+  R PerformActionAndPrintResult(const void* const untyped_action,
+                                ArgumentTuple&& args,
+                                const std::string& call_description,
+                                std::ostream& os) {
+    R result = PerformAction(untyped_action, std::move(args), call_description);
+
+    PrintAsActionResult(result, os);
+    return std::forward<R>(result);
+  }
+
+  // An overload for when it's not possible to print the result. In this case we
+  // simply perform the action.
+  template <typename T = R,
+            typename std::enable_if<
+                internal::negation<can_print_result<T>>::value, int>::type = 0>
+  R PerformActionAndPrintResult(const void* const untyped_action,
+                                ArgumentTuple&& args,
+                                const std::string& call_description,
+                                std::ostream&) {
+    return PerformAction(untyped_action, std::move(args), call_description);
+  }
+
+  // Returns the result of invoking this mock function with the given
+  // arguments. This function can be safely called from multiple
+  // threads concurrently.
+  R InvokeWith(ArgumentTuple&& args) GTEST_LOCK_EXCLUDED_(g_gmock_mutex);
+};  // class FunctionMocker
+
+// Calculates the result of invoking this mock function with the given
+// arguments, prints it, and returns it.
+template <typename R, typename... Args>
+R FunctionMocker<R(Args...)>::InvokeWith(ArgumentTuple&& args)
+    GTEST_LOCK_EXCLUDED_(g_gmock_mutex) {
+  // See the definition of untyped_expectations_ for why access to it
+  // is unprotected here.
+  if (untyped_expectations_.size() == 0) {
+    // No expectation is set on this mock method - we have an
+    // uninteresting call.
+
+    // We must get Google Mock's reaction on uninteresting calls
+    // made on this mock object BEFORE performing the action,
+    // because the action may DELETE the mock object and make the
+    // following expression meaningless.
+    const CallReaction reaction =
+        Mock::GetReactionOnUninterestingCalls(MockObject());
+
+    // True if and only if we need to print this call's arguments and return
+    // value.  This definition must be kept in sync with
+    // the behavior of ReportUninterestingCall().
+    const bool need_to_report_uninteresting_call =
+        // If the user allows this uninteresting call, we print it
+        // only when they want informational messages.
+        reaction == kAllow ? LogIsVisible(kInfo) :
+                           // If the user wants this to be a warning, we print
+                           // it only when they want to see warnings.
+            reaction == kWarn
+            ? LogIsVisible(kWarning)
+            :
+            // Otherwise, the user wants this to be an error, and we
+            // should always print detailed information in the error.
+            true;
+
+    if (!need_to_report_uninteresting_call) {
+      // Perform the action without printing the call information.
+      return this->PerformDefaultAction(
+          std::move(args), "Function call: " + std::string(Name()));
+    }
+
+    // Warns about the uninteresting call.
+    ::std::stringstream ss;
+    this->UntypedDescribeUninterestingCall(&args, &ss);
+
+    // Perform the action, print the result, and then report the uninteresting
+    // call.
+    //
+    // We use RAII to do the latter in case R is void or a non-moveable type. In
+    // either case we can't assign it to a local variable.
+    //
+    // Note that std::bind() is essential here.
+    // We *don't* use any local callback types (like lambdas).
+    // Doing so slows down compilation dramatically because the *constructor* of
+    // std::function<T> is re-instantiated with different template
+    // parameters each time.
+    const UninterestingCallCleanupHandler report_uninteresting_call = {
+        reaction, ss
+    };
+
+    return PerformActionAndPrintResult(nullptr, std::move(args), ss.str(), ss);
+  }
+
+  bool is_excessive = false;
+  ::std::stringstream ss;
+  ::std::stringstream why;
+  ::std::stringstream loc;
+  const void* untyped_action = nullptr;
+
+  // The UntypedFindMatchingExpectation() function acquires and
+  // releases g_gmock_mutex.
+
+  const ExpectationBase* const untyped_expectation =
+      this->UntypedFindMatchingExpectation(&args, &untyped_action,
+                                           &is_excessive, &ss, &why);
+  const bool found = untyped_expectation != nullptr;
+
+  // True if and only if we need to print the call's arguments
+  // and return value.
+  // This definition must be kept in sync with the uses of Expect()
+  // and Log() in this function.
+  const bool need_to_report_call =
+      !found || is_excessive || LogIsVisible(kInfo);
+  if (!need_to_report_call) {
+    // Perform the action without printing the call information.
+    return PerformAction(untyped_action, std::move(args), "");
+  }
+
+  ss << "    Function call: " << Name();
+  this->UntypedPrintArgs(&args, &ss);
+
+  // In case the action deletes a piece of the expectation, we
+  // generate the message beforehand.
+  if (found && !is_excessive) {
+    untyped_expectation->DescribeLocationTo(&loc);
+  }
+
+  // Perform the action, print the result, and then fail or log in whatever way
+  // is appropriate.
+  //
+  // We use RAII to do the latter in case R is void or a non-moveable type. In
+  // either case we can't assign it to a local variable.
+  //
+  // Note that we *don't* use any local callback types (like lambdas) here.
+  // Doing so slows down compilation dramatically because the *constructor* of
+  // std::function<T> is re-instantiated with different template
+  // parameters each time.
+  const FailureCleanupHandler handle_failures = {
+      ss, why, loc, untyped_expectation, found, is_excessive
+  };
+
+  return PerformActionAndPrintResult(untyped_action, std::move(args), ss.str(),
+                                     ss);
+}
+
+}  // namespace internal
+
+namespace internal {
+
+template <typename F>
+class MockFunction;
+
+template <typename R, typename... Args>
+class MockFunction<R(Args...)> {
+ public:
+  MockFunction(const MockFunction&) = delete;
+  MockFunction& operator=(const MockFunction&) = delete;
+
+  std::function<R(Args...)> AsStdFunction() {
+    return [this](Args... args) -> R {
+      return this->Call(std::forward<Args>(args)...);
+    };
+  }
+
+  // Implementation detail: the expansion of the MOCK_METHOD macro.
+  R Call(Args... args) {
+    mock_.SetOwnerAndName(this, "Call");
+    return mock_.Invoke(std::forward<Args>(args)...);
+  }
+
+  MockSpec<R(Args...)> gmock_Call(Matcher<Args>... m) {
+    mock_.RegisterOwner(this);
+    return mock_.With(std::move(m)...);
+  }
+
+  MockSpec<R(Args...)> gmock_Call(const WithoutMatchers&, R (*)(Args...)) {
+    return this->gmock_Call(::testing::A<Args>()...);
+  }
+
+ protected:
+  MockFunction() = default;
+  ~MockFunction() = default;
+
+ private:
+  FunctionMocker<R(Args...)> mock_;
+};
+
+/*
+The SignatureOf<F> struct is a meta-function returning function signature
+corresponding to the provided F argument.
+
+It makes use of MockFunction easier by allowing it to accept more F arguments
+than just function signatures.
+
+Specializations provided here cover a signature type itself and any template
+that can be parameterized with a signature, including std::function and
+boost::function.
+*/
+
+template <typename F, typename = void>
+struct SignatureOf;
+
+template <typename R, typename... Args>
+struct SignatureOf<R(Args...)> {
+  using type = R(Args...);
+};
+
+template <template <typename> class C, typename F>
+struct SignatureOf<C<F>,
+                   typename std::enable_if<std::is_function<F>::value>::type>
+    : SignatureOf<F> {};
+
+template <typename F>
+using SignatureOfT = typename SignatureOf<F>::type;
+
+}  // namespace internal
+
+// A MockFunction<F> type has one mock method whose type is
+// internal::SignatureOfT<F>.  It is useful when you just want your
+// test code to emit some messages and have Google Mock verify the
+// right messages are sent (and perhaps at the right times).  For
+// example, if you are exercising code:
+//
+//   Foo(1);
+//   Foo(2);
+//   Foo(3);
+//
+// and want to verify that Foo(1) and Foo(3) both invoke
+// mock.Bar("a"), but Foo(2) doesn't invoke anything, you can write:
+//
+// TEST(FooTest, InvokesBarCorrectly) {
+//   MyMock mock;
+//   MockFunction<void(string check_point_name)> check;
+//   {
+//     InSequence s;
+//
+//     EXPECT_CALL(mock, Bar("a"));
+//     EXPECT_CALL(check, Call("1"));
+//     EXPECT_CALL(check, Call("2"));
+//     EXPECT_CALL(mock, Bar("a"));
+//   }
+//   Foo(1);
+//   check.Call("1");
+//   Foo(2);
+//   check.Call("2");
+//   Foo(3);
+// }
+//
+// The expectation spec says that the first Bar("a") must happen
+// before check point "1", the second Bar("a") must happen after check
+// point "2", and nothing should happen between the two check
+// points. The explicit check points make it easy to tell which
+// Bar("a") is called by which call to Foo().
+//
+// MockFunction<F> can also be used to exercise code that accepts
+// std::function<internal::SignatureOfT<F>> callbacks. To do so, use
+// AsStdFunction() method to create std::function proxy forwarding to
+// original object's Call. Example:
+//
+// TEST(FooTest, RunsCallbackWithBarArgument) {
+//   MockFunction<int(string)> callback;
+//   EXPECT_CALL(callback, Call("bar")).WillOnce(Return(1));
+//   Foo(callback.AsStdFunction());
+// }
+//
+// The internal::SignatureOfT<F> indirection allows to use other types
+// than just function signature type. This is typically useful when
+// providing a mock for a predefined std::function type. Example:
+//
+// using FilterPredicate = std::function<bool(string)>;
+// void MyFilterAlgorithm(FilterPredicate predicate);
+//
+// TEST(FooTest, FilterPredicateAlwaysAccepts) {
+//   MockFunction<FilterPredicate> predicateMock;
+//   EXPECT_CALL(predicateMock, Call(_)).WillRepeatedly(Return(true));
+//   MyFilterAlgorithm(predicateMock.AsStdFunction());
+// }
+template <typename F>
+class MockFunction : public internal::MockFunction<internal::SignatureOfT<F>> {
+  using Base = internal::MockFunction<internal::SignatureOfT<F>>;
+
+ public:
+  using Base::Base;
+};
+
+// The style guide prohibits "using" statements in a namespace scope
+// inside a header file.  However, the MockSpec class template is
+// meant to be defined in the ::testing namespace.  The following line
+// is just a trick for working around a bug in MSVC 8.0, which cannot
+// handle it if we define MockSpec in ::testing.
+using internal::MockSpec;
+
+// Const(x) is a convenient function for obtaining a const reference
+// to x.  This is useful for setting expectations on an overloaded
+// const mock method, e.g.
+//
+//   class MockFoo : public FooInterface {
+//    public:
+//     MOCK_METHOD0(Bar, int());
+//     MOCK_CONST_METHOD0(Bar, int&());
+//   };
+//
+//   MockFoo foo;
+//   // Expects a call to non-const MockFoo::Bar().
+//   EXPECT_CALL(foo, Bar());
+//   // Expects a call to const MockFoo::Bar().
+//   EXPECT_CALL(Const(foo), Bar());
+template <typename T>
+inline const T& Const(const T& x) {
+  return x;
+}
+
+// Constructs an Expectation object that references and co-owns exp.
+inline Expectation::Expectation(internal::ExpectationBase& exp)  // NOLINT
+    : expectation_base_(exp.GetHandle().expectation_base()) {}
+
+}  // namespace testing
+
+GTEST_DISABLE_MSC_WARNINGS_POP_()  //  4251
+
+// Implementation for ON_CALL and EXPECT_CALL macros. A separate macro is
+// required to avoid compile errors when the name of the method used in call is
+// a result of macro expansion. See CompilesWithMethodNameExpandedFromMacro
+// tests in internal/gmock-spec-builders_test.cc for more details.
+//
+// This macro supports statements both with and without parameter matchers. If
+// the parameter list is omitted, gMock will accept any parameters, which allows
+// tests to be written that don't need to encode the number of method
+// parameter. This technique may only be used for non-overloaded methods.
+//
+//   // These are the same:
+//   ON_CALL(mock, NoArgsMethod()).WillByDefault(...);
+//   ON_CALL(mock, NoArgsMethod).WillByDefault(...);
+//
+//   // As are these:
+//   ON_CALL(mock, TwoArgsMethod(_, _)).WillByDefault(...);
+//   ON_CALL(mock, TwoArgsMethod).WillByDefault(...);
+//
+//   // Can also specify args if you want, of course:
+//   ON_CALL(mock, TwoArgsMethod(_, 45)).WillByDefault(...);
+//
+//   // Overloads work as long as you specify parameters:
+//   ON_CALL(mock, OverloadedMethod(_)).WillByDefault(...);
+//   ON_CALL(mock, OverloadedMethod(_, _)).WillByDefault(...);
+//
+//   // Oops! Which overload did you want?
+//   ON_CALL(mock, OverloadedMethod).WillByDefault(...);
+//     => ERROR: call to member function 'gmock_OverloadedMethod' is ambiguous
+//
+// How this works: The mock class uses two overloads of the gmock_Method
+// expectation setter method plus an operator() overload on the MockSpec object.
+// In the matcher list form, the macro expands to:
+//
+//   // This statement:
+//   ON_CALL(mock, TwoArgsMethod(_, 45))...
+//
+//   // ...expands to:
+//   mock.gmock_TwoArgsMethod(_, 45)(WithoutMatchers(), nullptr)...
+//   |-------------v---------------||------------v-------------|
+//       invokes first overload        swallowed by operator()
+//
+//   // ...which is essentially:
+//   mock.gmock_TwoArgsMethod(_, 45)...
+//
+// Whereas the form without a matcher list:
+//
+//   // This statement:
+//   ON_CALL(mock, TwoArgsMethod)...
+//
+//   // ...expands to:
+//   mock.gmock_TwoArgsMethod(WithoutMatchers(), nullptr)...
+//   |-----------------------v--------------------------|
+//                 invokes second overload
+//
+//   // ...which is essentially:
+//   mock.gmock_TwoArgsMethod(_, _)...
+//
+// The WithoutMatchers() argument is used to disambiguate overloads and to
+// block the caller from accidentally invoking the second overload directly. The
+// second argument is an internal type derived from the method signature. The
+// failure to disambiguate two overloads of this method in the ON_CALL statement
+// is how we block callers from setting expectations on overloaded methods.
+#define GMOCK_ON_CALL_IMPL_(mock_expr, Setter, call)                    \
+  ((mock_expr).gmock_##call)(::testing::internal::GetWithoutMatchers(), \
+                             nullptr)                                   \
+      .Setter(__FILE__, __LINE__, #mock_expr, #call)
+
+#define ON_CALL(obj, call) \
+  GMOCK_ON_CALL_IMPL_(obj, InternalDefaultActionSetAt, call)
+
+#define EXPECT_CALL(obj, call) \
+  GMOCK_ON_CALL_IMPL_(obj, InternalExpectedAt, call)
+
+#endif  // GOOGLEMOCK_INCLUDE_GMOCK_GMOCK_SPEC_BUILDERS_H_
diff --git a/third_party/googletest/googlemock/include/gmock/gmock.h b/third_party/googletest/googlemock/include/gmock/gmock.h
new file mode 100644
index 0000000..568c8c7
--- /dev/null
+++ b/third_party/googletest/googlemock/include/gmock/gmock.h
@@ -0,0 +1,96 @@
+// Copyright 2007, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Google Mock - a framework for writing C++ mock classes.
+//
+// This is the main header file a user should include.
+
+#ifndef GOOGLEMOCK_INCLUDE_GMOCK_GMOCK_H_
+#define GOOGLEMOCK_INCLUDE_GMOCK_GMOCK_H_
+
+// This file implements the following syntax:
+//
+//   ON_CALL(mock_object, Method(...))
+//     .With(...) ?
+//     .WillByDefault(...);
+//
+// where With() is optional and WillByDefault() must appear exactly
+// once.
+//
+//   EXPECT_CALL(mock_object, Method(...))
+//     .With(...) ?
+//     .Times(...) ?
+//     .InSequence(...) *
+//     .WillOnce(...) *
+//     .WillRepeatedly(...) ?
+//     .RetiresOnSaturation() ? ;
+//
+// where all clauses are optional and WillOnce() can be repeated.
+
+#include "gmock/gmock-actions.h"
+#include "gmock/gmock-cardinalities.h"
+#include "gmock/gmock-function-mocker.h"
+#include "gmock/gmock-matchers.h"
+#include "gmock/gmock-more-actions.h"
+#include "gmock/gmock-more-matchers.h"
+#include "gmock/gmock-nice-strict.h"
+#include "gmock/internal/gmock-internal-utils.h"
+#include "gmock/internal/gmock-port.h"
+
+// Declares Google Mock flags that we want a user to use programmatically.
+GMOCK_DECLARE_bool_(catch_leaked_mocks);
+GMOCK_DECLARE_string_(verbose);
+GMOCK_DECLARE_int32_(default_mock_behavior);
+
+namespace testing {
+
+// Initializes Google Mock.  This must be called before running the
+// tests.  In particular, it parses the command line for the flags
+// that Google Mock recognizes.  Whenever a Google Mock flag is seen,
+// it is removed from argv, and *argc is decremented.
+//
+// No value is returned.  Instead, the Google Mock flag variables are
+// updated.
+//
+// Since Google Test is needed for Google Mock to work, this function
+// also initializes Google Test and parses its flags, if that hasn't
+// been done.
+GTEST_API_ void InitGoogleMock(int* argc, char** argv);
+
+// This overloaded version can be used in Windows programs compiled in
+// UNICODE mode.
+GTEST_API_ void InitGoogleMock(int* argc, wchar_t** argv);
+
+// This overloaded version can be used on Arduino/embedded platforms where
+// there is no argc/argv.
+GTEST_API_ void InitGoogleMock();
+
+}  // namespace testing
+
+#endif  // GOOGLEMOCK_INCLUDE_GMOCK_GMOCK_H_
diff --git a/third_party/googletest/googlemock/include/gmock/internal/custom/README.md b/third_party/googletest/googlemock/include/gmock/internal/custom/README.md
new file mode 100644
index 0000000..9c4874f
--- /dev/null
+++ b/third_party/googletest/googlemock/include/gmock/internal/custom/README.md
@@ -0,0 +1,18 @@
+# Customization Points
+
+The custom directory is an injection point for custom user configurations.
+
+## Header `gmock-port.h`
+
+The following macros can be defined:
+
+### Flag related macros:
+
+*   `GMOCK_DECLARE_bool_(name)`
+*   `GMOCK_DECLARE_int32_(name)`
+*   `GMOCK_DECLARE_string_(name)`
+*   `GMOCK_DEFINE_bool_(name, default_val, doc)`
+*   `GMOCK_DEFINE_int32_(name, default_val, doc)`
+*   `GMOCK_DEFINE_string_(name, default_val, doc)`
+*   `GMOCK_FLAG_GET(flag_name)`
+*   `GMOCK_FLAG_SET(flag_name, value)`
diff --git a/third_party/googletest/googlemock/include/gmock/internal/custom/gmock-generated-actions.h b/third_party/googletest/googlemock/include/gmock/internal/custom/gmock-generated-actions.h
new file mode 100644
index 0000000..bbcad31
--- /dev/null
+++ b/third_party/googletest/googlemock/include/gmock/internal/custom/gmock-generated-actions.h
@@ -0,0 +1,7 @@
+// IWYU pragma: private, include "gmock/gmock.h"
+// IWYU pragma: friend gmock/.*
+
+#ifndef GOOGLEMOCK_INCLUDE_GMOCK_INTERNAL_CUSTOM_GMOCK_GENERATED_ACTIONS_H_
+#define GOOGLEMOCK_INCLUDE_GMOCK_INTERNAL_CUSTOM_GMOCK_GENERATED_ACTIONS_H_
+
+#endif  // GOOGLEMOCK_INCLUDE_GMOCK_INTERNAL_CUSTOM_GMOCK_GENERATED_ACTIONS_H_
diff --git a/third_party/googletest/googlemock/include/gmock/internal/custom/gmock-matchers.h b/third_party/googletest/googlemock/include/gmock/internal/custom/gmock-matchers.h
new file mode 100644
index 0000000..bb7dcba
--- /dev/null
+++ b/third_party/googletest/googlemock/include/gmock/internal/custom/gmock-matchers.h
@@ -0,0 +1,37 @@
+// Copyright 2015, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Injection point for custom user configurations. See README for details
+
+// IWYU pragma: private, include "gmock/gmock.h"
+// IWYU pragma: friend gmock/.*
+
+#ifndef GOOGLEMOCK_INCLUDE_GMOCK_INTERNAL_CUSTOM_GMOCK_MATCHERS_H_
+#define GOOGLEMOCK_INCLUDE_GMOCK_INTERNAL_CUSTOM_GMOCK_MATCHERS_H_
+#endif  // GOOGLEMOCK_INCLUDE_GMOCK_INTERNAL_CUSTOM_GMOCK_MATCHERS_H_
diff --git a/third_party/googletest/googlemock/include/gmock/internal/custom/gmock-port.h b/third_party/googletest/googlemock/include/gmock/internal/custom/gmock-port.h
new file mode 100644
index 0000000..f055f75
--- /dev/null
+++ b/third_party/googletest/googlemock/include/gmock/internal/custom/gmock-port.h
@@ -0,0 +1,40 @@
+// Copyright 2015, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Injection point for custom user configurations. See README for details
+//
+// ** Custom implementation starts here **
+
+// IWYU pragma: private, include "gmock/gmock.h"
+// IWYU pragma: friend gmock/.*
+
+#ifndef GOOGLEMOCK_INCLUDE_GMOCK_INTERNAL_CUSTOM_GMOCK_PORT_H_
+#define GOOGLEMOCK_INCLUDE_GMOCK_INTERNAL_CUSTOM_GMOCK_PORT_H_
+
+#endif  // GOOGLEMOCK_INCLUDE_GMOCK_INTERNAL_CUSTOM_GMOCK_PORT_H_
diff --git a/third_party/googletest/googlemock/include/gmock/internal/gmock-internal-utils.h b/third_party/googletest/googlemock/include/gmock/internal/gmock-internal-utils.h
new file mode 100644
index 0000000..ead6d7c
--- /dev/null
+++ b/third_party/googletest/googlemock/include/gmock/internal/gmock-internal-utils.h
@@ -0,0 +1,487 @@
+// Copyright 2007, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Google Mock - a framework for writing C++ mock classes.
+//
+// This file defines some utilities useful for implementing Google
+// Mock.  They are subject to change without notice, so please DO NOT
+// USE THEM IN USER CODE.
+
+// IWYU pragma: private, include "gmock/gmock.h"
+// IWYU pragma: friend gmock/.*
+
+#ifndef GOOGLEMOCK_INCLUDE_GMOCK_INTERNAL_GMOCK_INTERNAL_UTILS_H_
+#define GOOGLEMOCK_INCLUDE_GMOCK_INTERNAL_GMOCK_INTERNAL_UTILS_H_
+
+#include <stdio.h>
+
+#include <ostream>  // NOLINT
+#include <string>
+#include <type_traits>
+#include <vector>
+
+#include "gmock/internal/gmock-port.h"
+#include "gtest/gtest.h"
+
+namespace testing {
+
+template <typename>
+class Matcher;
+
+namespace internal {
+
+// Silence MSVC C4100 (unreferenced formal parameter) and
+// C4805('==': unsafe mix of type 'const int' and type 'const bool')
+GTEST_DISABLE_MSC_WARNINGS_PUSH_(4100 4805)
+
+// Joins a vector of strings as if they are fields of a tuple; returns
+// the joined string.
+GTEST_API_ std::string JoinAsKeyValueTuple(
+    const std::vector<const char*>& names, const Strings& values);
+
+// Converts an identifier name to a space-separated list of lower-case
+// words.  Each maximum substring of the form [A-Za-z][a-z]*|\d+ is
+// treated as one word.  For example, both "FooBar123" and
+// "foo_bar_123" are converted to "foo bar 123".
+GTEST_API_ std::string ConvertIdentifierNameToWords(const char* id_name);
+
+// GetRawPointer(p) returns the raw pointer underlying p when p is a
+// smart pointer, or returns p itself when p is already a raw pointer.
+// The following default implementation is for the smart pointer case.
+template <typename Pointer>
+inline const typename Pointer::element_type* GetRawPointer(const Pointer& p) {
+  return p.get();
+}
+// This overload version is for std::reference_wrapper, which does not work with
+// the overload above, as it does not have an `element_type`.
+template <typename Element>
+inline const Element* GetRawPointer(const std::reference_wrapper<Element>& r) {
+  return &r.get();
+}
+
+// This overloaded version is for the raw pointer case.
+template <typename Element>
+inline Element* GetRawPointer(Element* p) {
+  return p;
+}
+
+// Default definitions for all compilers.
+// NOTE: If you implement support for other compilers, make sure to avoid
+// unexpected overlaps.
+// (e.g., Clang also processes #pragma GCC, and clang-cl also handles _MSC_VER.)
+#define GMOCK_INTERNAL_WARNING_PUSH()
+#define GMOCK_INTERNAL_WARNING_CLANG(Level, Name)
+#define GMOCK_INTERNAL_WARNING_POP()
+
+#if defined(__clang__)
+#undef GMOCK_INTERNAL_WARNING_PUSH
+#define GMOCK_INTERNAL_WARNING_PUSH() _Pragma("clang diagnostic push")
+#undef GMOCK_INTERNAL_WARNING_CLANG
+#define GMOCK_INTERNAL_WARNING_CLANG(Level, Warning) \
+  _Pragma(GMOCK_PP_INTERNAL_STRINGIZE(clang diagnostic Level Warning))
+#undef GMOCK_INTERNAL_WARNING_POP
+#define GMOCK_INTERNAL_WARNING_POP() _Pragma("clang diagnostic pop")
+#endif
+
+// MSVC treats wchar_t as a native type usually, but treats it as the
+// same as unsigned short when the compiler option /Zc:wchar_t- is
+// specified.  It defines _NATIVE_WCHAR_T_DEFINED symbol when wchar_t
+// is a native type.
+#if defined(_MSC_VER) && !defined(_NATIVE_WCHAR_T_DEFINED)
+// wchar_t is a typedef.
+#else
+#define GMOCK_WCHAR_T_IS_NATIVE_ 1
+#endif
+
+// In what follows, we use the term "kind" to indicate whether a type
+// is bool, an integer type (excluding bool), a floating-point type,
+// or none of them.  This categorization is useful for determining
+// when a matcher argument type can be safely converted to another
+// type in the implementation of SafeMatcherCast.
+enum TypeKind { kBool, kInteger, kFloatingPoint, kOther };
+
+// KindOf<T>::value is the kind of type T.
+template <typename T>
+struct KindOf {
+  enum { value = kOther };  // The default kind.
+};
+
+// This macro declares that the kind of 'type' is 'kind'.
+#define GMOCK_DECLARE_KIND_(type, kind) \
+  template <>                           \
+  struct KindOf<type> {                 \
+    enum { value = kind };              \
+  }
+
+GMOCK_DECLARE_KIND_(bool, kBool);
+
+// All standard integer types.
+GMOCK_DECLARE_KIND_(char, kInteger);
+GMOCK_DECLARE_KIND_(signed char, kInteger);
+GMOCK_DECLARE_KIND_(unsigned char, kInteger);
+GMOCK_DECLARE_KIND_(short, kInteger);           // NOLINT
+GMOCK_DECLARE_KIND_(unsigned short, kInteger);  // NOLINT
+GMOCK_DECLARE_KIND_(int, kInteger);
+GMOCK_DECLARE_KIND_(unsigned int, kInteger);
+GMOCK_DECLARE_KIND_(long, kInteger);                // NOLINT
+GMOCK_DECLARE_KIND_(unsigned long, kInteger);       // NOLINT
+GMOCK_DECLARE_KIND_(long long, kInteger);           // NOLINT
+GMOCK_DECLARE_KIND_(unsigned long long, kInteger);  // NOLINT
+
+#if GMOCK_WCHAR_T_IS_NATIVE_
+GMOCK_DECLARE_KIND_(wchar_t, kInteger);
+#endif
+
+// All standard floating-point types.
+GMOCK_DECLARE_KIND_(float, kFloatingPoint);
+GMOCK_DECLARE_KIND_(double, kFloatingPoint);
+GMOCK_DECLARE_KIND_(long double, kFloatingPoint);
+
+#undef GMOCK_DECLARE_KIND_
+
+// Evaluates to the kind of 'type'.
+#define GMOCK_KIND_OF_(type)                   \
+  static_cast< ::testing::internal::TypeKind>( \
+      ::testing::internal::KindOf<type>::value)
+
+// LosslessArithmeticConvertibleImpl<kFromKind, From, kToKind, To>::value
+// is true if and only if arithmetic type From can be losslessly converted to
+// arithmetic type To.
+//
+// It's the user's responsibility to ensure that both From and To are
+// raw (i.e. has no CV modifier, is not a pointer, and is not a
+// reference) built-in arithmetic types, kFromKind is the kind of
+// From, and kToKind is the kind of To; the value is
+// implementation-defined when the above pre-condition is violated.
+template <TypeKind kFromKind, typename From, TypeKind kToKind, typename To>
+using LosslessArithmeticConvertibleImpl = std::integral_constant<
+    bool,
+    // clang-format off
+      // Converting from bool is always lossless
+      (kFromKind == kBool) ? true
+      // Converting between any other type kinds will be lossy if the type
+      // kinds are not the same.
+    : (kFromKind != kToKind) ? false
+    : (kFromKind == kInteger &&
+       // Converting between integers of different widths is allowed so long
+       // as the conversion does not go from signed to unsigned.
+      (((sizeof(From) < sizeof(To)) &&
+        !(std::is_signed<From>::value && !std::is_signed<To>::value)) ||
+       // Converting between integers of the same width only requires the
+       // two types to have the same signedness.
+       ((sizeof(From) == sizeof(To)) &&
+        (std::is_signed<From>::value == std::is_signed<To>::value)))
+       ) ? true
+      // Floating point conversions are lossless if and only if `To` is at least
+      // as wide as `From`.
+    : (kFromKind == kFloatingPoint && (sizeof(From) <= sizeof(To))) ? true
+    : false
+    // clang-format on
+    >;
+
+// LosslessArithmeticConvertible<From, To>::value is true if and only if
+// arithmetic type From can be losslessly converted to arithmetic type To.
+//
+// It's the user's responsibility to ensure that both From and To are
+// raw (i.e. has no CV modifier, is not a pointer, and is not a
+// reference) built-in arithmetic types; the value is
+// implementation-defined when the above pre-condition is violated.
+template <typename From, typename To>
+using LosslessArithmeticConvertible =
+    LosslessArithmeticConvertibleImpl<GMOCK_KIND_OF_(From), From,
+                                      GMOCK_KIND_OF_(To), To>;
+
+// This interface knows how to report a Google Mock failure (either
+// non-fatal or fatal).
+class FailureReporterInterface {
+ public:
+  // The type of a failure (either non-fatal or fatal).
+  enum FailureType { kNonfatal, kFatal };
+
+  virtual ~FailureReporterInterface() = default;
+
+  // Reports a failure that occurred at the given source file location.
+  virtual void ReportFailure(FailureType type, const char* file, int line,
+                             const std::string& message) = 0;
+};
+
+// Returns the failure reporter used by Google Mock.
+GTEST_API_ FailureReporterInterface* GetFailureReporter();
+
+// Asserts that condition is true; aborts the process with the given
+// message if condition is false.  We cannot use LOG(FATAL) or CHECK()
+// as Google Mock might be used to mock the log sink itself.  We
+// inline this function to prevent it from showing up in the stack
+// trace.
+inline void Assert(bool condition, const char* file, int line,
+                   const std::string& msg) {
+  if (!condition) {
+    GetFailureReporter()->ReportFailure(FailureReporterInterface::kFatal, file,
+                                        line, msg);
+  }
+}
+inline void Assert(bool condition, const char* file, int line) {
+  Assert(condition, file, line, "Assertion failed.");
+}
+
+// Verifies that condition is true; generates a non-fatal failure if
+// condition is false.
+inline void Expect(bool condition, const char* file, int line,
+                   const std::string& msg) {
+  if (!condition) {
+    GetFailureReporter()->ReportFailure(FailureReporterInterface::kNonfatal,
+                                        file, line, msg);
+  }
+}
+inline void Expect(bool condition, const char* file, int line) {
+  Expect(condition, file, line, "Expectation failed.");
+}
+
+// Severity level of a log.
+enum LogSeverity { kInfo = 0, kWarning = 1 };
+
+// Valid values for the --gmock_verbose flag.
+
+// All logs (informational and warnings) are printed.
+const char kInfoVerbosity[] = "info";
+// Only warnings are printed.
+const char kWarningVerbosity[] = "warning";
+// No logs are printed.
+const char kErrorVerbosity[] = "error";
+
+// Returns true if and only if a log with the given severity is visible
+// according to the --gmock_verbose flag.
+GTEST_API_ bool LogIsVisible(LogSeverity severity);
+
+// Prints the given message to stdout if and only if 'severity' >= the level
+// specified by the --gmock_verbose flag.  If stack_frames_to_skip >=
+// 0, also prints the stack trace excluding the top
+// stack_frames_to_skip frames.  In opt mode, any positive
+// stack_frames_to_skip is treated as 0, since we don't know which
+// function calls will be inlined by the compiler and need to be
+// conservative.
+GTEST_API_ void Log(LogSeverity severity, const std::string& message,
+                    int stack_frames_to_skip);
+
+// A marker class that is used to resolve parameterless expectations to the
+// correct overload. This must not be instantiable, to prevent client code from
+// accidentally resolving to the overload; for example:
+//
+//    ON_CALL(mock, Method({}, nullptr))...
+//
+class WithoutMatchers {
+ private:
+  WithoutMatchers() {}
+  friend GTEST_API_ WithoutMatchers GetWithoutMatchers();
+};
+
+// Internal use only: access the singleton instance of WithoutMatchers.
+GTEST_API_ WithoutMatchers GetWithoutMatchers();
+
+// Invalid<T>() is usable as an expression of type T, but will terminate
+// the program with an assertion failure if actually run.  This is useful
+// when a value of type T is needed for compilation, but the statement
+// will not really be executed (or we don't care if the statement
+// crashes).
+template <typename T>
+inline T Invalid() {
+  Assert(/*condition=*/false, /*file=*/"", /*line=*/-1,
+         "Internal error: attempt to return invalid value");
+#if defined(__GNUC__) || defined(__clang__)
+  __builtin_unreachable();
+#elif defined(_MSC_VER)
+  __assume(0);
+#else
+  return Invalid<T>();
+#endif
+}
+
+// Given a raw type (i.e. having no top-level reference or const
+// modifier) RawContainer that's either an STL-style container or a
+// native array, class StlContainerView<RawContainer> has the
+// following members:
+//
+//   - type is a type that provides an STL-style container view to
+//     (i.e. implements the STL container concept for) RawContainer;
+//   - const_reference is a type that provides a reference to a const
+//     RawContainer;
+//   - ConstReference(raw_container) returns a const reference to an STL-style
+//     container view to raw_container, which is a RawContainer.
+//   - Copy(raw_container) returns an STL-style container view of a
+//     copy of raw_container, which is a RawContainer.
+//
+// This generic version is used when RawContainer itself is already an
+// STL-style container.
+template <class RawContainer>
+class StlContainerView {
+ public:
+  typedef RawContainer type;
+  typedef const type& const_reference;
+
+  static const_reference ConstReference(const RawContainer& container) {
+    static_assert(!std::is_const<RawContainer>::value,
+                  "RawContainer type must not be const");
+    return container;
+  }
+  static type Copy(const RawContainer& container) { return container; }
+};
+
+// This specialization is used when RawContainer is a native array type.
+template <typename Element, size_t N>
+class StlContainerView<Element[N]> {
+ public:
+  typedef typename std::remove_const<Element>::type RawElement;
+  typedef internal::NativeArray<RawElement> type;
+  // NativeArray<T> can represent a native array either by value or by
+  // reference (selected by a constructor argument), so 'const type'
+  // can be used to reference a const native array.  We cannot
+  // 'typedef const type& const_reference' here, as that would mean
+  // ConstReference() has to return a reference to a local variable.
+  typedef const type const_reference;
+
+  static const_reference ConstReference(const Element (&array)[N]) {
+    static_assert(std::is_same<Element, RawElement>::value,
+                  "Element type must not be const");
+    return type(array, N, RelationToSourceReference());
+  }
+  static type Copy(const Element (&array)[N]) {
+    return type(array, N, RelationToSourceCopy());
+  }
+};
+
+// This specialization is used when RawContainer is a native array
+// represented as a (pointer, size) tuple.
+template <typename ElementPointer, typename Size>
+class StlContainerView< ::std::tuple<ElementPointer, Size> > {
+ public:
+  typedef typename std::remove_const<
+      typename std::pointer_traits<ElementPointer>::element_type>::type
+      RawElement;
+  typedef internal::NativeArray<RawElement> type;
+  typedef const type const_reference;
+
+  static const_reference ConstReference(
+      const ::std::tuple<ElementPointer, Size>& array) {
+    return type(std::get<0>(array), std::get<1>(array),
+                RelationToSourceReference());
+  }
+  static type Copy(const ::std::tuple<ElementPointer, Size>& array) {
+    return type(std::get<0>(array), std::get<1>(array), RelationToSourceCopy());
+  }
+};
+
+// The following specialization prevents the user from instantiating
+// StlContainer with a reference type.
+template <typename T>
+class StlContainerView<T&>;
+
+// A type transform to remove constness from the first part of a pair.
+// Pairs like that are used as the value_type of associative containers,
+// and this transform produces a similar but assignable pair.
+template <typename T>
+struct RemoveConstFromKey {
+  typedef T type;
+};
+
+// Partially specialized to remove constness from std::pair<const K, V>.
+template <typename K, typename V>
+struct RemoveConstFromKey<std::pair<const K, V> > {
+  typedef std::pair<K, V> type;
+};
+
+// Emit an assertion failure due to incorrect DoDefault() usage. Out-of-lined to
+// reduce code size.
+GTEST_API_ void IllegalDoDefault(const char* file, int line);
+
+template <typename F, typename Tuple, size_t... Idx>
+auto ApplyImpl(F&& f, Tuple&& args, IndexSequence<Idx...>)
+    -> decltype(std::forward<F>(f)(
+        std::get<Idx>(std::forward<Tuple>(args))...)) {
+  return std::forward<F>(f)(std::get<Idx>(std::forward<Tuple>(args))...);
+}
+
+// Apply the function to a tuple of arguments.
+template <typename F, typename Tuple>
+auto Apply(F&& f, Tuple&& args) -> decltype(ApplyImpl(
+    std::forward<F>(f), std::forward<Tuple>(args),
+    MakeIndexSequence<std::tuple_size<
+        typename std::remove_reference<Tuple>::type>::value>())) {
+  return ApplyImpl(std::forward<F>(f), std::forward<Tuple>(args),
+                   MakeIndexSequence<std::tuple_size<
+                       typename std::remove_reference<Tuple>::type>::value>());
+}
+
+// Template struct Function<F>, where F must be a function type, contains
+// the following typedefs:
+//
+//   Result:               the function's return type.
+//   Arg<N>:               the type of the N-th argument, where N starts with 0.
+//   ArgumentTuple:        the tuple type consisting of all parameters of F.
+//   ArgumentMatcherTuple: the tuple type consisting of Matchers for all
+//                         parameters of F.
+//   MakeResultVoid:       the function type obtained by substituting void
+//                         for the return type of F.
+//   MakeResultIgnoredValue:
+//                         the function type obtained by substituting Something
+//                         for the return type of F.
+template <typename T>
+struct Function;
+
+template <typename R, typename... Args>
+struct Function<R(Args...)> {
+  using Result = R;
+  static constexpr size_t ArgumentCount = sizeof...(Args);
+  template <size_t I>
+  using Arg = ElemFromList<I, Args...>;
+  using ArgumentTuple = std::tuple<Args...>;
+  using ArgumentMatcherTuple = std::tuple<Matcher<Args>...>;
+  using MakeResultVoid = void(Args...);
+  using MakeResultIgnoredValue = IgnoredValue(Args...);
+};
+
+#ifdef GTEST_INTERNAL_NEED_REDUNDANT_CONSTEXPR_DECL
+template <typename R, typename... Args>
+constexpr size_t Function<R(Args...)>::ArgumentCount;
+#endif
+
+// Workaround for MSVC error C2039: 'type': is not a member of 'std'
+// when std::tuple_element is used.
+// See: https://github.com/google/googletest/issues/3931
+// Can be replaced with std::tuple_element_t in C++14.
+template <size_t I, typename T>
+using TupleElement = typename std::tuple_element<I, T>::type;
+
+bool Base64Unescape(const std::string& encoded, std::string* decoded);
+
+GTEST_DISABLE_MSC_WARNINGS_POP_()  // 4100 4805
+
+}  // namespace internal
+}  // namespace testing
+
+#endif  // GOOGLEMOCK_INCLUDE_GMOCK_INTERNAL_GMOCK_INTERNAL_UTILS_H_
diff --git a/third_party/googletest/googlemock/include/gmock/internal/gmock-port.h b/third_party/googletest/googlemock/include/gmock/internal/gmock-port.h
new file mode 100644
index 0000000..55ddfb6
--- /dev/null
+++ b/third_party/googletest/googlemock/include/gmock/internal/gmock-port.h
@@ -0,0 +1,139 @@
+// Copyright 2008, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Low-level types and utilities for porting Google Mock to various
+// platforms.  All macros ending with _ and symbols defined in an
+// internal namespace are subject to change without notice.  Code
+// outside Google Mock MUST NOT USE THEM DIRECTLY.  Macros that don't
+// end with _ are part of Google Mock's public API and can be used by
+// code outside Google Mock.
+
+// IWYU pragma: private, include "gmock/gmock.h"
+// IWYU pragma: friend gmock/.*
+
+#ifndef GOOGLEMOCK_INCLUDE_GMOCK_INTERNAL_GMOCK_PORT_H_
+#define GOOGLEMOCK_INCLUDE_GMOCK_INTERNAL_GMOCK_PORT_H_
+
+#include <assert.h>
+#include <stdlib.h>
+#include <cstdint>
+#include <iostream>
+
+// Most of the utilities needed for porting Google Mock are also
+// required for Google Test and are defined in gtest-port.h.
+//
+// Note to maintainers: to reduce code duplication, prefer adding
+// portability utilities to Google Test's gtest-port.h instead of
+// here, as Google Mock depends on Google Test.  Only add a utility
+// here if it's truly specific to Google Mock.
+
+#include "gmock/internal/custom/gmock-port.h"
+#include "gtest/internal/gtest-port.h"
+
+#ifdef GTEST_HAS_ABSL
+#include "absl/flags/declare.h"
+#include "absl/flags/flag.h"
+#endif
+
+// For MS Visual C++, check the compiler version. At least VS 2015 is
+// required to compile Google Mock.
+#if defined(_MSC_VER) && _MSC_VER < 1900
+#error "At least Visual C++ 2015 (14.0) is required to compile Google Mock."
+#endif
+
+// Macro for referencing flags.  This is public as we want the user to
+// use this syntax to reference Google Mock flags.
+#define GMOCK_FLAG_NAME_(name) gmock_##name
+#define GMOCK_FLAG(name) FLAGS_gmock_##name
+
+// Pick a command line flags implementation.
+#ifdef GTEST_HAS_ABSL
+
+// Macros for defining flags.
+#define GMOCK_DEFINE_bool_(name, default_val, doc) \
+  ABSL_FLAG(bool, GMOCK_FLAG_NAME_(name), default_val, doc)
+#define GMOCK_DEFINE_int32_(name, default_val, doc) \
+  ABSL_FLAG(int32_t, GMOCK_FLAG_NAME_(name), default_val, doc)
+#define GMOCK_DEFINE_string_(name, default_val, doc) \
+  ABSL_FLAG(std::string, GMOCK_FLAG_NAME_(name), default_val, doc)
+
+// Macros for declaring flags.
+#define GMOCK_DECLARE_bool_(name) \
+  ABSL_DECLARE_FLAG(bool, GMOCK_FLAG_NAME_(name))
+#define GMOCK_DECLARE_int32_(name) \
+  ABSL_DECLARE_FLAG(int32_t, GMOCK_FLAG_NAME_(name))
+#define GMOCK_DECLARE_string_(name) \
+  ABSL_DECLARE_FLAG(std::string, GMOCK_FLAG_NAME_(name))
+
+#define GMOCK_FLAG_GET(name) ::absl::GetFlag(GMOCK_FLAG(name))
+#define GMOCK_FLAG_SET(name, value) \
+  (void)(::absl::SetFlag(&GMOCK_FLAG(name), value))
+
+#else  // GTEST_HAS_ABSL
+
+// Macros for defining flags.
+#define GMOCK_DEFINE_bool_(name, default_val, doc)  \
+  namespace testing {                               \
+  GTEST_API_ bool GMOCK_FLAG(name) = (default_val); \
+  }                                                 \
+  static_assert(true, "no-op to require trailing semicolon")
+#define GMOCK_DEFINE_int32_(name, default_val, doc)    \
+  namespace testing {                                  \
+  GTEST_API_ int32_t GMOCK_FLAG(name) = (default_val); \
+  }                                                    \
+  static_assert(true, "no-op to require trailing semicolon")
+#define GMOCK_DEFINE_string_(name, default_val, doc)         \
+  namespace testing {                                        \
+  GTEST_API_ ::std::string GMOCK_FLAG(name) = (default_val); \
+  }                                                          \
+  static_assert(true, "no-op to require trailing semicolon")
+
+// Macros for declaring flags.
+#define GMOCK_DECLARE_bool_(name)          \
+  namespace testing {                      \
+  GTEST_API_ extern bool GMOCK_FLAG(name); \
+  }                                        \
+  static_assert(true, "no-op to require trailing semicolon")
+#define GMOCK_DECLARE_int32_(name)            \
+  namespace testing {                         \
+  GTEST_API_ extern int32_t GMOCK_FLAG(name); \
+  }                                           \
+  static_assert(true, "no-op to require trailing semicolon")
+#define GMOCK_DECLARE_string_(name)                 \
+  namespace testing {                               \
+  GTEST_API_ extern ::std::string GMOCK_FLAG(name); \
+  }                                                 \
+  static_assert(true, "no-op to require trailing semicolon")
+
+#define GMOCK_FLAG_GET(name) ::testing::GMOCK_FLAG(name)
+#define GMOCK_FLAG_SET(name, value) (void)(::testing::GMOCK_FLAG(name) = value)
+
+#endif  // GTEST_HAS_ABSL
+
+#endif  // GOOGLEMOCK_INCLUDE_GMOCK_INTERNAL_GMOCK_PORT_H_
diff --git a/third_party/googletest/googlemock/include/gmock/internal/gmock-pp.h b/third_party/googletest/googlemock/include/gmock/internal/gmock-pp.h
new file mode 100644
index 0000000..94d61c0
--- /dev/null
+++ b/third_party/googletest/googlemock/include/gmock/internal/gmock-pp.h
@@ -0,0 +1,279 @@
+#ifndef GOOGLEMOCK_INCLUDE_GMOCK_INTERNAL_GMOCK_PP_H_
+#define GOOGLEMOCK_INCLUDE_GMOCK_INTERNAL_GMOCK_PP_H_
+
+// Expands and concatenates the arguments. Constructed macros reevaluate.
+#define GMOCK_PP_CAT(_1, _2) GMOCK_PP_INTERNAL_CAT(_1, _2)
+
+// Expands and stringifies the only argument.
+#define GMOCK_PP_STRINGIZE(...) GMOCK_PP_INTERNAL_STRINGIZE(__VA_ARGS__)
+
+// Returns empty. Given a variadic number of arguments.
+#define GMOCK_PP_EMPTY(...)
+
+// Returns a comma. Given a variadic number of arguments.
+#define GMOCK_PP_COMMA(...) ,
+
+// Returns the only argument.
+#define GMOCK_PP_IDENTITY(_1) _1
+
+// Evaluates to the number of arguments after expansion.
+//
+//   #define PAIR x, y
+//
+//   GMOCK_PP_NARG() => 1
+//   GMOCK_PP_NARG(x) => 1
+//   GMOCK_PP_NARG(x, y) => 2
+//   GMOCK_PP_NARG(PAIR) => 2
+//
+// Requires: the number of arguments after expansion is at most 15.
+#define GMOCK_PP_NARG(...) \
+  GMOCK_PP_INTERNAL_16TH(  \
+      (__VA_ARGS__, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0))
+
+// Returns 1 if the expansion of arguments has an unprotected comma. Otherwise
+// returns 0. Requires no more than 15 unprotected commas.
+#define GMOCK_PP_HAS_COMMA(...) \
+  GMOCK_PP_INTERNAL_16TH(       \
+      (__VA_ARGS__, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0))
+
+// Returns the first argument.
+#define GMOCK_PP_HEAD(...) GMOCK_PP_INTERNAL_HEAD((__VA_ARGS__, unusedArg))
+
+// Returns the tail. A variadic list of all arguments minus the first. Requires
+// at least one argument.
+#define GMOCK_PP_TAIL(...) GMOCK_PP_INTERNAL_TAIL((__VA_ARGS__))
+
+// Calls CAT(_Macro, NARG(__VA_ARGS__))(__VA_ARGS__)
+#define GMOCK_PP_VARIADIC_CALL(_Macro, ...) \
+  GMOCK_PP_IDENTITY(                        \
+      GMOCK_PP_CAT(_Macro, GMOCK_PP_NARG(__VA_ARGS__))(__VA_ARGS__))
+
+// If the arguments after expansion have no tokens, evaluates to `1`. Otherwise
+// evaluates to `0`.
+//
+// Requires: * the number of arguments after expansion is at most 15.
+//           * If the argument is a macro, it must be able to be called with one
+//             argument.
+//
+// Implementation details:
+//
+// There is one case when it generates a compile error: if the argument is macro
+// that cannot be called with one argument.
+//
+//   #define M(a, b)  // it doesn't matter what it expands to
+//
+//   // Expected: expands to `0`.
+//   // Actual: compile error.
+//   GMOCK_PP_IS_EMPTY(M)
+//
+// There are 4 cases tested:
+//
+// * __VA_ARGS__ possible expansion has no unparen'd commas. Expected 0.
+// * __VA_ARGS__ possible expansion is not enclosed in parenthesis. Expected 0.
+// * __VA_ARGS__ possible expansion is not a macro that ()-evaluates to a comma.
+//   Expected 0
+// * __VA_ARGS__ is empty, or has unparen'd commas, or is enclosed in
+//   parenthesis, or is a macro that ()-evaluates to comma. Expected 1.
+//
+// We trigger detection on '0001', i.e. on empty.
+#define GMOCK_PP_IS_EMPTY(...)                                               \
+  GMOCK_PP_INTERNAL_IS_EMPTY(GMOCK_PP_HAS_COMMA(__VA_ARGS__),                \
+                             GMOCK_PP_HAS_COMMA(GMOCK_PP_COMMA __VA_ARGS__), \
+                             GMOCK_PP_HAS_COMMA(__VA_ARGS__()),              \
+                             GMOCK_PP_HAS_COMMA(GMOCK_PP_COMMA __VA_ARGS__()))
+
+// Evaluates to _Then if _Cond is 1 and _Else if _Cond is 0.
+#define GMOCK_PP_IF(_Cond, _Then, _Else) \
+  GMOCK_PP_CAT(GMOCK_PP_INTERNAL_IF_, _Cond)(_Then, _Else)
+
+// Similar to GMOCK_PP_IF but takes _Then and _Else in parentheses.
+//
+// GMOCK_PP_GENERIC_IF(1, (a, b, c), (d, e, f)) => a, b, c
+// GMOCK_PP_GENERIC_IF(0, (a, b, c), (d, e, f)) => d, e, f
+//
+#define GMOCK_PP_GENERIC_IF(_Cond, _Then, _Else) \
+  GMOCK_PP_REMOVE_PARENS(GMOCK_PP_IF(_Cond, _Then, _Else))
+
+// Evaluates to the number of arguments after expansion. Identifies 'empty' as
+// 0.
+//
+//   #define PAIR x, y
+//
+//   GMOCK_PP_NARG0() => 0
+//   GMOCK_PP_NARG0(x) => 1
+//   GMOCK_PP_NARG0(x, y) => 2
+//   GMOCK_PP_NARG0(PAIR) => 2
+//
+// Requires: * the number of arguments after expansion is at most 15.
+//           * If the argument is a macro, it must be able to be called with one
+//             argument.
+#define GMOCK_PP_NARG0(...) \
+  GMOCK_PP_IF(GMOCK_PP_IS_EMPTY(__VA_ARGS__), 0, GMOCK_PP_NARG(__VA_ARGS__))
+
+// Expands to 1 if the first argument starts with something in parentheses,
+// otherwise to 0.
+#define GMOCK_PP_IS_BEGIN_PARENS(...)                              \
+  GMOCK_PP_HEAD(GMOCK_PP_CAT(GMOCK_PP_INTERNAL_IBP_IS_VARIADIC_R_, \
+                             GMOCK_PP_INTERNAL_IBP_IS_VARIADIC_C __VA_ARGS__))
+
+// Expands to 1 is there is only one argument and it is enclosed in parentheses.
+#define GMOCK_PP_IS_ENCLOSED_PARENS(...)             \
+  GMOCK_PP_IF(GMOCK_PP_IS_BEGIN_PARENS(__VA_ARGS__), \
+              GMOCK_PP_IS_EMPTY(GMOCK_PP_EMPTY __VA_ARGS__), 0)
+
+// Remove the parens, requires GMOCK_PP_IS_ENCLOSED_PARENS(args) => 1.
+#define GMOCK_PP_REMOVE_PARENS(...) GMOCK_PP_INTERNAL_REMOVE_PARENS __VA_ARGS__
+
+// Expands to _Macro(0, _Data, e1) _Macro(1, _Data, e2) ... _Macro(K -1, _Data,
+// eK) as many of GMOCK_INTERNAL_NARG0 _Tuple.
+// Requires: * |_Macro| can be called with 3 arguments.
+//           * |_Tuple| expansion has no more than 15 elements.
+#define GMOCK_PP_FOR_EACH(_Macro, _Data, _Tuple)                        \
+  GMOCK_PP_CAT(GMOCK_PP_INTERNAL_FOR_EACH_IMPL_, GMOCK_PP_NARG0 _Tuple) \
+  (0, _Macro, _Data, _Tuple)
+
+// Expands to _Macro(0, _Data, ) _Macro(1, _Data, ) ... _Macro(K - 1, _Data, )
+// Empty if _K = 0.
+// Requires: * |_Macro| can be called with 3 arguments.
+//           * |_K| literal between 0 and 15
+#define GMOCK_PP_REPEAT(_Macro, _Data, _N)           \
+  GMOCK_PP_CAT(GMOCK_PP_INTERNAL_FOR_EACH_IMPL_, _N) \
+  (0, _Macro, _Data, GMOCK_PP_INTENRAL_EMPTY_TUPLE)
+
+// Increments the argument, requires the argument to be between 0 and 15.
+#define GMOCK_PP_INC(_i) GMOCK_PP_CAT(GMOCK_PP_INTERNAL_INC_, _i)
+
+// Returns comma if _i != 0. Requires _i to be between 0 and 15.
+#define GMOCK_PP_COMMA_IF(_i) GMOCK_PP_CAT(GMOCK_PP_INTERNAL_COMMA_IF_, _i)
+
+// Internal details follow. Do not use any of these symbols outside of this
+// file or we will break your code.
+#define GMOCK_PP_INTENRAL_EMPTY_TUPLE (, , , , , , , , , , , , , , , )
+#define GMOCK_PP_INTERNAL_CAT(_1, _2) _1##_2
+#define GMOCK_PP_INTERNAL_STRINGIZE(...) #__VA_ARGS__
+#define GMOCK_PP_INTERNAL_CAT_5(_1, _2, _3, _4, _5) _1##_2##_3##_4##_5
+#define GMOCK_PP_INTERNAL_IS_EMPTY(_1, _2, _3, _4)                             \
+  GMOCK_PP_HAS_COMMA(GMOCK_PP_INTERNAL_CAT_5(GMOCK_PP_INTERNAL_IS_EMPTY_CASE_, \
+                                             _1, _2, _3, _4))
+#define GMOCK_PP_INTERNAL_IS_EMPTY_CASE_0001 ,
+#define GMOCK_PP_INTERNAL_IF_1(_Then, _Else) _Then
+#define GMOCK_PP_INTERNAL_IF_0(_Then, _Else) _Else
+
+// Because of MSVC treating a token with a comma in it as a single token when
+// passed to another macro, we need to force it to evaluate it as multiple
+// tokens. We do that by using a "IDENTITY(MACRO PARENTHESIZED_ARGS)" macro. We
+// define one per possible macro that relies on this behavior. Note "_Args" must
+// be parenthesized.
+#define GMOCK_PP_INTERNAL_INTERNAL_16TH(_1, _2, _3, _4, _5, _6, _7, _8, _9, \
+                                        _10, _11, _12, _13, _14, _15, _16,  \
+                                        ...)                                \
+  _16
+#define GMOCK_PP_INTERNAL_16TH(_Args) \
+  GMOCK_PP_IDENTITY(GMOCK_PP_INTERNAL_INTERNAL_16TH _Args)
+#define GMOCK_PP_INTERNAL_INTERNAL_HEAD(_1, ...) _1
+#define GMOCK_PP_INTERNAL_HEAD(_Args) \
+  GMOCK_PP_IDENTITY(GMOCK_PP_INTERNAL_INTERNAL_HEAD _Args)
+#define GMOCK_PP_INTERNAL_INTERNAL_TAIL(_1, ...) __VA_ARGS__
+#define GMOCK_PP_INTERNAL_TAIL(_Args) \
+  GMOCK_PP_IDENTITY(GMOCK_PP_INTERNAL_INTERNAL_TAIL _Args)
+
+#define GMOCK_PP_INTERNAL_IBP_IS_VARIADIC_C(...) 1 _
+#define GMOCK_PP_INTERNAL_IBP_IS_VARIADIC_R_1 1,
+#define GMOCK_PP_INTERNAL_IBP_IS_VARIADIC_R_GMOCK_PP_INTERNAL_IBP_IS_VARIADIC_C \
+  0,
+#define GMOCK_PP_INTERNAL_REMOVE_PARENS(...) __VA_ARGS__
+#define GMOCK_PP_INTERNAL_INC_0 1
+#define GMOCK_PP_INTERNAL_INC_1 2
+#define GMOCK_PP_INTERNAL_INC_2 3
+#define GMOCK_PP_INTERNAL_INC_3 4
+#define GMOCK_PP_INTERNAL_INC_4 5
+#define GMOCK_PP_INTERNAL_INC_5 6
+#define GMOCK_PP_INTERNAL_INC_6 7
+#define GMOCK_PP_INTERNAL_INC_7 8
+#define GMOCK_PP_INTERNAL_INC_8 9
+#define GMOCK_PP_INTERNAL_INC_9 10
+#define GMOCK_PP_INTERNAL_INC_10 11
+#define GMOCK_PP_INTERNAL_INC_11 12
+#define GMOCK_PP_INTERNAL_INC_12 13
+#define GMOCK_PP_INTERNAL_INC_13 14
+#define GMOCK_PP_INTERNAL_INC_14 15
+#define GMOCK_PP_INTERNAL_INC_15 16
+#define GMOCK_PP_INTERNAL_COMMA_IF_0
+#define GMOCK_PP_INTERNAL_COMMA_IF_1 ,
+#define GMOCK_PP_INTERNAL_COMMA_IF_2 ,
+#define GMOCK_PP_INTERNAL_COMMA_IF_3 ,
+#define GMOCK_PP_INTERNAL_COMMA_IF_4 ,
+#define GMOCK_PP_INTERNAL_COMMA_IF_5 ,
+#define GMOCK_PP_INTERNAL_COMMA_IF_6 ,
+#define GMOCK_PP_INTERNAL_COMMA_IF_7 ,
+#define GMOCK_PP_INTERNAL_COMMA_IF_8 ,
+#define GMOCK_PP_INTERNAL_COMMA_IF_9 ,
+#define GMOCK_PP_INTERNAL_COMMA_IF_10 ,
+#define GMOCK_PP_INTERNAL_COMMA_IF_11 ,
+#define GMOCK_PP_INTERNAL_COMMA_IF_12 ,
+#define GMOCK_PP_INTERNAL_COMMA_IF_13 ,
+#define GMOCK_PP_INTERNAL_COMMA_IF_14 ,
+#define GMOCK_PP_INTERNAL_COMMA_IF_15 ,
+#define GMOCK_PP_INTERNAL_CALL_MACRO(_Macro, _i, _Data, _element) \
+  _Macro(_i, _Data, _element)
+#define GMOCK_PP_INTERNAL_FOR_EACH_IMPL_0(_i, _Macro, _Data, _Tuple)
+#define GMOCK_PP_INTERNAL_FOR_EACH_IMPL_1(_i, _Macro, _Data, _Tuple) \
+  GMOCK_PP_INTERNAL_CALL_MACRO(_Macro, _i, _Data, GMOCK_PP_HEAD _Tuple)
+#define GMOCK_PP_INTERNAL_FOR_EACH_IMPL_2(_i, _Macro, _Data, _Tuple)    \
+  GMOCK_PP_INTERNAL_CALL_MACRO(_Macro, _i, _Data, GMOCK_PP_HEAD _Tuple) \
+  GMOCK_PP_INTERNAL_FOR_EACH_IMPL_1(GMOCK_PP_INC(_i), _Macro, _Data,    \
+                                    (GMOCK_PP_TAIL _Tuple))
+#define GMOCK_PP_INTERNAL_FOR_EACH_IMPL_3(_i, _Macro, _Data, _Tuple)    \
+  GMOCK_PP_INTERNAL_CALL_MACRO(_Macro, _i, _Data, GMOCK_PP_HEAD _Tuple) \
+  GMOCK_PP_INTERNAL_FOR_EACH_IMPL_2(GMOCK_PP_INC(_i), _Macro, _Data,    \
+                                    (GMOCK_PP_TAIL _Tuple))
+#define GMOCK_PP_INTERNAL_FOR_EACH_IMPL_4(_i, _Macro, _Data, _Tuple)    \
+  GMOCK_PP_INTERNAL_CALL_MACRO(_Macro, _i, _Data, GMOCK_PP_HEAD _Tuple) \
+  GMOCK_PP_INTERNAL_FOR_EACH_IMPL_3(GMOCK_PP_INC(_i), _Macro, _Data,    \
+                                    (GMOCK_PP_TAIL _Tuple))
+#define GMOCK_PP_INTERNAL_FOR_EACH_IMPL_5(_i, _Macro, _Data, _Tuple)    \
+  GMOCK_PP_INTERNAL_CALL_MACRO(_Macro, _i, _Data, GMOCK_PP_HEAD _Tuple) \
+  GMOCK_PP_INTERNAL_FOR_EACH_IMPL_4(GMOCK_PP_INC(_i), _Macro, _Data,    \
+                                    (GMOCK_PP_TAIL _Tuple))
+#define GMOCK_PP_INTERNAL_FOR_EACH_IMPL_6(_i, _Macro, _Data, _Tuple)    \
+  GMOCK_PP_INTERNAL_CALL_MACRO(_Macro, _i, _Data, GMOCK_PP_HEAD _Tuple) \
+  GMOCK_PP_INTERNAL_FOR_EACH_IMPL_5(GMOCK_PP_INC(_i), _Macro, _Data,    \
+                                    (GMOCK_PP_TAIL _Tuple))
+#define GMOCK_PP_INTERNAL_FOR_EACH_IMPL_7(_i, _Macro, _Data, _Tuple)    \
+  GMOCK_PP_INTERNAL_CALL_MACRO(_Macro, _i, _Data, GMOCK_PP_HEAD _Tuple) \
+  GMOCK_PP_INTERNAL_FOR_EACH_IMPL_6(GMOCK_PP_INC(_i), _Macro, _Data,    \
+                                    (GMOCK_PP_TAIL _Tuple))
+#define GMOCK_PP_INTERNAL_FOR_EACH_IMPL_8(_i, _Macro, _Data, _Tuple)    \
+  GMOCK_PP_INTERNAL_CALL_MACRO(_Macro, _i, _Data, GMOCK_PP_HEAD _Tuple) \
+  GMOCK_PP_INTERNAL_FOR_EACH_IMPL_7(GMOCK_PP_INC(_i), _Macro, _Data,    \
+                                    (GMOCK_PP_TAIL _Tuple))
+#define GMOCK_PP_INTERNAL_FOR_EACH_IMPL_9(_i, _Macro, _Data, _Tuple)    \
+  GMOCK_PP_INTERNAL_CALL_MACRO(_Macro, _i, _Data, GMOCK_PP_HEAD _Tuple) \
+  GMOCK_PP_INTERNAL_FOR_EACH_IMPL_8(GMOCK_PP_INC(_i), _Macro, _Data,    \
+                                    (GMOCK_PP_TAIL _Tuple))
+#define GMOCK_PP_INTERNAL_FOR_EACH_IMPL_10(_i, _Macro, _Data, _Tuple)   \
+  GMOCK_PP_INTERNAL_CALL_MACRO(_Macro, _i, _Data, GMOCK_PP_HEAD _Tuple) \
+  GMOCK_PP_INTERNAL_FOR_EACH_IMPL_9(GMOCK_PP_INC(_i), _Macro, _Data,    \
+                                    (GMOCK_PP_TAIL _Tuple))
+#define GMOCK_PP_INTERNAL_FOR_EACH_IMPL_11(_i, _Macro, _Data, _Tuple)   \
+  GMOCK_PP_INTERNAL_CALL_MACRO(_Macro, _i, _Data, GMOCK_PP_HEAD _Tuple) \
+  GMOCK_PP_INTERNAL_FOR_EACH_IMPL_10(GMOCK_PP_INC(_i), _Macro, _Data,   \
+                                     (GMOCK_PP_TAIL _Tuple))
+#define GMOCK_PP_INTERNAL_FOR_EACH_IMPL_12(_i, _Macro, _Data, _Tuple)   \
+  GMOCK_PP_INTERNAL_CALL_MACRO(_Macro, _i, _Data, GMOCK_PP_HEAD _Tuple) \
+  GMOCK_PP_INTERNAL_FOR_EACH_IMPL_11(GMOCK_PP_INC(_i), _Macro, _Data,   \
+                                     (GMOCK_PP_TAIL _Tuple))
+#define GMOCK_PP_INTERNAL_FOR_EACH_IMPL_13(_i, _Macro, _Data, _Tuple)   \
+  GMOCK_PP_INTERNAL_CALL_MACRO(_Macro, _i, _Data, GMOCK_PP_HEAD _Tuple) \
+  GMOCK_PP_INTERNAL_FOR_EACH_IMPL_12(GMOCK_PP_INC(_i), _Macro, _Data,   \
+                                     (GMOCK_PP_TAIL _Tuple))
+#define GMOCK_PP_INTERNAL_FOR_EACH_IMPL_14(_i, _Macro, _Data, _Tuple)   \
+  GMOCK_PP_INTERNAL_CALL_MACRO(_Macro, _i, _Data, GMOCK_PP_HEAD _Tuple) \
+  GMOCK_PP_INTERNAL_FOR_EACH_IMPL_13(GMOCK_PP_INC(_i), _Macro, _Data,   \
+                                     (GMOCK_PP_TAIL _Tuple))
+#define GMOCK_PP_INTERNAL_FOR_EACH_IMPL_15(_i, _Macro, _Data, _Tuple)   \
+  GMOCK_PP_INTERNAL_CALL_MACRO(_Macro, _i, _Data, GMOCK_PP_HEAD _Tuple) \
+  GMOCK_PP_INTERNAL_FOR_EACH_IMPL_14(GMOCK_PP_INC(_i), _Macro, _Data,   \
+                                     (GMOCK_PP_TAIL _Tuple))
+
+#endif  // GOOGLEMOCK_INCLUDE_GMOCK_INTERNAL_GMOCK_PP_H_
diff --git a/third_party/googletest/googlemock/src/gmock-all.cc b/third_party/googletest/googlemock/src/gmock-all.cc
new file mode 100644
index 0000000..e43c9b7
--- /dev/null
+++ b/third_party/googletest/googlemock/src/gmock-all.cc
@@ -0,0 +1,46 @@
+// Copyright 2008, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+//
+// Google C++ Mocking Framework (Google Mock)
+//
+// This file #includes all Google Mock implementation .cc files.  The
+// purpose is to allow a user to build Google Mock by compiling this
+// file alone.
+
+// This line ensures that gmock.h can be compiled on its own, even
+// when it's fused.
+#include "gmock/gmock.h"
+
+// The following lines pull in the real gmock *.cc files.
+#include "src/gmock-cardinalities.cc"
+#include "src/gmock-internal-utils.cc"
+#include "src/gmock-matchers.cc"
+#include "src/gmock-spec-builders.cc"
+#include "src/gmock.cc"
diff --git a/third_party/googletest/googlemock/src/gmock-cardinalities.cc b/third_party/googletest/googlemock/src/gmock-cardinalities.cc
new file mode 100644
index 0000000..92cde34
--- /dev/null
+++ b/third_party/googletest/googlemock/src/gmock-cardinalities.cc
@@ -0,0 +1,155 @@
+// Copyright 2007, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Google Mock - a framework for writing C++ mock classes.
+//
+// This file implements cardinalities.
+
+#include "gmock/gmock-cardinalities.h"
+
+#include <limits.h>
+
+#include <ostream>  // NOLINT
+#include <sstream>
+#include <string>
+
+#include "gmock/internal/gmock-internal-utils.h"
+#include "gtest/gtest.h"
+
+namespace testing {
+
+namespace {
+
+// Implements the Between(m, n) cardinality.
+class BetweenCardinalityImpl : public CardinalityInterface {
+ public:
+  BetweenCardinalityImpl(int min, int max)
+      : min_(min >= 0 ? min : 0), max_(max >= min_ ? max : min_) {
+    std::stringstream ss;
+    if (min < 0) {
+      ss << "The invocation lower bound must be >= 0, "
+         << "but is actually " << min << ".";
+      internal::Expect(false, __FILE__, __LINE__, ss.str());
+    } else if (max < 0) {
+      ss << "The invocation upper bound must be >= 0, "
+         << "but is actually " << max << ".";
+      internal::Expect(false, __FILE__, __LINE__, ss.str());
+    } else if (min > max) {
+      ss << "The invocation upper bound (" << max
+         << ") must be >= the invocation lower bound (" << min << ").";
+      internal::Expect(false, __FILE__, __LINE__, ss.str());
+    }
+  }
+
+  // Conservative estimate on the lower/upper bound of the number of
+  // calls allowed.
+  int ConservativeLowerBound() const override { return min_; }
+  int ConservativeUpperBound() const override { return max_; }
+
+  bool IsSatisfiedByCallCount(int call_count) const override {
+    return min_ <= call_count && call_count <= max_;
+  }
+
+  bool IsSaturatedByCallCount(int call_count) const override {
+    return call_count >= max_;
+  }
+
+  void DescribeTo(::std::ostream* os) const override;
+
+ private:
+  const int min_;
+  const int max_;
+
+  BetweenCardinalityImpl(const BetweenCardinalityImpl&) = delete;
+  BetweenCardinalityImpl& operator=(const BetweenCardinalityImpl&) = delete;
+};
+
+// Formats "n times" in a human-friendly way.
+inline std::string FormatTimes(int n) {
+  if (n == 1) {
+    return "once";
+  } else if (n == 2) {
+    return "twice";
+  } else {
+    std::stringstream ss;
+    ss << n << " times";
+    return ss.str();
+  }
+}
+
+// Describes the Between(m, n) cardinality in human-friendly text.
+void BetweenCardinalityImpl::DescribeTo(::std::ostream* os) const {
+  if (min_ == 0) {
+    if (max_ == 0) {
+      *os << "never called";
+    } else if (max_ == INT_MAX) {
+      *os << "called any number of times";
+    } else {
+      *os << "called at most " << FormatTimes(max_);
+    }
+  } else if (min_ == max_) {
+    *os << "called " << FormatTimes(min_);
+  } else if (max_ == INT_MAX) {
+    *os << "called at least " << FormatTimes(min_);
+  } else {
+    // 0 < min_ < max_ < INT_MAX
+    *os << "called between " << min_ << " and " << max_ << " times";
+  }
+}
+
+}  // Unnamed namespace
+
+// Describes the given call count to an ostream.
+void Cardinality::DescribeActualCallCountTo(int actual_call_count,
+                                            ::std::ostream* os) {
+  if (actual_call_count > 0) {
+    *os << "called " << FormatTimes(actual_call_count);
+  } else {
+    *os << "never called";
+  }
+}
+
+// Creates a cardinality that allows at least n calls.
+GTEST_API_ Cardinality AtLeast(int n) { return Between(n, INT_MAX); }
+
+// Creates a cardinality that allows at most n calls.
+GTEST_API_ Cardinality AtMost(int n) { return Between(0, n); }
+
+// Creates a cardinality that allows any number of calls.
+GTEST_API_ Cardinality AnyNumber() { return AtLeast(0); }
+
+// Creates a cardinality that allows between min and max calls.
+GTEST_API_ Cardinality Between(int min, int max) {
+  return Cardinality(new BetweenCardinalityImpl(min, max));
+}
+
+// Creates a cardinality that allows exactly n calls.
+GTEST_API_ Cardinality Exactly(int n) { return Between(n, n); }
+
+}  // namespace testing
diff --git a/third_party/googletest/googlemock/src/gmock-internal-utils.cc b/third_party/googletest/googlemock/src/gmock-internal-utils.cc
new file mode 100644
index 0000000..5c2ce0d
--- /dev/null
+++ b/third_party/googletest/googlemock/src/gmock-internal-utils.cc
@@ -0,0 +1,257 @@
+// Copyright 2007, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Google Mock - a framework for writing C++ mock classes.
+//
+// This file defines some utilities useful for implementing Google
+// Mock.  They are subject to change without notice, so please DO NOT
+// USE THEM IN USER CODE.
+
+#include "gmock/internal/gmock-internal-utils.h"
+
+#include <ctype.h>
+
+#include <array>
+#include <cctype>
+#include <cstdint>
+#include <cstring>
+#include <iostream>
+#include <ostream>  // NOLINT
+#include <string>
+#include <vector>
+
+#include "gmock/gmock.h"
+#include "gmock/internal/gmock-port.h"
+#include "gtest/gtest.h"
+
+namespace testing {
+namespace internal {
+
+// Joins a vector of strings as if they are fields of a tuple; returns
+// the joined string.
+GTEST_API_ std::string JoinAsKeyValueTuple(
+    const std::vector<const char*>& names, const Strings& values) {
+  GTEST_CHECK_(names.size() == values.size());
+  if (values.empty()) {
+    return "";
+  }
+  const auto build_one = [&](const size_t i) {
+    return std::string(names[i]) + ": " + values[i];
+  };
+  std::string result = "(" + build_one(0);
+  for (size_t i = 1; i < values.size(); i++) {
+    result += ", ";
+    result += build_one(i);
+  }
+  result += ")";
+  return result;
+}
+
+// Converts an identifier name to a space-separated list of lower-case
+// words.  Each maximum substring of the form [A-Za-z][a-z]*|\d+ is
+// treated as one word.  For example, both "FooBar123" and
+// "foo_bar_123" are converted to "foo bar 123".
+GTEST_API_ std::string ConvertIdentifierNameToWords(const char* id_name) {
+  std::string result;
+  char prev_char = '\0';
+  for (const char* p = id_name; *p != '\0'; prev_char = *(p++)) {
+    // We don't care about the current locale as the input is
+    // guaranteed to be a valid C++ identifier name.
+    const bool starts_new_word = IsUpper(*p) ||
+                                 (!IsAlpha(prev_char) && IsLower(*p)) ||
+                                 (!IsDigit(prev_char) && IsDigit(*p));
+
+    if (IsAlNum(*p)) {
+      if (starts_new_word && !result.empty()) result += ' ';
+      result += ToLower(*p);
+    }
+  }
+  return result;
+}
+
+// This class reports Google Mock failures as Google Test failures.  A
+// user can define another class in a similar fashion if they intend to
+// use Google Mock with a testing framework other than Google Test.
+class GoogleTestFailureReporter : public FailureReporterInterface {
+ public:
+  void ReportFailure(FailureType type, const char* file, int line,
+                     const std::string& message) override {
+    AssertHelper(type == kFatal ? TestPartResult::kFatalFailure
+                                : TestPartResult::kNonFatalFailure,
+                 file, line, message.c_str()) = Message();
+    if (type == kFatal) {
+      posix::Abort();
+    }
+  }
+};
+
+// Returns the global failure reporter.  Will create a
+// GoogleTestFailureReporter and return it the first time called.
+GTEST_API_ FailureReporterInterface* GetFailureReporter() {
+  // Points to the global failure reporter used by Google Mock.  gcc
+  // guarantees that the following use of failure_reporter is
+  // thread-safe.  We may need to add additional synchronization to
+  // protect failure_reporter if we port Google Mock to other
+  // compilers.
+  static FailureReporterInterface* const failure_reporter =
+      new GoogleTestFailureReporter();
+  return failure_reporter;
+}
+
+// Protects global resources (stdout in particular) used by Log().
+static GTEST_DEFINE_STATIC_MUTEX_(g_log_mutex);
+
+// Returns true if and only if a log with the given severity is visible
+// according to the --gmock_verbose flag.
+GTEST_API_ bool LogIsVisible(LogSeverity severity) {
+  if (GMOCK_FLAG_GET(verbose) == kInfoVerbosity) {
+    // Always show the log if --gmock_verbose=info.
+    return true;
+  } else if (GMOCK_FLAG_GET(verbose) == kErrorVerbosity) {
+    // Always hide it if --gmock_verbose=error.
+    return false;
+  } else {
+    // If --gmock_verbose is neither "info" nor "error", we treat it
+    // as "warning" (its default value).
+    return severity == kWarning;
+  }
+}
+
+// Prints the given message to stdout if and only if 'severity' >= the level
+// specified by the --gmock_verbose flag.  If stack_frames_to_skip >=
+// 0, also prints the stack trace excluding the top
+// stack_frames_to_skip frames.  In opt mode, any positive
+// stack_frames_to_skip is treated as 0, since we don't know which
+// function calls will be inlined by the compiler and need to be
+// conservative.
+GTEST_API_ void Log(LogSeverity severity, const std::string& message,
+                    int stack_frames_to_skip) {
+  if (!LogIsVisible(severity)) return;
+
+  // Ensures that logs from different threads don't interleave.
+  MutexLock l(&g_log_mutex);
+
+  if (severity == kWarning) {
+    // Prints a GMOCK WARNING marker to make the warnings easily searchable.
+    std::cout << "\nGMOCK WARNING:";
+  }
+  // Pre-pends a new-line to message if it doesn't start with one.
+  if (message.empty() || message[0] != '\n') {
+    std::cout << "\n";
+  }
+  std::cout << message;
+  if (stack_frames_to_skip >= 0) {
+#ifdef NDEBUG
+    // In opt mode, we have to be conservative and skip no stack frame.
+    const int actual_to_skip = 0;
+#else
+    // In dbg mode, we can do what the caller tell us to do (plus one
+    // for skipping this function's stack frame).
+    const int actual_to_skip = stack_frames_to_skip + 1;
+#endif  // NDEBUG
+
+    // Appends a new-line to message if it doesn't end with one.
+    if (!message.empty() && *message.rbegin() != '\n') {
+      std::cout << "\n";
+    }
+    std::cout << "Stack trace:\n"
+              << ::testing::internal::GetCurrentOsStackTraceExceptTop(
+                     actual_to_skip);
+  }
+  std::cout << ::std::flush;
+}
+
+GTEST_API_ WithoutMatchers GetWithoutMatchers() { return WithoutMatchers(); }
+
+GTEST_API_ void IllegalDoDefault(const char* file, int line) {
+  internal::Assert(
+      false, file, line,
+      "You are using DoDefault() inside a composite action like "
+      "DoAll() or WithArgs().  This is not supported for technical "
+      "reasons.  Please instead spell out the default action, or "
+      "assign the default action to an Action variable and use "
+      "the variable in various places.");
+}
+
+constexpr char UndoWebSafeEncoding(char c) {
+  return c == '-' ? '+' : c == '_' ? '/' : c;
+}
+
+constexpr char UnBase64Impl(char c, const char* const base64, char carry) {
+  return *base64 == 0 ? static_cast<char>(65)
+         : *base64 == c
+             ? carry
+             : UnBase64Impl(c, base64 + 1, static_cast<char>(carry + 1));
+}
+
+template <size_t... I>
+constexpr std::array<char, 256> UnBase64Impl(IndexSequence<I...>,
+                                             const char* const base64) {
+  return {
+      {UnBase64Impl(UndoWebSafeEncoding(static_cast<char>(I)), base64, 0)...}};
+}
+
+constexpr std::array<char, 256> UnBase64(const char* const base64) {
+  return UnBase64Impl(MakeIndexSequence<256>{}, base64);
+}
+
+static constexpr char kBase64[] =
+    "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
+static constexpr std::array<char, 256> kUnBase64 = UnBase64(kBase64);
+
+bool Base64Unescape(const std::string& encoded, std::string* decoded) {
+  decoded->clear();
+  size_t encoded_len = encoded.size();
+  decoded->reserve(3 * (encoded_len / 4) + (encoded_len % 4));
+  int bit_pos = 0;
+  char dst = 0;
+  for (int src : encoded) {
+    if (std::isspace(src) || src == '=') {
+      continue;
+    }
+    char src_bin = kUnBase64[static_cast<size_t>(src)];
+    if (src_bin >= 64) {
+      decoded->clear();
+      return false;
+    }
+    if (bit_pos == 0) {
+      dst |= static_cast<char>(src_bin << 2);
+      bit_pos = 6;
+    } else {
+      dst |= static_cast<char>(src_bin >> (bit_pos - 2));
+      decoded->push_back(dst);
+      dst = static_cast<char>(src_bin << (10 - bit_pos));
+      bit_pos = (bit_pos + 6) % 8;
+    }
+  }
+  return true;
+}
+
+}  // namespace internal
+}  // namespace testing
diff --git a/third_party/googletest/googlemock/src/gmock-matchers.cc b/third_party/googletest/googlemock/src/gmock-matchers.cc
new file mode 100644
index 0000000..81a5b7e
--- /dev/null
+++ b/third_party/googletest/googlemock/src/gmock-matchers.cc
@@ -0,0 +1,479 @@
+// Copyright 2007, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Google Mock - a framework for writing C++ mock classes.
+//
+// This file implements Matcher<const string&>, Matcher<string>, and
+// utilities for defining matchers.
+
+#include "gmock/gmock-matchers.h"
+
+#include <string.h>
+
+#include <iostream>
+#include <sstream>
+#include <string>
+#include <vector>
+
+namespace testing {
+namespace internal {
+
+// Returns the description for a matcher defined using the MATCHER*()
+// macro where the user-supplied description string is "", if
+// 'negation' is false; otherwise returns the description of the
+// negation of the matcher.  'param_values' contains a list of strings
+// that are the print-out of the matcher's parameters.
+GTEST_API_ std::string FormatMatcherDescription(
+    bool negation, const char* matcher_name,
+    const std::vector<const char*>& param_names, const Strings& param_values) {
+  std::string result = ConvertIdentifierNameToWords(matcher_name);
+  if (!param_values.empty()) {
+    result += " " + JoinAsKeyValueTuple(param_names, param_values);
+  }
+  return negation ? "not (" + result + ")" : result;
+}
+
+// FindMaxBipartiteMatching and its helper class.
+//
+// Uses the well-known Ford-Fulkerson max flow method to find a maximum
+// bipartite matching. Flow is considered to be from left to right.
+// There is an implicit source node that is connected to all of the left
+// nodes, and an implicit sink node that is connected to all of the
+// right nodes. All edges have unit capacity.
+//
+// Neither the flow graph nor the residual flow graph are represented
+// explicitly. Instead, they are implied by the information in 'graph' and
+// a vector<int> called 'left_' whose elements are initialized to the
+// value kUnused. This represents the initial state of the algorithm,
+// where the flow graph is empty, and the residual flow graph has the
+// following edges:
+//   - An edge from source to each left_ node
+//   - An edge from each right_ node to sink
+//   - An edge from each left_ node to each right_ node, if the
+//     corresponding edge exists in 'graph'.
+//
+// When the TryAugment() method adds a flow, it sets left_[l] = r for some
+// nodes l and r. This induces the following changes:
+//   - The edges (source, l), (l, r), and (r, sink) are added to the
+//     flow graph.
+//   - The same three edges are removed from the residual flow graph.
+//   - The reverse edges (l, source), (r, l), and (sink, r) are added
+//     to the residual flow graph, which is a directional graph
+//     representing unused flow capacity.
+//
+// When the method augments a flow (moving left_[l] from some r1 to some
+// other r2), this can be thought of as "undoing" the above steps with
+// respect to r1 and "redoing" them with respect to r2.
+//
+// It bears repeating that the flow graph and residual flow graph are
+// never represented explicitly, but can be derived by looking at the
+// information in 'graph' and in left_.
+//
+// As an optimization, there is a second vector<int> called right_ which
+// does not provide any new information. Instead, it enables more
+// efficient queries about edges entering or leaving the right-side nodes
+// of the flow or residual flow graphs. The following invariants are
+// maintained:
+//
+// left[l] == kUnused or right[left[l]] == l
+// right[r] == kUnused or left[right[r]] == r
+//
+// . [ source ]                                        .
+// .   |||                                             .
+// .   |||                                             .
+// .   ||\--> left[0]=1  ---\    right[0]=-1 ----\     .
+// .   ||                   |                    |     .
+// .   |\---> left[1]=-1    \--> right[1]=0  ---\|     .
+// .   |                                        ||     .
+// .   \----> left[2]=2  ------> right[2]=2  --\||     .
+// .                                           |||     .
+// .         elements           matchers       vvv     .
+// .                                         [ sink ]  .
+//
+// See Also:
+//   [1] Cormen, et al (2001). "Section 26.2: The Ford-Fulkerson method".
+//       "Introduction to Algorithms (Second ed.)", pp. 651-664.
+//   [2] "Ford-Fulkerson algorithm", Wikipedia,
+//       'https://en.wikipedia.org/wiki/Ford%E2%80%93Fulkerson_algorithm'
+class MaxBipartiteMatchState {
+ public:
+  explicit MaxBipartiteMatchState(const MatchMatrix& graph)
+      : graph_(&graph),
+        left_(graph_->LhsSize(), kUnused),
+        right_(graph_->RhsSize(), kUnused) {}
+
+  // Returns the edges of a maximal match, each in the form {left, right}.
+  ElementMatcherPairs Compute() {
+    // 'seen' is used for path finding { 0: unseen, 1: seen }.
+    ::std::vector<char> seen;
+    // Searches the residual flow graph for a path from each left node to
+    // the sink in the residual flow graph, and if one is found, add flow
+    // to the graph. It's okay to search through the left nodes once. The
+    // edge from the implicit source node to each previously-visited left
+    // node will have flow if that left node has any path to the sink
+    // whatsoever. Subsequent augmentations can only add flow to the
+    // network, and cannot take away that previous flow unit from the source.
+    // Since the source-to-left edge can only carry one flow unit (or,
+    // each element can be matched to only one matcher), there is no need
+    // to visit the left nodes more than once looking for augmented paths.
+    // The flow is known to be possible or impossible by looking at the
+    // node once.
+    for (size_t ilhs = 0; ilhs < graph_->LhsSize(); ++ilhs) {
+      // Reset the path-marking vector and try to find a path from
+      // source to sink starting at the left_[ilhs] node.
+      GTEST_CHECK_(left_[ilhs] == kUnused)
+          << "ilhs: " << ilhs << ", left_[ilhs]: " << left_[ilhs];
+      // 'seen' initialized to 'graph_->RhsSize()' copies of 0.
+      seen.assign(graph_->RhsSize(), 0);
+      TryAugment(ilhs, &seen);
+    }
+    ElementMatcherPairs result;
+    for (size_t ilhs = 0; ilhs < left_.size(); ++ilhs) {
+      size_t irhs = left_[ilhs];
+      if (irhs == kUnused) continue;
+      result.push_back(ElementMatcherPair(ilhs, irhs));
+    }
+    return result;
+  }
+
+ private:
+  static const size_t kUnused = static_cast<size_t>(-1);
+
+  // Perform a depth-first search from left node ilhs to the sink.  If a
+  // path is found, flow is added to the network by linking the left and
+  // right vector elements corresponding each segment of the path.
+  // Returns true if a path to sink was found, which means that a unit of
+  // flow was added to the network. The 'seen' vector elements correspond
+  // to right nodes and are marked to eliminate cycles from the search.
+  //
+  // Left nodes will only be explored at most once because they
+  // are accessible from at most one right node in the residual flow
+  // graph.
+  //
+  // Note that left_[ilhs] is the only element of left_ that TryAugment will
+  // potentially transition from kUnused to another value. Any other
+  // left_ element holding kUnused before TryAugment will be holding it
+  // when TryAugment returns.
+  //
+  bool TryAugment(size_t ilhs, ::std::vector<char>* seen) {
+    for (size_t irhs = 0; irhs < graph_->RhsSize(); ++irhs) {
+      if ((*seen)[irhs]) continue;
+      if (!graph_->HasEdge(ilhs, irhs)) continue;
+      // There's an available edge from ilhs to irhs.
+      (*seen)[irhs] = 1;
+      // Next a search is performed to determine whether
+      // this edge is a dead end or leads to the sink.
+      //
+      // right_[irhs] == kUnused means that there is residual flow from
+      // right node irhs to the sink, so we can use that to finish this
+      // flow path and return success.
+      //
+      // Otherwise there is residual flow to some ilhs. We push flow
+      // along that path and call ourselves recursively to see if this
+      // ultimately leads to sink.
+      if (right_[irhs] == kUnused || TryAugment(right_[irhs], seen)) {
+        // Add flow from left_[ilhs] to right_[irhs].
+        left_[ilhs] = irhs;
+        right_[irhs] = ilhs;
+        return true;
+      }
+    }
+    return false;
+  }
+
+  const MatchMatrix* graph_;  // not owned
+  // Each element of the left_ vector represents a left hand side node
+  // (i.e. an element) and each element of right_ is a right hand side
+  // node (i.e. a matcher). The values in the left_ vector indicate
+  // outflow from that node to a node on the right_ side. The values
+  // in the right_ indicate inflow, and specify which left_ node is
+  // feeding that right_ node, if any. For example, left_[3] == 1 means
+  // there's a flow from element #3 to matcher #1. Such a flow would also
+  // be redundantly represented in the right_ vector as right_[1] == 3.
+  // Elements of left_ and right_ are either kUnused or mutually
+  // referent. Mutually referent means that left_[right_[i]] = i and
+  // right_[left_[i]] = i.
+  ::std::vector<size_t> left_;
+  ::std::vector<size_t> right_;
+};
+
+const size_t MaxBipartiteMatchState::kUnused;
+
+GTEST_API_ ElementMatcherPairs FindMaxBipartiteMatching(const MatchMatrix& g) {
+  return MaxBipartiteMatchState(g).Compute();
+}
+
+static void LogElementMatcherPairVec(const ElementMatcherPairs& pairs,
+                                     ::std::ostream* stream) {
+  typedef ElementMatcherPairs::const_iterator Iter;
+  ::std::ostream& os = *stream;
+  os << "{";
+  const char* sep = "";
+  for (Iter it = pairs.begin(); it != pairs.end(); ++it) {
+    os << sep << "\n  ("
+       << "element #" << it->first << ", "
+       << "matcher #" << it->second << ")";
+    sep = ",";
+  }
+  os << "\n}";
+}
+
+bool MatchMatrix::NextGraph() {
+  for (size_t ilhs = 0; ilhs < LhsSize(); ++ilhs) {
+    for (size_t irhs = 0; irhs < RhsSize(); ++irhs) {
+      char& b = matched_[SpaceIndex(ilhs, irhs)];
+      if (!b) {
+        b = 1;
+        return true;
+      }
+      b = 0;
+    }
+  }
+  return false;
+}
+
+void MatchMatrix::Randomize() {
+  for (size_t ilhs = 0; ilhs < LhsSize(); ++ilhs) {
+    for (size_t irhs = 0; irhs < RhsSize(); ++irhs) {
+      char& b = matched_[SpaceIndex(ilhs, irhs)];
+      b = static_cast<char>(rand() & 1);  // NOLINT
+    }
+  }
+}
+
+std::string MatchMatrix::DebugString() const {
+  ::std::stringstream ss;
+  const char* sep = "";
+  for (size_t i = 0; i < LhsSize(); ++i) {
+    ss << sep;
+    for (size_t j = 0; j < RhsSize(); ++j) {
+      ss << HasEdge(i, j);
+    }
+    sep = ";";
+  }
+  return ss.str();
+}
+
+void UnorderedElementsAreMatcherImplBase::DescribeToImpl(
+    ::std::ostream* os) const {
+  switch (match_flags()) {
+    case UnorderedMatcherRequire::ExactMatch:
+      if (matcher_describers_.empty()) {
+        *os << "is empty";
+        return;
+      }
+      if (matcher_describers_.size() == 1) {
+        *os << "has " << Elements(1) << " and that element ";
+        matcher_describers_[0]->DescribeTo(os);
+        return;
+      }
+      *os << "has " << Elements(matcher_describers_.size())
+          << " and there exists some permutation of elements such that:\n";
+      break;
+    case UnorderedMatcherRequire::Superset:
+      *os << "a surjection from elements to requirements exists such that:\n";
+      break;
+    case UnorderedMatcherRequire::Subset:
+      *os << "an injection from elements to requirements exists such that:\n";
+      break;
+  }
+
+  const char* sep = "";
+  for (size_t i = 0; i != matcher_describers_.size(); ++i) {
+    *os << sep;
+    if (match_flags() == UnorderedMatcherRequire::ExactMatch) {
+      *os << " - element #" << i << " ";
+    } else {
+      *os << " - an element ";
+    }
+    matcher_describers_[i]->DescribeTo(os);
+    if (match_flags() == UnorderedMatcherRequire::ExactMatch) {
+      sep = ", and\n";
+    } else {
+      sep = "\n";
+    }
+  }
+}
+
+void UnorderedElementsAreMatcherImplBase::DescribeNegationToImpl(
+    ::std::ostream* os) const {
+  switch (match_flags()) {
+    case UnorderedMatcherRequire::ExactMatch:
+      if (matcher_describers_.empty()) {
+        *os << "isn't empty";
+        return;
+      }
+      if (matcher_describers_.size() == 1) {
+        *os << "doesn't have " << Elements(1) << ", or has " << Elements(1)
+            << " that ";
+        matcher_describers_[0]->DescribeNegationTo(os);
+        return;
+      }
+      *os << "doesn't have " << Elements(matcher_describers_.size())
+          << ", or there exists no permutation of elements such that:\n";
+      break;
+    case UnorderedMatcherRequire::Superset:
+      *os << "no surjection from elements to requirements exists such that:\n";
+      break;
+    case UnorderedMatcherRequire::Subset:
+      *os << "no injection from elements to requirements exists such that:\n";
+      break;
+  }
+  const char* sep = "";
+  for (size_t i = 0; i != matcher_describers_.size(); ++i) {
+    *os << sep;
+    if (match_flags() == UnorderedMatcherRequire::ExactMatch) {
+      *os << " - element #" << i << " ";
+    } else {
+      *os << " - an element ";
+    }
+    matcher_describers_[i]->DescribeTo(os);
+    if (match_flags() == UnorderedMatcherRequire::ExactMatch) {
+      sep = ", and\n";
+    } else {
+      sep = "\n";
+    }
+  }
+}
+
+// Checks that all matchers match at least one element, and that all
+// elements match at least one matcher. This enables faster matching
+// and better error reporting.
+// Returns false, writing an explanation to 'listener', if and only
+// if the success criteria are not met.
+bool UnorderedElementsAreMatcherImplBase::VerifyMatchMatrix(
+    const ::std::vector<std::string>& element_printouts,
+    const MatchMatrix& matrix, MatchResultListener* listener) const {
+  if (matrix.LhsSize() == 0 && matrix.RhsSize() == 0) {
+    return true;
+  }
+
+  if (match_flags() == UnorderedMatcherRequire::ExactMatch) {
+    if (matrix.LhsSize() != matrix.RhsSize()) {
+      // The element count doesn't match.  If the container is empty,
+      // there's no need to explain anything as Google Mock already
+      // prints the empty container. Otherwise we just need to show
+      // how many elements there actually are.
+      if (matrix.LhsSize() != 0 && listener->IsInterested()) {
+        *listener << "which has " << Elements(matrix.LhsSize());
+      }
+      return false;
+    }
+  }
+
+  bool result = true;
+  ::std::vector<char> element_matched(matrix.LhsSize(), 0);
+  ::std::vector<char> matcher_matched(matrix.RhsSize(), 0);
+
+  for (size_t ilhs = 0; ilhs < matrix.LhsSize(); ilhs++) {
+    for (size_t irhs = 0; irhs < matrix.RhsSize(); irhs++) {
+      char matched = matrix.HasEdge(ilhs, irhs);
+      element_matched[ilhs] |= matched;
+      matcher_matched[irhs] |= matched;
+    }
+  }
+
+  if (match_flags() & UnorderedMatcherRequire::Superset) {
+    const char* sep =
+        "where the following matchers don't match any elements:\n";
+    for (size_t mi = 0; mi < matcher_matched.size(); ++mi) {
+      if (matcher_matched[mi]) continue;
+      result = false;
+      if (listener->IsInterested()) {
+        *listener << sep << "matcher #" << mi << ": ";
+        matcher_describers_[mi]->DescribeTo(listener->stream());
+        sep = ",\n";
+      }
+    }
+  }
+
+  if (match_flags() & UnorderedMatcherRequire::Subset) {
+    const char* sep =
+        "where the following elements don't match any matchers:\n";
+    const char* outer_sep = "";
+    if (!result) {
+      outer_sep = "\nand ";
+    }
+    for (size_t ei = 0; ei < element_matched.size(); ++ei) {
+      if (element_matched[ei]) continue;
+      result = false;
+      if (listener->IsInterested()) {
+        *listener << outer_sep << sep << "element #" << ei << ": "
+                  << element_printouts[ei];
+        sep = ",\n";
+        outer_sep = "";
+      }
+    }
+  }
+  return result;
+}
+
+bool UnorderedElementsAreMatcherImplBase::FindPairing(
+    const MatchMatrix& matrix, MatchResultListener* listener) const {
+  ElementMatcherPairs matches = FindMaxBipartiteMatching(matrix);
+
+  size_t max_flow = matches.size();
+  if ((match_flags() & UnorderedMatcherRequire::Superset) &&
+      max_flow < matrix.RhsSize()) {
+    if (listener->IsInterested()) {
+      *listener << "where no permutation of the elements can satisfy all "
+                   "matchers, and the closest match is "
+                << max_flow << " of " << matrix.RhsSize()
+                << " matchers with the pairings:\n";
+      LogElementMatcherPairVec(matches, listener->stream());
+    }
+    return false;
+  }
+  if ((match_flags() & UnorderedMatcherRequire::Subset) &&
+      max_flow < matrix.LhsSize()) {
+    if (listener->IsInterested()) {
+      *listener
+          << "where not all elements can be matched, and the closest match is "
+          << max_flow << " of " << matrix.RhsSize()
+          << " matchers with the pairings:\n";
+      LogElementMatcherPairVec(matches, listener->stream());
+    }
+    return false;
+  }
+
+  if (matches.size() > 1) {
+    if (listener->IsInterested()) {
+      const char* sep = "where:\n";
+      for (size_t mi = 0; mi < matches.size(); ++mi) {
+        *listener << sep << " - element #" << matches[mi].first
+                  << " is matched by matcher #" << matches[mi].second;
+        sep = ",\n";
+      }
+    }
+  }
+  return true;
+}
+
+}  // namespace internal
+}  // namespace testing
diff --git a/third_party/googletest/googlemock/src/gmock-spec-builders.cc b/third_party/googletest/googlemock/src/gmock-spec-builders.cc
new file mode 100644
index 0000000..de89471
--- /dev/null
+++ b/third_party/googletest/googlemock/src/gmock-spec-builders.cc
@@ -0,0 +1,791 @@
+// Copyright 2007, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Google Mock - a framework for writing C++ mock classes.
+//
+// This file implements the spec builder syntax (ON_CALL and
+// EXPECT_CALL).
+
+#include "gmock/gmock-spec-builders.h"
+
+#include <stdlib.h>
+
+#include <iostream>  // NOLINT
+#include <map>
+#include <memory>
+#include <set>
+#include <sstream>
+#include <string>
+#include <unordered_map>
+#include <vector>
+
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+#include "gtest/internal/gtest-port.h"
+
+#if defined(GTEST_OS_CYGWIN) || defined(GTEST_OS_LINUX) || defined(GTEST_OS_MAC)
+#include <unistd.h>  // NOLINT
+#endif
+#ifdef GTEST_OS_QURT
+#include <qurt_event.h>
+#endif
+
+// Silence C4800 (C4800: 'int *const ': forcing value
+// to bool 'true' or 'false') for MSVC 15
+#if defined(_MSC_VER) && (_MSC_VER == 1900)
+GTEST_DISABLE_MSC_WARNINGS_PUSH_(4800)
+#endif
+
+namespace testing {
+namespace internal {
+
+// Protects the mock object registry (in class Mock), all function
+// mockers, and all expectations.
+GTEST_API_ GTEST_DEFINE_STATIC_MUTEX_(g_gmock_mutex);
+
+// Logs a message including file and line number information.
+GTEST_API_ void LogWithLocation(testing::internal::LogSeverity severity,
+                                const char* file, int line,
+                                const std::string& message) {
+  ::std::ostringstream s;
+  s << internal::FormatFileLocation(file, line) << " " << message
+    << ::std::endl;
+  Log(severity, s.str(), 0);
+}
+
+// Constructs an ExpectationBase object.
+ExpectationBase::ExpectationBase(const char* a_file, int a_line,
+                                 const std::string& a_source_text)
+    : file_(a_file),
+      line_(a_line),
+      source_text_(a_source_text),
+      cardinality_specified_(false),
+      cardinality_(Exactly(1)),
+      call_count_(0),
+      retired_(false),
+      extra_matcher_specified_(false),
+      repeated_action_specified_(false),
+      retires_on_saturation_(false),
+      last_clause_(kNone),
+      action_count_checked_(false) {}
+
+// Destructs an ExpectationBase object.
+ExpectationBase::~ExpectationBase() = default;
+
+// Explicitly specifies the cardinality of this expectation.  Used by
+// the subclasses to implement the .Times() clause.
+void ExpectationBase::SpecifyCardinality(const Cardinality& a_cardinality) {
+  cardinality_specified_ = true;
+  cardinality_ = a_cardinality;
+}
+
+// Retires all pre-requisites of this expectation.
+void ExpectationBase::RetireAllPreRequisites()
+    GTEST_EXCLUSIVE_LOCK_REQUIRED_(g_gmock_mutex) {
+  if (is_retired()) {
+    // We can take this short-cut as we never retire an expectation
+    // until we have retired all its pre-requisites.
+    return;
+  }
+
+  ::std::vector<ExpectationBase*> expectations(1, this);
+  while (!expectations.empty()) {
+    ExpectationBase* exp = expectations.back();
+    expectations.pop_back();
+
+    for (ExpectationSet::const_iterator it =
+             exp->immediate_prerequisites_.begin();
+         it != exp->immediate_prerequisites_.end(); ++it) {
+      ExpectationBase* next = it->expectation_base().get();
+      if (!next->is_retired()) {
+        next->Retire();
+        expectations.push_back(next);
+      }
+    }
+  }
+}
+
+// Returns true if and only if all pre-requisites of this expectation
+// have been satisfied.
+bool ExpectationBase::AllPrerequisitesAreSatisfied() const
+    GTEST_EXCLUSIVE_LOCK_REQUIRED_(g_gmock_mutex) {
+  g_gmock_mutex.AssertHeld();
+  ::std::vector<const ExpectationBase*> expectations(1, this);
+  while (!expectations.empty()) {
+    const ExpectationBase* exp = expectations.back();
+    expectations.pop_back();
+
+    for (ExpectationSet::const_iterator it =
+             exp->immediate_prerequisites_.begin();
+         it != exp->immediate_prerequisites_.end(); ++it) {
+      const ExpectationBase* next = it->expectation_base().get();
+      if (!next->IsSatisfied()) return false;
+      expectations.push_back(next);
+    }
+  }
+  return true;
+}
+
+// Adds unsatisfied pre-requisites of this expectation to 'result'.
+void ExpectationBase::FindUnsatisfiedPrerequisites(ExpectationSet* result) const
+    GTEST_EXCLUSIVE_LOCK_REQUIRED_(g_gmock_mutex) {
+  g_gmock_mutex.AssertHeld();
+  ::std::vector<const ExpectationBase*> expectations(1, this);
+  while (!expectations.empty()) {
+    const ExpectationBase* exp = expectations.back();
+    expectations.pop_back();
+
+    for (ExpectationSet::const_iterator it =
+             exp->immediate_prerequisites_.begin();
+         it != exp->immediate_prerequisites_.end(); ++it) {
+      const ExpectationBase* next = it->expectation_base().get();
+
+      if (next->IsSatisfied()) {
+        // If *it is satisfied and has a call count of 0, some of its
+        // pre-requisites may not be satisfied yet.
+        if (next->call_count_ == 0) {
+          expectations.push_back(next);
+        }
+      } else {
+        // Now that we know next is unsatisfied, we are not so interested
+        // in whether its pre-requisites are satisfied.  Therefore we
+        // don't iterate into it here.
+        *result += *it;
+      }
+    }
+  }
+}
+
+// Describes how many times a function call matching this
+// expectation has occurred.
+void ExpectationBase::DescribeCallCountTo(::std::ostream* os) const
+    GTEST_EXCLUSIVE_LOCK_REQUIRED_(g_gmock_mutex) {
+  g_gmock_mutex.AssertHeld();
+
+  // Describes how many times the function is expected to be called.
+  *os << "         Expected: to be ";
+  cardinality().DescribeTo(os);
+  *os << "\n           Actual: ";
+  Cardinality::DescribeActualCallCountTo(call_count(), os);
+
+  // Describes the state of the expectation (e.g. is it satisfied?
+  // is it active?).
+  *os << " - "
+      << (IsOverSaturated() ? "over-saturated"
+          : IsSaturated()   ? "saturated"
+          : IsSatisfied()   ? "satisfied"
+                            : "unsatisfied")
+      << " and " << (is_retired() ? "retired" : "active");
+}
+
+// Checks the action count (i.e. the number of WillOnce() and
+// WillRepeatedly() clauses) against the cardinality if this hasn't
+// been done before.  Prints a warning if there are too many or too
+// few actions.
+void ExpectationBase::CheckActionCountIfNotDone() const
+    GTEST_LOCK_EXCLUDED_(mutex_) {
+  bool should_check = false;
+  {
+    MutexLock l(&mutex_);
+    if (!action_count_checked_) {
+      action_count_checked_ = true;
+      should_check = true;
+    }
+  }
+
+  if (should_check) {
+    if (!cardinality_specified_) {
+      // The cardinality was inferred - no need to check the action
+      // count against it.
+      return;
+    }
+
+    // The cardinality was explicitly specified.
+    const int action_count = static_cast<int>(untyped_actions_.size());
+    const int upper_bound = cardinality().ConservativeUpperBound();
+    const int lower_bound = cardinality().ConservativeLowerBound();
+    bool too_many;  // True if there are too many actions, or false
+    // if there are too few.
+    if (action_count > upper_bound ||
+        (action_count == upper_bound && repeated_action_specified_)) {
+      too_many = true;
+    } else if (0 < action_count && action_count < lower_bound &&
+               !repeated_action_specified_) {
+      too_many = false;
+    } else {
+      return;
+    }
+
+    ::std::stringstream ss;
+    DescribeLocationTo(&ss);
+    ss << "Too " << (too_many ? "many" : "few") << " actions specified in "
+       << source_text() << "...\n"
+       << "Expected to be ";
+    cardinality().DescribeTo(&ss);
+    ss << ", but has " << (too_many ? "" : "only ") << action_count
+       << " WillOnce()" << (action_count == 1 ? "" : "s");
+    if (repeated_action_specified_) {
+      ss << " and a WillRepeatedly()";
+    }
+    ss << ".";
+    Log(kWarning, ss.str(), -1);  // -1 means "don't print stack trace".
+  }
+}
+
+// Implements the .Times() clause.
+void ExpectationBase::UntypedTimes(const Cardinality& a_cardinality) {
+  if (last_clause_ == kTimes) {
+    ExpectSpecProperty(false,
+                       ".Times() cannot appear "
+                       "more than once in an EXPECT_CALL().");
+  } else {
+    ExpectSpecProperty(
+        last_clause_ < kTimes,
+        ".Times() may only appear *before* .InSequence(), .WillOnce(), "
+        ".WillRepeatedly(), or .RetiresOnSaturation(), not after.");
+  }
+  last_clause_ = kTimes;
+
+  SpecifyCardinality(a_cardinality);
+}
+
+// Points to the implicit sequence introduced by a living InSequence
+// object (if any) in the current thread or NULL.
+GTEST_API_ ThreadLocal<Sequence*> g_gmock_implicit_sequence;
+
+// Reports an uninteresting call (whose description is in msg) in the
+// manner specified by 'reaction'.
+void ReportUninterestingCall(CallReaction reaction, const std::string& msg) {
+  // Include a stack trace only if --gmock_verbose=info is specified.
+  const int stack_frames_to_skip =
+      GMOCK_FLAG_GET(verbose) == kInfoVerbosity ? 3 : -1;
+  switch (reaction) {
+    case kAllow:
+      Log(kInfo, msg, stack_frames_to_skip);
+      break;
+    case kWarn:
+      Log(kWarning,
+          msg +
+              "\nNOTE: You can safely ignore the above warning unless this "
+              "call should not happen.  Do not suppress it by blindly adding "
+              "an EXPECT_CALL() if you don't mean to enforce the call.  "
+              "See "
+              "https://github.com/google/googletest/blob/main/docs/"
+              "gmock_cook_book.md#"
+              "knowing-when-to-expect-useoncall for details.\n",
+          stack_frames_to_skip);
+      break;
+    default:  // FAIL
+      Expect(false, nullptr, -1, msg);
+  }
+}
+
+UntypedFunctionMockerBase::UntypedFunctionMockerBase()
+    : mock_obj_(nullptr), name_("") {}
+
+UntypedFunctionMockerBase::~UntypedFunctionMockerBase() = default;
+
+// Sets the mock object this mock method belongs to, and registers
+// this information in the global mock registry.  Will be called
+// whenever an EXPECT_CALL() or ON_CALL() is executed on this mock
+// method.
+void UntypedFunctionMockerBase::RegisterOwner(const void* mock_obj)
+    GTEST_LOCK_EXCLUDED_(g_gmock_mutex) {
+  {
+    MutexLock l(&g_gmock_mutex);
+    mock_obj_ = mock_obj;
+  }
+  Mock::Register(mock_obj, this);
+}
+
+// Sets the mock object this mock method belongs to, and sets the name
+// of the mock function.  Will be called upon each invocation of this
+// mock function.
+void UntypedFunctionMockerBase::SetOwnerAndName(const void* mock_obj,
+                                                const char* name)
+    GTEST_LOCK_EXCLUDED_(g_gmock_mutex) {
+  // We protect name_ under g_gmock_mutex in case this mock function
+  // is called from two threads concurrently.
+  MutexLock l(&g_gmock_mutex);
+  mock_obj_ = mock_obj;
+  name_ = name;
+}
+
+// Returns the name of the function being mocked.  Must be called
+// after RegisterOwner() or SetOwnerAndName() has been called.
+const void* UntypedFunctionMockerBase::MockObject() const
+    GTEST_LOCK_EXCLUDED_(g_gmock_mutex) {
+  const void* mock_obj;
+  {
+    // We protect mock_obj_ under g_gmock_mutex in case this mock
+    // function is called from two threads concurrently.
+    MutexLock l(&g_gmock_mutex);
+    Assert(mock_obj_ != nullptr, __FILE__, __LINE__,
+           "MockObject() must not be called before RegisterOwner() or "
+           "SetOwnerAndName() has been called.");
+    mock_obj = mock_obj_;
+  }
+  return mock_obj;
+}
+
+// Returns the name of this mock method.  Must be called after
+// SetOwnerAndName() has been called.
+const char* UntypedFunctionMockerBase::Name() const
+    GTEST_LOCK_EXCLUDED_(g_gmock_mutex) {
+  const char* name;
+  {
+    // We protect name_ under g_gmock_mutex in case this mock
+    // function is called from two threads concurrently.
+    MutexLock l(&g_gmock_mutex);
+    Assert(name_ != nullptr, __FILE__, __LINE__,
+           "Name() must not be called before SetOwnerAndName() has "
+           "been called.");
+    name = name_;
+  }
+  return name;
+}
+
+// Returns an Expectation object that references and co-owns exp,
+// which must be an expectation on this mock function.
+Expectation UntypedFunctionMockerBase::GetHandleOf(ExpectationBase* exp) {
+  // See the definition of untyped_expectations_ for why access to it
+  // is unprotected here.
+  for (UntypedExpectations::const_iterator it = untyped_expectations_.begin();
+       it != untyped_expectations_.end(); ++it) {
+    if (it->get() == exp) {
+      return Expectation(*it);
+    }
+  }
+
+  Assert(false, __FILE__, __LINE__, "Cannot find expectation.");
+  return Expectation();
+  // The above statement is just to make the code compile, and will
+  // never be executed.
+}
+
+// Verifies that all expectations on this mock function have been
+// satisfied.  Reports one or more Google Test non-fatal failures
+// and returns false if not.
+bool UntypedFunctionMockerBase::VerifyAndClearExpectationsLocked()
+    GTEST_EXCLUSIVE_LOCK_REQUIRED_(g_gmock_mutex) {
+  g_gmock_mutex.AssertHeld();
+  bool expectations_met = true;
+  for (UntypedExpectations::const_iterator it = untyped_expectations_.begin();
+       it != untyped_expectations_.end(); ++it) {
+    ExpectationBase* const untyped_expectation = it->get();
+    if (untyped_expectation->IsOverSaturated()) {
+      // There was an upper-bound violation.  Since the error was
+      // already reported when it occurred, there is no need to do
+      // anything here.
+      expectations_met = false;
+    } else if (!untyped_expectation->IsSatisfied()) {
+      expectations_met = false;
+      ::std::stringstream ss;
+
+      const ::std::string& expectation_name =
+          untyped_expectation->GetDescription();
+      ss << "Actual function ";
+      if (!expectation_name.empty()) {
+        ss << "\"" << expectation_name << "\" ";
+      }
+      ss << "call count doesn't match " << untyped_expectation->source_text()
+         << "...\n";
+      // No need to show the source file location of the expectation
+      // in the description, as the Expect() call that follows already
+      // takes care of it.
+      untyped_expectation->MaybeDescribeExtraMatcherTo(&ss);
+      untyped_expectation->DescribeCallCountTo(&ss);
+      Expect(false, untyped_expectation->file(), untyped_expectation->line(),
+             ss.str());
+    }
+  }
+
+  // Deleting our expectations may trigger other mock objects to be deleted, for
+  // example if an action contains a reference counted smart pointer to that
+  // mock object, and that is the last reference. So if we delete our
+  // expectations within the context of the global mutex we may deadlock when
+  // this method is called again. Instead, make a copy of the set of
+  // expectations to delete, clear our set within the mutex, and then clear the
+  // copied set outside of it.
+  UntypedExpectations expectations_to_delete;
+  untyped_expectations_.swap(expectations_to_delete);
+
+  g_gmock_mutex.Unlock();
+  expectations_to_delete.clear();
+  g_gmock_mutex.Lock();
+
+  return expectations_met;
+}
+
+static CallReaction intToCallReaction(int mock_behavior) {
+  if (mock_behavior >= kAllow && mock_behavior <= kFail) {
+    return static_cast<internal::CallReaction>(mock_behavior);
+  }
+  return kWarn;
+}
+
+}  // namespace internal
+
+// Class Mock.
+
+namespace {
+
+typedef std::set<internal::UntypedFunctionMockerBase*> FunctionMockers;
+
+// The current state of a mock object.  Such information is needed for
+// detecting leaked mock objects and explicitly verifying a mock's
+// expectations.
+struct MockObjectState {
+  MockObjectState()
+      : first_used_file(nullptr), first_used_line(-1), leakable(false) {}
+
+  // Where in the source file an ON_CALL or EXPECT_CALL is first
+  // invoked on this mock object.
+  const char* first_used_file;
+  int first_used_line;
+  ::std::string first_used_test_suite;
+  ::std::string first_used_test;
+  bool leakable;  // true if and only if it's OK to leak the object.
+  FunctionMockers function_mockers;  // All registered methods of the object.
+};
+
+// A global registry holding the state of all mock objects that are
+// alive.  A mock object is added to this registry the first time
+// Mock::AllowLeak(), ON_CALL(), or EXPECT_CALL() is called on it.  It
+// is removed from the registry in the mock object's destructor.
+class MockObjectRegistry {
+ public:
+  // Maps a mock object (identified by its address) to its state.
+  typedef std::map<const void*, MockObjectState> StateMap;
+
+  // This destructor will be called when a program exits, after all
+  // tests in it have been run.  By then, there should be no mock
+  // object alive.  Therefore we report any living object as test
+  // failure, unless the user explicitly asked us to ignore it.
+  ~MockObjectRegistry() {
+    if (!GMOCK_FLAG_GET(catch_leaked_mocks)) return;
+
+    int leaked_count = 0;
+    for (StateMap::const_iterator it = states_.begin(); it != states_.end();
+         ++it) {
+      if (it->second.leakable)  // The user said it's fine to leak this object.
+        continue;
+
+      // FIXME: Print the type of the leaked object.
+      // This can help the user identify the leaked object.
+      std::cout << "\n";
+      const MockObjectState& state = it->second;
+      std::cout << internal::FormatFileLocation(state.first_used_file,
+                                                state.first_used_line);
+      std::cout << " ERROR: this mock object";
+      if (!state.first_used_test.empty()) {
+        std::cout << " (used in test " << state.first_used_test_suite << "."
+                  << state.first_used_test << ")";
+      }
+      std::cout << " should be deleted but never is. Its address is @"
+                << it->first << ".";
+      leaked_count++;
+    }
+    if (leaked_count > 0) {
+      std::cout << "\nERROR: " << leaked_count << " leaked mock "
+                << (leaked_count == 1 ? "object" : "objects")
+                << " found at program exit. Expectations on a mock object are "
+                   "verified when the object is destructed. Leaking a mock "
+                   "means that its expectations aren't verified, which is "
+                   "usually a test bug. If you really intend to leak a mock, "
+                   "you can suppress this error using "
+                   "testing::Mock::AllowLeak(mock_object), or you may use a "
+                   "fake or stub instead of a mock.\n";
+      std::cout.flush();
+      ::std::cerr.flush();
+      // RUN_ALL_TESTS() has already returned when this destructor is
+      // called.  Therefore we cannot use the normal Google Test
+      // failure reporting mechanism.
+#ifdef GTEST_OS_QURT
+      qurt_exception_raise_fatal();
+#else
+      _exit(1);  // We cannot call exit() as it is not reentrant and
+                 // may already have been called.
+#endif
+    }
+  }
+
+  StateMap& states() { return states_; }
+
+ private:
+  StateMap states_;
+};
+
+// Protected by g_gmock_mutex.
+MockObjectRegistry g_mock_object_registry;
+
+// Maps a mock object to the reaction Google Mock should have when an
+// uninteresting method is called.  Protected by g_gmock_mutex.
+std::unordered_map<uintptr_t, internal::CallReaction>&
+UninterestingCallReactionMap() {
+  static auto* map = new std::unordered_map<uintptr_t, internal::CallReaction>;
+  return *map;
+}
+
+// Sets the reaction Google Mock should have when an uninteresting
+// method of the given mock object is called.
+void SetReactionOnUninterestingCalls(uintptr_t mock_obj,
+                                     internal::CallReaction reaction)
+    GTEST_LOCK_EXCLUDED_(internal::g_gmock_mutex) {
+  internal::MutexLock l(&internal::g_gmock_mutex);
+  UninterestingCallReactionMap()[mock_obj] = reaction;
+}
+
+}  // namespace
+
+// Tells Google Mock to allow uninteresting calls on the given mock
+// object.
+void Mock::AllowUninterestingCalls(uintptr_t mock_obj)
+    GTEST_LOCK_EXCLUDED_(internal::g_gmock_mutex) {
+  SetReactionOnUninterestingCalls(mock_obj, internal::kAllow);
+}
+
+// Tells Google Mock to warn the user about uninteresting calls on the
+// given mock object.
+void Mock::WarnUninterestingCalls(uintptr_t mock_obj)
+    GTEST_LOCK_EXCLUDED_(internal::g_gmock_mutex) {
+  SetReactionOnUninterestingCalls(mock_obj, internal::kWarn);
+}
+
+// Tells Google Mock to fail uninteresting calls on the given mock
+// object.
+void Mock::FailUninterestingCalls(uintptr_t mock_obj)
+    GTEST_LOCK_EXCLUDED_(internal::g_gmock_mutex) {
+  SetReactionOnUninterestingCalls(mock_obj, internal::kFail);
+}
+
+// Tells Google Mock the given mock object is being destroyed and its
+// entry in the call-reaction table should be removed.
+void Mock::UnregisterCallReaction(uintptr_t mock_obj)
+    GTEST_LOCK_EXCLUDED_(internal::g_gmock_mutex) {
+  internal::MutexLock l(&internal::g_gmock_mutex);
+  UninterestingCallReactionMap().erase(static_cast<uintptr_t>(mock_obj));
+}
+
+// Returns the reaction Google Mock will have on uninteresting calls
+// made on the given mock object.
+internal::CallReaction Mock::GetReactionOnUninterestingCalls(
+    const void* mock_obj) GTEST_LOCK_EXCLUDED_(internal::g_gmock_mutex) {
+  internal::MutexLock l(&internal::g_gmock_mutex);
+  return (UninterestingCallReactionMap().count(
+              reinterpret_cast<uintptr_t>(mock_obj)) == 0)
+             ? internal::intToCallReaction(
+                   GMOCK_FLAG_GET(default_mock_behavior))
+             : UninterestingCallReactionMap()[reinterpret_cast<uintptr_t>(
+                   mock_obj)];
+}
+
+// Tells Google Mock to ignore mock_obj when checking for leaked mock
+// objects.
+void Mock::AllowLeak(const void* mock_obj)
+    GTEST_LOCK_EXCLUDED_(internal::g_gmock_mutex) {
+  internal::MutexLock l(&internal::g_gmock_mutex);
+  g_mock_object_registry.states()[mock_obj].leakable = true;
+}
+
+// Verifies and clears all expectations on the given mock object.  If
+// the expectations aren't satisfied, generates one or more Google
+// Test non-fatal failures and returns false.
+bool Mock::VerifyAndClearExpectations(void* mock_obj)
+    GTEST_LOCK_EXCLUDED_(internal::g_gmock_mutex) {
+  internal::MutexLock l(&internal::g_gmock_mutex);
+  return VerifyAndClearExpectationsLocked(mock_obj);
+}
+
+// Verifies all expectations on the given mock object and clears its
+// default actions and expectations.  Returns true if and only if the
+// verification was successful.
+bool Mock::VerifyAndClear(void* mock_obj)
+    GTEST_LOCK_EXCLUDED_(internal::g_gmock_mutex) {
+  internal::MutexLock l(&internal::g_gmock_mutex);
+  ClearDefaultActionsLocked(mock_obj);
+  return VerifyAndClearExpectationsLocked(mock_obj);
+}
+
+// Verifies and clears all expectations on the given mock object.  If
+// the expectations aren't satisfied, generates one or more Google
+// Test non-fatal failures and returns false.
+bool Mock::VerifyAndClearExpectationsLocked(void* mock_obj)
+    GTEST_EXCLUSIVE_LOCK_REQUIRED_(internal::g_gmock_mutex) {
+  internal::g_gmock_mutex.AssertHeld();
+  if (g_mock_object_registry.states().count(mock_obj) == 0) {
+    // No EXPECT_CALL() was set on the given mock object.
+    return true;
+  }
+
+  // Verifies and clears the expectations on each mock method in the
+  // given mock object.
+  bool expectations_met = true;
+  FunctionMockers& mockers =
+      g_mock_object_registry.states()[mock_obj].function_mockers;
+  for (FunctionMockers::const_iterator it = mockers.begin();
+       it != mockers.end(); ++it) {
+    if (!(*it)->VerifyAndClearExpectationsLocked()) {
+      expectations_met = false;
+    }
+  }
+
+  // We don't clear the content of mockers, as they may still be
+  // needed by ClearDefaultActionsLocked().
+  return expectations_met;
+}
+
+bool Mock::IsNaggy(void* mock_obj)
+    GTEST_LOCK_EXCLUDED_(internal::g_gmock_mutex) {
+  return Mock::GetReactionOnUninterestingCalls(mock_obj) == internal::kWarn;
+}
+bool Mock::IsNice(void* mock_obj)
+    GTEST_LOCK_EXCLUDED_(internal::g_gmock_mutex) {
+  return Mock::GetReactionOnUninterestingCalls(mock_obj) == internal::kAllow;
+}
+bool Mock::IsStrict(void* mock_obj)
+    GTEST_LOCK_EXCLUDED_(internal::g_gmock_mutex) {
+  return Mock::GetReactionOnUninterestingCalls(mock_obj) == internal::kFail;
+}
+
+// Registers a mock object and a mock method it owns.
+void Mock::Register(const void* mock_obj,
+                    internal::UntypedFunctionMockerBase* mocker)
+    GTEST_LOCK_EXCLUDED_(internal::g_gmock_mutex) {
+  internal::MutexLock l(&internal::g_gmock_mutex);
+  g_mock_object_registry.states()[mock_obj].function_mockers.insert(mocker);
+}
+
+// Tells Google Mock where in the source code mock_obj is used in an
+// ON_CALL or EXPECT_CALL.  In case mock_obj is leaked, this
+// information helps the user identify which object it is.
+void Mock::RegisterUseByOnCallOrExpectCall(const void* mock_obj,
+                                           const char* file, int line)
+    GTEST_LOCK_EXCLUDED_(internal::g_gmock_mutex) {
+  internal::MutexLock l(&internal::g_gmock_mutex);
+  MockObjectState& state = g_mock_object_registry.states()[mock_obj];
+  if (state.first_used_file == nullptr) {
+    state.first_used_file = file;
+    state.first_used_line = line;
+    const TestInfo* const test_info =
+        UnitTest::GetInstance()->current_test_info();
+    if (test_info != nullptr) {
+      state.first_used_test_suite = test_info->test_suite_name();
+      state.first_used_test = test_info->name();
+    }
+  }
+}
+
+// Unregisters a mock method; removes the owning mock object from the
+// registry when the last mock method associated with it has been
+// unregistered.  This is called only in the destructor of
+// FunctionMockerBase.
+void Mock::UnregisterLocked(internal::UntypedFunctionMockerBase* mocker)
+    GTEST_EXCLUSIVE_LOCK_REQUIRED_(internal::g_gmock_mutex) {
+  internal::g_gmock_mutex.AssertHeld();
+  for (MockObjectRegistry::StateMap::iterator it =
+           g_mock_object_registry.states().begin();
+       it != g_mock_object_registry.states().end(); ++it) {
+    FunctionMockers& mockers = it->second.function_mockers;
+    if (mockers.erase(mocker) > 0) {
+      // mocker was in mockers and has been just removed.
+      if (mockers.empty()) {
+        g_mock_object_registry.states().erase(it);
+      }
+      return;
+    }
+  }
+}
+
+// Clears all ON_CALL()s set on the given mock object.
+void Mock::ClearDefaultActionsLocked(void* mock_obj)
+    GTEST_EXCLUSIVE_LOCK_REQUIRED_(internal::g_gmock_mutex) {
+  internal::g_gmock_mutex.AssertHeld();
+
+  if (g_mock_object_registry.states().count(mock_obj) == 0) {
+    // No ON_CALL() was set on the given mock object.
+    return;
+  }
+
+  // Clears the default actions for each mock method in the given mock
+  // object.
+  FunctionMockers& mockers =
+      g_mock_object_registry.states()[mock_obj].function_mockers;
+  for (FunctionMockers::const_iterator it = mockers.begin();
+       it != mockers.end(); ++it) {
+    (*it)->ClearDefaultActionsLocked();
+  }
+
+  // We don't clear the content of mockers, as they may still be
+  // needed by VerifyAndClearExpectationsLocked().
+}
+
+Expectation::Expectation() = default;
+
+Expectation::Expectation(
+    const std::shared_ptr<internal::ExpectationBase>& an_expectation_base)
+    : expectation_base_(an_expectation_base) {}
+
+Expectation::~Expectation() = default;
+
+// Adds an expectation to a sequence.
+void Sequence::AddExpectation(const Expectation& expectation) const {
+  if (*last_expectation_ != expectation) {
+    if (last_expectation_->expectation_base() != nullptr) {
+      expectation.expectation_base()->immediate_prerequisites_ +=
+          *last_expectation_;
+    }
+    *last_expectation_ = expectation;
+  }
+}
+
+// Creates the implicit sequence if there isn't one.
+InSequence::InSequence() {
+  if (internal::g_gmock_implicit_sequence.get() == nullptr) {
+    internal::g_gmock_implicit_sequence.set(new Sequence);
+    sequence_created_ = true;
+  } else {
+    sequence_created_ = false;
+  }
+}
+
+// Deletes the implicit sequence if it was created by the constructor
+// of this object.
+InSequence::~InSequence() {
+  if (sequence_created_) {
+    delete internal::g_gmock_implicit_sequence.get();
+    internal::g_gmock_implicit_sequence.set(nullptr);
+  }
+}
+
+}  // namespace testing
+
+#if defined(_MSC_VER) && (_MSC_VER == 1900)
+GTEST_DISABLE_MSC_WARNINGS_POP_()  // 4800
+#endif
diff --git a/third_party/googletest/googlemock/src/gmock.cc b/third_party/googletest/googlemock/src/gmock.cc
new file mode 100644
index 0000000..b5e714d
--- /dev/null
+++ b/third_party/googletest/googlemock/src/gmock.cc
@@ -0,0 +1,225 @@
+// Copyright 2008, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include "gmock/gmock.h"
+
+#include <string>
+
+#include "gmock/internal/gmock-port.h"
+
+GMOCK_DEFINE_bool_(catch_leaked_mocks, true,
+                   "true if and only if Google Mock should report leaked "
+                   "mock objects as failures.");
+
+GMOCK_DEFINE_string_(verbose, testing::internal::kWarningVerbosity,
+                     "Controls how verbose Google Mock's output is."
+                     "  Valid values:\n"
+                     "  info    - prints all messages.\n"
+                     "  warning - prints warnings and errors.\n"
+                     "  error   - prints errors only.");
+
+GMOCK_DEFINE_int32_(default_mock_behavior, 1,
+                    "Controls the default behavior of mocks."
+                    "  Valid values:\n"
+                    "  0 - by default, mocks act as NiceMocks.\n"
+                    "  1 - by default, mocks act as NaggyMocks.\n"
+                    "  2 - by default, mocks act as StrictMocks.");
+
+namespace testing {
+namespace internal {
+
+// Parses a string as a command line flag.  The string should have the
+// format "--gmock_flag=value".  When def_optional is true, the
+// "=value" part can be omitted.
+//
+// Returns the value of the flag, or NULL if the parsing failed.
+static const char* ParseGoogleMockFlagValue(const char* str,
+                                            const char* flag_name,
+                                            bool def_optional) {
+  // str and flag must not be NULL.
+  if (str == nullptr || flag_name == nullptr) return nullptr;
+
+  // The flag must start with "--gmock_".
+  const std::string flag_name_str = std::string("--gmock_") + flag_name;
+  const size_t flag_name_len = flag_name_str.length();
+  if (strncmp(str, flag_name_str.c_str(), flag_name_len) != 0) return nullptr;
+
+  // Skips the flag name.
+  const char* flag_end = str + flag_name_len;
+
+  // When def_optional is true, it's OK to not have a "=value" part.
+  if (def_optional && (flag_end[0] == '\0')) {
+    return flag_end;
+  }
+
+  // If def_optional is true and there are more characters after the
+  // flag name, or if def_optional is false, there must be a '=' after
+  // the flag name.
+  if (flag_end[0] != '=') return nullptr;
+
+  // Returns the string after "=".
+  return flag_end + 1;
+}
+
+// Parses a string for a Google Mock bool flag, in the form of
+// "--gmock_flag=value".
+//
+// On success, stores the value of the flag in *value, and returns
+// true.  On failure, returns false without changing *value.
+static bool ParseGoogleMockFlag(const char* str, const char* flag_name,
+                                bool* value) {
+  // Gets the value of the flag as a string.
+  const char* const value_str = ParseGoogleMockFlagValue(str, flag_name, true);
+
+  // Aborts if the parsing failed.
+  if (value_str == nullptr) return false;
+
+  // Converts the string value to a bool.
+  *value = !(*value_str == '0' || *value_str == 'f' || *value_str == 'F');
+  return true;
+}
+
+// Parses a string for a Google Mock string flag, in the form of
+// "--gmock_flag=value".
+//
+// On success, stores the value of the flag in *value, and returns
+// true.  On failure, returns false without changing *value.
+template <typename String>
+static bool ParseGoogleMockFlag(const char* str, const char* flag_name,
+                                String* value) {
+  // Gets the value of the flag as a string.
+  const char* const value_str = ParseGoogleMockFlagValue(str, flag_name, false);
+
+  // Aborts if the parsing failed.
+  if (value_str == nullptr) return false;
+
+  // Sets *value to the value of the flag.
+  *value = value_str;
+  return true;
+}
+
+static bool ParseGoogleMockFlag(const char* str, const char* flag_name,
+                                int32_t* value) {
+  // Gets the value of the flag as a string.
+  const char* const value_str = ParseGoogleMockFlagValue(str, flag_name, true);
+
+  // Aborts if the parsing failed.
+  if (value_str == nullptr) return false;
+
+  // Sets *value to the value of the flag.
+  return ParseInt32(Message() << "The value of flag --" << flag_name, value_str,
+                    value);
+}
+
+// The internal implementation of InitGoogleMock().
+//
+// The type parameter CharType can be instantiated to either char or
+// wchar_t.
+template <typename CharType>
+void InitGoogleMockImpl(int* argc, CharType** argv) {
+  // Makes sure Google Test is initialized.  InitGoogleTest() is
+  // idempotent, so it's fine if the user has already called it.
+  InitGoogleTest(argc, argv);
+  if (*argc <= 0) return;
+
+  for (int i = 1; i != *argc; i++) {
+    const std::string arg_string = StreamableToString(argv[i]);
+    const char* const arg = arg_string.c_str();
+
+    // Do we see a Google Mock flag?
+    bool found_gmock_flag = false;
+
+#define GMOCK_INTERNAL_PARSE_FLAG(flag_name)            \
+  if (!found_gmock_flag) {                              \
+    auto value = GMOCK_FLAG_GET(flag_name);             \
+    if (ParseGoogleMockFlag(arg, #flag_name, &value)) { \
+      GMOCK_FLAG_SET(flag_name, value);                 \
+      found_gmock_flag = true;                          \
+    }                                                   \
+  }
+
+    GMOCK_INTERNAL_PARSE_FLAG(catch_leaked_mocks)
+    GMOCK_INTERNAL_PARSE_FLAG(verbose)
+    GMOCK_INTERNAL_PARSE_FLAG(default_mock_behavior)
+
+    if (found_gmock_flag) {
+      // Yes.  Shift the remainder of the argv list left by one.  Note
+      // that argv has (*argc + 1) elements, the last one always being
+      // NULL.  The following loop moves the trailing NULL element as
+      // well.
+      for (int j = i; j != *argc; j++) {
+        argv[j] = argv[j + 1];
+      }
+
+      // Decrements the argument count.
+      (*argc)--;
+
+      // We also need to decrement the iterator as we just removed
+      // an element.
+      i--;
+    }
+  }
+}
+
+}  // namespace internal
+
+// Initializes Google Mock.  This must be called before running the
+// tests.  In particular, it parses a command line for the flags that
+// Google Mock recognizes.  Whenever a Google Mock flag is seen, it is
+// removed from argv, and *argc is decremented.
+//
+// No value is returned.  Instead, the Google Mock flag variables are
+// updated.
+//
+// Since Google Test is needed for Google Mock to work, this function
+// also initializes Google Test and parses its flags, if that hasn't
+// been done.
+GTEST_API_ void InitGoogleMock(int* argc, char** argv) {
+  internal::InitGoogleMockImpl(argc, argv);
+}
+
+// This overloaded version can be used in Windows programs compiled in
+// UNICODE mode.
+GTEST_API_ void InitGoogleMock(int* argc, wchar_t** argv) {
+  internal::InitGoogleMockImpl(argc, argv);
+}
+
+// This overloaded version can be used on Arduino/embedded platforms where
+// there is no argc/argv.
+GTEST_API_ void InitGoogleMock() {
+  // Since Arduino doesn't have a command line, fake out the argc/argv arguments
+  int argc = 1;
+  const auto arg0 = "dummy";
+  char* argv0 = const_cast<char*>(arg0);
+  char** argv = &argv0;
+
+  internal::InitGoogleMockImpl(&argc, argv);
+}
+
+}  // namespace testing
diff --git a/third_party/googletest/googlemock/src/gmock_main.cc b/third_party/googletest/googlemock/src/gmock_main.cc
new file mode 100644
index 0000000..6b55412
--- /dev/null
+++ b/third_party/googletest/googlemock/src/gmock_main.cc
@@ -0,0 +1,73 @@
+// Copyright 2008, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <iostream>
+
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+
+#if defined(GTEST_OS_ESP8266) || defined(GTEST_OS_ESP32) || \
+    (defined(GTEST_OS_NRF52) && defined(ARDUINO))
+#ifdef GTEST_OS_ESP8266
+extern "C" {
+#endif
+void setup() {
+  // Since Google Mock depends on Google Test, InitGoogleMock() is
+  // also responsible for initializing Google Test.  Therefore there's
+  // no need for calling testing::InitGoogleTest() separately.
+  testing::InitGoogleMock();
+}
+void loop() { RUN_ALL_TESTS(); }
+#ifdef GTEST_OS_ESP8266
+}
+#endif
+
+#else
+
+// MS C++ compiler/linker has a bug on Windows (not on Windows CE), which
+// causes a link error when _tmain is defined in a static library and UNICODE
+// is enabled. For this reason instead of _tmain, main function is used on
+// Windows. See the following link to track the current status of this bug:
+// https://web.archive.org/web/20170912203238/connect.microsoft.com/VisualStudio/feedback/details/394464/wmain-link-error-in-the-static-library
+// // NOLINT
+#ifdef GTEST_OS_WINDOWS_MOBILE
+#include <tchar.h>  // NOLINT
+
+GTEST_API_ int _tmain(int argc, TCHAR** argv) {
+#else
+GTEST_API_ int main(int argc, char** argv) {
+#endif  // GTEST_OS_WINDOWS_MOBILE
+  std::cout << "Running main() from gmock_main.cc\n";
+  // Since Google Mock depends on Google Test, InitGoogleMock() is
+  // also responsible for initializing Google Test.  Therefore there's
+  // no need for calling testing::InitGoogleTest() separately.
+  testing::InitGoogleMock(&argc, argv);
+  return RUN_ALL_TESTS();
+}
+#endif
diff --git a/third_party/googletest/googlemock/test/BUILD.bazel b/third_party/googletest/googlemock/test/BUILD.bazel
new file mode 100644
index 0000000..d4297c8
--- /dev/null
+++ b/third_party/googletest/googlemock/test/BUILD.bazel
@@ -0,0 +1,118 @@
+# Copyright 2017 Google Inc.
+# All Rights Reserved.
+#
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#
+#   Bazel Build for Google C++ Testing Framework(Google Test)-googlemock
+
+load("@rules_python//python:defs.bzl", "py_library", "py_test")
+
+licenses(["notice"])
+
+# Tests for GMock itself
+cc_test(
+    name = "gmock_all_test",
+    size = "small",
+    srcs = glob(include = ["gmock-*.cc"]) + ["gmock-matchers_test.h"],
+    linkopts = select({
+        "//:qnx": [],
+        "//:windows": [],
+        "//conditions:default": ["-pthread"],
+    }),
+    deps = ["//:gtest"],
+)
+
+# Python tests
+py_library(
+    name = "gmock_test_utils",
+    testonly = 1,
+    srcs = ["gmock_test_utils.py"],
+    deps = [
+        "//googletest/test:gtest_test_utils",
+    ],
+)
+
+cc_binary(
+    name = "gmock_leak_test_",
+    testonly = 1,
+    srcs = ["gmock_leak_test_.cc"],
+    deps = ["//:gtest_main"],
+)
+
+py_test(
+    name = "gmock_leak_test",
+    size = "medium",
+    srcs = ["gmock_leak_test.py"],
+    data = [
+        ":gmock_leak_test_",
+        ":gmock_test_utils",
+    ],
+    tags = [
+        "no_test_msvc2015",
+        "no_test_msvc2017",
+    ],
+)
+
+cc_test(
+    name = "gmock_link_test",
+    size = "small",
+    srcs = [
+        "gmock_link2_test.cc",
+        "gmock_link_test.cc",
+        "gmock_link_test.h",
+    ],
+    deps = ["//:gtest_main"],
+)
+
+cc_binary(
+    name = "gmock_output_test_",
+    srcs = ["gmock_output_test_.cc"],
+    deps = ["//:gtest"],
+)
+
+py_test(
+    name = "gmock_output_test",
+    size = "medium",
+    srcs = ["gmock_output_test.py"],
+    data = [
+        ":gmock_output_test_",
+        ":gmock_output_test_golden.txt",
+    ],
+    tags = [
+        "no_test_msvc2015",
+        "no_test_msvc2017",
+    ],
+    deps = [":gmock_test_utils"],
+)
+
+cc_test(
+    name = "gmock_test",
+    size = "small",
+    srcs = ["gmock_test.cc"],
+    deps = ["//:gtest_main"],
+)
diff --git a/third_party/googletest/googlemock/test/gmock-actions_test.cc b/third_party/googletest/googlemock/test/gmock-actions_test.cc
new file mode 100644
index 0000000..da1675c
--- /dev/null
+++ b/third_party/googletest/googlemock/test/gmock-actions_test.cc
@@ -0,0 +1,2169 @@
+// Copyright 2007, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Google Mock - a framework for writing C++ mock classes.
+//
+// This file tests the built-in actions.
+
+#include "gmock/gmock-actions.h"
+
+#include <algorithm>
+#include <functional>
+#include <iterator>
+#include <memory>
+#include <sstream>
+#include <string>
+#include <tuple>
+#include <type_traits>
+#include <utility>
+#include <vector>
+
+#include "gmock/gmock.h"
+#include "gmock/internal/gmock-port.h"
+#include "gtest/gtest-spi.h"
+#include "gtest/gtest.h"
+#include "gtest/internal/gtest-port.h"
+
+// Silence C4100 (unreferenced formal parameter) and C4503 (decorated name
+// length exceeded) for MSVC.
+GTEST_DISABLE_MSC_WARNINGS_PUSH_(4100 4503)
+#if defined(_MSC_VER) && (_MSC_VER == 1900)
+// and silence C4800 (C4800: 'int *const ': forcing value
+// to bool 'true' or 'false') for MSVC 15
+GTEST_DISABLE_MSC_WARNINGS_PUSH_(4800)
+#endif
+
+namespace testing {
+namespace {
+
+using ::testing::internal::BuiltInDefaultValue;
+
+TEST(TypeTraits, Negation) {
+  // Direct use with std types.
+  static_assert(std::is_base_of<std::false_type,
+                                internal::negation<std::true_type>>::value,
+                "");
+
+  static_assert(std::is_base_of<std::true_type,
+                                internal::negation<std::false_type>>::value,
+                "");
+
+  // With other types that fit the requirement of a value member that is
+  // convertible to bool.
+  static_assert(std::is_base_of<
+                    std::true_type,
+                    internal::negation<std::integral_constant<int, 0>>>::value,
+                "");
+
+  static_assert(std::is_base_of<
+                    std::false_type,
+                    internal::negation<std::integral_constant<int, 1>>>::value,
+                "");
+
+  static_assert(std::is_base_of<
+                    std::false_type,
+                    internal::negation<std::integral_constant<int, -1>>>::value,
+                "");
+}
+
+// Weird false/true types that aren't actually bool constants (but should still
+// be legal according to [meta.logical] because `bool(T::value)` is valid), are
+// distinct from std::false_type and std::true_type, and are distinct from other
+// instantiations of the same template.
+//
+// These let us check finicky details mandated by the standard like
+// "std::conjunction should evaluate to a type that inherits from the first
+// false-y input".
+template <int>
+struct MyFalse : std::integral_constant<int, 0> {};
+
+template <int>
+struct MyTrue : std::integral_constant<int, -1> {};
+
+TEST(TypeTraits, Conjunction) {
+  // Base case: always true.
+  static_assert(std::is_base_of<std::true_type, internal::conjunction<>>::value,
+                "");
+
+  // One predicate: inherits from that predicate, regardless of value.
+  static_assert(
+      std::is_base_of<MyFalse<0>, internal::conjunction<MyFalse<0>>>::value,
+      "");
+
+  static_assert(
+      std::is_base_of<MyTrue<0>, internal::conjunction<MyTrue<0>>>::value, "");
+
+  // Multiple predicates, with at least one false: inherits from that one.
+  static_assert(
+      std::is_base_of<MyFalse<1>, internal::conjunction<MyTrue<0>, MyFalse<1>,
+                                                        MyTrue<2>>>::value,
+      "");
+
+  static_assert(
+      std::is_base_of<MyFalse<1>, internal::conjunction<MyTrue<0>, MyFalse<1>,
+                                                        MyFalse<2>>>::value,
+      "");
+
+  // Short circuiting: in the case above, additional predicates need not even
+  // define a value member.
+  struct Empty {};
+  static_assert(
+      std::is_base_of<MyFalse<1>, internal::conjunction<MyTrue<0>, MyFalse<1>,
+                                                        Empty>>::value,
+      "");
+
+  // All predicates true: inherits from the last.
+  static_assert(
+      std::is_base_of<MyTrue<2>, internal::conjunction<MyTrue<0>, MyTrue<1>,
+                                                       MyTrue<2>>>::value,
+      "");
+}
+
+TEST(TypeTraits, Disjunction) {
+  // Base case: always false.
+  static_assert(
+      std::is_base_of<std::false_type, internal::disjunction<>>::value, "");
+
+  // One predicate: inherits from that predicate, regardless of value.
+  static_assert(
+      std::is_base_of<MyFalse<0>, internal::disjunction<MyFalse<0>>>::value,
+      "");
+
+  static_assert(
+      std::is_base_of<MyTrue<0>, internal::disjunction<MyTrue<0>>>::value, "");
+
+  // Multiple predicates, with at least one true: inherits from that one.
+  static_assert(
+      std::is_base_of<MyTrue<1>, internal::disjunction<MyFalse<0>, MyTrue<1>,
+                                                       MyFalse<2>>>::value,
+      "");
+
+  static_assert(
+      std::is_base_of<MyTrue<1>, internal::disjunction<MyFalse<0>, MyTrue<1>,
+                                                       MyTrue<2>>>::value,
+      "");
+
+  // Short circuiting: in the case above, additional predicates need not even
+  // define a value member.
+  struct Empty {};
+  static_assert(
+      std::is_base_of<MyTrue<1>, internal::disjunction<MyFalse<0>, MyTrue<1>,
+                                                       Empty>>::value,
+      "");
+
+  // All predicates false: inherits from the last.
+  static_assert(
+      std::is_base_of<MyFalse<2>, internal::disjunction<MyFalse<0>, MyFalse<1>,
+                                                        MyFalse<2>>>::value,
+      "");
+}
+
+TEST(TypeTraits, IsInvocableRV) {
+  struct C {
+    int operator()() const { return 0; }
+    void operator()(int) & {}
+    std::string operator()(int) && { return ""; };
+  };
+
+  // The first overload is callable for const and non-const rvalues and lvalues.
+  // It can be used to obtain an int, cv void, or anything int is convertible
+  // to.
+  static_assert(internal::is_callable_r<int, C>::value, "");
+  static_assert(internal::is_callable_r<int, C&>::value, "");
+  static_assert(internal::is_callable_r<int, const C>::value, "");
+  static_assert(internal::is_callable_r<int, const C&>::value, "");
+
+  static_assert(internal::is_callable_r<void, C>::value, "");
+  static_assert(internal::is_callable_r<const volatile void, C>::value, "");
+  static_assert(internal::is_callable_r<char, C>::value, "");
+
+  // It's possible to provide an int. If it's given to an lvalue, the result is
+  // void. Otherwise it is std::string (which is also treated as allowed for a
+  // void result type).
+  static_assert(internal::is_callable_r<void, C&, int>::value, "");
+  static_assert(!internal::is_callable_r<int, C&, int>::value, "");
+  static_assert(!internal::is_callable_r<std::string, C&, int>::value, "");
+  static_assert(!internal::is_callable_r<void, const C&, int>::value, "");
+
+  static_assert(internal::is_callable_r<std::string, C, int>::value, "");
+  static_assert(internal::is_callable_r<void, C, int>::value, "");
+  static_assert(!internal::is_callable_r<int, C, int>::value, "");
+
+  // It's not possible to provide other arguments.
+  static_assert(!internal::is_callable_r<void, C, std::string>::value, "");
+  static_assert(!internal::is_callable_r<void, C, int, int>::value, "");
+
+  // In C++17 and above, where it's guaranteed that functions can return
+  // non-moveable objects, everything should work fine for non-moveable rsult
+  // types too.
+#if defined(GTEST_INTERNAL_CPLUSPLUS_LANG) && \
+    GTEST_INTERNAL_CPLUSPLUS_LANG >= 201703L
+  {
+    struct NonMoveable {
+      NonMoveable() = default;
+      NonMoveable(NonMoveable&&) = delete;
+    };
+
+    static_assert(!std::is_move_constructible_v<NonMoveable>);
+
+    struct Callable {
+      NonMoveable operator()() { return NonMoveable(); }
+    };
+
+    static_assert(internal::is_callable_r<NonMoveable, Callable>::value);
+    static_assert(internal::is_callable_r<void, Callable>::value);
+    static_assert(
+        internal::is_callable_r<const volatile void, Callable>::value);
+
+    static_assert(!internal::is_callable_r<int, Callable>::value);
+    static_assert(!internal::is_callable_r<NonMoveable, Callable, int>::value);
+  }
+#endif  // C++17 and above
+
+  // Nothing should choke when we try to call other arguments besides directly
+  // callable objects, but they should not show up as callable.
+  static_assert(!internal::is_callable_r<void, int>::value, "");
+  static_assert(!internal::is_callable_r<void, void (C::*)()>::value, "");
+  static_assert(!internal::is_callable_r<void, void (C::*)(), C*>::value, "");
+}
+
+// Tests that BuiltInDefaultValue<T*>::Get() returns NULL.
+TEST(BuiltInDefaultValueTest, IsNullForPointerTypes) {
+  EXPECT_TRUE(BuiltInDefaultValue<int*>::Get() == nullptr);
+  EXPECT_TRUE(BuiltInDefaultValue<const char*>::Get() == nullptr);
+  EXPECT_TRUE(BuiltInDefaultValue<void*>::Get() == nullptr);
+}
+
+// Tests that BuiltInDefaultValue<T*>::Exists() return true.
+TEST(BuiltInDefaultValueTest, ExistsForPointerTypes) {
+  EXPECT_TRUE(BuiltInDefaultValue<int*>::Exists());
+  EXPECT_TRUE(BuiltInDefaultValue<const char*>::Exists());
+  EXPECT_TRUE(BuiltInDefaultValue<void*>::Exists());
+}
+
+// Tests that BuiltInDefaultValue<T>::Get() returns 0 when T is a
+// built-in numeric type.
+TEST(BuiltInDefaultValueTest, IsZeroForNumericTypes) {
+  EXPECT_EQ(0U, BuiltInDefaultValue<unsigned char>::Get());
+  EXPECT_EQ(0, BuiltInDefaultValue<signed char>::Get());
+  EXPECT_EQ(0, BuiltInDefaultValue<char>::Get());
+#if GMOCK_WCHAR_T_IS_NATIVE_
+#if !defined(__WCHAR_UNSIGNED__)
+  EXPECT_EQ(0, BuiltInDefaultValue<wchar_t>::Get());
+#else
+  EXPECT_EQ(0U, BuiltInDefaultValue<wchar_t>::Get());
+#endif
+#endif
+  EXPECT_EQ(0U, BuiltInDefaultValue<unsigned short>::Get());  // NOLINT
+  EXPECT_EQ(0, BuiltInDefaultValue<signed short>::Get());     // NOLINT
+  EXPECT_EQ(0, BuiltInDefaultValue<short>::Get());            // NOLINT
+  EXPECT_EQ(0U, BuiltInDefaultValue<unsigned int>::Get());
+  EXPECT_EQ(0, BuiltInDefaultValue<signed int>::Get());
+  EXPECT_EQ(0, BuiltInDefaultValue<int>::Get());
+  EXPECT_EQ(0U, BuiltInDefaultValue<unsigned long>::Get());       // NOLINT
+  EXPECT_EQ(0, BuiltInDefaultValue<signed long>::Get());          // NOLINT
+  EXPECT_EQ(0, BuiltInDefaultValue<long>::Get());                 // NOLINT
+  EXPECT_EQ(0U, BuiltInDefaultValue<unsigned long long>::Get());  // NOLINT
+  EXPECT_EQ(0, BuiltInDefaultValue<signed long long>::Get());     // NOLINT
+  EXPECT_EQ(0, BuiltInDefaultValue<long long>::Get());            // NOLINT
+  EXPECT_EQ(0, BuiltInDefaultValue<float>::Get());
+  EXPECT_EQ(0, BuiltInDefaultValue<double>::Get());
+}
+
+// Tests that BuiltInDefaultValue<T>::Exists() returns true when T is a
+// built-in numeric type.
+TEST(BuiltInDefaultValueTest, ExistsForNumericTypes) {
+  EXPECT_TRUE(BuiltInDefaultValue<unsigned char>::Exists());
+  EXPECT_TRUE(BuiltInDefaultValue<signed char>::Exists());
+  EXPECT_TRUE(BuiltInDefaultValue<char>::Exists());
+#if GMOCK_WCHAR_T_IS_NATIVE_
+  EXPECT_TRUE(BuiltInDefaultValue<wchar_t>::Exists());
+#endif
+  EXPECT_TRUE(BuiltInDefaultValue<unsigned short>::Exists());  // NOLINT
+  EXPECT_TRUE(BuiltInDefaultValue<signed short>::Exists());    // NOLINT
+  EXPECT_TRUE(BuiltInDefaultValue<short>::Exists());           // NOLINT
+  EXPECT_TRUE(BuiltInDefaultValue<unsigned int>::Exists());
+  EXPECT_TRUE(BuiltInDefaultValue<signed int>::Exists());
+  EXPECT_TRUE(BuiltInDefaultValue<int>::Exists());
+  EXPECT_TRUE(BuiltInDefaultValue<unsigned long>::Exists());       // NOLINT
+  EXPECT_TRUE(BuiltInDefaultValue<signed long>::Exists());         // NOLINT
+  EXPECT_TRUE(BuiltInDefaultValue<long>::Exists());                // NOLINT
+  EXPECT_TRUE(BuiltInDefaultValue<unsigned long long>::Exists());  // NOLINT
+  EXPECT_TRUE(BuiltInDefaultValue<signed long long>::Exists());    // NOLINT
+  EXPECT_TRUE(BuiltInDefaultValue<long long>::Exists());           // NOLINT
+  EXPECT_TRUE(BuiltInDefaultValue<float>::Exists());
+  EXPECT_TRUE(BuiltInDefaultValue<double>::Exists());
+}
+
+// Tests that BuiltInDefaultValue<bool>::Get() returns false.
+TEST(BuiltInDefaultValueTest, IsFalseForBool) {
+  EXPECT_FALSE(BuiltInDefaultValue<bool>::Get());
+}
+
+// Tests that BuiltInDefaultValue<bool>::Exists() returns true.
+TEST(BuiltInDefaultValueTest, BoolExists) {
+  EXPECT_TRUE(BuiltInDefaultValue<bool>::Exists());
+}
+
+// Tests that BuiltInDefaultValue<T>::Get() returns "" when T is a
+// string type.
+TEST(BuiltInDefaultValueTest, IsEmptyStringForString) {
+  EXPECT_EQ("", BuiltInDefaultValue<::std::string>::Get());
+}
+
+// Tests that BuiltInDefaultValue<T>::Exists() returns true when T is a
+// string type.
+TEST(BuiltInDefaultValueTest, ExistsForString) {
+  EXPECT_TRUE(BuiltInDefaultValue<::std::string>::Exists());
+}
+
+// Tests that BuiltInDefaultValue<const T>::Get() returns the same
+// value as BuiltInDefaultValue<T>::Get() does.
+TEST(BuiltInDefaultValueTest, WorksForConstTypes) {
+  EXPECT_EQ("", BuiltInDefaultValue<const std::string>::Get());
+  EXPECT_EQ(0, BuiltInDefaultValue<const int>::Get());
+  EXPECT_TRUE(BuiltInDefaultValue<char* const>::Get() == nullptr);
+  EXPECT_FALSE(BuiltInDefaultValue<const bool>::Get());
+}
+
+// A type that's default constructible.
+class MyDefaultConstructible {
+ public:
+  MyDefaultConstructible() : value_(42) {}
+
+  int value() const { return value_; }
+
+ private:
+  int value_;
+};
+
+// A type that's not default constructible.
+class MyNonDefaultConstructible {
+ public:
+  // Does not have a default ctor.
+  explicit MyNonDefaultConstructible(int a_value) : value_(a_value) {}
+
+  int value() const { return value_; }
+
+ private:
+  int value_;
+};
+
+TEST(BuiltInDefaultValueTest, ExistsForDefaultConstructibleType) {
+  EXPECT_TRUE(BuiltInDefaultValue<MyDefaultConstructible>::Exists());
+}
+
+TEST(BuiltInDefaultValueTest, IsDefaultConstructedForDefaultConstructibleType) {
+  EXPECT_EQ(42, BuiltInDefaultValue<MyDefaultConstructible>::Get().value());
+}
+
+TEST(BuiltInDefaultValueTest, DoesNotExistForNonDefaultConstructibleType) {
+  EXPECT_FALSE(BuiltInDefaultValue<MyNonDefaultConstructible>::Exists());
+}
+
+// Tests that BuiltInDefaultValue<T&>::Get() aborts the program.
+TEST(BuiltInDefaultValueDeathTest, IsUndefinedForReferences) {
+  EXPECT_DEATH_IF_SUPPORTED({ BuiltInDefaultValue<int&>::Get(); }, "");
+  EXPECT_DEATH_IF_SUPPORTED({ BuiltInDefaultValue<const char&>::Get(); }, "");
+}
+
+TEST(BuiltInDefaultValueDeathTest, IsUndefinedForNonDefaultConstructibleType) {
+  EXPECT_DEATH_IF_SUPPORTED(
+      { BuiltInDefaultValue<MyNonDefaultConstructible>::Get(); }, "");
+}
+
+// Tests that DefaultValue<T>::IsSet() is false initially.
+TEST(DefaultValueTest, IsInitiallyUnset) {
+  EXPECT_FALSE(DefaultValue<int>::IsSet());
+  EXPECT_FALSE(DefaultValue<MyDefaultConstructible>::IsSet());
+  EXPECT_FALSE(DefaultValue<const MyNonDefaultConstructible>::IsSet());
+}
+
+// Tests that DefaultValue<T> can be set and then unset.
+TEST(DefaultValueTest, CanBeSetAndUnset) {
+  EXPECT_TRUE(DefaultValue<int>::Exists());
+  EXPECT_FALSE(DefaultValue<const MyNonDefaultConstructible>::Exists());
+
+  DefaultValue<int>::Set(1);
+  DefaultValue<const MyNonDefaultConstructible>::Set(
+      MyNonDefaultConstructible(42));
+
+  EXPECT_EQ(1, DefaultValue<int>::Get());
+  EXPECT_EQ(42, DefaultValue<const MyNonDefaultConstructible>::Get().value());
+
+  EXPECT_TRUE(DefaultValue<int>::Exists());
+  EXPECT_TRUE(DefaultValue<const MyNonDefaultConstructible>::Exists());
+
+  DefaultValue<int>::Clear();
+  DefaultValue<const MyNonDefaultConstructible>::Clear();
+
+  EXPECT_FALSE(DefaultValue<int>::IsSet());
+  EXPECT_FALSE(DefaultValue<const MyNonDefaultConstructible>::IsSet());
+
+  EXPECT_TRUE(DefaultValue<int>::Exists());
+  EXPECT_FALSE(DefaultValue<const MyNonDefaultConstructible>::Exists());
+}
+
+// Tests that DefaultValue<T>::Get() returns the
+// BuiltInDefaultValue<T>::Get() when DefaultValue<T>::IsSet() is
+// false.
+TEST(DefaultValueDeathTest, GetReturnsBuiltInDefaultValueWhenUnset) {
+  EXPECT_FALSE(DefaultValue<int>::IsSet());
+  EXPECT_TRUE(DefaultValue<int>::Exists());
+  EXPECT_FALSE(DefaultValue<MyNonDefaultConstructible>::IsSet());
+  EXPECT_FALSE(DefaultValue<MyNonDefaultConstructible>::Exists());
+
+  EXPECT_EQ(0, DefaultValue<int>::Get());
+
+  EXPECT_DEATH_IF_SUPPORTED({ DefaultValue<MyNonDefaultConstructible>::Get(); },
+                            "");
+}
+
+TEST(DefaultValueTest, GetWorksForMoveOnlyIfSet) {
+  EXPECT_TRUE(DefaultValue<std::unique_ptr<int>>::Exists());
+  EXPECT_TRUE(DefaultValue<std::unique_ptr<int>>::Get() == nullptr);
+  DefaultValue<std::unique_ptr<int>>::SetFactory(
+      [] { return std::make_unique<int>(42); });
+  EXPECT_TRUE(DefaultValue<std::unique_ptr<int>>::Exists());
+  std::unique_ptr<int> i = DefaultValue<std::unique_ptr<int>>::Get();
+  EXPECT_EQ(42, *i);
+}
+
+// Tests that DefaultValue<void>::Get() returns void.
+TEST(DefaultValueTest, GetWorksForVoid) { return DefaultValue<void>::Get(); }
+
+// Tests using DefaultValue with a reference type.
+
+// Tests that DefaultValue<T&>::IsSet() is false initially.
+TEST(DefaultValueOfReferenceTest, IsInitiallyUnset) {
+  EXPECT_FALSE(DefaultValue<int&>::IsSet());
+  EXPECT_FALSE(DefaultValue<MyDefaultConstructible&>::IsSet());
+  EXPECT_FALSE(DefaultValue<MyNonDefaultConstructible&>::IsSet());
+}
+
+// Tests that DefaultValue<T&>::Exists is false initially.
+TEST(DefaultValueOfReferenceTest, IsInitiallyNotExisting) {
+  EXPECT_FALSE(DefaultValue<int&>::Exists());
+  EXPECT_FALSE(DefaultValue<MyDefaultConstructible&>::Exists());
+  EXPECT_FALSE(DefaultValue<MyNonDefaultConstructible&>::Exists());
+}
+
+// Tests that DefaultValue<T&> can be set and then unset.
+TEST(DefaultValueOfReferenceTest, CanBeSetAndUnset) {
+  int n = 1;
+  DefaultValue<const int&>::Set(n);
+  MyNonDefaultConstructible x(42);
+  DefaultValue<MyNonDefaultConstructible&>::Set(x);
+
+  EXPECT_TRUE(DefaultValue<const int&>::Exists());
+  EXPECT_TRUE(DefaultValue<MyNonDefaultConstructible&>::Exists());
+
+  EXPECT_EQ(&n, &(DefaultValue<const int&>::Get()));
+  EXPECT_EQ(&x, &(DefaultValue<MyNonDefaultConstructible&>::Get()));
+
+  DefaultValue<const int&>::Clear();
+  DefaultValue<MyNonDefaultConstructible&>::Clear();
+
+  EXPECT_FALSE(DefaultValue<const int&>::Exists());
+  EXPECT_FALSE(DefaultValue<MyNonDefaultConstructible&>::Exists());
+
+  EXPECT_FALSE(DefaultValue<const int&>::IsSet());
+  EXPECT_FALSE(DefaultValue<MyNonDefaultConstructible&>::IsSet());
+}
+
+// Tests that DefaultValue<T&>::Get() returns the
+// BuiltInDefaultValue<T&>::Get() when DefaultValue<T&>::IsSet() is
+// false.
+TEST(DefaultValueOfReferenceDeathTest, GetReturnsBuiltInDefaultValueWhenUnset) {
+  EXPECT_FALSE(DefaultValue<int&>::IsSet());
+  EXPECT_FALSE(DefaultValue<MyNonDefaultConstructible&>::IsSet());
+
+  EXPECT_DEATH_IF_SUPPORTED({ DefaultValue<int&>::Get(); }, "");
+  EXPECT_DEATH_IF_SUPPORTED({ DefaultValue<MyNonDefaultConstructible>::Get(); },
+                            "");
+}
+
+// Tests that ActionInterface can be implemented by defining the
+// Perform method.
+
+typedef int MyGlobalFunction(bool, int);
+
+class MyActionImpl : public ActionInterface<MyGlobalFunction> {
+ public:
+  int Perform(const std::tuple<bool, int>& args) override {
+    return std::get<0>(args) ? std::get<1>(args) : 0;
+  }
+};
+
+TEST(ActionInterfaceTest, CanBeImplementedByDefiningPerform) {
+  MyActionImpl my_action_impl;
+  (void)my_action_impl;
+}
+
+TEST(ActionInterfaceTest, MakeAction) {
+  Action<MyGlobalFunction> action = MakeAction(new MyActionImpl);
+
+  // When exercising the Perform() method of Action<F>, we must pass
+  // it a tuple whose size and type are compatible with F's argument
+  // types.  For example, if F is int(), then Perform() takes a
+  // 0-tuple; if F is void(bool, int), then Perform() takes a
+  // std::tuple<bool, int>, and so on.
+  EXPECT_EQ(5, action.Perform(std::make_tuple(true, 5)));
+}
+
+// Tests that Action<F> can be constructed from a pointer to
+// ActionInterface<F>.
+TEST(ActionTest, CanBeConstructedFromActionInterface) {
+  Action<MyGlobalFunction> action(new MyActionImpl);
+}
+
+// Tests that Action<F> delegates actual work to ActionInterface<F>.
+TEST(ActionTest, DelegatesWorkToActionInterface) {
+  const Action<MyGlobalFunction> action(new MyActionImpl);
+
+  EXPECT_EQ(5, action.Perform(std::make_tuple(true, 5)));
+  EXPECT_EQ(0, action.Perform(std::make_tuple(false, 1)));
+}
+
+// Tests that Action<F> can be copied.
+TEST(ActionTest, IsCopyable) {
+  Action<MyGlobalFunction> a1(new MyActionImpl);
+  Action<MyGlobalFunction> a2(a1);  // Tests the copy constructor.
+
+  // a1 should continue to work after being copied from.
+  EXPECT_EQ(5, a1.Perform(std::make_tuple(true, 5)));
+  EXPECT_EQ(0, a1.Perform(std::make_tuple(false, 1)));
+
+  // a2 should work like the action it was copied from.
+  EXPECT_EQ(5, a2.Perform(std::make_tuple(true, 5)));
+  EXPECT_EQ(0, a2.Perform(std::make_tuple(false, 1)));
+
+  a2 = a1;  // Tests the assignment operator.
+
+  // a1 should continue to work after being copied from.
+  EXPECT_EQ(5, a1.Perform(std::make_tuple(true, 5)));
+  EXPECT_EQ(0, a1.Perform(std::make_tuple(false, 1)));
+
+  // a2 should work like the action it was copied from.
+  EXPECT_EQ(5, a2.Perform(std::make_tuple(true, 5)));
+  EXPECT_EQ(0, a2.Perform(std::make_tuple(false, 1)));
+}
+
+// Tests that an Action<From> object can be converted to a
+// compatible Action<To> object.
+
+class IsNotZero : public ActionInterface<bool(int)> {  // NOLINT
+ public:
+  bool Perform(const std::tuple<int>& arg) override {
+    return std::get<0>(arg) != 0;
+  }
+};
+
+TEST(ActionTest, CanBeConvertedToOtherActionType) {
+  const Action<bool(int)> a1(new IsNotZero);           // NOLINT
+  const Action<int(char)> a2 = Action<int(char)>(a1);  // NOLINT
+  EXPECT_EQ(1, a2.Perform(std::make_tuple('a')));
+  EXPECT_EQ(0, a2.Perform(std::make_tuple('\0')));
+}
+
+// The following two classes are for testing MakePolymorphicAction().
+
+// Implements a polymorphic action that returns the second of the
+// arguments it receives.
+class ReturnSecondArgumentAction {
+ public:
+  // We want to verify that MakePolymorphicAction() can work with a
+  // polymorphic action whose Perform() method template is either
+  // const or not.  This lets us verify the non-const case.
+  template <typename Result, typename ArgumentTuple>
+  Result Perform(const ArgumentTuple& args) {
+    return std::get<1>(args);
+  }
+};
+
+// Implements a polymorphic action that can be used in a nullary
+// function to return 0.
+class ReturnZeroFromNullaryFunctionAction {
+ public:
+  // For testing that MakePolymorphicAction() works when the
+  // implementation class' Perform() method template takes only one
+  // template parameter.
+  //
+  // We want to verify that MakePolymorphicAction() can work with a
+  // polymorphic action whose Perform() method template is either
+  // const or not.  This lets us verify the const case.
+  template <typename Result>
+  Result Perform(const std::tuple<>&) const {
+    return 0;
+  }
+};
+
+// These functions verify that MakePolymorphicAction() returns a
+// PolymorphicAction<T> where T is the argument's type.
+
+PolymorphicAction<ReturnSecondArgumentAction> ReturnSecondArgument() {
+  return MakePolymorphicAction(ReturnSecondArgumentAction());
+}
+
+PolymorphicAction<ReturnZeroFromNullaryFunctionAction>
+ReturnZeroFromNullaryFunction() {
+  return MakePolymorphicAction(ReturnZeroFromNullaryFunctionAction());
+}
+
+// Tests that MakePolymorphicAction() turns a polymorphic action
+// implementation class into a polymorphic action.
+TEST(MakePolymorphicActionTest, ConstructsActionFromImpl) {
+  Action<int(bool, int, double)> a1 = ReturnSecondArgument();  // NOLINT
+  EXPECT_EQ(5, a1.Perform(std::make_tuple(false, 5, 2.0)));
+}
+
+// Tests that MakePolymorphicAction() works when the implementation
+// class' Perform() method template has only one template parameter.
+TEST(MakePolymorphicActionTest, WorksWhenPerformHasOneTemplateParameter) {
+  Action<int()> a1 = ReturnZeroFromNullaryFunction();
+  EXPECT_EQ(0, a1.Perform(std::make_tuple()));
+
+  Action<void*()> a2 = ReturnZeroFromNullaryFunction();
+  EXPECT_TRUE(a2.Perform(std::make_tuple()) == nullptr);
+}
+
+// Tests that Return() works as an action for void-returning
+// functions.
+TEST(ReturnTest, WorksForVoid) {
+  const Action<void(int)> ret = Return();  // NOLINT
+  return ret.Perform(std::make_tuple(1));
+}
+
+// Tests that Return(v) returns v.
+TEST(ReturnTest, ReturnsGivenValue) {
+  Action<int()> ret = Return(1);  // NOLINT
+  EXPECT_EQ(1, ret.Perform(std::make_tuple()));
+
+  ret = Return(-5);
+  EXPECT_EQ(-5, ret.Perform(std::make_tuple()));
+}
+
+// Tests that Return("string literal") works.
+TEST(ReturnTest, AcceptsStringLiteral) {
+  Action<const char*()> a1 = Return("Hello");
+  EXPECT_STREQ("Hello", a1.Perform(std::make_tuple()));
+
+  Action<std::string()> a2 = Return("world");
+  EXPECT_EQ("world", a2.Perform(std::make_tuple()));
+}
+
+// Return(x) should work fine when the mock function's return type is a
+// reference-like wrapper for decltype(x), as when x is a std::string and the
+// mock function returns std::string_view.
+TEST(ReturnTest, SupportsReferenceLikeReturnType) {
+  // A reference wrapper for std::vector<int>, implicitly convertible from it.
+  struct Result {
+    const std::vector<int>* v;
+    Result(const std::vector<int>& vec) : v(&vec) {}  // NOLINT
+  };
+
+  // Set up an action for a mock function that returns the reference wrapper
+  // type, initializing it with an actual vector.
+  //
+  // The returned wrapper should be initialized with a copy of that vector
+  // that's embedded within the action itself (which should stay alive as long
+  // as the mock object is alive), rather than e.g. a reference to the temporary
+  // we feed to Return. This should work fine both for WillOnce and
+  // WillRepeatedly.
+  MockFunction<Result()> mock;
+  EXPECT_CALL(mock, Call)
+      .WillOnce(Return(std::vector<int>{17, 19, 23}))
+      .WillRepeatedly(Return(std::vector<int>{29, 31, 37}));
+
+  EXPECT_THAT(mock.AsStdFunction()(),
+              Field(&Result::v, Pointee(ElementsAre(17, 19, 23))));
+
+  EXPECT_THAT(mock.AsStdFunction()(),
+              Field(&Result::v, Pointee(ElementsAre(29, 31, 37))));
+}
+
+TEST(ReturnTest, PrefersConversionOperator) {
+  // Define types In and Out such that:
+  //
+  //  *  In is implicitly convertible to Out.
+  //  *  Out also has an explicit constructor from In.
+  //
+  struct In;
+  struct Out {
+    int x;
+
+    explicit Out(const int val) : x(val) {}
+    explicit Out(const In&) : x(0) {}
+  };
+
+  struct In {
+    operator Out() const { return Out{19}; }  // NOLINT
+  };
+
+  // Assumption check: the C++ language rules are such that a function that
+  // returns Out which uses In a return statement will use the implicit
+  // conversion path rather than the explicit constructor.
+  EXPECT_THAT([]() -> Out { return In(); }(), Field(&Out::x, 19));
+
+  // Return should work the same way: if the mock function's return type is Out
+  // and we feed Return an In value, then the Out should be created through the
+  // implicit conversion path rather than the explicit constructor.
+  MockFunction<Out()> mock;
+  EXPECT_CALL(mock, Call).WillOnce(Return(In()));
+  EXPECT_THAT(mock.AsStdFunction()(), Field(&Out::x, 19));
+}
+
+// It should be possible to use Return(R) with a mock function result type U
+// that is convertible from const R& but *not* R (such as
+// std::reference_wrapper). This should work for both WillOnce and
+// WillRepeatedly.
+TEST(ReturnTest, ConversionRequiresConstLvalueReference) {
+  using R = int;
+  using U = std::reference_wrapper<const int>;
+
+  static_assert(std::is_convertible<const R&, U>::value, "");
+  static_assert(!std::is_convertible<R, U>::value, "");
+
+  MockFunction<U()> mock;
+  EXPECT_CALL(mock, Call).WillOnce(Return(17)).WillRepeatedly(Return(19));
+
+  EXPECT_EQ(17, mock.AsStdFunction()());
+  EXPECT_EQ(19, mock.AsStdFunction()());
+}
+
+// Return(x) should not be usable with a mock function result type that's
+// implicitly convertible from decltype(x) but requires a non-const lvalue
+// reference to the input. It doesn't make sense for the conversion operator to
+// modify the input.
+TEST(ReturnTest, ConversionRequiresMutableLvalueReference) {
+  // Set up a type that is implicitly convertible from std::string&, but not
+  // std::string&& or `const std::string&`.
+  //
+  // Avoid asserting about conversion from std::string on MSVC, which seems to
+  // implement std::is_convertible incorrectly in this case.
+  struct S {
+    S(std::string&) {}  // NOLINT
+  };
+
+  static_assert(std::is_convertible<std::string&, S>::value, "");
+#ifndef _MSC_VER
+  static_assert(!std::is_convertible<std::string&&, S>::value, "");
+#endif
+  static_assert(!std::is_convertible<const std::string&, S>::value, "");
+
+  // It shouldn't be possible to use the result of Return(std::string) in a
+  // context where an S is needed.
+  //
+  // Here too we disable the assertion for MSVC, since its incorrect
+  // implementation of is_convertible causes our SFINAE to be wrong.
+  using RA = decltype(Return(std::string()));
+
+  static_assert(!std::is_convertible<RA, Action<S()>>::value, "");
+#ifndef _MSC_VER
+  static_assert(!std::is_convertible<RA, OnceAction<S()>>::value, "");
+#endif
+}
+
+TEST(ReturnTest, MoveOnlyResultType) {
+  // Return should support move-only result types when used with WillOnce.
+  {
+    MockFunction<std::unique_ptr<int>()> mock;
+    EXPECT_CALL(mock, Call)
+        // NOLINTNEXTLINE
+        .WillOnce(Return(std::unique_ptr<int>(new int(17))));
+
+    EXPECT_THAT(mock.AsStdFunction()(), Pointee(17));
+  }
+
+  // The result of Return should not be convertible to Action (so it can't be
+  // used with WillRepeatedly).
+  static_assert(!std::is_convertible<decltype(Return(std::unique_ptr<int>())),
+                                     Action<std::unique_ptr<int>()>>::value,
+                "");
+}
+
+// Tests that Return(v) is covariant.
+
+struct Base {
+  bool operator==(const Base&) { return true; }
+};
+
+struct Derived : public Base {
+  bool operator==(const Derived&) { return true; }
+};
+
+TEST(ReturnTest, IsCovariant) {
+  Base base;
+  Derived derived;
+  Action<Base*()> ret = Return(&base);
+  EXPECT_EQ(&base, ret.Perform(std::make_tuple()));
+
+  ret = Return(&derived);
+  EXPECT_EQ(&derived, ret.Perform(std::make_tuple()));
+}
+
+// Tests that the type of the value passed into Return is converted into T
+// when the action is cast to Action<T(...)> rather than when the action is
+// performed. See comments on testing::internal::ReturnAction in
+// gmock-actions.h for more information.
+class FromType {
+ public:
+  explicit FromType(bool* is_converted) : converted_(is_converted) {}
+  bool* converted() const { return converted_; }
+
+ private:
+  bool* const converted_;
+};
+
+class ToType {
+ public:
+  // Must allow implicit conversion due to use in ImplicitCast_<T>.
+  ToType(const FromType& x) { *x.converted() = true; }  // NOLINT
+};
+
+TEST(ReturnTest, ConvertsArgumentWhenConverted) {
+  bool converted = false;
+  FromType x(&converted);
+  Action<ToType()> action(Return(x));
+  EXPECT_TRUE(converted) << "Return must convert its argument in its own "
+                         << "conversion operator.";
+  converted = false;
+  action.Perform(std::tuple<>());
+  EXPECT_FALSE(converted) << "Action must NOT convert its argument "
+                          << "when performed.";
+}
+
+// Tests that ReturnNull() returns NULL in a pointer-returning function.
+TEST(ReturnNullTest, WorksInPointerReturningFunction) {
+  const Action<int*()> a1 = ReturnNull();
+  EXPECT_TRUE(a1.Perform(std::make_tuple()) == nullptr);
+
+  const Action<const char*(bool)> a2 = ReturnNull();  // NOLINT
+  EXPECT_TRUE(a2.Perform(std::make_tuple(true)) == nullptr);
+}
+
+// Tests that ReturnNull() returns NULL for shared_ptr and unique_ptr returning
+// functions.
+TEST(ReturnNullTest, WorksInSmartPointerReturningFunction) {
+  const Action<std::unique_ptr<const int>()> a1 = ReturnNull();
+  EXPECT_TRUE(a1.Perform(std::make_tuple()) == nullptr);
+
+  const Action<std::shared_ptr<int>(std::string)> a2 = ReturnNull();
+  EXPECT_TRUE(a2.Perform(std::make_tuple("foo")) == nullptr);
+}
+
+// Tests that ReturnRef(v) works for reference types.
+TEST(ReturnRefTest, WorksForReference) {
+  const int n = 0;
+  const Action<const int&(bool)> ret = ReturnRef(n);  // NOLINT
+
+  EXPECT_EQ(&n, &ret.Perform(std::make_tuple(true)));
+}
+
+// Tests that ReturnRef(v) is covariant.
+TEST(ReturnRefTest, IsCovariant) {
+  Base base;
+  Derived derived;
+  Action<Base&()> a = ReturnRef(base);
+  EXPECT_EQ(&base, &a.Perform(std::make_tuple()));
+
+  a = ReturnRef(derived);
+  EXPECT_EQ(&derived, &a.Perform(std::make_tuple()));
+}
+
+template <typename T, typename = decltype(ReturnRef(std::declval<T&&>()))>
+bool CanCallReturnRef(T&&) {
+  return true;
+}
+bool CanCallReturnRef(Unused) { return false; }
+
+// Tests that ReturnRef(v) is working with non-temporaries (T&)
+TEST(ReturnRefTest, WorksForNonTemporary) {
+  int scalar_value = 123;
+  EXPECT_TRUE(CanCallReturnRef(scalar_value));
+
+  std::string non_scalar_value("ABC");
+  EXPECT_TRUE(CanCallReturnRef(non_scalar_value));
+
+  const int const_scalar_value{321};
+  EXPECT_TRUE(CanCallReturnRef(const_scalar_value));
+
+  const std::string const_non_scalar_value("CBA");
+  EXPECT_TRUE(CanCallReturnRef(const_non_scalar_value));
+}
+
+// Tests that ReturnRef(v) is not working with temporaries (T&&)
+TEST(ReturnRefTest, DoesNotWorkForTemporary) {
+  auto scalar_value = []() -> int { return 123; };
+  EXPECT_FALSE(CanCallReturnRef(scalar_value()));
+
+  auto non_scalar_value = []() -> std::string { return "ABC"; };
+  EXPECT_FALSE(CanCallReturnRef(non_scalar_value()));
+
+  // cannot use here callable returning "const scalar type",
+  // because such const for scalar return type is ignored
+  EXPECT_FALSE(CanCallReturnRef(static_cast<const int>(321)));
+
+  auto const_non_scalar_value = []() -> const std::string { return "CBA"; };
+  EXPECT_FALSE(CanCallReturnRef(const_non_scalar_value()));
+}
+
+// Tests that ReturnRefOfCopy(v) works for reference types.
+TEST(ReturnRefOfCopyTest, WorksForReference) {
+  int n = 42;
+  const Action<const int&()> ret = ReturnRefOfCopy(n);
+
+  EXPECT_NE(&n, &ret.Perform(std::make_tuple()));
+  EXPECT_EQ(42, ret.Perform(std::make_tuple()));
+
+  n = 43;
+  EXPECT_NE(&n, &ret.Perform(std::make_tuple()));
+  EXPECT_EQ(42, ret.Perform(std::make_tuple()));
+}
+
+// Tests that ReturnRefOfCopy(v) is covariant.
+TEST(ReturnRefOfCopyTest, IsCovariant) {
+  Base base;
+  Derived derived;
+  Action<Base&()> a = ReturnRefOfCopy(base);
+  EXPECT_NE(&base, &a.Perform(std::make_tuple()));
+
+  a = ReturnRefOfCopy(derived);
+  EXPECT_NE(&derived, &a.Perform(std::make_tuple()));
+}
+
+// Tests that ReturnRoundRobin(v) works with initializer lists
+TEST(ReturnRoundRobinTest, WorksForInitList) {
+  Action<int()> ret = ReturnRoundRobin({1, 2, 3});
+
+  EXPECT_EQ(1, ret.Perform(std::make_tuple()));
+  EXPECT_EQ(2, ret.Perform(std::make_tuple()));
+  EXPECT_EQ(3, ret.Perform(std::make_tuple()));
+  EXPECT_EQ(1, ret.Perform(std::make_tuple()));
+  EXPECT_EQ(2, ret.Perform(std::make_tuple()));
+  EXPECT_EQ(3, ret.Perform(std::make_tuple()));
+}
+
+// Tests that ReturnRoundRobin(v) works with vectors
+TEST(ReturnRoundRobinTest, WorksForVector) {
+  std::vector<double> v = {4.4, 5.5, 6.6};
+  Action<double()> ret = ReturnRoundRobin(v);
+
+  EXPECT_EQ(4.4, ret.Perform(std::make_tuple()));
+  EXPECT_EQ(5.5, ret.Perform(std::make_tuple()));
+  EXPECT_EQ(6.6, ret.Perform(std::make_tuple()));
+  EXPECT_EQ(4.4, ret.Perform(std::make_tuple()));
+  EXPECT_EQ(5.5, ret.Perform(std::make_tuple()));
+  EXPECT_EQ(6.6, ret.Perform(std::make_tuple()));
+}
+
+// Tests that DoDefault() does the default action for the mock method.
+
+class MockClass {
+ public:
+  MockClass() = default;
+
+  MOCK_METHOD1(IntFunc, int(bool flag));  // NOLINT
+  MOCK_METHOD0(Foo, MyNonDefaultConstructible());
+  MOCK_METHOD0(MakeUnique, std::unique_ptr<int>());
+  MOCK_METHOD0(MakeUniqueBase, std::unique_ptr<Base>());
+  MOCK_METHOD0(MakeVectorUnique, std::vector<std::unique_ptr<int>>());
+  MOCK_METHOD1(TakeUnique, int(std::unique_ptr<int>));
+  MOCK_METHOD2(TakeUnique,
+               int(const std::unique_ptr<int>&, std::unique_ptr<int>));
+
+ private:
+  MockClass(const MockClass&) = delete;
+  MockClass& operator=(const MockClass&) = delete;
+};
+
+// Tests that DoDefault() returns the built-in default value for the
+// return type by default.
+TEST(DoDefaultTest, ReturnsBuiltInDefaultValueByDefault) {
+  MockClass mock;
+  EXPECT_CALL(mock, IntFunc(_)).WillOnce(DoDefault());
+  EXPECT_EQ(0, mock.IntFunc(true));
+}
+
+// Tests that DoDefault() throws (when exceptions are enabled) or aborts
+// the process when there is no built-in default value for the return type.
+TEST(DoDefaultDeathTest, DiesForUnknowType) {
+  MockClass mock;
+  EXPECT_CALL(mock, Foo()).WillRepeatedly(DoDefault());
+#if GTEST_HAS_EXCEPTIONS
+  EXPECT_ANY_THROW(mock.Foo());
+#else
+  EXPECT_DEATH_IF_SUPPORTED({ mock.Foo(); }, "");
+#endif
+}
+
+// Tests that using DoDefault() inside a composite action leads to a
+// run-time error.
+
+void VoidFunc(bool /* flag */) {}
+
+TEST(DoDefaultDeathTest, DiesIfUsedInCompositeAction) {
+  MockClass mock;
+  EXPECT_CALL(mock, IntFunc(_))
+      .WillRepeatedly(DoAll(Invoke(VoidFunc), DoDefault()));
+
+  // Ideally we should verify the error message as well.  Sadly,
+  // EXPECT_DEATH() can only capture stderr, while Google Mock's
+  // errors are printed on stdout.  Therefore we have to settle for
+  // not verifying the message.
+  EXPECT_DEATH_IF_SUPPORTED({ mock.IntFunc(true); }, "");
+}
+
+// Tests that DoDefault() returns the default value set by
+// DefaultValue<T>::Set() when it's not overridden by an ON_CALL().
+TEST(DoDefaultTest, ReturnsUserSpecifiedPerTypeDefaultValueWhenThereIsOne) {
+  DefaultValue<int>::Set(1);
+  MockClass mock;
+  EXPECT_CALL(mock, IntFunc(_)).WillOnce(DoDefault());
+  EXPECT_EQ(1, mock.IntFunc(false));
+  DefaultValue<int>::Clear();
+}
+
+// Tests that DoDefault() does the action specified by ON_CALL().
+TEST(DoDefaultTest, DoesWhatOnCallSpecifies) {
+  MockClass mock;
+  ON_CALL(mock, IntFunc(_)).WillByDefault(Return(2));
+  EXPECT_CALL(mock, IntFunc(_)).WillOnce(DoDefault());
+  EXPECT_EQ(2, mock.IntFunc(false));
+}
+
+// Tests that using DoDefault() in ON_CALL() leads to a run-time failure.
+TEST(DoDefaultTest, CannotBeUsedInOnCall) {
+  MockClass mock;
+  EXPECT_NONFATAL_FAILURE(
+      {  // NOLINT
+        ON_CALL(mock, IntFunc(_)).WillByDefault(DoDefault());
+      },
+      "DoDefault() cannot be used in ON_CALL()");
+}
+
+// Tests that SetArgPointee<N>(v) sets the variable pointed to by
+// the N-th (0-based) argument to v.
+TEST(SetArgPointeeTest, SetsTheNthPointee) {
+  typedef void MyFunction(bool, int*, char*);
+  Action<MyFunction> a = SetArgPointee<1>(2);
+
+  int n = 0;
+  char ch = '\0';
+  a.Perform(std::make_tuple(true, &n, &ch));
+  EXPECT_EQ(2, n);
+  EXPECT_EQ('\0', ch);
+
+  a = SetArgPointee<2>('a');
+  n = 0;
+  ch = '\0';
+  a.Perform(std::make_tuple(true, &n, &ch));
+  EXPECT_EQ(0, n);
+  EXPECT_EQ('a', ch);
+}
+
+// Tests that SetArgPointee<N>() accepts a string literal.
+TEST(SetArgPointeeTest, AcceptsStringLiteral) {
+  typedef void MyFunction(std::string*, const char**);
+  Action<MyFunction> a = SetArgPointee<0>("hi");
+  std::string str;
+  const char* ptr = nullptr;
+  a.Perform(std::make_tuple(&str, &ptr));
+  EXPECT_EQ("hi", str);
+  EXPECT_TRUE(ptr == nullptr);
+
+  a = SetArgPointee<1>("world");
+  str = "";
+  a.Perform(std::make_tuple(&str, &ptr));
+  EXPECT_EQ("", str);
+  EXPECT_STREQ("world", ptr);
+}
+
+TEST(SetArgPointeeTest, AcceptsWideStringLiteral) {
+  typedef void MyFunction(const wchar_t**);
+  Action<MyFunction> a = SetArgPointee<0>(L"world");
+  const wchar_t* ptr = nullptr;
+  a.Perform(std::make_tuple(&ptr));
+  EXPECT_STREQ(L"world", ptr);
+
+#if GTEST_HAS_STD_WSTRING
+
+  typedef void MyStringFunction(std::wstring*);
+  Action<MyStringFunction> a2 = SetArgPointee<0>(L"world");
+  std::wstring str = L"";
+  a2.Perform(std::make_tuple(&str));
+  EXPECT_EQ(L"world", str);
+
+#endif
+}
+
+// Tests that SetArgPointee<N>() accepts a char pointer.
+TEST(SetArgPointeeTest, AcceptsCharPointer) {
+  typedef void MyFunction(bool, std::string*, const char**);
+  const char* const hi = "hi";
+  Action<MyFunction> a = SetArgPointee<1>(hi);
+  std::string str;
+  const char* ptr = nullptr;
+  a.Perform(std::make_tuple(true, &str, &ptr));
+  EXPECT_EQ("hi", str);
+  EXPECT_TRUE(ptr == nullptr);
+
+  char world_array[] = "world";
+  char* const world = world_array;
+  a = SetArgPointee<2>(world);
+  str = "";
+  a.Perform(std::make_tuple(true, &str, &ptr));
+  EXPECT_EQ("", str);
+  EXPECT_EQ(world, ptr);
+}
+
+TEST(SetArgPointeeTest, AcceptsWideCharPointer) {
+  typedef void MyFunction(bool, const wchar_t**);
+  const wchar_t* const hi = L"hi";
+  Action<MyFunction> a = SetArgPointee<1>(hi);
+  const wchar_t* ptr = nullptr;
+  a.Perform(std::make_tuple(true, &ptr));
+  EXPECT_EQ(hi, ptr);
+
+#if GTEST_HAS_STD_WSTRING
+
+  typedef void MyStringFunction(bool, std::wstring*);
+  wchar_t world_array[] = L"world";
+  wchar_t* const world = world_array;
+  Action<MyStringFunction> a2 = SetArgPointee<1>(world);
+  std::wstring str;
+  a2.Perform(std::make_tuple(true, &str));
+  EXPECT_EQ(world_array, str);
+#endif
+}
+
+// Tests that SetArgumentPointee<N>(v) sets the variable pointed to by
+// the N-th (0-based) argument to v.
+TEST(SetArgumentPointeeTest, SetsTheNthPointee) {
+  typedef void MyFunction(bool, int*, char*);
+  Action<MyFunction> a = SetArgumentPointee<1>(2);
+
+  int n = 0;
+  char ch = '\0';
+  a.Perform(std::make_tuple(true, &n, &ch));
+  EXPECT_EQ(2, n);
+  EXPECT_EQ('\0', ch);
+
+  a = SetArgumentPointee<2>('a');
+  n = 0;
+  ch = '\0';
+  a.Perform(std::make_tuple(true, &n, &ch));
+  EXPECT_EQ(0, n);
+  EXPECT_EQ('a', ch);
+}
+
+// Sample functions and functors for testing Invoke() and etc.
+int Nullary() { return 1; }
+
+class NullaryFunctor {
+ public:
+  int operator()() { return 2; }
+};
+
+bool g_done = false;
+void VoidNullary() { g_done = true; }
+
+class VoidNullaryFunctor {
+ public:
+  void operator()() { g_done = true; }
+};
+
+short Short(short n) { return n; }  // NOLINT
+char Char(char ch) { return ch; }
+
+const char* CharPtr(const char* s) { return s; }
+
+bool Unary(int x) { return x < 0; }
+
+const char* Binary(const char* input, short n) { return input + n; }  // NOLINT
+
+void VoidBinary(int, char) { g_done = true; }
+
+int Ternary(int x, char y, short z) { return x + y + z; }  // NOLINT
+
+int SumOf4(int a, int b, int c, int d) { return a + b + c + d; }
+
+class Foo {
+ public:
+  Foo() : value_(123) {}
+
+  int Nullary() const { return value_; }
+
+ private:
+  int value_;
+};
+
+// Tests InvokeWithoutArgs(function).
+TEST(InvokeWithoutArgsTest, Function) {
+  // As an action that takes one argument.
+  Action<int(int)> a = InvokeWithoutArgs(Nullary);  // NOLINT
+  EXPECT_EQ(1, a.Perform(std::make_tuple(2)));
+
+  // As an action that takes two arguments.
+  Action<int(int, double)> a2 = InvokeWithoutArgs(Nullary);  // NOLINT
+  EXPECT_EQ(1, a2.Perform(std::make_tuple(2, 3.5)));
+
+  // As an action that returns void.
+  Action<void(int)> a3 = InvokeWithoutArgs(VoidNullary);  // NOLINT
+  g_done = false;
+  a3.Perform(std::make_tuple(1));
+  EXPECT_TRUE(g_done);
+}
+
+// Tests InvokeWithoutArgs(functor).
+TEST(InvokeWithoutArgsTest, Functor) {
+  // As an action that takes no argument.
+  Action<int()> a = InvokeWithoutArgs(NullaryFunctor());  // NOLINT
+  EXPECT_EQ(2, a.Perform(std::make_tuple()));
+
+  // As an action that takes three arguments.
+  Action<int(int, double, char)> a2 =  // NOLINT
+      InvokeWithoutArgs(NullaryFunctor());
+  EXPECT_EQ(2, a2.Perform(std::make_tuple(3, 3.5, 'a')));
+
+  // As an action that returns void.
+  Action<void()> a3 = InvokeWithoutArgs(VoidNullaryFunctor());
+  g_done = false;
+  a3.Perform(std::make_tuple());
+  EXPECT_TRUE(g_done);
+}
+
+// Tests InvokeWithoutArgs(obj_ptr, method).
+TEST(InvokeWithoutArgsTest, Method) {
+  Foo foo;
+  Action<int(bool, char)> a =  // NOLINT
+      InvokeWithoutArgs(&foo, &Foo::Nullary);
+  EXPECT_EQ(123, a.Perform(std::make_tuple(true, 'a')));
+}
+
+// Tests using IgnoreResult() on a polymorphic action.
+TEST(IgnoreResultTest, PolymorphicAction) {
+  Action<void(int)> a = IgnoreResult(Return(5));  // NOLINT
+  a.Perform(std::make_tuple(1));
+}
+
+// Tests using IgnoreResult() on a monomorphic action.
+
+int ReturnOne() {
+  g_done = true;
+  return 1;
+}
+
+TEST(IgnoreResultTest, MonomorphicAction) {
+  g_done = false;
+  Action<void()> a = IgnoreResult(Invoke(ReturnOne));
+  a.Perform(std::make_tuple());
+  EXPECT_TRUE(g_done);
+}
+
+// Tests using IgnoreResult() on an action that returns a class type.
+
+MyNonDefaultConstructible ReturnMyNonDefaultConstructible(double /* x */) {
+  g_done = true;
+  return MyNonDefaultConstructible(42);
+}
+
+TEST(IgnoreResultTest, ActionReturningClass) {
+  g_done = false;
+  Action<void(int)> a =
+      IgnoreResult(Invoke(ReturnMyNonDefaultConstructible));  // NOLINT
+  a.Perform(std::make_tuple(2));
+  EXPECT_TRUE(g_done);
+}
+
+TEST(AssignTest, Int) {
+  int x = 0;
+  Action<void(int)> a = Assign(&x, 5);
+  a.Perform(std::make_tuple(0));
+  EXPECT_EQ(5, x);
+}
+
+TEST(AssignTest, String) {
+  ::std::string x;
+  Action<void(void)> a = Assign(&x, "Hello, world");
+  a.Perform(std::make_tuple());
+  EXPECT_EQ("Hello, world", x);
+}
+
+TEST(AssignTest, CompatibleTypes) {
+  double x = 0;
+  Action<void(int)> a = Assign(&x, 5);
+  a.Perform(std::make_tuple(0));
+  EXPECT_DOUBLE_EQ(5, x);
+}
+
+// DoAll should support &&-qualified actions when used with WillOnce.
+TEST(DoAll, SupportsRefQualifiedActions) {
+  struct InitialAction {
+    void operator()(const int arg) && { EXPECT_EQ(17, arg); }
+  };
+
+  struct FinalAction {
+    int operator()() && { return 19; }
+  };
+
+  MockFunction<int(int)> mock;
+  EXPECT_CALL(mock, Call).WillOnce(DoAll(InitialAction{}, FinalAction{}));
+  EXPECT_EQ(19, mock.AsStdFunction()(17));
+}
+
+// DoAll should never provide rvalue references to the initial actions. If the
+// mock action itself accepts an rvalue reference or a non-scalar object by
+// value then the final action should receive an rvalue reference, but initial
+// actions should receive only lvalue references.
+TEST(DoAll, ProvidesLvalueReferencesToInitialActions) {
+  struct Obj {};
+
+  // Mock action accepts by value: the initial action should be fed a const
+  // lvalue reference, and the final action an rvalue reference.
+  {
+    struct InitialAction {
+      void operator()(Obj&) const { FAIL() << "Unexpected call"; }
+      void operator()(const Obj&) const {}
+      void operator()(Obj&&) const { FAIL() << "Unexpected call"; }
+      void operator()(const Obj&&) const { FAIL() << "Unexpected call"; }
+    };
+
+    MockFunction<void(Obj)> mock;
+    EXPECT_CALL(mock, Call)
+        .WillOnce(DoAll(InitialAction{}, InitialAction{}, [](Obj&&) {}))
+        .WillRepeatedly(DoAll(InitialAction{}, InitialAction{}, [](Obj&&) {}));
+
+    mock.AsStdFunction()(Obj{});
+    mock.AsStdFunction()(Obj{});
+  }
+
+  // Mock action accepts by const lvalue reference: both actions should receive
+  // a const lvalue reference.
+  {
+    struct InitialAction {
+      void operator()(Obj&) const { FAIL() << "Unexpected call"; }
+      void operator()(const Obj&) const {}
+      void operator()(Obj&&) const { FAIL() << "Unexpected call"; }
+      void operator()(const Obj&&) const { FAIL() << "Unexpected call"; }
+    };
+
+    MockFunction<void(const Obj&)> mock;
+    EXPECT_CALL(mock, Call)
+        .WillOnce(DoAll(InitialAction{}, InitialAction{}, [](const Obj&) {}))
+        .WillRepeatedly(
+            DoAll(InitialAction{}, InitialAction{}, [](const Obj&) {}));
+
+    mock.AsStdFunction()(Obj{});
+    mock.AsStdFunction()(Obj{});
+  }
+
+  // Mock action accepts by non-const lvalue reference: both actions should get
+  // a non-const lvalue reference if they want them.
+  {
+    struct InitialAction {
+      void operator()(Obj&) const {}
+      void operator()(Obj&&) const { FAIL() << "Unexpected call"; }
+    };
+
+    MockFunction<void(Obj&)> mock;
+    EXPECT_CALL(mock, Call)
+        .WillOnce(DoAll(InitialAction{}, InitialAction{}, [](Obj&) {}))
+        .WillRepeatedly(DoAll(InitialAction{}, InitialAction{}, [](Obj&) {}));
+
+    Obj obj;
+    mock.AsStdFunction()(obj);
+    mock.AsStdFunction()(obj);
+  }
+
+  // Mock action accepts by rvalue reference: the initial actions should receive
+  // a non-const lvalue reference if it wants it, and the final action an rvalue
+  // reference.
+  {
+    struct InitialAction {
+      void operator()(Obj&) const {}
+      void operator()(Obj&&) const { FAIL() << "Unexpected call"; }
+    };
+
+    MockFunction<void(Obj&&)> mock;
+    EXPECT_CALL(mock, Call)
+        .WillOnce(DoAll(InitialAction{}, InitialAction{}, [](Obj&&) {}))
+        .WillRepeatedly(DoAll(InitialAction{}, InitialAction{}, [](Obj&&) {}));
+
+    mock.AsStdFunction()(Obj{});
+    mock.AsStdFunction()(Obj{});
+  }
+
+  // &&-qualified initial actions should also be allowed with WillOnce.
+  {
+    struct InitialAction {
+      void operator()(Obj&) && {}
+    };
+
+    MockFunction<void(Obj&)> mock;
+    EXPECT_CALL(mock, Call)
+        .WillOnce(DoAll(InitialAction{}, InitialAction{}, [](Obj&) {}));
+
+    Obj obj;
+    mock.AsStdFunction()(obj);
+  }
+
+  {
+    struct InitialAction {
+      void operator()(Obj&) && {}
+    };
+
+    MockFunction<void(Obj&&)> mock;
+    EXPECT_CALL(mock, Call)
+        .WillOnce(DoAll(InitialAction{}, InitialAction{}, [](Obj&&) {}));
+
+    mock.AsStdFunction()(Obj{});
+  }
+}
+
+// DoAll should support being used with type-erased Action objects, both through
+// WillOnce and WillRepeatedly.
+TEST(DoAll, SupportsTypeErasedActions) {
+  // With only type-erased actions.
+  const Action<void()> initial_action = [] {};
+  const Action<int()> final_action = [] { return 17; };
+
+  MockFunction<int()> mock;
+  EXPECT_CALL(mock, Call)
+      .WillOnce(DoAll(initial_action, initial_action, final_action))
+      .WillRepeatedly(DoAll(initial_action, initial_action, final_action));
+
+  EXPECT_EQ(17, mock.AsStdFunction()());
+
+  // With &&-qualified and move-only final action.
+  {
+    struct FinalAction {
+      FinalAction() = default;
+      FinalAction(FinalAction&&) = default;
+
+      int operator()() && { return 17; }
+    };
+
+    EXPECT_CALL(mock, Call)
+        .WillOnce(DoAll(initial_action, initial_action, FinalAction{}));
+
+    EXPECT_EQ(17, mock.AsStdFunction()());
+  }
+}
+
+// Tests using WithArgs and with an action that takes 1 argument.
+TEST(WithArgsTest, OneArg) {
+  Action<bool(double x, int n)> a = WithArgs<1>(Invoke(Unary));  // NOLINT
+  EXPECT_TRUE(a.Perform(std::make_tuple(1.5, -1)));
+  EXPECT_FALSE(a.Perform(std::make_tuple(1.5, 1)));
+}
+
+// Tests using WithArgs with an action that takes 2 arguments.
+TEST(WithArgsTest, TwoArgs) {
+  Action<const char*(const char* s, double x, short n)> a =  // NOLINT
+      WithArgs<0, 2>(Invoke(Binary));
+  const char s[] = "Hello";
+  EXPECT_EQ(s + 2, a.Perform(std::make_tuple(CharPtr(s), 0.5, Short(2))));
+}
+
+struct ConcatAll {
+  std::string operator()() const { return {}; }
+  template <typename... I>
+  std::string operator()(const char* a, I... i) const {
+    return a + ConcatAll()(i...);
+  }
+};
+
+// Tests using WithArgs with an action that takes 10 arguments.
+TEST(WithArgsTest, TenArgs) {
+  Action<std::string(const char*, const char*, const char*, const char*)> a =
+      WithArgs<0, 1, 2, 3, 2, 1, 0, 1, 2, 3>(Invoke(ConcatAll{}));
+  EXPECT_EQ("0123210123",
+            a.Perform(std::make_tuple(CharPtr("0"), CharPtr("1"), CharPtr("2"),
+                                      CharPtr("3"))));
+}
+
+// Tests using WithArgs with an action that is not Invoke().
+class SubtractAction : public ActionInterface<int(int, int)> {
+ public:
+  int Perform(const std::tuple<int, int>& args) override {
+    return std::get<0>(args) - std::get<1>(args);
+  }
+};
+
+TEST(WithArgsTest, NonInvokeAction) {
+  Action<int(const std::string&, int, int)> a =
+      WithArgs<2, 1>(MakeAction(new SubtractAction));
+  std::tuple<std::string, int, int> dummy =
+      std::make_tuple(std::string("hi"), 2, 10);
+  EXPECT_EQ(8, a.Perform(dummy));
+}
+
+// Tests using WithArgs to pass all original arguments in the original order.
+TEST(WithArgsTest, Identity) {
+  Action<int(int x, char y, short z)> a =  // NOLINT
+      WithArgs<0, 1, 2>(Invoke(Ternary));
+  EXPECT_EQ(123, a.Perform(std::make_tuple(100, Char(20), Short(3))));
+}
+
+// Tests using WithArgs with repeated arguments.
+TEST(WithArgsTest, RepeatedArguments) {
+  Action<int(bool, int m, int n)> a =  // NOLINT
+      WithArgs<1, 1, 1, 1>(Invoke(SumOf4));
+  EXPECT_EQ(4, a.Perform(std::make_tuple(false, 1, 10)));
+}
+
+// Tests using WithArgs with reversed argument order.
+TEST(WithArgsTest, ReversedArgumentOrder) {
+  Action<const char*(short n, const char* input)> a =  // NOLINT
+      WithArgs<1, 0>(Invoke(Binary));
+  const char s[] = "Hello";
+  EXPECT_EQ(s + 2, a.Perform(std::make_tuple(Short(2), CharPtr(s))));
+}
+
+// Tests using WithArgs with compatible, but not identical, argument types.
+TEST(WithArgsTest, ArgsOfCompatibleTypes) {
+  Action<long(short x, char y, double z, char c)> a =  // NOLINT
+      WithArgs<0, 1, 3>(Invoke(Ternary));
+  EXPECT_EQ(123,
+            a.Perform(std::make_tuple(Short(100), Char(20), 5.6, Char(3))));
+}
+
+// Tests using WithArgs with an action that returns void.
+TEST(WithArgsTest, VoidAction) {
+  Action<void(double x, char c, int n)> a = WithArgs<2, 1>(Invoke(VoidBinary));
+  g_done = false;
+  a.Perform(std::make_tuple(1.5, 'a', 3));
+  EXPECT_TRUE(g_done);
+}
+
+TEST(WithArgsTest, ReturnReference) {
+  Action<int&(int&, void*)> aa = WithArgs<0>([](int& a) -> int& { return a; });
+  int i = 0;
+  const int& res = aa.Perform(std::forward_as_tuple(i, nullptr));
+  EXPECT_EQ(&i, &res);
+}
+
+TEST(WithArgsTest, InnerActionWithConversion) {
+  Action<Derived*()> inner = [] { return nullptr; };
+
+  MockFunction<Base*(double)> mock;
+  EXPECT_CALL(mock, Call)
+      .WillOnce(WithoutArgs(inner))
+      .WillRepeatedly(WithoutArgs(inner));
+
+  EXPECT_EQ(nullptr, mock.AsStdFunction()(1.1));
+  EXPECT_EQ(nullptr, mock.AsStdFunction()(1.1));
+}
+
+// It should be possible to use an &&-qualified inner action as long as the
+// whole shebang is used as an rvalue with WillOnce.
+TEST(WithArgsTest, RefQualifiedInnerAction) {
+  struct SomeAction {
+    int operator()(const int arg) && {
+      EXPECT_EQ(17, arg);
+      return 19;
+    }
+  };
+
+  MockFunction<int(int, int)> mock;
+  EXPECT_CALL(mock, Call).WillOnce(WithArg<1>(SomeAction{}));
+  EXPECT_EQ(19, mock.AsStdFunction()(0, 17));
+}
+
+#ifndef GTEST_OS_WINDOWS_MOBILE
+
+class SetErrnoAndReturnTest : public testing::Test {
+ protected:
+  void SetUp() override { errno = 0; }
+  void TearDown() override { errno = 0; }
+};
+
+TEST_F(SetErrnoAndReturnTest, Int) {
+  Action<int(void)> a = SetErrnoAndReturn(ENOTTY, -5);
+  EXPECT_EQ(-5, a.Perform(std::make_tuple()));
+  EXPECT_EQ(ENOTTY, errno);
+}
+
+TEST_F(SetErrnoAndReturnTest, Ptr) {
+  int x;
+  Action<int*(void)> a = SetErrnoAndReturn(ENOTTY, &x);
+  EXPECT_EQ(&x, a.Perform(std::make_tuple()));
+  EXPECT_EQ(ENOTTY, errno);
+}
+
+TEST_F(SetErrnoAndReturnTest, CompatibleTypes) {
+  Action<double()> a = SetErrnoAndReturn(EINVAL, 5);
+  EXPECT_DOUBLE_EQ(5.0, a.Perform(std::make_tuple()));
+  EXPECT_EQ(EINVAL, errno);
+}
+
+#endif  // !GTEST_OS_WINDOWS_MOBILE
+
+// Tests ByRef().
+
+// Tests that the result of ByRef() is copyable.
+TEST(ByRefTest, IsCopyable) {
+  const std::string s1 = "Hi";
+  const std::string s2 = "Hello";
+
+  auto ref_wrapper = ByRef(s1);
+  const std::string& r1 = ref_wrapper;
+  EXPECT_EQ(&s1, &r1);
+
+  // Assigns a new value to ref_wrapper.
+  ref_wrapper = ByRef(s2);
+  const std::string& r2 = ref_wrapper;
+  EXPECT_EQ(&s2, &r2);
+
+  auto ref_wrapper1 = ByRef(s1);
+  // Copies ref_wrapper1 to ref_wrapper.
+  ref_wrapper = ref_wrapper1;
+  const std::string& r3 = ref_wrapper;
+  EXPECT_EQ(&s1, &r3);
+}
+
+// Tests using ByRef() on a const value.
+TEST(ByRefTest, ConstValue) {
+  const int n = 0;
+  // int& ref = ByRef(n);  // This shouldn't compile - we have a
+  // negative compilation test to catch it.
+  const int& const_ref = ByRef(n);
+  EXPECT_EQ(&n, &const_ref);
+}
+
+// Tests using ByRef() on a non-const value.
+TEST(ByRefTest, NonConstValue) {
+  int n = 0;
+
+  // ByRef(n) can be used as either an int&,
+  int& ref = ByRef(n);
+  EXPECT_EQ(&n, &ref);
+
+  // or a const int&.
+  const int& const_ref = ByRef(n);
+  EXPECT_EQ(&n, &const_ref);
+}
+
+// Tests explicitly specifying the type when using ByRef().
+TEST(ByRefTest, ExplicitType) {
+  int n = 0;
+  const int& r1 = ByRef<const int>(n);
+  EXPECT_EQ(&n, &r1);
+
+  // ByRef<char>(n);  // This shouldn't compile - we have a negative
+  // compilation test to catch it.
+
+  Derived d;
+  Derived& r2 = ByRef<Derived>(d);
+  EXPECT_EQ(&d, &r2);
+
+  const Derived& r3 = ByRef<const Derived>(d);
+  EXPECT_EQ(&d, &r3);
+
+  Base& r4 = ByRef<Base>(d);
+  EXPECT_EQ(&d, &r4);
+
+  const Base& r5 = ByRef<const Base>(d);
+  EXPECT_EQ(&d, &r5);
+
+  // The following shouldn't compile - we have a negative compilation
+  // test for it.
+  //
+  // Base b;
+  // ByRef<Derived>(b);
+}
+
+// Tests that Google Mock prints expression ByRef(x) as a reference to x.
+TEST(ByRefTest, PrintsCorrectly) {
+  int n = 42;
+  ::std::stringstream expected, actual;
+  testing::internal::UniversalPrinter<const int&>::Print(n, &expected);
+  testing::internal::UniversalPrint(ByRef(n), &actual);
+  EXPECT_EQ(expected.str(), actual.str());
+}
+
+struct UnaryConstructorClass {
+  explicit UnaryConstructorClass(int v) : value(v) {}
+  int value;
+};
+
+// Tests using ReturnNew() with a unary constructor.
+TEST(ReturnNewTest, Unary) {
+  Action<UnaryConstructorClass*()> a = ReturnNew<UnaryConstructorClass>(4000);
+  UnaryConstructorClass* c = a.Perform(std::make_tuple());
+  EXPECT_EQ(4000, c->value);
+  delete c;
+}
+
+TEST(ReturnNewTest, UnaryWorksWhenMockMethodHasArgs) {
+  Action<UnaryConstructorClass*(bool, int)> a =
+      ReturnNew<UnaryConstructorClass>(4000);
+  UnaryConstructorClass* c = a.Perform(std::make_tuple(false, 5));
+  EXPECT_EQ(4000, c->value);
+  delete c;
+}
+
+TEST(ReturnNewTest, UnaryWorksWhenMockMethodReturnsPointerToConst) {
+  Action<const UnaryConstructorClass*()> a =
+      ReturnNew<UnaryConstructorClass>(4000);
+  const UnaryConstructorClass* c = a.Perform(std::make_tuple());
+  EXPECT_EQ(4000, c->value);
+  delete c;
+}
+
+class TenArgConstructorClass {
+ public:
+  TenArgConstructorClass(int a1, int a2, int a3, int a4, int a5, int a6, int a7,
+                         int a8, int a9, int a10)
+      : value_(a1 + a2 + a3 + a4 + a5 + a6 + a7 + a8 + a9 + a10) {}
+  int value_;
+};
+
+// Tests using ReturnNew() with a 10-argument constructor.
+TEST(ReturnNewTest, ConstructorThatTakes10Arguments) {
+  Action<TenArgConstructorClass*()> a = ReturnNew<TenArgConstructorClass>(
+      1000000000, 200000000, 30000000, 4000000, 500000, 60000, 7000, 800, 90,
+      0);
+  TenArgConstructorClass* c = a.Perform(std::make_tuple());
+  EXPECT_EQ(1234567890, c->value_);
+  delete c;
+}
+
+std::unique_ptr<int> UniquePtrSource() { return std::make_unique<int>(19); }
+
+std::vector<std::unique_ptr<int>> VectorUniquePtrSource() {
+  std::vector<std::unique_ptr<int>> out;
+  out.emplace_back(new int(7));
+  return out;
+}
+
+TEST(MockMethodTest, CanReturnMoveOnlyValue_Return) {
+  MockClass mock;
+  std::unique_ptr<int> i(new int(19));
+  EXPECT_CALL(mock, MakeUnique()).WillOnce(Return(ByMove(std::move(i))));
+  EXPECT_CALL(mock, MakeVectorUnique())
+      .WillOnce(Return(ByMove(VectorUniquePtrSource())));
+  Derived* d = new Derived;
+  EXPECT_CALL(mock, MakeUniqueBase())
+      .WillOnce(Return(ByMove(std::unique_ptr<Derived>(d))));
+
+  std::unique_ptr<int> result1 = mock.MakeUnique();
+  EXPECT_EQ(19, *result1);
+
+  std::vector<std::unique_ptr<int>> vresult = mock.MakeVectorUnique();
+  EXPECT_EQ(1u, vresult.size());
+  EXPECT_NE(nullptr, vresult[0]);
+  EXPECT_EQ(7, *vresult[0]);
+
+  std::unique_ptr<Base> result2 = mock.MakeUniqueBase();
+  EXPECT_EQ(d, result2.get());
+}
+
+TEST(MockMethodTest, CanReturnMoveOnlyValue_DoAllReturn) {
+  testing::MockFunction<void()> mock_function;
+  MockClass mock;
+  std::unique_ptr<int> i(new int(19));
+  EXPECT_CALL(mock_function, Call());
+  EXPECT_CALL(mock, MakeUnique())
+      .WillOnce(DoAll(InvokeWithoutArgs(&mock_function,
+                                        &testing::MockFunction<void()>::Call),
+                      Return(ByMove(std::move(i)))));
+
+  std::unique_ptr<int> result1 = mock.MakeUnique();
+  EXPECT_EQ(19, *result1);
+}
+
+TEST(MockMethodTest, CanReturnMoveOnlyValue_Invoke) {
+  MockClass mock;
+
+  // Check default value
+  DefaultValue<std::unique_ptr<int>>::SetFactory(
+      [] { return std::make_unique<int>(42); });
+  EXPECT_EQ(42, *mock.MakeUnique());
+
+  EXPECT_CALL(mock, MakeUnique()).WillRepeatedly(Invoke(UniquePtrSource));
+  EXPECT_CALL(mock, MakeVectorUnique())
+      .WillRepeatedly(Invoke(VectorUniquePtrSource));
+  std::unique_ptr<int> result1 = mock.MakeUnique();
+  EXPECT_EQ(19, *result1);
+  std::unique_ptr<int> result2 = mock.MakeUnique();
+  EXPECT_EQ(19, *result2);
+  EXPECT_NE(result1, result2);
+
+  std::vector<std::unique_ptr<int>> vresult = mock.MakeVectorUnique();
+  EXPECT_EQ(1u, vresult.size());
+  EXPECT_NE(nullptr, vresult[0]);
+  EXPECT_EQ(7, *vresult[0]);
+}
+
+TEST(MockMethodTest, CanTakeMoveOnlyValue) {
+  MockClass mock;
+  auto make = [](int i) { return std::make_unique<int>(i); };
+
+  EXPECT_CALL(mock, TakeUnique(_)).WillRepeatedly([](std::unique_ptr<int> i) {
+    return *i;
+  });
+  // DoAll() does not compile, since it would move from its arguments twice.
+  // EXPECT_CALL(mock, TakeUnique(_, _))
+  //     .WillRepeatedly(DoAll(Invoke([](std::unique_ptr<int> j) {}),
+  //     Return(1)));
+  EXPECT_CALL(mock, TakeUnique(testing::Pointee(7)))
+      .WillOnce(Return(-7))
+      .RetiresOnSaturation();
+  EXPECT_CALL(mock, TakeUnique(testing::IsNull()))
+      .WillOnce(Return(-1))
+      .RetiresOnSaturation();
+
+  EXPECT_EQ(5, mock.TakeUnique(make(5)));
+  EXPECT_EQ(-7, mock.TakeUnique(make(7)));
+  EXPECT_EQ(7, mock.TakeUnique(make(7)));
+  EXPECT_EQ(7, mock.TakeUnique(make(7)));
+  EXPECT_EQ(-1, mock.TakeUnique({}));
+
+  // Some arguments are moved, some passed by reference.
+  auto lvalue = make(6);
+  EXPECT_CALL(mock, TakeUnique(_, _))
+      .WillOnce([](const std::unique_ptr<int>& i, std::unique_ptr<int> j) {
+        return *i * *j;
+      });
+  EXPECT_EQ(42, mock.TakeUnique(lvalue, make(7)));
+
+  // The unique_ptr can be saved by the action.
+  std::unique_ptr<int> saved;
+  EXPECT_CALL(mock, TakeUnique(_)).WillOnce([&saved](std::unique_ptr<int> i) {
+    saved = std::move(i);
+    return 0;
+  });
+  EXPECT_EQ(0, mock.TakeUnique(make(42)));
+  EXPECT_EQ(42, *saved);
+}
+
+// It should be possible to use callables with an &&-qualified call operator
+// with WillOnce, since they will be called only once. This allows actions to
+// contain and manipulate move-only types.
+TEST(MockMethodTest, ActionHasRvalueRefQualifiedCallOperator) {
+  struct Return17 {
+    int operator()() && { return 17; }
+  };
+
+  // Action is directly compatible with mocked function type.
+  {
+    MockFunction<int()> mock;
+    EXPECT_CALL(mock, Call).WillOnce(Return17());
+
+    EXPECT_EQ(17, mock.AsStdFunction()());
+  }
+
+  // Action doesn't want mocked function arguments.
+  {
+    MockFunction<int(int)> mock;
+    EXPECT_CALL(mock, Call).WillOnce(Return17());
+
+    EXPECT_EQ(17, mock.AsStdFunction()(0));
+  }
+}
+
+// Edge case: if an action has both a const-qualified and an &&-qualified call
+// operator, there should be no "ambiguous call" errors. The &&-qualified
+// operator should be used by WillOnce (since it doesn't need to retain the
+// action beyond one call), and the const-qualified one by WillRepeatedly.
+TEST(MockMethodTest, ActionHasMultipleCallOperators) {
+  struct ReturnInt {
+    int operator()() && { return 17; }
+    int operator()() const& { return 19; }
+  };
+
+  // Directly compatible with mocked function type.
+  {
+    MockFunction<int()> mock;
+    EXPECT_CALL(mock, Call).WillOnce(ReturnInt()).WillRepeatedly(ReturnInt());
+
+    EXPECT_EQ(17, mock.AsStdFunction()());
+    EXPECT_EQ(19, mock.AsStdFunction()());
+    EXPECT_EQ(19, mock.AsStdFunction()());
+  }
+
+  // Ignores function arguments.
+  {
+    MockFunction<int(int)> mock;
+    EXPECT_CALL(mock, Call).WillOnce(ReturnInt()).WillRepeatedly(ReturnInt());
+
+    EXPECT_EQ(17, mock.AsStdFunction()(0));
+    EXPECT_EQ(19, mock.AsStdFunction()(0));
+    EXPECT_EQ(19, mock.AsStdFunction()(0));
+  }
+}
+
+// WillOnce should have no problem coping with a move-only action, whether it is
+// &&-qualified or not.
+TEST(MockMethodTest, MoveOnlyAction) {
+  // &&-qualified
+  {
+    struct Return17 {
+      Return17() = default;
+      Return17(Return17&&) = default;
+
+      Return17(const Return17&) = delete;
+      Return17 operator=(const Return17&) = delete;
+
+      int operator()() && { return 17; }
+    };
+
+    MockFunction<int()> mock;
+    EXPECT_CALL(mock, Call).WillOnce(Return17());
+    EXPECT_EQ(17, mock.AsStdFunction()());
+  }
+
+  // Not &&-qualified
+  {
+    struct Return17 {
+      Return17() = default;
+      Return17(Return17&&) = default;
+
+      Return17(const Return17&) = delete;
+      Return17 operator=(const Return17&) = delete;
+
+      int operator()() const { return 17; }
+    };
+
+    MockFunction<int()> mock;
+    EXPECT_CALL(mock, Call).WillOnce(Return17());
+    EXPECT_EQ(17, mock.AsStdFunction()());
+  }
+}
+
+// It should be possible to use an action that returns a value with a mock
+// function that doesn't, both through WillOnce and WillRepeatedly.
+TEST(MockMethodTest, ActionReturnsIgnoredValue) {
+  struct ReturnInt {
+    int operator()() const { return 0; }
+  };
+
+  MockFunction<void()> mock;
+  EXPECT_CALL(mock, Call).WillOnce(ReturnInt()).WillRepeatedly(ReturnInt());
+
+  mock.AsStdFunction()();
+  mock.AsStdFunction()();
+}
+
+// Despite the fanciness around move-only actions and so on, it should still be
+// possible to hand an lvalue reference to a copyable action to WillOnce.
+TEST(MockMethodTest, WillOnceCanAcceptLvalueReference) {
+  MockFunction<int()> mock;
+
+  const auto action = [] { return 17; };
+  EXPECT_CALL(mock, Call).WillOnce(action);
+
+  EXPECT_EQ(17, mock.AsStdFunction()());
+}
+
+// A callable that doesn't use SFINAE to restrict its call operator's overload
+// set, but is still picky about which arguments it will accept.
+struct StaticAssertSingleArgument {
+  template <typename... Args>
+  static constexpr bool CheckArgs() {
+    static_assert(sizeof...(Args) == 1, "");
+    return true;
+  }
+
+  template <typename... Args, bool = CheckArgs<Args...>()>
+  int operator()(Args...) const {
+    return 17;
+  }
+};
+
+// WillOnce and WillRepeatedly should both work fine with naïve implementations
+// of actions that don't use SFINAE to limit the overload set for their call
+// operator. If they are compatible with the actual mocked signature, we
+// shouldn't probe them with no arguments and trip a static_assert.
+TEST(MockMethodTest, ActionSwallowsAllArguments) {
+  MockFunction<int(int)> mock;
+  EXPECT_CALL(mock, Call)
+      .WillOnce(StaticAssertSingleArgument{})
+      .WillRepeatedly(StaticAssertSingleArgument{});
+
+  EXPECT_EQ(17, mock.AsStdFunction()(0));
+  EXPECT_EQ(17, mock.AsStdFunction()(0));
+}
+
+struct ActionWithTemplatedConversionOperators {
+  template <typename... Args>
+  operator OnceAction<int(Args...)>() && {  // NOLINT
+    return [] { return 17; };
+  }
+
+  template <typename... Args>
+  operator Action<int(Args...)>() const {  // NOLINT
+    return [] { return 19; };
+  }
+};
+
+// It should be fine to hand both WillOnce and WillRepeatedly a function that
+// defines templated conversion operators to OnceAction and Action. WillOnce
+// should prefer the OnceAction version.
+TEST(MockMethodTest, ActionHasTemplatedConversionOperators) {
+  MockFunction<int()> mock;
+  EXPECT_CALL(mock, Call)
+      .WillOnce(ActionWithTemplatedConversionOperators{})
+      .WillRepeatedly(ActionWithTemplatedConversionOperators{});
+
+  EXPECT_EQ(17, mock.AsStdFunction()());
+  EXPECT_EQ(19, mock.AsStdFunction()());
+}
+
+// Tests for std::function based action.
+
+int Add(int val, int& ref, int* ptr) {  // NOLINT
+  int result = val + ref + *ptr;
+  ref = 42;
+  *ptr = 43;
+  return result;
+}
+
+int Deref(std::unique_ptr<int> ptr) { return *ptr; }
+
+struct Double {
+  template <typename T>
+  T operator()(T t) {
+    return 2 * t;
+  }
+};
+
+std::unique_ptr<int> UniqueInt(int i) { return std::make_unique<int>(i); }
+
+TEST(FunctorActionTest, ActionFromFunction) {
+  Action<int(int, int&, int*)> a = &Add;
+  int x = 1, y = 2, z = 3;
+  EXPECT_EQ(6, a.Perform(std::forward_as_tuple(x, y, &z)));
+  EXPECT_EQ(42, y);
+  EXPECT_EQ(43, z);
+
+  Action<int(std::unique_ptr<int>)> a1 = &Deref;
+  EXPECT_EQ(7, a1.Perform(std::make_tuple(UniqueInt(7))));
+}
+
+TEST(FunctorActionTest, ActionFromLambda) {
+  Action<int(bool, int)> a1 = [](bool b, int i) { return b ? i : 0; };
+  EXPECT_EQ(5, a1.Perform(std::make_tuple(true, 5)));
+  EXPECT_EQ(0, a1.Perform(std::make_tuple(false, 5)));
+
+  std::unique_ptr<int> saved;
+  Action<void(std::unique_ptr<int>)> a2 = [&saved](std::unique_ptr<int> p) {
+    saved = std::move(p);
+  };
+  a2.Perform(std::make_tuple(UniqueInt(5)));
+  EXPECT_EQ(5, *saved);
+}
+
+TEST(FunctorActionTest, PolymorphicFunctor) {
+  Action<int(int)> ai = Double();
+  EXPECT_EQ(2, ai.Perform(std::make_tuple(1)));
+  Action<double(double)> ad = Double();  // Double? Double double!
+  EXPECT_EQ(3.0, ad.Perform(std::make_tuple(1.5)));
+}
+
+TEST(FunctorActionTest, TypeConversion) {
+  // Numeric promotions are allowed.
+  const Action<bool(int)> a1 = [](int i) { return i > 1; };
+  const Action<int(bool)> a2 = Action<int(bool)>(a1);
+  EXPECT_EQ(1, a1.Perform(std::make_tuple(42)));
+  EXPECT_EQ(0, a2.Perform(std::make_tuple(42)));
+
+  // Implicit constructors are allowed.
+  const Action<bool(std::string)> s1 = [](std::string s) { return !s.empty(); };
+  const Action<int(const char*)> s2 = Action<int(const char*)>(s1);
+  EXPECT_EQ(0, s2.Perform(std::make_tuple("")));
+  EXPECT_EQ(1, s2.Perform(std::make_tuple("hello")));
+
+  // Also between the lambda and the action itself.
+  const Action<bool(std::string)> x1 = [](Unused) { return 42; };
+  const Action<bool(std::string)> x2 = [] { return 42; };
+  EXPECT_TRUE(x1.Perform(std::make_tuple("hello")));
+  EXPECT_TRUE(x2.Perform(std::make_tuple("hello")));
+
+  // Ensure decay occurs where required.
+  std::function<int()> f = [] { return 7; };
+  Action<int(int)> d = f;
+  f = nullptr;
+  EXPECT_EQ(7, d.Perform(std::make_tuple(1)));
+
+  // Ensure creation of an empty action succeeds.
+  Action<void(int)>(nullptr);
+}
+
+TEST(FunctorActionTest, UnusedArguments) {
+  // Verify that users can ignore uninteresting arguments.
+  Action<int(int, double y, double z)> a = [](int i, Unused, Unused) {
+    return 2 * i;
+  };
+  std::tuple<int, double, double> dummy = std::make_tuple(3, 7.3, 9.44);
+  EXPECT_EQ(6, a.Perform(dummy));
+}
+
+// Test that basic built-in actions work with move-only arguments.
+TEST(MoveOnlyArgumentsTest, ReturningActions) {
+  Action<int(std::unique_ptr<int>)> a = Return(1);
+  EXPECT_EQ(1, a.Perform(std::make_tuple(nullptr)));
+
+  a = testing::WithoutArgs([]() { return 7; });
+  EXPECT_EQ(7, a.Perform(std::make_tuple(nullptr)));
+
+  Action<void(std::unique_ptr<int>, int*)> a2 = testing::SetArgPointee<1>(3);
+  int x = 0;
+  a2.Perform(std::make_tuple(nullptr, &x));
+  EXPECT_EQ(x, 3);
+}
+
+ACTION(ReturnArity) { return std::tuple_size<args_type>::value; }
+
+TEST(ActionMacro, LargeArity) {
+  EXPECT_EQ(
+      1, testing::Action<int(int)>(ReturnArity()).Perform(std::make_tuple(0)));
+  EXPECT_EQ(
+      10,
+      testing::Action<int(int, int, int, int, int, int, int, int, int, int)>(
+          ReturnArity())
+          .Perform(std::make_tuple(0, 1, 2, 3, 4, 5, 6, 7, 8, 9)));
+  EXPECT_EQ(
+      20,
+      testing::Action<int(int, int, int, int, int, int, int, int, int, int, int,
+                          int, int, int, int, int, int, int, int, int)>(
+          ReturnArity())
+          .Perform(std::make_tuple(0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13,
+                                   14, 15, 16, 17, 18, 19)));
+}
+
+}  // namespace
+}  // namespace testing
+
+#if defined(_MSC_VER) && (_MSC_VER == 1900)
+GTEST_DISABLE_MSC_WARNINGS_POP_()  // 4800
+#endif
+GTEST_DISABLE_MSC_WARNINGS_POP_()  // 4100 4503
diff --git a/third_party/googletest/googlemock/test/gmock-cardinalities_test.cc b/third_party/googletest/googlemock/test/gmock-cardinalities_test.cc
new file mode 100644
index 0000000..ad49752
--- /dev/null
+++ b/third_party/googletest/googlemock/test/gmock-cardinalities_test.cc
@@ -0,0 +1,424 @@
+// Copyright 2007, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Google Mock - a framework for writing C++ mock classes.
+//
+// This file tests the built-in cardinalities.
+
+#include <ostream>
+
+#include "gmock/gmock.h"
+#include "gtest/gtest-spi.h"
+#include "gtest/gtest.h"
+
+namespace {
+
+using std::stringstream;
+using testing::AnyNumber;
+using testing::AtLeast;
+using testing::AtMost;
+using testing::Between;
+using testing::Cardinality;
+using testing::CardinalityInterface;
+using testing::Exactly;
+using testing::IsSubstring;
+using testing::MakeCardinality;
+
+class MockFoo {
+ public:
+  MockFoo() = default;
+  MOCK_METHOD0(Bar, int());  // NOLINT
+
+ private:
+  MockFoo(const MockFoo&) = delete;
+  MockFoo& operator=(const MockFoo&) = delete;
+};
+
+// Tests that Cardinality objects can be default constructed.
+TEST(CardinalityTest, IsDefaultConstructable) { Cardinality c; }
+
+// Tests that Cardinality objects are copyable.
+TEST(CardinalityTest, IsCopyable) {
+  // Tests the copy constructor.
+  Cardinality c = Exactly(1);
+  EXPECT_FALSE(c.IsSatisfiedByCallCount(0));
+  EXPECT_TRUE(c.IsSatisfiedByCallCount(1));
+  EXPECT_TRUE(c.IsSaturatedByCallCount(1));
+
+  // Tests the assignment operator.
+  c = Exactly(2);
+  EXPECT_FALSE(c.IsSatisfiedByCallCount(1));
+  EXPECT_TRUE(c.IsSatisfiedByCallCount(2));
+  EXPECT_TRUE(c.IsSaturatedByCallCount(2));
+}
+
+TEST(CardinalityTest, IsOverSaturatedByCallCountWorks) {
+  const Cardinality c = AtMost(5);
+  EXPECT_FALSE(c.IsOverSaturatedByCallCount(4));
+  EXPECT_FALSE(c.IsOverSaturatedByCallCount(5));
+  EXPECT_TRUE(c.IsOverSaturatedByCallCount(6));
+}
+
+// Tests that Cardinality::DescribeActualCallCountTo() creates the
+// correct description.
+TEST(CardinalityTest, CanDescribeActualCallCount) {
+  stringstream ss0;
+  Cardinality::DescribeActualCallCountTo(0, &ss0);
+  EXPECT_EQ("never called", ss0.str());
+
+  stringstream ss1;
+  Cardinality::DescribeActualCallCountTo(1, &ss1);
+  EXPECT_EQ("called once", ss1.str());
+
+  stringstream ss2;
+  Cardinality::DescribeActualCallCountTo(2, &ss2);
+  EXPECT_EQ("called twice", ss2.str());
+
+  stringstream ss3;
+  Cardinality::DescribeActualCallCountTo(3, &ss3);
+  EXPECT_EQ("called 3 times", ss3.str());
+}
+
+// Tests AnyNumber()
+TEST(AnyNumber, Works) {
+  const Cardinality c = AnyNumber();
+  EXPECT_TRUE(c.IsSatisfiedByCallCount(0));
+  EXPECT_FALSE(c.IsSaturatedByCallCount(0));
+
+  EXPECT_TRUE(c.IsSatisfiedByCallCount(1));
+  EXPECT_FALSE(c.IsSaturatedByCallCount(1));
+
+  EXPECT_TRUE(c.IsSatisfiedByCallCount(9));
+  EXPECT_FALSE(c.IsSaturatedByCallCount(9));
+
+  stringstream ss;
+  c.DescribeTo(&ss);
+  EXPECT_PRED_FORMAT2(IsSubstring, "called any number of times", ss.str());
+}
+
+TEST(AnyNumberTest, HasCorrectBounds) {
+  const Cardinality c = AnyNumber();
+  EXPECT_EQ(0, c.ConservativeLowerBound());
+  EXPECT_EQ(INT_MAX, c.ConservativeUpperBound());
+}
+
+// Tests AtLeast(n).
+
+TEST(AtLeastTest, OnNegativeNumber) {
+  EXPECT_NONFATAL_FAILURE(
+      {  // NOLINT
+        AtLeast(-1);
+      },
+      "The invocation lower bound must be >= 0");
+}
+
+TEST(AtLeastTest, OnZero) {
+  const Cardinality c = AtLeast(0);
+  EXPECT_TRUE(c.IsSatisfiedByCallCount(0));
+  EXPECT_FALSE(c.IsSaturatedByCallCount(0));
+
+  EXPECT_TRUE(c.IsSatisfiedByCallCount(1));
+  EXPECT_FALSE(c.IsSaturatedByCallCount(1));
+
+  stringstream ss;
+  c.DescribeTo(&ss);
+  EXPECT_PRED_FORMAT2(IsSubstring, "any number of times", ss.str());
+}
+
+TEST(AtLeastTest, OnPositiveNumber) {
+  const Cardinality c = AtLeast(2);
+  EXPECT_FALSE(c.IsSatisfiedByCallCount(0));
+  EXPECT_FALSE(c.IsSaturatedByCallCount(0));
+
+  EXPECT_FALSE(c.IsSatisfiedByCallCount(1));
+  EXPECT_FALSE(c.IsSaturatedByCallCount(1));
+
+  EXPECT_TRUE(c.IsSatisfiedByCallCount(2));
+  EXPECT_FALSE(c.IsSaturatedByCallCount(2));
+
+  stringstream ss1;
+  AtLeast(1).DescribeTo(&ss1);
+  EXPECT_PRED_FORMAT2(IsSubstring, "at least once", ss1.str());
+
+  stringstream ss2;
+  c.DescribeTo(&ss2);
+  EXPECT_PRED_FORMAT2(IsSubstring, "at least twice", ss2.str());
+
+  stringstream ss3;
+  AtLeast(3).DescribeTo(&ss3);
+  EXPECT_PRED_FORMAT2(IsSubstring, "at least 3 times", ss3.str());
+}
+
+TEST(AtLeastTest, HasCorrectBounds) {
+  const Cardinality c = AtLeast(2);
+  EXPECT_EQ(2, c.ConservativeLowerBound());
+  EXPECT_EQ(INT_MAX, c.ConservativeUpperBound());
+}
+
+// Tests AtMost(n).
+
+TEST(AtMostTest, OnNegativeNumber) {
+  EXPECT_NONFATAL_FAILURE(
+      {  // NOLINT
+        AtMost(-1);
+      },
+      "The invocation upper bound must be >= 0");
+}
+
+TEST(AtMostTest, OnZero) {
+  const Cardinality c = AtMost(0);
+  EXPECT_TRUE(c.IsSatisfiedByCallCount(0));
+  EXPECT_TRUE(c.IsSaturatedByCallCount(0));
+
+  EXPECT_FALSE(c.IsSatisfiedByCallCount(1));
+  EXPECT_TRUE(c.IsSaturatedByCallCount(1));
+
+  stringstream ss;
+  c.DescribeTo(&ss);
+  EXPECT_PRED_FORMAT2(IsSubstring, "never called", ss.str());
+}
+
+TEST(AtMostTest, OnPositiveNumber) {
+  const Cardinality c = AtMost(2);
+  EXPECT_TRUE(c.IsSatisfiedByCallCount(0));
+  EXPECT_FALSE(c.IsSaturatedByCallCount(0));
+
+  EXPECT_TRUE(c.IsSatisfiedByCallCount(1));
+  EXPECT_FALSE(c.IsSaturatedByCallCount(1));
+
+  EXPECT_TRUE(c.IsSatisfiedByCallCount(2));
+  EXPECT_TRUE(c.IsSaturatedByCallCount(2));
+
+  stringstream ss1;
+  AtMost(1).DescribeTo(&ss1);
+  EXPECT_PRED_FORMAT2(IsSubstring, "called at most once", ss1.str());
+
+  stringstream ss2;
+  c.DescribeTo(&ss2);
+  EXPECT_PRED_FORMAT2(IsSubstring, "called at most twice", ss2.str());
+
+  stringstream ss3;
+  AtMost(3).DescribeTo(&ss3);
+  EXPECT_PRED_FORMAT2(IsSubstring, "called at most 3 times", ss3.str());
+}
+
+TEST(AtMostTest, HasCorrectBounds) {
+  const Cardinality c = AtMost(2);
+  EXPECT_EQ(0, c.ConservativeLowerBound());
+  EXPECT_EQ(2, c.ConservativeUpperBound());
+}
+
+// Tests Between(m, n).
+
+TEST(BetweenTest, OnNegativeStart) {
+  EXPECT_NONFATAL_FAILURE(
+      {  // NOLINT
+        Between(-1, 2);
+      },
+      "The invocation lower bound must be >= 0, but is actually -1");
+}
+
+TEST(BetweenTest, OnNegativeEnd) {
+  EXPECT_NONFATAL_FAILURE(
+      {  // NOLINT
+        Between(1, -2);
+      },
+      "The invocation upper bound must be >= 0, but is actually -2");
+}
+
+TEST(BetweenTest, OnStartBiggerThanEnd) {
+  EXPECT_NONFATAL_FAILURE(
+      {  // NOLINT
+        Between(2, 1);
+      },
+      "The invocation upper bound (1) must be >= "
+      "the invocation lower bound (2)");
+}
+
+TEST(BetweenTest, OnZeroStartAndZeroEnd) {
+  const Cardinality c = Between(0, 0);
+
+  EXPECT_TRUE(c.IsSatisfiedByCallCount(0));
+  EXPECT_TRUE(c.IsSaturatedByCallCount(0));
+
+  EXPECT_FALSE(c.IsSatisfiedByCallCount(1));
+  EXPECT_TRUE(c.IsSaturatedByCallCount(1));
+
+  stringstream ss;
+  c.DescribeTo(&ss);
+  EXPECT_PRED_FORMAT2(IsSubstring, "never called", ss.str());
+}
+
+TEST(BetweenTest, OnZeroStartAndNonZeroEnd) {
+  const Cardinality c = Between(0, 2);
+
+  EXPECT_TRUE(c.IsSatisfiedByCallCount(0));
+  EXPECT_FALSE(c.IsSaturatedByCallCount(0));
+
+  EXPECT_TRUE(c.IsSatisfiedByCallCount(2));
+  EXPECT_TRUE(c.IsSaturatedByCallCount(2));
+
+  EXPECT_FALSE(c.IsSatisfiedByCallCount(4));
+  EXPECT_TRUE(c.IsSaturatedByCallCount(4));
+
+  stringstream ss;
+  c.DescribeTo(&ss);
+  EXPECT_PRED_FORMAT2(IsSubstring, "called at most twice", ss.str());
+}
+
+TEST(BetweenTest, OnSameStartAndEnd) {
+  const Cardinality c = Between(3, 3);
+
+  EXPECT_FALSE(c.IsSatisfiedByCallCount(2));
+  EXPECT_FALSE(c.IsSaturatedByCallCount(2));
+
+  EXPECT_TRUE(c.IsSatisfiedByCallCount(3));
+  EXPECT_TRUE(c.IsSaturatedByCallCount(3));
+
+  EXPECT_FALSE(c.IsSatisfiedByCallCount(4));
+  EXPECT_TRUE(c.IsSaturatedByCallCount(4));
+
+  stringstream ss;
+  c.DescribeTo(&ss);
+  EXPECT_PRED_FORMAT2(IsSubstring, "called 3 times", ss.str());
+}
+
+TEST(BetweenTest, OnDifferentStartAndEnd) {
+  const Cardinality c = Between(3, 5);
+
+  EXPECT_FALSE(c.IsSatisfiedByCallCount(2));
+  EXPECT_FALSE(c.IsSaturatedByCallCount(2));
+
+  EXPECT_TRUE(c.IsSatisfiedByCallCount(3));
+  EXPECT_FALSE(c.IsSaturatedByCallCount(3));
+
+  EXPECT_TRUE(c.IsSatisfiedByCallCount(5));
+  EXPECT_TRUE(c.IsSaturatedByCallCount(5));
+
+  EXPECT_FALSE(c.IsSatisfiedByCallCount(6));
+  EXPECT_TRUE(c.IsSaturatedByCallCount(6));
+
+  stringstream ss;
+  c.DescribeTo(&ss);
+  EXPECT_PRED_FORMAT2(IsSubstring, "called between 3 and 5 times", ss.str());
+}
+
+TEST(BetweenTest, HasCorrectBounds) {
+  const Cardinality c = Between(3, 5);
+  EXPECT_EQ(3, c.ConservativeLowerBound());
+  EXPECT_EQ(5, c.ConservativeUpperBound());
+}
+
+// Tests Exactly(n).
+
+TEST(ExactlyTest, OnNegativeNumber) {
+  EXPECT_NONFATAL_FAILURE(
+      {  // NOLINT
+        Exactly(-1);
+      },
+      "The invocation lower bound must be >= 0");
+}
+
+TEST(ExactlyTest, OnZero) {
+  const Cardinality c = Exactly(0);
+  EXPECT_TRUE(c.IsSatisfiedByCallCount(0));
+  EXPECT_TRUE(c.IsSaturatedByCallCount(0));
+
+  EXPECT_FALSE(c.IsSatisfiedByCallCount(1));
+  EXPECT_TRUE(c.IsSaturatedByCallCount(1));
+
+  stringstream ss;
+  c.DescribeTo(&ss);
+  EXPECT_PRED_FORMAT2(IsSubstring, "never called", ss.str());
+}
+
+TEST(ExactlyTest, OnPositiveNumber) {
+  const Cardinality c = Exactly(2);
+  EXPECT_FALSE(c.IsSatisfiedByCallCount(0));
+  EXPECT_FALSE(c.IsSaturatedByCallCount(0));
+
+  EXPECT_TRUE(c.IsSatisfiedByCallCount(2));
+  EXPECT_TRUE(c.IsSaturatedByCallCount(2));
+
+  stringstream ss1;
+  Exactly(1).DescribeTo(&ss1);
+  EXPECT_PRED_FORMAT2(IsSubstring, "called once", ss1.str());
+
+  stringstream ss2;
+  c.DescribeTo(&ss2);
+  EXPECT_PRED_FORMAT2(IsSubstring, "called twice", ss2.str());
+
+  stringstream ss3;
+  Exactly(3).DescribeTo(&ss3);
+  EXPECT_PRED_FORMAT2(IsSubstring, "called 3 times", ss3.str());
+}
+
+TEST(ExactlyTest, HasCorrectBounds) {
+  const Cardinality c = Exactly(3);
+  EXPECT_EQ(3, c.ConservativeLowerBound());
+  EXPECT_EQ(3, c.ConservativeUpperBound());
+}
+
+// Tests that a user can make their own cardinality by implementing
+// CardinalityInterface and calling MakeCardinality().
+
+class EvenCardinality : public CardinalityInterface {
+ public:
+  // Returns true if and only if call_count calls will satisfy this
+  // cardinality.
+  bool IsSatisfiedByCallCount(int call_count) const override {
+    return (call_count % 2 == 0);
+  }
+
+  // Returns true if and only if call_count calls will saturate this
+  // cardinality.
+  bool IsSaturatedByCallCount(int /* call_count */) const override {
+    return false;
+  }
+
+  // Describes self to an ostream.
+  void DescribeTo(::std::ostream* ss) const override {
+    *ss << "called even number of times";
+  }
+};
+
+TEST(MakeCardinalityTest, ConstructsCardinalityFromInterface) {
+  const Cardinality c = MakeCardinality(new EvenCardinality);
+
+  EXPECT_TRUE(c.IsSatisfiedByCallCount(2));
+  EXPECT_FALSE(c.IsSatisfiedByCallCount(3));
+
+  EXPECT_FALSE(c.IsSaturatedByCallCount(10000));
+
+  stringstream ss;
+  c.DescribeTo(&ss);
+  EXPECT_EQ("called even number of times", ss.str());
+}
+
+}  // Unnamed namespace
diff --git a/third_party/googletest/googlemock/test/gmock-function-mocker_test.cc b/third_party/googletest/googlemock/test/gmock-function-mocker_test.cc
new file mode 100644
index 0000000..f7b31ae
--- /dev/null
+++ b/third_party/googletest/googlemock/test/gmock-function-mocker_test.cc
@@ -0,0 +1,998 @@
+// Copyright 2007, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Google Mock - a framework for writing C++ mock classes.
+//
+// This file tests the function mocker classes.
+#include "gmock/gmock-function-mocker.h"
+
+// Silence C4503 (decorated name length exceeded) for MSVC.
+GTEST_DISABLE_MSC_WARNINGS_PUSH_(4503)
+
+#ifdef GTEST_OS_WINDOWS
+// MSDN says the header file to be included for STDMETHOD is BaseTyps.h but
+// we are getting compiler errors if we use basetyps.h, hence including
+// objbase.h for definition of STDMETHOD.
+#include <objbase.h>
+#endif  // GTEST_OS_WINDOWS
+
+#include <functional>
+#include <map>
+#include <string>
+#include <type_traits>
+
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+
+namespace testing {
+namespace gmock_function_mocker_test {
+
+using testing::_;
+using testing::A;
+using testing::An;
+using testing::AnyNumber;
+using testing::Const;
+using testing::DoDefault;
+using testing::Eq;
+using testing::Lt;
+using testing::MockFunction;
+using testing::Ref;
+using testing::Return;
+using testing::ReturnRef;
+using testing::TypedEq;
+
+template <typename T>
+class TemplatedCopyable {
+ public:
+  TemplatedCopyable() = default;
+
+  template <typename U>
+  TemplatedCopyable(const U& other) {}  // NOLINT
+};
+
+class FooInterface {
+ public:
+  virtual ~FooInterface() = default;
+
+  virtual void VoidReturning(int x) = 0;
+
+  virtual int Nullary() = 0;
+  virtual bool Unary(int x) = 0;
+  virtual long Binary(short x, int y) = 0;                     // NOLINT
+  virtual int Decimal(bool b, char c, short d, int e, long f,  // NOLINT
+                      float g, double h, unsigned i, char* j,
+                      const std::string& k) = 0;
+
+  virtual bool TakesNonConstReference(int& n) = 0;  // NOLINT
+  virtual std::string TakesConstReference(const int& n) = 0;
+  virtual bool TakesConst(const int x) = 0;
+
+  virtual int OverloadedOnArgumentNumber() = 0;
+  virtual int OverloadedOnArgumentNumber(int n) = 0;
+
+  virtual int OverloadedOnArgumentType(int n) = 0;
+  virtual char OverloadedOnArgumentType(char c) = 0;
+
+  virtual int OverloadedOnConstness() = 0;
+  virtual char OverloadedOnConstness() const = 0;
+
+  virtual int TypeWithHole(int (*func)()) = 0;
+  virtual int TypeWithComma(const std::map<int, std::string>& a_map) = 0;
+  virtual int TypeWithTemplatedCopyCtor(const TemplatedCopyable<int>&) = 0;
+
+  virtual int (*ReturnsFunctionPointer1(int))(bool) = 0;
+  using fn_ptr = int (*)(bool);
+  virtual fn_ptr ReturnsFunctionPointer2(int) = 0;
+
+  virtual int RefQualifiedConstRef() const& = 0;
+  virtual int RefQualifiedConstRefRef() const&& = 0;
+  virtual int RefQualifiedRef() & = 0;
+  virtual int RefQualifiedRefRef() && = 0;
+
+  virtual int RefQualifiedOverloaded() const& = 0;
+  virtual int RefQualifiedOverloaded() const&& = 0;
+  virtual int RefQualifiedOverloaded() & = 0;
+  virtual int RefQualifiedOverloaded() && = 0;
+
+#ifdef GTEST_OS_WINDOWS
+  STDMETHOD_(int, CTNullary)() = 0;
+  STDMETHOD_(bool, CTUnary)(int x) = 0;
+  STDMETHOD_(int, CTDecimal)
+  (bool b, char c, short d, int e, long f,  // NOLINT
+   float g, double h, unsigned i, char* j, const std::string& k) = 0;
+  STDMETHOD_(char, CTConst)(int x) const = 0;
+#endif  // GTEST_OS_WINDOWS
+};
+
+// Const qualifiers on arguments were once (incorrectly) considered
+// significant in determining whether two virtual functions had the same
+// signature. This was fixed in Visual Studio 2008. However, the compiler
+// still emits a warning that alerts about this change in behavior.
+GTEST_DISABLE_MSC_WARNINGS_PUSH_(4373)
+class MockFoo : public FooInterface {
+ public:
+  MockFoo() = default;
+
+  // Makes sure that a mock function parameter can be named.
+  MOCK_METHOD(void, VoidReturning, (int n));  // NOLINT
+
+  MOCK_METHOD(int, Nullary, ());  // NOLINT
+
+  // Makes sure that a mock function parameter can be unnamed.
+  MOCK_METHOD(bool, Unary, (int));          // NOLINT
+  MOCK_METHOD(long, Binary, (short, int));  // NOLINT
+  MOCK_METHOD(int, Decimal,
+              (bool, char, short, int, long, float,  // NOLINT
+               double, unsigned, char*, const std::string& str),
+              (override));
+
+  MOCK_METHOD(bool, TakesNonConstReference, (int&));  // NOLINT
+  MOCK_METHOD(std::string, TakesConstReference, (const int&));
+  MOCK_METHOD(bool, TakesConst, (const int));  // NOLINT
+
+  // Tests that the function return type can contain unprotected comma.
+  MOCK_METHOD((std::map<int, std::string>), ReturnTypeWithComma, (), ());
+  MOCK_METHOD((std::map<int, std::string>), ReturnTypeWithComma, (int),
+              (const));  // NOLINT
+
+  MOCK_METHOD(int, OverloadedOnArgumentNumber, ());     // NOLINT
+  MOCK_METHOD(int, OverloadedOnArgumentNumber, (int));  // NOLINT
+
+  MOCK_METHOD(int, OverloadedOnArgumentType, (int));    // NOLINT
+  MOCK_METHOD(char, OverloadedOnArgumentType, (char));  // NOLINT
+
+  MOCK_METHOD(int, OverloadedOnConstness, (), (override));          // NOLINT
+  MOCK_METHOD(char, OverloadedOnConstness, (), (override, const));  // NOLINT
+
+  MOCK_METHOD(int, TypeWithHole, (int (*)()), ());  // NOLINT
+  MOCK_METHOD(int, TypeWithComma, ((const std::map<int, std::string>&)));
+  MOCK_METHOD(int, TypeWithTemplatedCopyCtor,
+              (const TemplatedCopyable<int>&));  // NOLINT
+
+  MOCK_METHOD(int (*)(bool), ReturnsFunctionPointer1, (int), ());
+  MOCK_METHOD(fn_ptr, ReturnsFunctionPointer2, (int), ());
+
+#ifdef GTEST_OS_WINDOWS
+  MOCK_METHOD(int, CTNullary, (), (Calltype(STDMETHODCALLTYPE)));
+  MOCK_METHOD(bool, CTUnary, (int), (Calltype(STDMETHODCALLTYPE)));
+  MOCK_METHOD(int, CTDecimal,
+              (bool b, char c, short d, int e, long f, float g, double h,
+               unsigned i, char* j, const std::string& k),
+              (Calltype(STDMETHODCALLTYPE)));
+  MOCK_METHOD(char, CTConst, (int), (const, Calltype(STDMETHODCALLTYPE)));
+  MOCK_METHOD((std::map<int, std::string>), CTReturnTypeWithComma, (),
+              (Calltype(STDMETHODCALLTYPE)));
+#endif  // GTEST_OS_WINDOWS
+
+  // Test reference qualified functions.
+  MOCK_METHOD(int, RefQualifiedConstRef, (), (const, ref(&), override));
+  MOCK_METHOD(int, RefQualifiedConstRefRef, (), (const, ref(&&), override));
+  MOCK_METHOD(int, RefQualifiedRef, (), (ref(&), override));
+  MOCK_METHOD(int, RefQualifiedRefRef, (), (ref(&&), override));
+
+  MOCK_METHOD(int, RefQualifiedOverloaded, (), (const, ref(&), override));
+  MOCK_METHOD(int, RefQualifiedOverloaded, (), (const, ref(&&), override));
+  MOCK_METHOD(int, RefQualifiedOverloaded, (), (ref(&), override));
+  MOCK_METHOD(int, RefQualifiedOverloaded, (), (ref(&&), override));
+
+ private:
+  MockFoo(const MockFoo&) = delete;
+  MockFoo& operator=(const MockFoo&) = delete;
+};
+
+class LegacyMockFoo : public FooInterface {
+ public:
+  LegacyMockFoo() = default;
+
+  // Makes sure that a mock function parameter can be named.
+  MOCK_METHOD1(VoidReturning, void(int n));  // NOLINT
+
+  MOCK_METHOD0(Nullary, int());  // NOLINT
+
+  // Makes sure that a mock function parameter can be unnamed.
+  MOCK_METHOD1(Unary, bool(int));                                  // NOLINT
+  MOCK_METHOD2(Binary, long(short, int));                          // NOLINT
+  MOCK_METHOD10(Decimal, int(bool, char, short, int, long, float,  // NOLINT
+                             double, unsigned, char*, const std::string& str));
+
+  MOCK_METHOD1(TakesNonConstReference, bool(int&));  // NOLINT
+  MOCK_METHOD1(TakesConstReference, std::string(const int&));
+  MOCK_METHOD1(TakesConst, bool(const int));  // NOLINT
+
+  // Tests that the function return type can contain unprotected comma.
+  MOCK_METHOD0(ReturnTypeWithComma, std::map<int, std::string>());
+  MOCK_CONST_METHOD1(ReturnTypeWithComma,
+                     std::map<int, std::string>(int));  // NOLINT
+
+  MOCK_METHOD0(OverloadedOnArgumentNumber, int());     // NOLINT
+  MOCK_METHOD1(OverloadedOnArgumentNumber, int(int));  // NOLINT
+
+  MOCK_METHOD1(OverloadedOnArgumentType, int(int));    // NOLINT
+  MOCK_METHOD1(OverloadedOnArgumentType, char(char));  // NOLINT
+
+  MOCK_METHOD0(OverloadedOnConstness, int());         // NOLINT
+  MOCK_CONST_METHOD0(OverloadedOnConstness, char());  // NOLINT
+
+  MOCK_METHOD1(TypeWithHole, int(int (*)()));  // NOLINT
+  MOCK_METHOD1(TypeWithComma,
+               int(const std::map<int, std::string>&));  // NOLINT
+  MOCK_METHOD1(TypeWithTemplatedCopyCtor,
+               int(const TemplatedCopyable<int>&));  // NOLINT
+
+  MOCK_METHOD1(ReturnsFunctionPointer1, int (*(int))(bool));
+  MOCK_METHOD1(ReturnsFunctionPointer2, fn_ptr(int));
+
+#ifdef GTEST_OS_WINDOWS
+  MOCK_METHOD0_WITH_CALLTYPE(STDMETHODCALLTYPE, CTNullary, int());
+  MOCK_METHOD1_WITH_CALLTYPE(STDMETHODCALLTYPE, CTUnary, bool(int));  // NOLINT
+  MOCK_METHOD10_WITH_CALLTYPE(STDMETHODCALLTYPE, CTDecimal,
+                              int(bool b, char c, short d, int e,  // NOLINT
+                                  long f, float g, double h,       // NOLINT
+                                  unsigned i, char* j, const std::string& k));
+  MOCK_CONST_METHOD1_WITH_CALLTYPE(STDMETHODCALLTYPE, CTConst,
+                                   char(int));  // NOLINT
+
+  // Tests that the function return type can contain unprotected comma.
+  MOCK_METHOD0_WITH_CALLTYPE(STDMETHODCALLTYPE, CTReturnTypeWithComma,
+                             std::map<int, std::string>());
+#endif  // GTEST_OS_WINDOWS
+
+  // We can't mock these with the old macros, but we need to define them to make
+  // it concrete.
+  int RefQualifiedConstRef() const& override { return 0; }
+  int RefQualifiedConstRefRef() const&& override { return 0; }
+  int RefQualifiedRef() & override { return 0; }
+  int RefQualifiedRefRef() && override { return 0; }
+  int RefQualifiedOverloaded() const& override { return 0; }
+  int RefQualifiedOverloaded() const&& override { return 0; }
+  int RefQualifiedOverloaded() & override { return 0; }
+  int RefQualifiedOverloaded() && override { return 0; }
+
+ private:
+  LegacyMockFoo(const LegacyMockFoo&) = delete;
+  LegacyMockFoo& operator=(const LegacyMockFoo&) = delete;
+};
+
+GTEST_DISABLE_MSC_WARNINGS_POP_()  // 4373
+
+template <class T>
+class FunctionMockerTest : public testing::Test {
+ protected:
+  FunctionMockerTest() : foo_(&mock_foo_) {}
+
+  FooInterface* const foo_;
+  T mock_foo_;
+};
+using FunctionMockerTestTypes = ::testing::Types<MockFoo, LegacyMockFoo>;
+TYPED_TEST_SUITE(FunctionMockerTest, FunctionMockerTestTypes);
+
+// Tests mocking a void-returning function.
+TYPED_TEST(FunctionMockerTest, MocksVoidFunction) {
+  EXPECT_CALL(this->mock_foo_, VoidReturning(Lt(100)));
+  this->foo_->VoidReturning(0);
+}
+
+// Tests mocking a nullary function.
+TYPED_TEST(FunctionMockerTest, MocksNullaryFunction) {
+  EXPECT_CALL(this->mock_foo_, Nullary())
+      .WillOnce(DoDefault())
+      .WillOnce(Return(1));
+
+  EXPECT_EQ(0, this->foo_->Nullary());
+  EXPECT_EQ(1, this->foo_->Nullary());
+}
+
+// Tests mocking a unary function.
+TYPED_TEST(FunctionMockerTest, MocksUnaryFunction) {
+  EXPECT_CALL(this->mock_foo_, Unary(Eq(2))).Times(2).WillOnce(Return(true));
+
+  EXPECT_TRUE(this->foo_->Unary(2));
+  EXPECT_FALSE(this->foo_->Unary(2));
+}
+
+// Tests mocking a binary function.
+TYPED_TEST(FunctionMockerTest, MocksBinaryFunction) {
+  EXPECT_CALL(this->mock_foo_, Binary(2, _)).WillOnce(Return(3));
+
+  EXPECT_EQ(3, this->foo_->Binary(2, 1));
+}
+
+// Tests mocking a decimal function.
+TYPED_TEST(FunctionMockerTest, MocksDecimalFunction) {
+  EXPECT_CALL(this->mock_foo_,
+              Decimal(true, 'a', 0, 0, 1L, A<float>(), Lt(100), 5U, NULL, "hi"))
+      .WillOnce(Return(5));
+
+  EXPECT_EQ(5, this->foo_->Decimal(true, 'a', 0, 0, 1, 0, 0, 5, nullptr, "hi"));
+}
+
+// Tests mocking a function that takes a non-const reference.
+TYPED_TEST(FunctionMockerTest, MocksFunctionWithNonConstReferenceArgument) {
+  int a = 0;
+  EXPECT_CALL(this->mock_foo_, TakesNonConstReference(Ref(a)))
+      .WillOnce(Return(true));
+
+  EXPECT_TRUE(this->foo_->TakesNonConstReference(a));
+}
+
+// Tests mocking a function that takes a const reference.
+TYPED_TEST(FunctionMockerTest, MocksFunctionWithConstReferenceArgument) {
+  int a = 0;
+  EXPECT_CALL(this->mock_foo_, TakesConstReference(Ref(a)))
+      .WillOnce(Return("Hello"));
+
+  EXPECT_EQ("Hello", this->foo_->TakesConstReference(a));
+}
+
+// Tests mocking a function that takes a const variable.
+TYPED_TEST(FunctionMockerTest, MocksFunctionWithConstArgument) {
+  EXPECT_CALL(this->mock_foo_, TakesConst(Lt(10))).WillOnce(DoDefault());
+
+  EXPECT_FALSE(this->foo_->TakesConst(5));
+}
+
+// Tests mocking functions overloaded on the number of arguments.
+TYPED_TEST(FunctionMockerTest, MocksFunctionsOverloadedOnArgumentNumber) {
+  EXPECT_CALL(this->mock_foo_, OverloadedOnArgumentNumber())
+      .WillOnce(Return(1));
+  EXPECT_CALL(this->mock_foo_, OverloadedOnArgumentNumber(_))
+      .WillOnce(Return(2));
+
+  EXPECT_EQ(2, this->foo_->OverloadedOnArgumentNumber(1));
+  EXPECT_EQ(1, this->foo_->OverloadedOnArgumentNumber());
+}
+
+// Tests mocking functions overloaded on the types of argument.
+TYPED_TEST(FunctionMockerTest, MocksFunctionsOverloadedOnArgumentType) {
+  EXPECT_CALL(this->mock_foo_, OverloadedOnArgumentType(An<int>()))
+      .WillOnce(Return(1));
+  EXPECT_CALL(this->mock_foo_, OverloadedOnArgumentType(TypedEq<char>('a')))
+      .WillOnce(Return('b'));
+
+  EXPECT_EQ(1, this->foo_->OverloadedOnArgumentType(0));
+  EXPECT_EQ('b', this->foo_->OverloadedOnArgumentType('a'));
+}
+
+// Tests mocking functions overloaded on the const-ness of this object.
+TYPED_TEST(FunctionMockerTest, MocksFunctionsOverloadedOnConstnessOfThis) {
+  EXPECT_CALL(this->mock_foo_, OverloadedOnConstness());
+  EXPECT_CALL(Const(this->mock_foo_), OverloadedOnConstness())
+      .WillOnce(Return('a'));
+
+  EXPECT_EQ(0, this->foo_->OverloadedOnConstness());
+  EXPECT_EQ('a', Const(*this->foo_).OverloadedOnConstness());
+}
+
+TYPED_TEST(FunctionMockerTest, MocksReturnTypeWithComma) {
+  const std::map<int, std::string> a_map;
+  EXPECT_CALL(this->mock_foo_, ReturnTypeWithComma()).WillOnce(Return(a_map));
+  EXPECT_CALL(this->mock_foo_, ReturnTypeWithComma(42)).WillOnce(Return(a_map));
+
+  EXPECT_EQ(a_map, this->mock_foo_.ReturnTypeWithComma());
+  EXPECT_EQ(a_map, this->mock_foo_.ReturnTypeWithComma(42));
+}
+
+TYPED_TEST(FunctionMockerTest, MocksTypeWithTemplatedCopyCtor) {
+  EXPECT_CALL(this->mock_foo_, TypeWithTemplatedCopyCtor(_))
+      .WillOnce(Return(true));
+  EXPECT_TRUE(this->foo_->TypeWithTemplatedCopyCtor(TemplatedCopyable<int>()));
+}
+
+#ifdef GTEST_OS_WINDOWS
+// Tests mocking a nullary function with calltype.
+TYPED_TEST(FunctionMockerTest, MocksNullaryFunctionWithCallType) {
+  EXPECT_CALL(this->mock_foo_, CTNullary())
+      .WillOnce(Return(-1))
+      .WillOnce(Return(0));
+
+  EXPECT_EQ(-1, this->foo_->CTNullary());
+  EXPECT_EQ(0, this->foo_->CTNullary());
+}
+
+// Tests mocking a unary function with calltype.
+TYPED_TEST(FunctionMockerTest, MocksUnaryFunctionWithCallType) {
+  EXPECT_CALL(this->mock_foo_, CTUnary(Eq(2)))
+      .Times(2)
+      .WillOnce(Return(true))
+      .WillOnce(Return(false));
+
+  EXPECT_TRUE(this->foo_->CTUnary(2));
+  EXPECT_FALSE(this->foo_->CTUnary(2));
+}
+
+// Tests mocking a decimal function with calltype.
+TYPED_TEST(FunctionMockerTest, MocksDecimalFunctionWithCallType) {
+  EXPECT_CALL(this->mock_foo_, CTDecimal(true, 'a', 0, 0, 1L, A<float>(),
+                                         Lt(100), 5U, NULL, "hi"))
+      .WillOnce(Return(10));
+
+  EXPECT_EQ(10, this->foo_->CTDecimal(true, 'a', 0, 0, 1, 0, 0, 5, NULL, "hi"));
+}
+
+// Tests mocking functions overloaded on the const-ness of this object.
+TYPED_TEST(FunctionMockerTest, MocksFunctionsConstFunctionWithCallType) {
+  EXPECT_CALL(Const(this->mock_foo_), CTConst(_)).WillOnce(Return('a'));
+
+  EXPECT_EQ('a', Const(*this->foo_).CTConst(0));
+}
+
+TYPED_TEST(FunctionMockerTest, MocksReturnTypeWithCommaAndCallType) {
+  const std::map<int, std::string> a_map;
+  EXPECT_CALL(this->mock_foo_, CTReturnTypeWithComma()).WillOnce(Return(a_map));
+
+  EXPECT_EQ(a_map, this->mock_foo_.CTReturnTypeWithComma());
+}
+
+#endif  // GTEST_OS_WINDOWS
+
+TEST(FunctionMockerTest, RefQualified) {
+  MockFoo mock_foo;
+
+  EXPECT_CALL(mock_foo, RefQualifiedConstRef).WillOnce(Return(1));
+  EXPECT_CALL(std::move(mock_foo),  // NOLINT
+              RefQualifiedConstRefRef)
+      .WillOnce(Return(2));
+  EXPECT_CALL(mock_foo, RefQualifiedRef).WillOnce(Return(3));
+  EXPECT_CALL(std::move(mock_foo),  // NOLINT
+              RefQualifiedRefRef)
+      .WillOnce(Return(4));
+
+  EXPECT_CALL(static_cast<const MockFoo&>(mock_foo), RefQualifiedOverloaded())
+      .WillOnce(Return(5));
+  EXPECT_CALL(static_cast<const MockFoo&&>(mock_foo), RefQualifiedOverloaded())
+      .WillOnce(Return(6));
+  EXPECT_CALL(static_cast<MockFoo&>(mock_foo), RefQualifiedOverloaded())
+      .WillOnce(Return(7));
+  EXPECT_CALL(static_cast<MockFoo&&>(mock_foo), RefQualifiedOverloaded())
+      .WillOnce(Return(8));
+
+  EXPECT_EQ(mock_foo.RefQualifiedConstRef(), 1);
+  EXPECT_EQ(std::move(mock_foo).RefQualifiedConstRefRef(), 2);  // NOLINT
+  EXPECT_EQ(mock_foo.RefQualifiedRef(), 3);
+  EXPECT_EQ(std::move(mock_foo).RefQualifiedRefRef(), 4);  // NOLINT
+
+  EXPECT_EQ(std::cref(mock_foo).get().RefQualifiedOverloaded(), 5);
+  EXPECT_EQ(std::move(std::cref(mock_foo).get())  // NOLINT
+                .RefQualifiedOverloaded(),
+            6);
+  EXPECT_EQ(mock_foo.RefQualifiedOverloaded(), 7);
+  EXPECT_EQ(std::move(mock_foo).RefQualifiedOverloaded(), 8);  // NOLINT
+}
+
+class MockB {
+ public:
+  MockB() = default;
+
+  MOCK_METHOD(void, DoB, ());
+
+ private:
+  MockB(const MockB&) = delete;
+  MockB& operator=(const MockB&) = delete;
+};
+
+class LegacyMockB {
+ public:
+  LegacyMockB() = default;
+
+  MOCK_METHOD0(DoB, void());
+
+ private:
+  LegacyMockB(const LegacyMockB&) = delete;
+  LegacyMockB& operator=(const LegacyMockB&) = delete;
+};
+
+template <typename T>
+class ExpectCallTest : public ::testing::Test {};
+using ExpectCallTestTypes = ::testing::Types<MockB, LegacyMockB>;
+TYPED_TEST_SUITE(ExpectCallTest, ExpectCallTestTypes);
+
+// Tests that functions with no EXPECT_CALL() rules can be called any
+// number of times.
+TYPED_TEST(ExpectCallTest, UnmentionedFunctionCanBeCalledAnyNumberOfTimes) {
+  { TypeParam b; }
+
+  {
+    TypeParam b;
+    b.DoB();
+  }
+
+  {
+    TypeParam b;
+    b.DoB();
+    b.DoB();
+  }
+}
+
+// Tests mocking template interfaces.
+
+template <typename T>
+class StackInterface {
+ public:
+  virtual ~StackInterface() = default;
+
+  // Template parameter appears in function parameter.
+  virtual void Push(const T& value) = 0;
+  virtual void Pop() = 0;
+  virtual int GetSize() const = 0;
+  // Template parameter appears in function return type.
+  virtual const T& GetTop() const = 0;
+};
+
+template <typename T>
+class MockStack : public StackInterface<T> {
+ public:
+  MockStack() = default;
+
+  MOCK_METHOD(void, Push, (const T& elem), ());
+  MOCK_METHOD(void, Pop, (), (final));
+  MOCK_METHOD(int, GetSize, (), (const, override));
+  MOCK_METHOD(const T&, GetTop, (), (const));
+
+  // Tests that the function return type can contain unprotected comma.
+  MOCK_METHOD((std::map<int, int>), ReturnTypeWithComma, (), ());
+  MOCK_METHOD((std::map<int, int>), ReturnTypeWithComma, (int), (const));
+
+ private:
+  MockStack(const MockStack&) = delete;
+  MockStack& operator=(const MockStack&) = delete;
+};
+
+template <typename T>
+class LegacyMockStack : public StackInterface<T> {
+ public:
+  LegacyMockStack() = default;
+
+  MOCK_METHOD1_T(Push, void(const T& elem));
+  MOCK_METHOD0_T(Pop, void());
+  MOCK_CONST_METHOD0_T(GetSize, int());  // NOLINT
+  MOCK_CONST_METHOD0_T(GetTop, const T&());
+
+  // Tests that the function return type can contain unprotected comma.
+  MOCK_METHOD0_T(ReturnTypeWithComma, std::map<int, int>());
+  MOCK_CONST_METHOD1_T(ReturnTypeWithComma, std::map<int, int>(int));  // NOLINT
+
+ private:
+  LegacyMockStack(const LegacyMockStack&) = delete;
+  LegacyMockStack& operator=(const LegacyMockStack&) = delete;
+};
+
+template <typename T>
+class TemplateMockTest : public ::testing::Test {};
+using TemplateMockTestTypes =
+    ::testing::Types<MockStack<int>, LegacyMockStack<int>>;
+TYPED_TEST_SUITE(TemplateMockTest, TemplateMockTestTypes);
+
+// Tests that template mock works.
+TYPED_TEST(TemplateMockTest, Works) {
+  TypeParam mock;
+
+  EXPECT_CALL(mock, GetSize())
+      .WillOnce(Return(0))
+      .WillOnce(Return(1))
+      .WillOnce(Return(0));
+  EXPECT_CALL(mock, Push(_));
+  int n = 5;
+  EXPECT_CALL(mock, GetTop()).WillOnce(ReturnRef(n));
+  EXPECT_CALL(mock, Pop()).Times(AnyNumber());
+
+  EXPECT_EQ(0, mock.GetSize());
+  mock.Push(5);
+  EXPECT_EQ(1, mock.GetSize());
+  EXPECT_EQ(5, mock.GetTop());
+  mock.Pop();
+  EXPECT_EQ(0, mock.GetSize());
+}
+
+TYPED_TEST(TemplateMockTest, MethodWithCommaInReturnTypeWorks) {
+  TypeParam mock;
+
+  const std::map<int, int> a_map;
+  EXPECT_CALL(mock, ReturnTypeWithComma()).WillOnce(Return(a_map));
+  EXPECT_CALL(mock, ReturnTypeWithComma(1)).WillOnce(Return(a_map));
+
+  EXPECT_EQ(a_map, mock.ReturnTypeWithComma());
+  EXPECT_EQ(a_map, mock.ReturnTypeWithComma(1));
+}
+
+#ifdef GTEST_OS_WINDOWS
+// Tests mocking template interfaces with calltype.
+
+template <typename T>
+class StackInterfaceWithCallType {
+ public:
+  virtual ~StackInterfaceWithCallType() {}
+
+  // Template parameter appears in function parameter.
+  STDMETHOD_(void, Push)(const T& value) = 0;
+  STDMETHOD_(void, Pop)() = 0;
+  STDMETHOD_(int, GetSize)() const = 0;
+  // Template parameter appears in function return type.
+  STDMETHOD_(const T&, GetTop)() const = 0;
+};
+
+template <typename T>
+class MockStackWithCallType : public StackInterfaceWithCallType<T> {
+ public:
+  MockStackWithCallType() {}
+
+  MOCK_METHOD(void, Push, (const T& elem),
+              (Calltype(STDMETHODCALLTYPE), override));
+  MOCK_METHOD(void, Pop, (), (Calltype(STDMETHODCALLTYPE), override));
+  MOCK_METHOD(int, GetSize, (), (Calltype(STDMETHODCALLTYPE), override, const));
+  MOCK_METHOD(const T&, GetTop, (),
+              (Calltype(STDMETHODCALLTYPE), override, const));
+
+ private:
+  MockStackWithCallType(const MockStackWithCallType&) = delete;
+  MockStackWithCallType& operator=(const MockStackWithCallType&) = delete;
+};
+
+template <typename T>
+class LegacyMockStackWithCallType : public StackInterfaceWithCallType<T> {
+ public:
+  LegacyMockStackWithCallType() {}
+
+  MOCK_METHOD1_T_WITH_CALLTYPE(STDMETHODCALLTYPE, Push, void(const T& elem));
+  MOCK_METHOD0_T_WITH_CALLTYPE(STDMETHODCALLTYPE, Pop, void());
+  MOCK_CONST_METHOD0_T_WITH_CALLTYPE(STDMETHODCALLTYPE, GetSize, int());
+  MOCK_CONST_METHOD0_T_WITH_CALLTYPE(STDMETHODCALLTYPE, GetTop, const T&());
+
+ private:
+  LegacyMockStackWithCallType(const LegacyMockStackWithCallType&) = delete;
+  LegacyMockStackWithCallType& operator=(const LegacyMockStackWithCallType&) =
+      delete;
+};
+
+template <typename T>
+class TemplateMockTestWithCallType : public ::testing::Test {};
+using TemplateMockTestWithCallTypeTypes =
+    ::testing::Types<MockStackWithCallType<int>,
+                     LegacyMockStackWithCallType<int>>;
+TYPED_TEST_SUITE(TemplateMockTestWithCallType,
+                 TemplateMockTestWithCallTypeTypes);
+
+// Tests that template mock with calltype works.
+TYPED_TEST(TemplateMockTestWithCallType, Works) {
+  TypeParam mock;
+
+  EXPECT_CALL(mock, GetSize())
+      .WillOnce(Return(0))
+      .WillOnce(Return(1))
+      .WillOnce(Return(0));
+  EXPECT_CALL(mock, Push(_));
+  int n = 5;
+  EXPECT_CALL(mock, GetTop()).WillOnce(ReturnRef(n));
+  EXPECT_CALL(mock, Pop()).Times(AnyNumber());
+
+  EXPECT_EQ(0, mock.GetSize());
+  mock.Push(5);
+  EXPECT_EQ(1, mock.GetSize());
+  EXPECT_EQ(5, mock.GetTop());
+  mock.Pop();
+  EXPECT_EQ(0, mock.GetSize());
+}
+#endif  // GTEST_OS_WINDOWS
+
+#define MY_MOCK_METHODS1_                       \
+  MOCK_METHOD(void, Overloaded, ());            \
+  MOCK_METHOD(int, Overloaded, (int), (const)); \
+  MOCK_METHOD(bool, Overloaded, (bool f, int n))
+
+#define LEGACY_MY_MOCK_METHODS1_              \
+  MOCK_METHOD0(Overloaded, void());           \
+  MOCK_CONST_METHOD1(Overloaded, int(int n)); \
+  MOCK_METHOD2(Overloaded, bool(bool f, int n))
+
+class MockOverloadedOnArgNumber {
+ public:
+  MockOverloadedOnArgNumber() = default;
+
+  MY_MOCK_METHODS1_;
+
+ private:
+  MockOverloadedOnArgNumber(const MockOverloadedOnArgNumber&) = delete;
+  MockOverloadedOnArgNumber& operator=(const MockOverloadedOnArgNumber&) =
+      delete;
+};
+
+class LegacyMockOverloadedOnArgNumber {
+ public:
+  LegacyMockOverloadedOnArgNumber() = default;
+
+  LEGACY_MY_MOCK_METHODS1_;
+
+ private:
+  LegacyMockOverloadedOnArgNumber(const LegacyMockOverloadedOnArgNumber&) =
+      delete;
+  LegacyMockOverloadedOnArgNumber& operator=(
+      const LegacyMockOverloadedOnArgNumber&) = delete;
+};
+
+template <typename T>
+class OverloadedMockMethodTest : public ::testing::Test {};
+using OverloadedMockMethodTestTypes =
+    ::testing::Types<MockOverloadedOnArgNumber,
+                     LegacyMockOverloadedOnArgNumber>;
+TYPED_TEST_SUITE(OverloadedMockMethodTest, OverloadedMockMethodTestTypes);
+
+TYPED_TEST(OverloadedMockMethodTest, CanOverloadOnArgNumberInMacroBody) {
+  TypeParam mock;
+  EXPECT_CALL(mock, Overloaded());
+  EXPECT_CALL(mock, Overloaded(1)).WillOnce(Return(2));
+  EXPECT_CALL(mock, Overloaded(true, 1)).WillOnce(Return(true));
+
+  mock.Overloaded();
+  EXPECT_EQ(2, mock.Overloaded(1));
+  EXPECT_TRUE(mock.Overloaded(true, 1));
+}
+
+#define MY_MOCK_METHODS2_                     \
+  MOCK_CONST_METHOD1(Overloaded, int(int n)); \
+  MOCK_METHOD1(Overloaded, int(int n))
+
+class MockOverloadedOnConstness {
+ public:
+  MockOverloadedOnConstness() = default;
+
+  MY_MOCK_METHODS2_;
+
+ private:
+  MockOverloadedOnConstness(const MockOverloadedOnConstness&) = delete;
+  MockOverloadedOnConstness& operator=(const MockOverloadedOnConstness&) =
+      delete;
+};
+
+TEST(MockMethodOverloadedMockMethodTest, CanOverloadOnConstnessInMacroBody) {
+  MockOverloadedOnConstness mock;
+  const MockOverloadedOnConstness* const_mock = &mock;
+  EXPECT_CALL(mock, Overloaded(1)).WillOnce(Return(2));
+  EXPECT_CALL(*const_mock, Overloaded(1)).WillOnce(Return(3));
+
+  EXPECT_EQ(2, mock.Overloaded(1));
+  EXPECT_EQ(3, const_mock->Overloaded(1));
+}
+
+TEST(MockMethodMockFunctionTest, WorksForVoidNullary) {
+  MockFunction<void()> foo;
+  EXPECT_CALL(foo, Call());
+  foo.Call();
+}
+
+TEST(MockMethodMockFunctionTest, WorksForNonVoidNullary) {
+  MockFunction<int()> foo;
+  EXPECT_CALL(foo, Call()).WillOnce(Return(1)).WillOnce(Return(2));
+  EXPECT_EQ(1, foo.Call());
+  EXPECT_EQ(2, foo.Call());
+}
+
+TEST(MockMethodMockFunctionTest, WorksForVoidUnary) {
+  MockFunction<void(int)> foo;
+  EXPECT_CALL(foo, Call(1));
+  foo.Call(1);
+}
+
+TEST(MockMethodMockFunctionTest, WorksForNonVoidBinary) {
+  MockFunction<int(bool, int)> foo;
+  EXPECT_CALL(foo, Call(false, 42)).WillOnce(Return(1)).WillOnce(Return(2));
+  EXPECT_CALL(foo, Call(true, Ge(100))).WillOnce(Return(3));
+  EXPECT_EQ(1, foo.Call(false, 42));
+  EXPECT_EQ(2, foo.Call(false, 42));
+  EXPECT_EQ(3, foo.Call(true, 120));
+}
+
+TEST(MockMethodMockFunctionTest, WorksFor10Arguments) {
+  MockFunction<int(bool a0, char a1, int a2, int a3, int a4, int a5, int a6,
+                   char a7, int a8, bool a9)>
+      foo;
+  EXPECT_CALL(foo, Call(_, 'a', _, _, _, _, _, _, _, _))
+      .WillOnce(Return(1))
+      .WillOnce(Return(2));
+  EXPECT_EQ(1, foo.Call(false, 'a', 0, 0, 0, 0, 0, 'b', 0, true));
+  EXPECT_EQ(2, foo.Call(true, 'a', 0, 0, 0, 0, 0, 'b', 1, false));
+}
+
+TEST(MockMethodMockFunctionTest, AsStdFunction) {
+  MockFunction<int(int)> foo;
+  auto call = [](const std::function<int(int)>& f, int i) { return f(i); };
+  EXPECT_CALL(foo, Call(1)).WillOnce(Return(-1));
+  EXPECT_CALL(foo, Call(2)).WillOnce(Return(-2));
+  EXPECT_EQ(-1, call(foo.AsStdFunction(), 1));
+  EXPECT_EQ(-2, call(foo.AsStdFunction(), 2));
+}
+
+TEST(MockMethodMockFunctionTest, AsStdFunctionReturnsReference) {
+  MockFunction<int&()> foo;
+  int value = 1;
+  EXPECT_CALL(foo, Call()).WillOnce(ReturnRef(value));
+  int& ref = foo.AsStdFunction()();
+  EXPECT_EQ(1, ref);
+  value = 2;
+  EXPECT_EQ(2, ref);
+}
+
+TEST(MockMethodMockFunctionTest, AsStdFunctionWithReferenceParameter) {
+  MockFunction<int(int&)> foo;
+  auto call = [](const std::function<int(int&)>& f, int& i) { return f(i); };
+  int i = 42;
+  EXPECT_CALL(foo, Call(i)).WillOnce(Return(-1));
+  EXPECT_EQ(-1, call(foo.AsStdFunction(), i));
+}
+
+namespace {
+
+template <typename Expected, typename F>
+static constexpr bool IsMockFunctionTemplateArgumentDeducedTo(
+    const internal::MockFunction<F>&) {
+  return std::is_same<F, Expected>::value;
+}
+
+}  // namespace
+
+template <typename F>
+class MockMethodMockFunctionSignatureTest : public Test {};
+
+using MockMethodMockFunctionSignatureTypes =
+    Types<void(), int(), void(int), int(int), int(bool, int),
+          int(bool, char, int, int, int, int, int, char, int, bool)>;
+TYPED_TEST_SUITE(MockMethodMockFunctionSignatureTest,
+                 MockMethodMockFunctionSignatureTypes);
+
+TYPED_TEST(MockMethodMockFunctionSignatureTest,
+           IsMockFunctionTemplateArgumentDeducedForRawSignature) {
+  using Argument = TypeParam;
+  MockFunction<Argument> foo;
+  EXPECT_TRUE(IsMockFunctionTemplateArgumentDeducedTo<TypeParam>(foo));
+}
+
+TYPED_TEST(MockMethodMockFunctionSignatureTest,
+           IsMockFunctionTemplateArgumentDeducedForStdFunction) {
+  using Argument = std::function<TypeParam>;
+  MockFunction<Argument> foo;
+  EXPECT_TRUE(IsMockFunctionTemplateArgumentDeducedTo<TypeParam>(foo));
+}
+
+TYPED_TEST(
+    MockMethodMockFunctionSignatureTest,
+    IsMockFunctionCallMethodSignatureTheSameForRawSignatureAndStdFunction) {
+  using ForRawSignature = decltype(&MockFunction<TypeParam>::Call);
+  using ForStdFunction =
+      decltype(&MockFunction<std::function<TypeParam>>::Call);
+  EXPECT_TRUE((std::is_same<ForRawSignature, ForStdFunction>::value));
+}
+
+template <typename F>
+struct AlternateCallable {};
+
+TYPED_TEST(MockMethodMockFunctionSignatureTest,
+           IsMockFunctionTemplateArgumentDeducedForAlternateCallable) {
+  using Argument = AlternateCallable<TypeParam>;
+  MockFunction<Argument> foo;
+  EXPECT_TRUE(IsMockFunctionTemplateArgumentDeducedTo<TypeParam>(foo));
+}
+
+TYPED_TEST(MockMethodMockFunctionSignatureTest,
+           IsMockFunctionCallMethodSignatureTheSameForAlternateCallable) {
+  using ForRawSignature = decltype(&MockFunction<TypeParam>::Call);
+  using ForStdFunction =
+      decltype(&MockFunction<std::function<TypeParam>>::Call);
+  EXPECT_TRUE((std::is_same<ForRawSignature, ForStdFunction>::value));
+}
+
+struct MockMethodSizes0 {
+  MOCK_METHOD(void, func, ());
+};
+struct MockMethodSizes1 {
+  MOCK_METHOD(void, func, (int));
+};
+struct MockMethodSizes2 {
+  MOCK_METHOD(void, func, (int, int));
+};
+struct MockMethodSizes3 {
+  MOCK_METHOD(void, func, (int, int, int));
+};
+struct MockMethodSizes4 {
+  MOCK_METHOD(void, func, (int, int, int, int));
+};
+
+struct LegacyMockMethodSizes0 {
+  MOCK_METHOD0(func, void());
+};
+struct LegacyMockMethodSizes1 {
+  MOCK_METHOD1(func, void(int));
+};
+struct LegacyMockMethodSizes2 {
+  MOCK_METHOD2(func, void(int, int));
+};
+struct LegacyMockMethodSizes3 {
+  MOCK_METHOD3(func, void(int, int, int));
+};
+struct LegacyMockMethodSizes4 {
+  MOCK_METHOD4(func, void(int, int, int, int));
+};
+
+TEST(MockMethodMockFunctionTest, MockMethodSizeOverhead) {
+  EXPECT_EQ(sizeof(MockMethodSizes0), sizeof(MockMethodSizes1));
+  EXPECT_EQ(sizeof(MockMethodSizes0), sizeof(MockMethodSizes2));
+  EXPECT_EQ(sizeof(MockMethodSizes0), sizeof(MockMethodSizes3));
+  EXPECT_EQ(sizeof(MockMethodSizes0), sizeof(MockMethodSizes4));
+
+  EXPECT_EQ(sizeof(LegacyMockMethodSizes0), sizeof(LegacyMockMethodSizes1));
+  EXPECT_EQ(sizeof(LegacyMockMethodSizes0), sizeof(LegacyMockMethodSizes2));
+  EXPECT_EQ(sizeof(LegacyMockMethodSizes0), sizeof(LegacyMockMethodSizes3));
+  EXPECT_EQ(sizeof(LegacyMockMethodSizes0), sizeof(LegacyMockMethodSizes4));
+
+  EXPECT_EQ(sizeof(LegacyMockMethodSizes0), sizeof(MockMethodSizes0));
+}
+
+TEST(MockMethodMockFunctionTest, EnsureNoUnusedMemberFunction) {
+#ifdef __clang__
+#pragma clang diagnostic push
+#pragma clang diagnostic error "-Wunused-member-function"
+#endif
+  // https://github.com/google/googletest/issues/4052
+  struct Foo {
+    MOCK_METHOD(void, foo, ());
+  };
+  EXPECT_CALL(Foo(), foo()).Times(0);
+#ifdef __clang__
+#pragma clang diagnostic pop
+#endif
+}
+
+void hasTwoParams(int, int);
+void MaybeThrows();
+void DoesntThrow() noexcept;
+struct MockMethodNoexceptSpecifier {
+  MOCK_METHOD(void, func1, (), (noexcept));
+  MOCK_METHOD(void, func2, (), (noexcept(true)));
+  MOCK_METHOD(void, func3, (), (noexcept(false)));
+  MOCK_METHOD(void, func4, (), (noexcept(noexcept(MaybeThrows()))));
+  MOCK_METHOD(void, func5, (), (noexcept(noexcept(DoesntThrow()))));
+  MOCK_METHOD(void, func6, (), (noexcept(noexcept(DoesntThrow())), const));
+  MOCK_METHOD(void, func7, (), (const, noexcept(noexcept(DoesntThrow()))));
+  // Put commas in the noexcept expression
+  MOCK_METHOD(void, func8, (), (noexcept(noexcept(hasTwoParams(1, 2))), const));
+};
+
+TEST(MockMethodMockFunctionTest, NoexceptSpecifierPreserved) {
+  EXPECT_TRUE(noexcept(std::declval<MockMethodNoexceptSpecifier>().func1()));
+  EXPECT_TRUE(noexcept(std::declval<MockMethodNoexceptSpecifier>().func2()));
+  EXPECT_FALSE(noexcept(std::declval<MockMethodNoexceptSpecifier>().func3()));
+  EXPECT_FALSE(noexcept(std::declval<MockMethodNoexceptSpecifier>().func4()));
+  EXPECT_TRUE(noexcept(std::declval<MockMethodNoexceptSpecifier>().func5()));
+  EXPECT_TRUE(noexcept(std::declval<MockMethodNoexceptSpecifier>().func6()));
+  EXPECT_TRUE(noexcept(std::declval<MockMethodNoexceptSpecifier>().func7()));
+  EXPECT_EQ(noexcept(std::declval<MockMethodNoexceptSpecifier>().func8()),
+            noexcept(hasTwoParams(1, 2)));
+}
+
+}  // namespace gmock_function_mocker_test
+}  // namespace testing
+
+GTEST_DISABLE_MSC_WARNINGS_POP_()  // 4503
diff --git a/third_party/googletest/googlemock/test/gmock-internal-utils_test.cc b/third_party/googletest/googlemock/test/gmock-internal-utils_test.cc
new file mode 100644
index 0000000..6c769a8
--- /dev/null
+++ b/third_party/googletest/googlemock/test/gmock-internal-utils_test.cc
@@ -0,0 +1,766 @@
+// Copyright 2007, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Google Mock - a framework for writing C++ mock classes.
+//
+// This file tests the internal utilities.
+
+#include "gmock/internal/gmock-internal-utils.h"
+
+#include <stdlib.h>
+
+#include <cstdint>
+#include <map>
+#include <memory>
+#include <sstream>
+#include <string>
+#include <tuple>
+#include <vector>
+
+#include "gmock/gmock.h"
+#include "gmock/internal/gmock-port.h"
+#include "gtest/gtest-spi.h"
+#include "gtest/gtest.h"
+
+// Indicates that this translation unit is part of Google Test's
+// implementation.  It must come before gtest-internal-inl.h is
+// included, or there will be a compiler error.  This trick is to
+// prevent a user from accidentally including gtest-internal-inl.h in
+// their code.
+#define GTEST_IMPLEMENTATION_ 1
+#include "src/gtest-internal-inl.h"
+#undef GTEST_IMPLEMENTATION_
+
+#ifdef GTEST_OS_CYGWIN
+#include <sys/types.h>  // For ssize_t. NOLINT
+#endif
+
+namespace proto2 {
+class Message;
+}  // namespace proto2
+
+namespace testing {
+namespace internal {
+
+namespace {
+
+TEST(JoinAsKeyValueTupleTest, JoinsEmptyTuple) {
+  EXPECT_EQ("", JoinAsKeyValueTuple({}, Strings()));
+}
+
+TEST(JoinAsKeyValueTupleTest, JoinsOneTuple) {
+  EXPECT_EQ("(a: 1)", JoinAsKeyValueTuple({"a"}, {"1"}));
+}
+
+TEST(JoinAsKeyValueTupleTest, JoinsTwoTuple) {
+  EXPECT_EQ("(a: 1, b: 2)", JoinAsKeyValueTuple({"a", "b"}, {"1", "2"}));
+}
+
+TEST(JoinAsKeyValueTupleTest, JoinsTenTuple) {
+  EXPECT_EQ(
+      "(a: 1, b: 2, c: 3, d: 4, e: 5, f: 6, g: 7, h: 8, i: 9, j: 10)",
+      JoinAsKeyValueTuple({"a", "b", "c", "d", "e", "f", "g", "h", "i", "j"},
+                          {"1", "2", "3", "4", "5", "6", "7", "8", "9", "10"}));
+}
+
+TEST(ConvertIdentifierNameToWordsTest, WorksWhenNameContainsNoWord) {
+  EXPECT_EQ("", ConvertIdentifierNameToWords(""));
+  EXPECT_EQ("", ConvertIdentifierNameToWords("_"));
+  EXPECT_EQ("", ConvertIdentifierNameToWords("__"));
+}
+
+TEST(ConvertIdentifierNameToWordsTest, WorksWhenNameContainsDigits) {
+  EXPECT_EQ("1", ConvertIdentifierNameToWords("_1"));
+  EXPECT_EQ("2", ConvertIdentifierNameToWords("2_"));
+  EXPECT_EQ("34", ConvertIdentifierNameToWords("_34_"));
+  EXPECT_EQ("34 56", ConvertIdentifierNameToWords("_34_56"));
+}
+
+TEST(ConvertIdentifierNameToWordsTest, WorksWhenNameContainsCamelCaseWords) {
+  EXPECT_EQ("a big word", ConvertIdentifierNameToWords("ABigWord"));
+  EXPECT_EQ("foo bar", ConvertIdentifierNameToWords("FooBar"));
+  EXPECT_EQ("foo", ConvertIdentifierNameToWords("Foo_"));
+  EXPECT_EQ("foo bar", ConvertIdentifierNameToWords("_Foo_Bar_"));
+  EXPECT_EQ("foo and bar", ConvertIdentifierNameToWords("_Foo__And_Bar"));
+}
+
+TEST(ConvertIdentifierNameToWordsTest, WorksWhenNameContains_SeparatedWords) {
+  EXPECT_EQ("foo bar", ConvertIdentifierNameToWords("foo_bar"));
+  EXPECT_EQ("foo", ConvertIdentifierNameToWords("_foo_"));
+  EXPECT_EQ("foo bar", ConvertIdentifierNameToWords("_foo_bar_"));
+  EXPECT_EQ("foo and bar", ConvertIdentifierNameToWords("_foo__and_bar"));
+}
+
+TEST(ConvertIdentifierNameToWordsTest, WorksWhenNameIsMixture) {
+  EXPECT_EQ("foo bar 123", ConvertIdentifierNameToWords("Foo_bar123"));
+  EXPECT_EQ("chapter 11 section 1",
+            ConvertIdentifierNameToWords("_Chapter11Section_1_"));
+}
+
+TEST(GetRawPointerTest, WorksForSmartPointers) {
+  const char* const raw_p1 = new const char('a');  // NOLINT
+  const std::unique_ptr<const char> p1(raw_p1);
+  EXPECT_EQ(raw_p1, GetRawPointer(p1));
+  double* const raw_p2 = new double(2.5);  // NOLINT
+  const std::shared_ptr<double> p2(raw_p2);
+  EXPECT_EQ(raw_p2, GetRawPointer(p2));
+}
+
+TEST(GetRawPointerTest, WorksForRawPointers) {
+  int* p = nullptr;
+  EXPECT_TRUE(nullptr == GetRawPointer(p));
+  int n = 1;
+  EXPECT_EQ(&n, GetRawPointer(&n));
+}
+
+TEST(GetRawPointerTest, WorksForStdReferenceWrapper) {
+  int n = 1;
+  EXPECT_EQ(&n, GetRawPointer(std::ref(n)));
+  EXPECT_EQ(&n, GetRawPointer(std::cref(n)));
+}
+
+// Tests KindOf<T>.
+
+class Base {};
+class Derived : public Base {};
+
+TEST(KindOfTest, Bool) {
+  EXPECT_EQ(kBool, GMOCK_KIND_OF_(bool));  // NOLINT
+}
+
+TEST(KindOfTest, Integer) {
+  EXPECT_EQ(kInteger, GMOCK_KIND_OF_(char));                // NOLINT
+  EXPECT_EQ(kInteger, GMOCK_KIND_OF_(signed char));         // NOLINT
+  EXPECT_EQ(kInteger, GMOCK_KIND_OF_(unsigned char));       // NOLINT
+  EXPECT_EQ(kInteger, GMOCK_KIND_OF_(short));               // NOLINT
+  EXPECT_EQ(kInteger, GMOCK_KIND_OF_(unsigned short));      // NOLINT
+  EXPECT_EQ(kInteger, GMOCK_KIND_OF_(int));                 // NOLINT
+  EXPECT_EQ(kInteger, GMOCK_KIND_OF_(unsigned int));        // NOLINT
+  EXPECT_EQ(kInteger, GMOCK_KIND_OF_(long));                // NOLINT
+  EXPECT_EQ(kInteger, GMOCK_KIND_OF_(unsigned long));       // NOLINT
+  EXPECT_EQ(kInteger, GMOCK_KIND_OF_(long long));           // NOLINT
+  EXPECT_EQ(kInteger, GMOCK_KIND_OF_(unsigned long long));  // NOLINT
+  EXPECT_EQ(kInteger, GMOCK_KIND_OF_(wchar_t));             // NOLINT
+  EXPECT_EQ(kInteger, GMOCK_KIND_OF_(size_t));              // NOLINT
+#if defined(GTEST_OS_LINUX) || defined(GTEST_OS_MAC) || defined(GTEST_OS_CYGWIN)
+  // ssize_t is not defined on Windows and possibly some other OSes.
+  EXPECT_EQ(kInteger, GMOCK_KIND_OF_(ssize_t));  // NOLINT
+#endif
+}
+
+TEST(KindOfTest, FloatingPoint) {
+  EXPECT_EQ(kFloatingPoint, GMOCK_KIND_OF_(float));        // NOLINT
+  EXPECT_EQ(kFloatingPoint, GMOCK_KIND_OF_(double));       // NOLINT
+  EXPECT_EQ(kFloatingPoint, GMOCK_KIND_OF_(long double));  // NOLINT
+}
+
+TEST(KindOfTest, Other) {
+  EXPECT_EQ(kOther, GMOCK_KIND_OF_(void*));   // NOLINT
+  EXPECT_EQ(kOther, GMOCK_KIND_OF_(char**));  // NOLINT
+  EXPECT_EQ(kOther, GMOCK_KIND_OF_(Base));    // NOLINT
+}
+
+// Tests LosslessArithmeticConvertible<T, U>.
+
+TEST(LosslessArithmeticConvertibleTest, BoolToBool) {
+  EXPECT_TRUE((LosslessArithmeticConvertible<bool, bool>::value));
+}
+
+TEST(LosslessArithmeticConvertibleTest, BoolToInteger) {
+  EXPECT_TRUE((LosslessArithmeticConvertible<bool, char>::value));
+  EXPECT_TRUE((LosslessArithmeticConvertible<bool, int>::value));
+  EXPECT_TRUE(
+      (LosslessArithmeticConvertible<bool, unsigned long>::value));  // NOLINT
+}
+
+TEST(LosslessArithmeticConvertibleTest, BoolToFloatingPoint) {
+  EXPECT_TRUE((LosslessArithmeticConvertible<bool, float>::value));
+  EXPECT_TRUE((LosslessArithmeticConvertible<bool, double>::value));
+}
+
+TEST(LosslessArithmeticConvertibleTest, IntegerToBool) {
+  EXPECT_FALSE((LosslessArithmeticConvertible<unsigned char, bool>::value));
+  EXPECT_FALSE((LosslessArithmeticConvertible<int, bool>::value));
+}
+
+TEST(LosslessArithmeticConvertibleTest, IntegerToInteger) {
+  // Unsigned => larger signed is fine.
+  EXPECT_TRUE((LosslessArithmeticConvertible<unsigned char, int>::value));
+
+  // Unsigned => larger unsigned is fine.
+  EXPECT_TRUE((LosslessArithmeticConvertible<unsigned short,
+                                             uint64_t>::value));  // NOLINT
+
+  // Signed => unsigned is not fine.
+  EXPECT_FALSE(
+      (LosslessArithmeticConvertible<short, uint64_t>::value));  // NOLINT
+  EXPECT_FALSE((LosslessArithmeticConvertible<signed char,
+                                              unsigned int>::value));  // NOLINT
+
+  // Same size and same signedness: fine too.
+  EXPECT_TRUE(
+      (LosslessArithmeticConvertible<unsigned char, unsigned char>::value));
+  EXPECT_TRUE((LosslessArithmeticConvertible<int, int>::value));
+  EXPECT_TRUE((LosslessArithmeticConvertible<wchar_t, wchar_t>::value));
+  EXPECT_TRUE((LosslessArithmeticConvertible<unsigned long,
+                                             unsigned long>::value));  // NOLINT
+
+  // Same size, different signedness: not fine.
+  EXPECT_FALSE(
+      (LosslessArithmeticConvertible<unsigned char, signed char>::value));
+  EXPECT_FALSE((LosslessArithmeticConvertible<int, unsigned int>::value));
+  EXPECT_FALSE((LosslessArithmeticConvertible<uint64_t, int64_t>::value));
+
+  // Larger size => smaller size is not fine.
+  EXPECT_FALSE((LosslessArithmeticConvertible<long, char>::value));  // NOLINT
+  EXPECT_FALSE((LosslessArithmeticConvertible<int, signed char>::value));
+  EXPECT_FALSE((LosslessArithmeticConvertible<int64_t, unsigned int>::value));
+}
+
+TEST(LosslessArithmeticConvertibleTest, IntegerToFloatingPoint) {
+  // Integers cannot be losslessly converted to floating-points, as
+  // the format of the latter is implementation-defined.
+  EXPECT_FALSE((LosslessArithmeticConvertible<char, float>::value));
+  EXPECT_FALSE((LosslessArithmeticConvertible<int, double>::value));
+  EXPECT_FALSE(
+      (LosslessArithmeticConvertible<short, long double>::value));  // NOLINT
+}
+
+TEST(LosslessArithmeticConvertibleTest, FloatingPointToBool) {
+  EXPECT_FALSE((LosslessArithmeticConvertible<float, bool>::value));
+  EXPECT_FALSE((LosslessArithmeticConvertible<double, bool>::value));
+}
+
+TEST(LosslessArithmeticConvertibleTest, FloatingPointToInteger) {
+  EXPECT_FALSE((LosslessArithmeticConvertible<float, long>::value));  // NOLINT
+  EXPECT_FALSE((LosslessArithmeticConvertible<double, int64_t>::value));
+  EXPECT_FALSE((LosslessArithmeticConvertible<long double, int>::value));
+}
+
+TEST(LosslessArithmeticConvertibleTest, FloatingPointToFloatingPoint) {
+  // Smaller size => larger size is fine.
+  EXPECT_TRUE((LosslessArithmeticConvertible<float, double>::value));
+  EXPECT_TRUE((LosslessArithmeticConvertible<float, long double>::value));
+  EXPECT_TRUE((LosslessArithmeticConvertible<double, long double>::value));
+
+  // Same size: fine.
+  EXPECT_TRUE((LosslessArithmeticConvertible<float, float>::value));
+  EXPECT_TRUE((LosslessArithmeticConvertible<double, double>::value));
+
+  // Larger size => smaller size is not fine.
+  EXPECT_FALSE((LosslessArithmeticConvertible<double, float>::value));
+  GTEST_INTENTIONAL_CONST_COND_PUSH_()
+  if (sizeof(double) == sizeof(long double)) {  // NOLINT
+    GTEST_INTENTIONAL_CONST_COND_POP_()
+    // In some implementations (e.g. MSVC), double and long double
+    // have the same size.
+    EXPECT_TRUE((LosslessArithmeticConvertible<long double, double>::value));
+  } else {
+    EXPECT_FALSE((LosslessArithmeticConvertible<long double, double>::value));
+  }
+}
+
+// Tests the TupleMatches() template function.
+
+TEST(TupleMatchesTest, WorksForSize0) {
+  std::tuple<> matchers;
+  std::tuple<> values;
+
+  EXPECT_TRUE(TupleMatches(matchers, values));
+}
+
+TEST(TupleMatchesTest, WorksForSize1) {
+  std::tuple<Matcher<int>> matchers(Eq(1));
+  std::tuple<int> values1(1), values2(2);
+
+  EXPECT_TRUE(TupleMatches(matchers, values1));
+  EXPECT_FALSE(TupleMatches(matchers, values2));
+}
+
+TEST(TupleMatchesTest, WorksForSize2) {
+  std::tuple<Matcher<int>, Matcher<char>> matchers(Eq(1), Eq('a'));
+  std::tuple<int, char> values1(1, 'a'), values2(1, 'b'), values3(2, 'a'),
+      values4(2, 'b');
+
+  EXPECT_TRUE(TupleMatches(matchers, values1));
+  EXPECT_FALSE(TupleMatches(matchers, values2));
+  EXPECT_FALSE(TupleMatches(matchers, values3));
+  EXPECT_FALSE(TupleMatches(matchers, values4));
+}
+
+TEST(TupleMatchesTest, WorksForSize5) {
+  std::tuple<Matcher<int>, Matcher<char>, Matcher<bool>,
+             Matcher<long>,  // NOLINT
+             Matcher<std::string>>
+      matchers(Eq(1), Eq('a'), Eq(true), Eq(2L), Eq("hi"));
+  std::tuple<int, char, bool, long, std::string>  // NOLINT
+      values1(1, 'a', true, 2L, "hi"), values2(1, 'a', true, 2L, "hello"),
+      values3(2, 'a', true, 2L, "hi");
+
+  EXPECT_TRUE(TupleMatches(matchers, values1));
+  EXPECT_FALSE(TupleMatches(matchers, values2));
+  EXPECT_FALSE(TupleMatches(matchers, values3));
+}
+
+// Tests that Assert(true, ...) succeeds.
+TEST(AssertTest, SucceedsOnTrue) {
+  Assert(true, __FILE__, __LINE__, "This should succeed.");
+  Assert(true, __FILE__, __LINE__);  // This should succeed too.
+}
+
+// Tests that Assert(false, ...) generates a fatal failure.
+TEST(AssertTest, FailsFatallyOnFalse) {
+  EXPECT_DEATH_IF_SUPPORTED(
+      { Assert(false, __FILE__, __LINE__, "This should fail."); }, "");
+
+  EXPECT_DEATH_IF_SUPPORTED({ Assert(false, __FILE__, __LINE__); }, "");
+}
+
+// Tests that Expect(true, ...) succeeds.
+TEST(ExpectTest, SucceedsOnTrue) {
+  Expect(true, __FILE__, __LINE__, "This should succeed.");
+  Expect(true, __FILE__, __LINE__);  // This should succeed too.
+}
+
+// Tests that Expect(false, ...) generates a non-fatal failure.
+TEST(ExpectTest, FailsNonfatallyOnFalse) {
+  EXPECT_NONFATAL_FAILURE(
+      {  // NOLINT
+        Expect(false, __FILE__, __LINE__, "This should fail.");
+      },
+      "This should fail");
+
+  EXPECT_NONFATAL_FAILURE(
+      {  // NOLINT
+        Expect(false, __FILE__, __LINE__);
+      },
+      "Expectation failed");
+}
+
+// Tests LogIsVisible().
+
+class LogIsVisibleTest : public ::testing::Test {
+ protected:
+  void SetUp() override { original_verbose_ = GMOCK_FLAG_GET(verbose); }
+
+  void TearDown() override { GMOCK_FLAG_SET(verbose, original_verbose_); }
+
+  std::string original_verbose_;
+};
+
+TEST_F(LogIsVisibleTest, AlwaysReturnsTrueIfVerbosityIsInfo) {
+  GMOCK_FLAG_SET(verbose, kInfoVerbosity);
+  EXPECT_TRUE(LogIsVisible(kInfo));
+  EXPECT_TRUE(LogIsVisible(kWarning));
+}
+
+TEST_F(LogIsVisibleTest, AlwaysReturnsFalseIfVerbosityIsError) {
+  GMOCK_FLAG_SET(verbose, kErrorVerbosity);
+  EXPECT_FALSE(LogIsVisible(kInfo));
+  EXPECT_FALSE(LogIsVisible(kWarning));
+}
+
+TEST_F(LogIsVisibleTest, WorksWhenVerbosityIsWarning) {
+  GMOCK_FLAG_SET(verbose, kWarningVerbosity);
+  EXPECT_FALSE(LogIsVisible(kInfo));
+  EXPECT_TRUE(LogIsVisible(kWarning));
+}
+
+#if GTEST_HAS_STREAM_REDIRECTION
+
+// Tests the Log() function.
+
+// Verifies that Log() behaves correctly for the given verbosity level
+// and log severity.
+void TestLogWithSeverity(const std::string& verbosity, LogSeverity severity,
+                         bool should_print) {
+  const std::string old_flag = GMOCK_FLAG_GET(verbose);
+  GMOCK_FLAG_SET(verbose, verbosity);
+  CaptureStdout();
+  Log(severity, "Test log.\n", 0);
+  if (should_print) {
+    EXPECT_THAT(
+        GetCapturedStdout().c_str(),
+        ContainsRegex(severity == kWarning
+                          ? "^\nGMOCK WARNING:\nTest log\\.\nStack trace:\n"
+                          : "^\nTest log\\.\nStack trace:\n"));
+  } else {
+    EXPECT_STREQ("", GetCapturedStdout().c_str());
+  }
+  GMOCK_FLAG_SET(verbose, old_flag);
+}
+
+// Tests that when the stack_frames_to_skip parameter is negative,
+// Log() doesn't include the stack trace in the output.
+TEST(LogTest, NoStackTraceWhenStackFramesToSkipIsNegative) {
+  const std::string saved_flag = GMOCK_FLAG_GET(verbose);
+  GMOCK_FLAG_SET(verbose, kInfoVerbosity);
+  CaptureStdout();
+  Log(kInfo, "Test log.\n", -1);
+  EXPECT_STREQ("\nTest log.\n", GetCapturedStdout().c_str());
+  GMOCK_FLAG_SET(verbose, saved_flag);
+}
+
+struct MockStackTraceGetter : testing::internal::OsStackTraceGetterInterface {
+  std::string CurrentStackTrace(int max_depth, int skip_count) override {
+    return (testing::Message() << max_depth << "::" << skip_count << "\n")
+        .GetString();
+  }
+  void UponLeavingGTest() override {}
+};
+
+// Tests that in opt mode, a positive stack_frames_to_skip argument is
+// treated as 0.
+TEST(LogTest, NoSkippingStackFrameInOptMode) {
+  MockStackTraceGetter* mock_os_stack_trace_getter = new MockStackTraceGetter;
+  GetUnitTestImpl()->set_os_stack_trace_getter(mock_os_stack_trace_getter);
+
+  CaptureStdout();
+  Log(kWarning, "Test log.\n", 100);
+  const std::string log = GetCapturedStdout();
+
+  std::string expected_trace =
+      (testing::Message() << GTEST_FLAG_GET(stack_trace_depth) << "::")
+          .GetString();
+  std::string expected_message =
+      "\nGMOCK WARNING:\n"
+      "Test log.\n"
+      "Stack trace:\n" +
+      expected_trace;
+  EXPECT_THAT(log, HasSubstr(expected_message));
+  int skip_count = atoi(log.substr(expected_message.size()).c_str());
+
+#if defined(NDEBUG)
+  // In opt mode, no stack frame should be skipped.
+  const int expected_skip_count = 0;
+#else
+  // In dbg mode, the stack frames should be skipped.
+  const int expected_skip_count = 100;
+#endif
+
+  // Note that each inner implementation layer will +1 the number to remove
+  // itself from the trace. This means that the value is a little higher than
+  // expected, but close enough.
+  EXPECT_THAT(skip_count,
+              AllOf(Ge(expected_skip_count), Le(expected_skip_count + 10)));
+
+  // Restores the default OS stack trace getter.
+  GetUnitTestImpl()->set_os_stack_trace_getter(nullptr);
+}
+
+// Tests that all logs are printed when the value of the
+// --gmock_verbose flag is "info".
+TEST(LogTest, AllLogsArePrintedWhenVerbosityIsInfo) {
+  TestLogWithSeverity(kInfoVerbosity, kInfo, true);
+  TestLogWithSeverity(kInfoVerbosity, kWarning, true);
+}
+
+// Tests that only warnings are printed when the value of the
+// --gmock_verbose flag is "warning".
+TEST(LogTest, OnlyWarningsArePrintedWhenVerbosityIsWarning) {
+  TestLogWithSeverity(kWarningVerbosity, kInfo, false);
+  TestLogWithSeverity(kWarningVerbosity, kWarning, true);
+}
+
+// Tests that no logs are printed when the value of the
+// --gmock_verbose flag is "error".
+TEST(LogTest, NoLogsArePrintedWhenVerbosityIsError) {
+  TestLogWithSeverity(kErrorVerbosity, kInfo, false);
+  TestLogWithSeverity(kErrorVerbosity, kWarning, false);
+}
+
+// Tests that only warnings are printed when the value of the
+// --gmock_verbose flag is invalid.
+TEST(LogTest, OnlyWarningsArePrintedWhenVerbosityIsInvalid) {
+  TestLogWithSeverity("invalid", kInfo, false);
+  TestLogWithSeverity("invalid", kWarning, true);
+}
+
+// Verifies that Log() behaves correctly for the given verbosity level
+// and log severity.
+std::string GrabOutput(void (*logger)(), const char* verbosity) {
+  const std::string saved_flag = GMOCK_FLAG_GET(verbose);
+  GMOCK_FLAG_SET(verbose, verbosity);
+  CaptureStdout();
+  logger();
+  GMOCK_FLAG_SET(verbose, saved_flag);
+  return GetCapturedStdout();
+}
+
+class DummyMock {
+ public:
+  MOCK_METHOD0(TestMethod, void());
+  MOCK_METHOD1(TestMethodArg, void(int dummy));
+};
+
+void ExpectCallLogger() {
+  DummyMock mock;
+  EXPECT_CALL(mock, TestMethod());
+  mock.TestMethod();
+}
+
+// Verifies that EXPECT_CALL logs if the --gmock_verbose flag is set to "info".
+TEST(ExpectCallTest, LogsWhenVerbosityIsInfo) {
+  EXPECT_THAT(std::string(GrabOutput(ExpectCallLogger, kInfoVerbosity)),
+              HasSubstr("EXPECT_CALL(mock, TestMethod())"));
+}
+
+// Verifies that EXPECT_CALL doesn't log
+// if the --gmock_verbose flag is set to "warning".
+TEST(ExpectCallTest, DoesNotLogWhenVerbosityIsWarning) {
+  EXPECT_STREQ("", GrabOutput(ExpectCallLogger, kWarningVerbosity).c_str());
+}
+
+// Verifies that EXPECT_CALL doesn't log
+// if the --gmock_verbose flag is set to "error".
+TEST(ExpectCallTest, DoesNotLogWhenVerbosityIsError) {
+  EXPECT_STREQ("", GrabOutput(ExpectCallLogger, kErrorVerbosity).c_str());
+}
+
+void OnCallLogger() {
+  DummyMock mock;
+  ON_CALL(mock, TestMethod());
+}
+
+// Verifies that ON_CALL logs if the --gmock_verbose flag is set to "info".
+TEST(OnCallTest, LogsWhenVerbosityIsInfo) {
+  EXPECT_THAT(std::string(GrabOutput(OnCallLogger, kInfoVerbosity)),
+              HasSubstr("ON_CALL(mock, TestMethod())"));
+}
+
+// Verifies that ON_CALL doesn't log
+// if the --gmock_verbose flag is set to "warning".
+TEST(OnCallTest, DoesNotLogWhenVerbosityIsWarning) {
+  EXPECT_STREQ("", GrabOutput(OnCallLogger, kWarningVerbosity).c_str());
+}
+
+// Verifies that ON_CALL doesn't log if
+// the --gmock_verbose flag is set to "error".
+TEST(OnCallTest, DoesNotLogWhenVerbosityIsError) {
+  EXPECT_STREQ("", GrabOutput(OnCallLogger, kErrorVerbosity).c_str());
+}
+
+void OnCallAnyArgumentLogger() {
+  DummyMock mock;
+  ON_CALL(mock, TestMethodArg(_));
+}
+
+// Verifies that ON_CALL prints provided _ argument.
+TEST(OnCallTest, LogsAnythingArgument) {
+  EXPECT_THAT(std::string(GrabOutput(OnCallAnyArgumentLogger, kInfoVerbosity)),
+              HasSubstr("ON_CALL(mock, TestMethodArg(_)"));
+}
+
+#endif  // GTEST_HAS_STREAM_REDIRECTION
+
+// Tests StlContainerView.
+
+TEST(StlContainerViewTest, WorksForStlContainer) {
+  StaticAssertTypeEq<std::vector<int>,
+                     StlContainerView<std::vector<int>>::type>();
+  StaticAssertTypeEq<const std::vector<double>&,
+                     StlContainerView<std::vector<double>>::const_reference>();
+
+  typedef std::vector<char> Chars;
+  Chars v1;
+  const Chars& v2(StlContainerView<Chars>::ConstReference(v1));
+  EXPECT_EQ(&v1, &v2);
+
+  v1.push_back('a');
+  Chars v3 = StlContainerView<Chars>::Copy(v1);
+  EXPECT_THAT(v3, Eq(v3));
+}
+
+TEST(StlContainerViewTest, WorksForStaticNativeArray) {
+  StaticAssertTypeEq<NativeArray<int>, StlContainerView<int[3]>::type>();
+  StaticAssertTypeEq<NativeArray<double>,
+                     StlContainerView<const double[4]>::type>();
+  StaticAssertTypeEq<NativeArray<char[3]>,
+                     StlContainerView<const char[2][3]>::type>();
+
+  StaticAssertTypeEq<const NativeArray<int>,
+                     StlContainerView<int[2]>::const_reference>();
+
+  int a1[3] = {0, 1, 2};
+  NativeArray<int> a2 = StlContainerView<int[3]>::ConstReference(a1);
+  EXPECT_EQ(3U, a2.size());
+  EXPECT_EQ(a1, a2.begin());
+
+  const NativeArray<int> a3 = StlContainerView<int[3]>::Copy(a1);
+  ASSERT_EQ(3U, a3.size());
+  EXPECT_EQ(0, a3.begin()[0]);
+  EXPECT_EQ(1, a3.begin()[1]);
+  EXPECT_EQ(2, a3.begin()[2]);
+
+  // Makes sure a1 and a3 aren't aliases.
+  a1[0] = 3;
+  EXPECT_EQ(0, a3.begin()[0]);
+}
+
+TEST(StlContainerViewTest, WorksForDynamicNativeArray) {
+  StaticAssertTypeEq<NativeArray<int>,
+                     StlContainerView<std::tuple<const int*, size_t>>::type>();
+  StaticAssertTypeEq<
+      NativeArray<double>,
+      StlContainerView<std::tuple<std::shared_ptr<double>, int>>::type>();
+
+  StaticAssertTypeEq<
+      const NativeArray<int>,
+      StlContainerView<std::tuple<const int*, int>>::const_reference>();
+
+  int a1[3] = {0, 1, 2};
+  const int* const p1 = a1;
+  NativeArray<int> a2 =
+      StlContainerView<std::tuple<const int*, int>>::ConstReference(
+          std::make_tuple(p1, 3));
+  EXPECT_EQ(3U, a2.size());
+  EXPECT_EQ(a1, a2.begin());
+
+  const NativeArray<int> a3 = StlContainerView<std::tuple<int*, size_t>>::Copy(
+      std::make_tuple(static_cast<int*>(a1), 3));
+  ASSERT_EQ(3U, a3.size());
+  EXPECT_EQ(0, a3.begin()[0]);
+  EXPECT_EQ(1, a3.begin()[1]);
+  EXPECT_EQ(2, a3.begin()[2]);
+
+  // Makes sure a1 and a3 aren't aliases.
+  a1[0] = 3;
+  EXPECT_EQ(0, a3.begin()[0]);
+}
+
+// Tests the Function template struct.
+
+TEST(FunctionTest, Nullary) {
+  typedef Function<int()> F;  // NOLINT
+  EXPECT_EQ(0u, F::ArgumentCount);
+  EXPECT_TRUE((std::is_same<int, F::Result>::value));
+  EXPECT_TRUE((std::is_same<std::tuple<>, F::ArgumentTuple>::value));
+  EXPECT_TRUE((std::is_same<std::tuple<>, F::ArgumentMatcherTuple>::value));
+  EXPECT_TRUE((std::is_same<void(), F::MakeResultVoid>::value));
+  EXPECT_TRUE((std::is_same<IgnoredValue(), F::MakeResultIgnoredValue>::value));
+}
+
+TEST(FunctionTest, Unary) {
+  typedef Function<int(bool)> F;  // NOLINT
+  EXPECT_EQ(1u, F::ArgumentCount);
+  EXPECT_TRUE((std::is_same<int, F::Result>::value));
+  EXPECT_TRUE((std::is_same<bool, F::Arg<0>::type>::value));
+  EXPECT_TRUE((std::is_same<std::tuple<bool>, F::ArgumentTuple>::value));
+  EXPECT_TRUE((
+      std::is_same<std::tuple<Matcher<bool>>, F::ArgumentMatcherTuple>::value));
+  EXPECT_TRUE((std::is_same<void(bool), F::MakeResultVoid>::value));  // NOLINT
+  EXPECT_TRUE((std::is_same<IgnoredValue(bool),                       // NOLINT
+                            F::MakeResultIgnoredValue>::value));
+}
+
+TEST(FunctionTest, Binary) {
+  typedef Function<int(bool, const long&)> F;  // NOLINT
+  EXPECT_EQ(2u, F::ArgumentCount);
+  EXPECT_TRUE((std::is_same<int, F::Result>::value));
+  EXPECT_TRUE((std::is_same<bool, F::Arg<0>::type>::value));
+  EXPECT_TRUE((std::is_same<const long&, F::Arg<1>::type>::value));  // NOLINT
+  EXPECT_TRUE((std::is_same<std::tuple<bool, const long&>,           // NOLINT
+                            F::ArgumentTuple>::value));
+  EXPECT_TRUE(
+      (std::is_same<std::tuple<Matcher<bool>, Matcher<const long&>>,  // NOLINT
+                    F::ArgumentMatcherTuple>::value));
+  EXPECT_TRUE((std::is_same<void(bool, const long&),  // NOLINT
+                            F::MakeResultVoid>::value));
+  EXPECT_TRUE((std::is_same<IgnoredValue(bool, const long&),  // NOLINT
+                            F::MakeResultIgnoredValue>::value));
+}
+
+TEST(FunctionTest, LongArgumentList) {
+  typedef Function<char(bool, int, char*, int&, const long&)> F;  // NOLINT
+  EXPECT_EQ(5u, F::ArgumentCount);
+  EXPECT_TRUE((std::is_same<char, F::Result>::value));
+  EXPECT_TRUE((std::is_same<bool, F::Arg<0>::type>::value));
+  EXPECT_TRUE((std::is_same<int, F::Arg<1>::type>::value));
+  EXPECT_TRUE((std::is_same<char*, F::Arg<2>::type>::value));
+  EXPECT_TRUE((std::is_same<int&, F::Arg<3>::type>::value));
+  EXPECT_TRUE((std::is_same<const long&, F::Arg<4>::type>::value));  // NOLINT
+  EXPECT_TRUE(
+      (std::is_same<std::tuple<bool, int, char*, int&, const long&>,  // NOLINT
+                    F::ArgumentTuple>::value));
+  EXPECT_TRUE(
+      (std::is_same<
+          std::tuple<Matcher<bool>, Matcher<int>, Matcher<char*>, Matcher<int&>,
+                     Matcher<const long&>>,  // NOLINT
+          F::ArgumentMatcherTuple>::value));
+  EXPECT_TRUE(
+      (std::is_same<void(bool, int, char*, int&, const long&),  // NOLINT
+                    F::MakeResultVoid>::value));
+  EXPECT_TRUE((
+      std::is_same<IgnoredValue(bool, int, char*, int&, const long&),  // NOLINT
+                   F::MakeResultIgnoredValue>::value));
+}
+
+TEST(Base64Unescape, InvalidString) {
+  std::string unescaped;
+  EXPECT_FALSE(Base64Unescape("(invalid)", &unescaped));
+}
+
+TEST(Base64Unescape, ShortString) {
+  std::string unescaped;
+  EXPECT_TRUE(Base64Unescape("SGVsbG8gd29ybGQh", &unescaped));
+  EXPECT_EQ("Hello world!", unescaped);
+}
+
+TEST(Base64Unescape, ShortStringWithPadding) {
+  std::string unescaped;
+  EXPECT_TRUE(Base64Unescape("SGVsbG8gd29ybGQ=", &unescaped));
+  EXPECT_EQ("Hello world", unescaped);
+}
+
+TEST(Base64Unescape, ShortStringWithoutPadding) {
+  std::string unescaped;
+  EXPECT_TRUE(Base64Unescape("SGVsbG8gd29ybGQ", &unescaped));
+  EXPECT_EQ("Hello world", unescaped);
+}
+
+TEST(Base64Unescape, LongStringWithWhiteSpaces) {
+  std::string escaped =
+      R"(TWFuIGlzIGRpc3Rpbmd1aXNoZWQsIG5vdCBvbmx5IGJ5IGhpcyByZWFzb24sIGJ1dCBieSB0aGlz
+  IHNpbmd1bGFyIHBhc3Npb24gZnJvbSBvdGhlciBhbmltYWxzLCB3aGljaCBpcyBhIGx1c3Qgb2Yg
+  dGhlIG1pbmQsIHRoYXQgYnkgYSBwZXJzZXZlcmFuY2Ugb2YgZGVsaWdodCBpbiB0aGUgY29udGlu
+  dWVkIGFuZCBpbmRlZmF0aWdhYmxlIGdlbmVyYXRpb24gb2Yga25vd2xlZGdlLCBleGNlZWRzIHRo
+  ZSBzaG9ydCB2ZWhlbWVuY2Ugb2YgYW55IGNhcm5hbCBwbGVhc3VyZS4=)";
+  std::string expected =
+      "Man is distinguished, not only by his reason, but by this singular "
+      "passion from other animals, which is a lust of the mind, that by a "
+      "perseverance of delight in the continued and indefatigable generation "
+      "of knowledge, exceeds the short vehemence of any carnal pleasure.";
+  std::string unescaped;
+  EXPECT_TRUE(Base64Unescape(escaped, &unescaped));
+  EXPECT_EQ(expected, unescaped);
+}
+
+}  // namespace
+}  // namespace internal
+}  // namespace testing
diff --git a/third_party/googletest/googlemock/test/gmock-matchers-arithmetic_test.cc b/third_party/googletest/googlemock/test/gmock-matchers-arithmetic_test.cc
new file mode 100644
index 0000000..f176962
--- /dev/null
+++ b/third_party/googletest/googlemock/test/gmock-matchers-arithmetic_test.cc
@@ -0,0 +1,1516 @@
+// Copyright 2007, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Google Mock - a framework for writing C++ mock classes.
+//
+// This file tests some commonly used argument matchers.
+
+#include <cmath>
+#include <limits>
+#include <memory>
+#include <string>
+
+#include "test/gmock-matchers_test.h"
+
+// Silence warning C4244: 'initializing': conversion from 'int' to 'short',
+// possible loss of data and C4100, unreferenced local parameter
+GTEST_DISABLE_MSC_WARNINGS_PUSH_(4244 4100)
+
+namespace testing {
+namespace gmock_matchers_test {
+namespace {
+
+typedef ::std::tuple<long, int> Tuple2;  // NOLINT
+
+// Tests that Eq() matches a 2-tuple where the first field == the
+// second field.
+TEST(Eq2Test, MatchesEqualArguments) {
+  Matcher<const Tuple2&> m = Eq();
+  EXPECT_TRUE(m.Matches(Tuple2(5L, 5)));
+  EXPECT_FALSE(m.Matches(Tuple2(5L, 6)));
+}
+
+// Tests that Eq() describes itself properly.
+TEST(Eq2Test, CanDescribeSelf) {
+  Matcher<const Tuple2&> m = Eq();
+  EXPECT_EQ("are an equal pair", Describe(m));
+}
+
+// Tests that Ge() matches a 2-tuple where the first field >= the
+// second field.
+TEST(Ge2Test, MatchesGreaterThanOrEqualArguments) {
+  Matcher<const Tuple2&> m = Ge();
+  EXPECT_TRUE(m.Matches(Tuple2(5L, 4)));
+  EXPECT_TRUE(m.Matches(Tuple2(5L, 5)));
+  EXPECT_FALSE(m.Matches(Tuple2(5L, 6)));
+}
+
+// Tests that Ge() describes itself properly.
+TEST(Ge2Test, CanDescribeSelf) {
+  Matcher<const Tuple2&> m = Ge();
+  EXPECT_EQ("are a pair where the first >= the second", Describe(m));
+}
+
+// Tests that Gt() matches a 2-tuple where the first field > the
+// second field.
+TEST(Gt2Test, MatchesGreaterThanArguments) {
+  Matcher<const Tuple2&> m = Gt();
+  EXPECT_TRUE(m.Matches(Tuple2(5L, 4)));
+  EXPECT_FALSE(m.Matches(Tuple2(5L, 5)));
+  EXPECT_FALSE(m.Matches(Tuple2(5L, 6)));
+}
+
+// Tests that Gt() describes itself properly.
+TEST(Gt2Test, CanDescribeSelf) {
+  Matcher<const Tuple2&> m = Gt();
+  EXPECT_EQ("are a pair where the first > the second", Describe(m));
+}
+
+// Tests that Le() matches a 2-tuple where the first field <= the
+// second field.
+TEST(Le2Test, MatchesLessThanOrEqualArguments) {
+  Matcher<const Tuple2&> m = Le();
+  EXPECT_TRUE(m.Matches(Tuple2(5L, 6)));
+  EXPECT_TRUE(m.Matches(Tuple2(5L, 5)));
+  EXPECT_FALSE(m.Matches(Tuple2(5L, 4)));
+}
+
+// Tests that Le() describes itself properly.
+TEST(Le2Test, CanDescribeSelf) {
+  Matcher<const Tuple2&> m = Le();
+  EXPECT_EQ("are a pair where the first <= the second", Describe(m));
+}
+
+// Tests that Lt() matches a 2-tuple where the first field < the
+// second field.
+TEST(Lt2Test, MatchesLessThanArguments) {
+  Matcher<const Tuple2&> m = Lt();
+  EXPECT_TRUE(m.Matches(Tuple2(5L, 6)));
+  EXPECT_FALSE(m.Matches(Tuple2(5L, 5)));
+  EXPECT_FALSE(m.Matches(Tuple2(5L, 4)));
+}
+
+// Tests that Lt() describes itself properly.
+TEST(Lt2Test, CanDescribeSelf) {
+  Matcher<const Tuple2&> m = Lt();
+  EXPECT_EQ("are a pair where the first < the second", Describe(m));
+}
+
+// Tests that Ne() matches a 2-tuple where the first field != the
+// second field.
+TEST(Ne2Test, MatchesUnequalArguments) {
+  Matcher<const Tuple2&> m = Ne();
+  EXPECT_TRUE(m.Matches(Tuple2(5L, 6)));
+  EXPECT_TRUE(m.Matches(Tuple2(5L, 4)));
+  EXPECT_FALSE(m.Matches(Tuple2(5L, 5)));
+}
+
+// Tests that Ne() describes itself properly.
+TEST(Ne2Test, CanDescribeSelf) {
+  Matcher<const Tuple2&> m = Ne();
+  EXPECT_EQ("are an unequal pair", Describe(m));
+}
+
+TEST(PairMatchBaseTest, WorksWithMoveOnly) {
+  using Pointers = std::tuple<std::unique_ptr<int>, std::unique_ptr<int>>;
+  Matcher<Pointers> matcher = Eq();
+  Pointers pointers;
+  // Tested values don't matter; the point is that matcher does not copy the
+  // matched values.
+  EXPECT_TRUE(matcher.Matches(pointers));
+}
+
+// Tests that IsNan() matches a NaN, with float.
+TEST(IsNan, FloatMatchesNan) {
+  float quiet_nan = std::numeric_limits<float>::quiet_NaN();
+  float other_nan = std::nanf("1");
+  float real_value = 1.0f;
+
+  Matcher<float> m = IsNan();
+  EXPECT_TRUE(m.Matches(quiet_nan));
+  EXPECT_TRUE(m.Matches(other_nan));
+  EXPECT_FALSE(m.Matches(real_value));
+
+  Matcher<float&> m_ref = IsNan();
+  EXPECT_TRUE(m_ref.Matches(quiet_nan));
+  EXPECT_TRUE(m_ref.Matches(other_nan));
+  EXPECT_FALSE(m_ref.Matches(real_value));
+
+  Matcher<const float&> m_cref = IsNan();
+  EXPECT_TRUE(m_cref.Matches(quiet_nan));
+  EXPECT_TRUE(m_cref.Matches(other_nan));
+  EXPECT_FALSE(m_cref.Matches(real_value));
+}
+
+// Tests that IsNan() matches a NaN, with double.
+TEST(IsNan, DoubleMatchesNan) {
+  double quiet_nan = std::numeric_limits<double>::quiet_NaN();
+  double other_nan = std::nan("1");
+  double real_value = 1.0;
+
+  Matcher<double> m = IsNan();
+  EXPECT_TRUE(m.Matches(quiet_nan));
+  EXPECT_TRUE(m.Matches(other_nan));
+  EXPECT_FALSE(m.Matches(real_value));
+
+  Matcher<double&> m_ref = IsNan();
+  EXPECT_TRUE(m_ref.Matches(quiet_nan));
+  EXPECT_TRUE(m_ref.Matches(other_nan));
+  EXPECT_FALSE(m_ref.Matches(real_value));
+
+  Matcher<const double&> m_cref = IsNan();
+  EXPECT_TRUE(m_cref.Matches(quiet_nan));
+  EXPECT_TRUE(m_cref.Matches(other_nan));
+  EXPECT_FALSE(m_cref.Matches(real_value));
+}
+
+// Tests that IsNan() matches a NaN, with long double.
+TEST(IsNan, LongDoubleMatchesNan) {
+  long double quiet_nan = std::numeric_limits<long double>::quiet_NaN();
+  long double other_nan = std::nan("1");
+  long double real_value = 1.0;
+
+  Matcher<long double> m = IsNan();
+  EXPECT_TRUE(m.Matches(quiet_nan));
+  EXPECT_TRUE(m.Matches(other_nan));
+  EXPECT_FALSE(m.Matches(real_value));
+
+  Matcher<long double&> m_ref = IsNan();
+  EXPECT_TRUE(m_ref.Matches(quiet_nan));
+  EXPECT_TRUE(m_ref.Matches(other_nan));
+  EXPECT_FALSE(m_ref.Matches(real_value));
+
+  Matcher<const long double&> m_cref = IsNan();
+  EXPECT_TRUE(m_cref.Matches(quiet_nan));
+  EXPECT_TRUE(m_cref.Matches(other_nan));
+  EXPECT_FALSE(m_cref.Matches(real_value));
+}
+
+// Tests that IsNan() works with Not.
+TEST(IsNan, NotMatchesNan) {
+  Matcher<float> mf = Not(IsNan());
+  EXPECT_FALSE(mf.Matches(std::numeric_limits<float>::quiet_NaN()));
+  EXPECT_FALSE(mf.Matches(std::nanf("1")));
+  EXPECT_TRUE(mf.Matches(1.0));
+
+  Matcher<double> md = Not(IsNan());
+  EXPECT_FALSE(md.Matches(std::numeric_limits<double>::quiet_NaN()));
+  EXPECT_FALSE(md.Matches(std::nan("1")));
+  EXPECT_TRUE(md.Matches(1.0));
+
+  Matcher<long double> mld = Not(IsNan());
+  EXPECT_FALSE(mld.Matches(std::numeric_limits<long double>::quiet_NaN()));
+  EXPECT_FALSE(mld.Matches(std::nanl("1")));
+  EXPECT_TRUE(mld.Matches(1.0));
+}
+
+// Tests that IsNan() can describe itself.
+TEST(IsNan, CanDescribeSelf) {
+  Matcher<float> mf = IsNan();
+  EXPECT_EQ("is NaN", Describe(mf));
+
+  Matcher<double> md = IsNan();
+  EXPECT_EQ("is NaN", Describe(md));
+
+  Matcher<long double> mld = IsNan();
+  EXPECT_EQ("is NaN", Describe(mld));
+}
+
+// Tests that IsNan() can describe itself with Not.
+TEST(IsNan, CanDescribeSelfWithNot) {
+  Matcher<float> mf = Not(IsNan());
+  EXPECT_EQ("isn't NaN", Describe(mf));
+
+  Matcher<double> md = Not(IsNan());
+  EXPECT_EQ("isn't NaN", Describe(md));
+
+  Matcher<long double> mld = Not(IsNan());
+  EXPECT_EQ("isn't NaN", Describe(mld));
+}
+
+// Tests that FloatEq() matches a 2-tuple where
+// FloatEq(first field) matches the second field.
+TEST(FloatEq2Test, MatchesEqualArguments) {
+  typedef ::std::tuple<float, float> Tpl;
+  Matcher<const Tpl&> m = FloatEq();
+  EXPECT_TRUE(m.Matches(Tpl(1.0f, 1.0f)));
+  EXPECT_TRUE(m.Matches(Tpl(0.3f, 0.1f + 0.1f + 0.1f)));
+  EXPECT_FALSE(m.Matches(Tpl(1.1f, 1.0f)));
+}
+
+// Tests that FloatEq() describes itself properly.
+TEST(FloatEq2Test, CanDescribeSelf) {
+  Matcher<const ::std::tuple<float, float>&> m = FloatEq();
+  EXPECT_EQ("are an almost-equal pair", Describe(m));
+}
+
+// Tests that NanSensitiveFloatEq() matches a 2-tuple where
+// NanSensitiveFloatEq(first field) matches the second field.
+TEST(NanSensitiveFloatEqTest, MatchesEqualArgumentsWithNaN) {
+  typedef ::std::tuple<float, float> Tpl;
+  Matcher<const Tpl&> m = NanSensitiveFloatEq();
+  EXPECT_TRUE(m.Matches(Tpl(1.0f, 1.0f)));
+  EXPECT_TRUE(m.Matches(Tpl(std::numeric_limits<float>::quiet_NaN(),
+                            std::numeric_limits<float>::quiet_NaN())));
+  EXPECT_FALSE(m.Matches(Tpl(1.1f, 1.0f)));
+  EXPECT_FALSE(m.Matches(Tpl(1.0f, std::numeric_limits<float>::quiet_NaN())));
+  EXPECT_FALSE(m.Matches(Tpl(std::numeric_limits<float>::quiet_NaN(), 1.0f)));
+}
+
+// Tests that NanSensitiveFloatEq() describes itself properly.
+TEST(NanSensitiveFloatEqTest, CanDescribeSelfWithNaNs) {
+  Matcher<const ::std::tuple<float, float>&> m = NanSensitiveFloatEq();
+  EXPECT_EQ("are an almost-equal pair", Describe(m));
+}
+
+// Tests that DoubleEq() matches a 2-tuple where
+// DoubleEq(first field) matches the second field.
+TEST(DoubleEq2Test, MatchesEqualArguments) {
+  typedef ::std::tuple<double, double> Tpl;
+  Matcher<const Tpl&> m = DoubleEq();
+  EXPECT_TRUE(m.Matches(Tpl(1.0, 1.0)));
+  EXPECT_TRUE(m.Matches(Tpl(0.3, 0.1 + 0.1 + 0.1)));
+  EXPECT_FALSE(m.Matches(Tpl(1.1, 1.0)));
+}
+
+// Tests that DoubleEq() describes itself properly.
+TEST(DoubleEq2Test, CanDescribeSelf) {
+  Matcher<const ::std::tuple<double, double>&> m = DoubleEq();
+  EXPECT_EQ("are an almost-equal pair", Describe(m));
+}
+
+// Tests that NanSensitiveDoubleEq() matches a 2-tuple where
+// NanSensitiveDoubleEq(first field) matches the second field.
+TEST(NanSensitiveDoubleEqTest, MatchesEqualArgumentsWithNaN) {
+  typedef ::std::tuple<double, double> Tpl;
+  Matcher<const Tpl&> m = NanSensitiveDoubleEq();
+  EXPECT_TRUE(m.Matches(Tpl(1.0f, 1.0f)));
+  EXPECT_TRUE(m.Matches(Tpl(std::numeric_limits<double>::quiet_NaN(),
+                            std::numeric_limits<double>::quiet_NaN())));
+  EXPECT_FALSE(m.Matches(Tpl(1.1f, 1.0f)));
+  EXPECT_FALSE(m.Matches(Tpl(1.0f, std::numeric_limits<double>::quiet_NaN())));
+  EXPECT_FALSE(m.Matches(Tpl(std::numeric_limits<double>::quiet_NaN(), 1.0f)));
+}
+
+// Tests that DoubleEq() describes itself properly.
+TEST(NanSensitiveDoubleEqTest, CanDescribeSelfWithNaNs) {
+  Matcher<const ::std::tuple<double, double>&> m = NanSensitiveDoubleEq();
+  EXPECT_EQ("are an almost-equal pair", Describe(m));
+}
+
+// Tests that FloatEq() matches a 2-tuple where
+// FloatNear(first field, max_abs_error) matches the second field.
+TEST(FloatNear2Test, MatchesEqualArguments) {
+  typedef ::std::tuple<float, float> Tpl;
+  Matcher<const Tpl&> m = FloatNear(0.5f);
+  EXPECT_TRUE(m.Matches(Tpl(1.0f, 1.0f)));
+  EXPECT_TRUE(m.Matches(Tpl(1.3f, 1.0f)));
+  EXPECT_FALSE(m.Matches(Tpl(1.8f, 1.0f)));
+}
+
+// Tests that FloatNear() describes itself properly.
+TEST(FloatNear2Test, CanDescribeSelf) {
+  Matcher<const ::std::tuple<float, float>&> m = FloatNear(0.5f);
+  EXPECT_EQ("are an almost-equal pair", Describe(m));
+}
+
+// Tests that NanSensitiveFloatNear() matches a 2-tuple where
+// NanSensitiveFloatNear(first field) matches the second field.
+TEST(NanSensitiveFloatNearTest, MatchesNearbyArgumentsWithNaN) {
+  typedef ::std::tuple<float, float> Tpl;
+  Matcher<const Tpl&> m = NanSensitiveFloatNear(0.5f);
+  EXPECT_TRUE(m.Matches(Tpl(1.0f, 1.0f)));
+  EXPECT_TRUE(m.Matches(Tpl(1.1f, 1.0f)));
+  EXPECT_TRUE(m.Matches(Tpl(std::numeric_limits<float>::quiet_NaN(),
+                            std::numeric_limits<float>::quiet_NaN())));
+  EXPECT_FALSE(m.Matches(Tpl(1.6f, 1.0f)));
+  EXPECT_FALSE(m.Matches(Tpl(1.0f, std::numeric_limits<float>::quiet_NaN())));
+  EXPECT_FALSE(m.Matches(Tpl(std::numeric_limits<float>::quiet_NaN(), 1.0f)));
+}
+
+// Tests that NanSensitiveFloatNear() describes itself properly.
+TEST(NanSensitiveFloatNearTest, CanDescribeSelfWithNaNs) {
+  Matcher<const ::std::tuple<float, float>&> m = NanSensitiveFloatNear(0.5f);
+  EXPECT_EQ("are an almost-equal pair", Describe(m));
+}
+
+// Tests that FloatEq() matches a 2-tuple where
+// DoubleNear(first field, max_abs_error) matches the second field.
+TEST(DoubleNear2Test, MatchesEqualArguments) {
+  typedef ::std::tuple<double, double> Tpl;
+  Matcher<const Tpl&> m = DoubleNear(0.5);
+  EXPECT_TRUE(m.Matches(Tpl(1.0, 1.0)));
+  EXPECT_TRUE(m.Matches(Tpl(1.3, 1.0)));
+  EXPECT_FALSE(m.Matches(Tpl(1.8, 1.0)));
+}
+
+// Tests that DoubleNear() describes itself properly.
+TEST(DoubleNear2Test, CanDescribeSelf) {
+  Matcher<const ::std::tuple<double, double>&> m = DoubleNear(0.5);
+  EXPECT_EQ("are an almost-equal pair", Describe(m));
+}
+
+// Tests that NanSensitiveDoubleNear() matches a 2-tuple where
+// NanSensitiveDoubleNear(first field) matches the second field.
+TEST(NanSensitiveDoubleNearTest, MatchesNearbyArgumentsWithNaN) {
+  typedef ::std::tuple<double, double> Tpl;
+  Matcher<const Tpl&> m = NanSensitiveDoubleNear(0.5f);
+  EXPECT_TRUE(m.Matches(Tpl(1.0f, 1.0f)));
+  EXPECT_TRUE(m.Matches(Tpl(1.1f, 1.0f)));
+  EXPECT_TRUE(m.Matches(Tpl(std::numeric_limits<double>::quiet_NaN(),
+                            std::numeric_limits<double>::quiet_NaN())));
+  EXPECT_FALSE(m.Matches(Tpl(1.6f, 1.0f)));
+  EXPECT_FALSE(m.Matches(Tpl(1.0f, std::numeric_limits<double>::quiet_NaN())));
+  EXPECT_FALSE(m.Matches(Tpl(std::numeric_limits<double>::quiet_NaN(), 1.0f)));
+}
+
+// Tests that NanSensitiveDoubleNear() describes itself properly.
+TEST(NanSensitiveDoubleNearTest, CanDescribeSelfWithNaNs) {
+  Matcher<const ::std::tuple<double, double>&> m = NanSensitiveDoubleNear(0.5f);
+  EXPECT_EQ("are an almost-equal pair", Describe(m));
+}
+
+// Tests that Not(m) matches any value that doesn't match m.
+TEST(NotTest, NegatesMatcher) {
+  Matcher<int> m;
+  m = Not(Eq(2));
+  EXPECT_TRUE(m.Matches(3));
+  EXPECT_FALSE(m.Matches(2));
+}
+
+// Tests that Not(m) describes itself properly.
+TEST(NotTest, CanDescribeSelf) {
+  Matcher<int> m = Not(Eq(5));
+  EXPECT_EQ("isn't equal to 5", Describe(m));
+}
+
+// Tests that monomorphic matchers are safely cast by the Not matcher.
+TEST(NotTest, NotMatcherSafelyCastsMonomorphicMatchers) {
+  // greater_than_5 is a monomorphic matcher.
+  Matcher<int> greater_than_5 = Gt(5);
+
+  Matcher<const int&> m = Not(greater_than_5);
+  Matcher<int&> m2 = Not(greater_than_5);
+  Matcher<int&> m3 = Not(m);
+}
+
+// Helper to allow easy testing of AllOf matchers with num parameters.
+void AllOfMatches(int num, const Matcher<int>& m) {
+  SCOPED_TRACE(Describe(m));
+  EXPECT_TRUE(m.Matches(0));
+  for (int i = 1; i <= num; ++i) {
+    EXPECT_FALSE(m.Matches(i));
+  }
+  EXPECT_TRUE(m.Matches(num + 1));
+}
+
+INSTANTIATE_GTEST_MATCHER_TEST_P(AllOfTest);
+
+// Tests that AllOf(m1, ..., mn) matches any value that matches all of
+// the given matchers.
+TEST(AllOfTest, MatchesWhenAllMatch) {
+  Matcher<int> m;
+  m = AllOf(Le(2), Ge(1));
+  EXPECT_TRUE(m.Matches(1));
+  EXPECT_TRUE(m.Matches(2));
+  EXPECT_FALSE(m.Matches(0));
+  EXPECT_FALSE(m.Matches(3));
+
+  m = AllOf(Gt(0), Ne(1), Ne(2));
+  EXPECT_TRUE(m.Matches(3));
+  EXPECT_FALSE(m.Matches(2));
+  EXPECT_FALSE(m.Matches(1));
+  EXPECT_FALSE(m.Matches(0));
+
+  m = AllOf(Gt(0), Ne(1), Ne(2), Ne(3));
+  EXPECT_TRUE(m.Matches(4));
+  EXPECT_FALSE(m.Matches(3));
+  EXPECT_FALSE(m.Matches(2));
+  EXPECT_FALSE(m.Matches(1));
+  EXPECT_FALSE(m.Matches(0));
+
+  m = AllOf(Ge(0), Lt(10), Ne(3), Ne(5), Ne(7));
+  EXPECT_TRUE(m.Matches(0));
+  EXPECT_TRUE(m.Matches(1));
+  EXPECT_FALSE(m.Matches(3));
+
+  // The following tests for varying number of sub-matchers. Due to the way
+  // the sub-matchers are handled it is enough to test every sub-matcher once
+  // with sub-matchers using the same matcher type. Varying matcher types are
+  // checked for above.
+  AllOfMatches(2, AllOf(Ne(1), Ne(2)));
+  AllOfMatches(3, AllOf(Ne(1), Ne(2), Ne(3)));
+  AllOfMatches(4, AllOf(Ne(1), Ne(2), Ne(3), Ne(4)));
+  AllOfMatches(5, AllOf(Ne(1), Ne(2), Ne(3), Ne(4), Ne(5)));
+  AllOfMatches(6, AllOf(Ne(1), Ne(2), Ne(3), Ne(4), Ne(5), Ne(6)));
+  AllOfMatches(7, AllOf(Ne(1), Ne(2), Ne(3), Ne(4), Ne(5), Ne(6), Ne(7)));
+  AllOfMatches(8,
+               AllOf(Ne(1), Ne(2), Ne(3), Ne(4), Ne(5), Ne(6), Ne(7), Ne(8)));
+  AllOfMatches(
+      9, AllOf(Ne(1), Ne(2), Ne(3), Ne(4), Ne(5), Ne(6), Ne(7), Ne(8), Ne(9)));
+  AllOfMatches(10, AllOf(Ne(1), Ne(2), Ne(3), Ne(4), Ne(5), Ne(6), Ne(7), Ne(8),
+                         Ne(9), Ne(10)));
+  AllOfMatches(
+      50, AllOf(Ne(1), Ne(2), Ne(3), Ne(4), Ne(5), Ne(6), Ne(7), Ne(8), Ne(9),
+                Ne(10), Ne(11), Ne(12), Ne(13), Ne(14), Ne(15), Ne(16), Ne(17),
+                Ne(18), Ne(19), Ne(20), Ne(21), Ne(22), Ne(23), Ne(24), Ne(25),
+                Ne(26), Ne(27), Ne(28), Ne(29), Ne(30), Ne(31), Ne(32), Ne(33),
+                Ne(34), Ne(35), Ne(36), Ne(37), Ne(38), Ne(39), Ne(40), Ne(41),
+                Ne(42), Ne(43), Ne(44), Ne(45), Ne(46), Ne(47), Ne(48), Ne(49),
+                Ne(50)));
+}
+
+// Tests that AllOf(m1, ..., mn) describes itself properly.
+TEST(AllOfTest, CanDescribeSelf) {
+  Matcher<int> m;
+  m = AllOf(Le(2), Ge(1));
+  EXPECT_EQ("(is <= 2) and (is >= 1)", Describe(m));
+
+  m = AllOf(Gt(0), Ne(1), Ne(2));
+  std::string expected_descr1 =
+      "(is > 0) and (isn't equal to 1) and (isn't equal to 2)";
+  EXPECT_EQ(expected_descr1, Describe(m));
+
+  m = AllOf(Gt(0), Ne(1), Ne(2), Ne(3));
+  std::string expected_descr2 =
+      "(is > 0) and (isn't equal to 1) and (isn't equal to 2) and (isn't equal "
+      "to 3)";
+  EXPECT_EQ(expected_descr2, Describe(m));
+
+  m = AllOf(Ge(0), Lt(10), Ne(3), Ne(5), Ne(7));
+  std::string expected_descr3 =
+      "(is >= 0) and (is < 10) and (isn't equal to 3) and (isn't equal to 5) "
+      "and (isn't equal to 7)";
+  EXPECT_EQ(expected_descr3, Describe(m));
+}
+
+// Tests that AllOf(m1, ..., mn) describes its negation properly.
+TEST(AllOfTest, CanDescribeNegation) {
+  Matcher<int> m;
+  m = AllOf(Le(2), Ge(1));
+  std::string expected_descr4 = "(isn't <= 2) or (isn't >= 1)";
+  EXPECT_EQ(expected_descr4, DescribeNegation(m));
+
+  m = AllOf(Gt(0), Ne(1), Ne(2));
+  std::string expected_descr5 =
+      "(isn't > 0) or (is equal to 1) or (is equal to 2)";
+  EXPECT_EQ(expected_descr5, DescribeNegation(m));
+
+  m = AllOf(Gt(0), Ne(1), Ne(2), Ne(3));
+  std::string expected_descr6 =
+      "(isn't > 0) or (is equal to 1) or (is equal to 2) or (is equal to 3)";
+  EXPECT_EQ(expected_descr6, DescribeNegation(m));
+
+  m = AllOf(Ge(0), Lt(10), Ne(3), Ne(5), Ne(7));
+  std::string expected_desr7 =
+      "(isn't >= 0) or (isn't < 10) or (is equal to 3) or (is equal to 5) or "
+      "(is equal to 7)";
+  EXPECT_EQ(expected_desr7, DescribeNegation(m));
+
+  m = AllOf(Ne(1), Ne(2), Ne(3), Ne(4), Ne(5), Ne(6), Ne(7), Ne(8), Ne(9),
+            Ne(10), Ne(11));
+  AllOf(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11);
+  EXPECT_THAT(Describe(m), EndsWith("and (isn't equal to 11)"));
+  AllOfMatches(11, m);
+}
+
+// Tests that monomorphic matchers are safely cast by the AllOf matcher.
+TEST(AllOfTest, AllOfMatcherSafelyCastsMonomorphicMatchers) {
+  // greater_than_5 and less_than_10 are monomorphic matchers.
+  Matcher<int> greater_than_5 = Gt(5);
+  Matcher<int> less_than_10 = Lt(10);
+
+  Matcher<const int&> m = AllOf(greater_than_5, less_than_10);
+  Matcher<int&> m2 = AllOf(greater_than_5, less_than_10);
+  Matcher<int&> m3 = AllOf(greater_than_5, m2);
+
+  // Tests that BothOf works when composing itself.
+  Matcher<const int&> m4 = AllOf(greater_than_5, less_than_10, less_than_10);
+  Matcher<int&> m5 = AllOf(greater_than_5, less_than_10, less_than_10);
+}
+
+TEST_P(AllOfTestP, ExplainsResult) {
+  Matcher<int> m;
+
+  // Successful match.  Both matchers need to explain.  The second
+  // matcher doesn't give an explanation, so only the first matcher's
+  // explanation is printed.
+  m = AllOf(GreaterThan(10), Lt(30));
+  EXPECT_EQ("which is 15 more than 10", Explain(m, 25));
+
+  // Successful match.  Both matchers need to explain.
+  m = AllOf(GreaterThan(10), GreaterThan(20));
+  EXPECT_EQ("which is 20 more than 10, and which is 10 more than 20",
+            Explain(m, 30));
+
+  // Successful match.  All matchers need to explain.  The second
+  // matcher doesn't given an explanation.
+  m = AllOf(GreaterThan(10), Lt(30), GreaterThan(20));
+  EXPECT_EQ("which is 15 more than 10, and which is 5 more than 20",
+            Explain(m, 25));
+
+  // Successful match.  All matchers need to explain.
+  m = AllOf(GreaterThan(10), GreaterThan(20), GreaterThan(30));
+  EXPECT_EQ(
+      "which is 30 more than 10, and which is 20 more than 20, "
+      "and which is 10 more than 30",
+      Explain(m, 40));
+
+  // Failed match.  The first matcher, which failed, needs to
+  // explain.
+  m = AllOf(GreaterThan(10), GreaterThan(20));
+  EXPECT_EQ("which is 5 less than 10", Explain(m, 5));
+
+  // Failed match.  The second matcher, which failed, needs to
+  // explain.  Since it doesn't given an explanation, nothing is
+  // printed.
+  m = AllOf(GreaterThan(10), Lt(30));
+  EXPECT_EQ("", Explain(m, 40));
+
+  // Failed match.  The second matcher, which failed, needs to
+  // explain.
+  m = AllOf(GreaterThan(10), GreaterThan(20));
+  EXPECT_EQ("which is 5 less than 20", Explain(m, 15));
+}
+
+// Helper to allow easy testing of AnyOf matchers with num parameters.
+static void AnyOfMatches(int num, const Matcher<int>& m) {
+  SCOPED_TRACE(Describe(m));
+  EXPECT_FALSE(m.Matches(0));
+  for (int i = 1; i <= num; ++i) {
+    EXPECT_TRUE(m.Matches(i));
+  }
+  EXPECT_FALSE(m.Matches(num + 1));
+}
+
+static void AnyOfStringMatches(int num, const Matcher<std::string>& m) {
+  SCOPED_TRACE(Describe(m));
+  EXPECT_FALSE(m.Matches(std::to_string(0)));
+
+  for (int i = 1; i <= num; ++i) {
+    EXPECT_TRUE(m.Matches(std::to_string(i)));
+  }
+  EXPECT_FALSE(m.Matches(std::to_string(num + 1)));
+}
+
+INSTANTIATE_GTEST_MATCHER_TEST_P(AnyOfTest);
+
+// Tests that AnyOf(m1, ..., mn) matches any value that matches at
+// least one of the given matchers.
+TEST(AnyOfTest, MatchesWhenAnyMatches) {
+  Matcher<int> m;
+  m = AnyOf(Le(1), Ge(3));
+  EXPECT_TRUE(m.Matches(1));
+  EXPECT_TRUE(m.Matches(4));
+  EXPECT_FALSE(m.Matches(2));
+
+  m = AnyOf(Lt(0), Eq(1), Eq(2));
+  EXPECT_TRUE(m.Matches(-1));
+  EXPECT_TRUE(m.Matches(1));
+  EXPECT_TRUE(m.Matches(2));
+  EXPECT_FALSE(m.Matches(0));
+
+  m = AnyOf(Lt(0), Eq(1), Eq(2), Eq(3));
+  EXPECT_TRUE(m.Matches(-1));
+  EXPECT_TRUE(m.Matches(1));
+  EXPECT_TRUE(m.Matches(2));
+  EXPECT_TRUE(m.Matches(3));
+  EXPECT_FALSE(m.Matches(0));
+
+  m = AnyOf(Le(0), Gt(10), 3, 5, 7);
+  EXPECT_TRUE(m.Matches(0));
+  EXPECT_TRUE(m.Matches(11));
+  EXPECT_TRUE(m.Matches(3));
+  EXPECT_FALSE(m.Matches(2));
+
+  // The following tests for varying number of sub-matchers. Due to the way
+  // the sub-matchers are handled it is enough to test every sub-matcher once
+  // with sub-matchers using the same matcher type. Varying matcher types are
+  // checked for above.
+  AnyOfMatches(2, AnyOf(1, 2));
+  AnyOfMatches(3, AnyOf(1, 2, 3));
+  AnyOfMatches(4, AnyOf(1, 2, 3, 4));
+  AnyOfMatches(5, AnyOf(1, 2, 3, 4, 5));
+  AnyOfMatches(6, AnyOf(1, 2, 3, 4, 5, 6));
+  AnyOfMatches(7, AnyOf(1, 2, 3, 4, 5, 6, 7));
+  AnyOfMatches(8, AnyOf(1, 2, 3, 4, 5, 6, 7, 8));
+  AnyOfMatches(9, AnyOf(1, 2, 3, 4, 5, 6, 7, 8, 9));
+  AnyOfMatches(10, AnyOf(1, 2, 3, 4, 5, 6, 7, 8, 9, 10));
+}
+
+// Tests the variadic version of the AnyOfMatcher.
+TEST(AnyOfTest, VariadicMatchesWhenAnyMatches) {
+  // Also make sure AnyOf is defined in the right namespace and does not depend
+  // on ADL.
+  Matcher<int> m = ::testing::AnyOf(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11);
+
+  EXPECT_THAT(Describe(m), EndsWith("or (is equal to 11)"));
+  AnyOfMatches(11, m);
+  AnyOfMatches(50, AnyOf(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16,
+                         17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30,
+                         31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44,
+                         45, 46, 47, 48, 49, 50));
+  AnyOfStringMatches(
+      50, AnyOf("1", "2", "3", "4", "5", "6", "7", "8", "9", "10", "11", "12",
+                "13", "14", "15", "16", "17", "18", "19", "20", "21", "22",
+                "23", "24", "25", "26", "27", "28", "29", "30", "31", "32",
+                "33", "34", "35", "36", "37", "38", "39", "40", "41", "42",
+                "43", "44", "45", "46", "47", "48", "49", "50"));
+}
+
+TEST(ConditionalTest, MatchesFirstIfCondition) {
+  Matcher<std::string> eq_red = Eq("red");
+  Matcher<std::string> ne_red = Ne("red");
+  Matcher<std::string> m = Conditional(true, eq_red, ne_red);
+  EXPECT_TRUE(m.Matches("red"));
+  EXPECT_FALSE(m.Matches("green"));
+
+  StringMatchResultListener listener;
+  StringMatchResultListener expected;
+  EXPECT_FALSE(m.MatchAndExplain("green", &listener));
+  EXPECT_FALSE(eq_red.MatchAndExplain("green", &expected));
+  EXPECT_THAT(listener.str(), Eq(expected.str()));
+}
+
+TEST(ConditionalTest, MatchesSecondIfCondition) {
+  Matcher<std::string> eq_red = Eq("red");
+  Matcher<std::string> ne_red = Ne("red");
+  Matcher<std::string> m = Conditional(false, eq_red, ne_red);
+  EXPECT_FALSE(m.Matches("red"));
+  EXPECT_TRUE(m.Matches("green"));
+
+  StringMatchResultListener listener;
+  StringMatchResultListener expected;
+  EXPECT_FALSE(m.MatchAndExplain("red", &listener));
+  EXPECT_FALSE(ne_red.MatchAndExplain("red", &expected));
+  EXPECT_THAT(listener.str(), Eq(expected.str()));
+}
+
+// Tests that AnyOf(m1, ..., mn) describes itself properly.
+TEST(AnyOfTest, CanDescribeSelf) {
+  Matcher<int> m;
+  m = AnyOf(Le(1), Ge(3));
+
+  EXPECT_EQ("(is <= 1) or (is >= 3)", Describe(m));
+
+  m = AnyOf(Lt(0), Eq(1), Eq(2));
+  EXPECT_EQ("(is < 0) or (is equal to 1) or (is equal to 2)", Describe(m));
+
+  m = AnyOf(Lt(0), Eq(1), Eq(2), Eq(3));
+  EXPECT_EQ("(is < 0) or (is equal to 1) or (is equal to 2) or (is equal to 3)",
+            Describe(m));
+
+  m = AnyOf(Le(0), Gt(10), 3, 5, 7);
+  EXPECT_EQ(
+      "(is <= 0) or (is > 10) or (is equal to 3) or (is equal to 5) or (is "
+      "equal to 7)",
+      Describe(m));
+}
+
+// Tests that AnyOf(m1, ..., mn) describes its negation properly.
+TEST(AnyOfTest, CanDescribeNegation) {
+  Matcher<int> m;
+  m = AnyOf(Le(1), Ge(3));
+  EXPECT_EQ("(isn't <= 1) and (isn't >= 3)", DescribeNegation(m));
+
+  m = AnyOf(Lt(0), Eq(1), Eq(2));
+  EXPECT_EQ("(isn't < 0) and (isn't equal to 1) and (isn't equal to 2)",
+            DescribeNegation(m));
+
+  m = AnyOf(Lt(0), Eq(1), Eq(2), Eq(3));
+  EXPECT_EQ(
+      "(isn't < 0) and (isn't equal to 1) and (isn't equal to 2) and (isn't "
+      "equal to 3)",
+      DescribeNegation(m));
+
+  m = AnyOf(Le(0), Gt(10), 3, 5, 7);
+  EXPECT_EQ(
+      "(isn't <= 0) and (isn't > 10) and (isn't equal to 3) and (isn't equal "
+      "to 5) and (isn't equal to 7)",
+      DescribeNegation(m));
+}
+
+// Tests that monomorphic matchers are safely cast by the AnyOf matcher.
+TEST(AnyOfTest, AnyOfMatcherSafelyCastsMonomorphicMatchers) {
+  // greater_than_5 and less_than_10 are monomorphic matchers.
+  Matcher<int> greater_than_5 = Gt(5);
+  Matcher<int> less_than_10 = Lt(10);
+
+  Matcher<const int&> m = AnyOf(greater_than_5, less_than_10);
+  Matcher<int&> m2 = AnyOf(greater_than_5, less_than_10);
+  Matcher<int&> m3 = AnyOf(greater_than_5, m2);
+
+  // Tests that EitherOf works when composing itself.
+  Matcher<const int&> m4 = AnyOf(greater_than_5, less_than_10, less_than_10);
+  Matcher<int&> m5 = AnyOf(greater_than_5, less_than_10, less_than_10);
+}
+
+TEST_P(AnyOfTestP, ExplainsResult) {
+  Matcher<int> m;
+
+  // Failed match.  Both matchers need to explain.  The second
+  // matcher doesn't give an explanation, so only the first matcher's
+  // explanation is printed.
+  m = AnyOf(GreaterThan(10), Lt(0));
+  EXPECT_EQ("which is 5 less than 10", Explain(m, 5));
+
+  // Failed match.  Both matchers need to explain.
+  m = AnyOf(GreaterThan(10), GreaterThan(20));
+  EXPECT_EQ("which is 5 less than 10, and which is 15 less than 20",
+            Explain(m, 5));
+
+  // Failed match.  All matchers need to explain.  The second
+  // matcher doesn't given an explanation.
+  m = AnyOf(GreaterThan(10), Gt(20), GreaterThan(30));
+  EXPECT_EQ("which is 5 less than 10, and which is 25 less than 30",
+            Explain(m, 5));
+
+  // Failed match.  All matchers need to explain.
+  m = AnyOf(GreaterThan(10), GreaterThan(20), GreaterThan(30));
+  EXPECT_EQ(
+      "which is 5 less than 10, and which is 15 less than 20, "
+      "and which is 25 less than 30",
+      Explain(m, 5));
+
+  // Successful match.  The first matcher, which succeeded, needs to
+  // explain.
+  m = AnyOf(GreaterThan(10), GreaterThan(20));
+  EXPECT_EQ("which is 5 more than 10", Explain(m, 15));
+
+  // Successful match.  The second matcher, which succeeded, needs to
+  // explain.  Since it doesn't given an explanation, nothing is
+  // printed.
+  m = AnyOf(GreaterThan(10), Lt(30));
+  EXPECT_EQ("", Explain(m, 0));
+
+  // Successful match.  The second matcher, which succeeded, needs to
+  // explain.
+  m = AnyOf(GreaterThan(30), GreaterThan(20));
+  EXPECT_EQ("which is 5 more than 20", Explain(m, 25));
+}
+
+// The following predicate function and predicate functor are for
+// testing the Truly(predicate) matcher.
+
+// Returns non-zero if the input is positive.  Note that the return
+// type of this function is not bool.  It's OK as Truly() accepts any
+// unary function or functor whose return type can be implicitly
+// converted to bool.
+int IsPositive(double x) { return x > 0 ? 1 : 0; }
+
+// This functor returns true if the input is greater than the given
+// number.
+class IsGreaterThan {
+ public:
+  explicit IsGreaterThan(int threshold) : threshold_(threshold) {}
+
+  bool operator()(int n) const { return n > threshold_; }
+
+ private:
+  int threshold_;
+};
+
+// For testing Truly().
+const int foo = 0;
+
+// This predicate returns true if and only if the argument references foo and
+// has a zero value.
+bool ReferencesFooAndIsZero(const int& n) { return (&n == &foo) && (n == 0); }
+
+// Tests that Truly(predicate) matches what satisfies the given
+// predicate.
+TEST(TrulyTest, MatchesWhatSatisfiesThePredicate) {
+  Matcher<double> m = Truly(IsPositive);
+  EXPECT_TRUE(m.Matches(2.0));
+  EXPECT_FALSE(m.Matches(-1.5));
+}
+
+// Tests that Truly(predicate_functor) works too.
+TEST(TrulyTest, CanBeUsedWithFunctor) {
+  Matcher<int> m = Truly(IsGreaterThan(5));
+  EXPECT_TRUE(m.Matches(6));
+  EXPECT_FALSE(m.Matches(4));
+}
+
+// A class that can be implicitly converted to bool.
+class ConvertibleToBool {
+ public:
+  explicit ConvertibleToBool(int number) : number_(number) {}
+  operator bool() const { return number_ != 0; }
+
+ private:
+  int number_;
+};
+
+ConvertibleToBool IsNotZero(int number) { return ConvertibleToBool(number); }
+
+// Tests that the predicate used in Truly() may return a class that's
+// implicitly convertible to bool, even when the class has no
+// operator!().
+TEST(TrulyTest, PredicateCanReturnAClassConvertibleToBool) {
+  Matcher<int> m = Truly(IsNotZero);
+  EXPECT_TRUE(m.Matches(1));
+  EXPECT_FALSE(m.Matches(0));
+}
+
+// Tests that Truly(predicate) can describe itself properly.
+TEST(TrulyTest, CanDescribeSelf) {
+  Matcher<double> m = Truly(IsPositive);
+  EXPECT_EQ("satisfies the given predicate", Describe(m));
+}
+
+// Tests that Truly(predicate) works when the matcher takes its
+// argument by reference.
+TEST(TrulyTest, WorksForByRefArguments) {
+  Matcher<const int&> m = Truly(ReferencesFooAndIsZero);
+  EXPECT_TRUE(m.Matches(foo));
+  int n = 0;
+  EXPECT_FALSE(m.Matches(n));
+}
+
+// Tests that Truly(predicate) provides a helpful reason when it fails.
+TEST(TrulyTest, ExplainsFailures) {
+  StringMatchResultListener listener;
+  EXPECT_FALSE(ExplainMatchResult(Truly(IsPositive), -1, &listener));
+  EXPECT_EQ(listener.str(), "didn't satisfy the given predicate");
+}
+
+// Tests that Matches(m) is a predicate satisfied by whatever that
+// matches matcher m.
+TEST(MatchesTest, IsSatisfiedByWhatMatchesTheMatcher) {
+  EXPECT_TRUE(Matches(Ge(0))(1));
+  EXPECT_FALSE(Matches(Eq('a'))('b'));
+}
+
+// Tests that Matches(m) works when the matcher takes its argument by
+// reference.
+TEST(MatchesTest, WorksOnByRefArguments) {
+  int m = 0, n = 0;
+  EXPECT_TRUE(Matches(AllOf(Ref(n), Eq(0)))(n));
+  EXPECT_FALSE(Matches(Ref(m))(n));
+}
+
+// Tests that a Matcher on non-reference type can be used in
+// Matches().
+TEST(MatchesTest, WorksWithMatcherOnNonRefType) {
+  Matcher<int> eq5 = Eq(5);
+  EXPECT_TRUE(Matches(eq5)(5));
+  EXPECT_FALSE(Matches(eq5)(2));
+}
+
+// Tests Value(value, matcher).  Since Value() is a simple wrapper for
+// Matches(), which has been tested already, we don't spend a lot of
+// effort on testing Value().
+TEST(ValueTest, WorksWithPolymorphicMatcher) {
+  EXPECT_TRUE(Value("hi", StartsWith("h")));
+  EXPECT_FALSE(Value(5, Gt(10)));
+}
+
+TEST(ValueTest, WorksWithMonomorphicMatcher) {
+  const Matcher<int> is_zero = Eq(0);
+  EXPECT_TRUE(Value(0, is_zero));
+  EXPECT_FALSE(Value('a', is_zero));
+
+  int n = 0;
+  const Matcher<const int&> ref_n = Ref(n);
+  EXPECT_TRUE(Value(n, ref_n));
+  EXPECT_FALSE(Value(1, ref_n));
+}
+
+TEST(AllArgsTest, WorksForTuple) {
+  EXPECT_THAT(std::make_tuple(1, 2L), AllArgs(Lt()));
+  EXPECT_THAT(std::make_tuple(2L, 1), Not(AllArgs(Lt())));
+}
+
+TEST(AllArgsTest, WorksForNonTuple) {
+  EXPECT_THAT(42, AllArgs(Gt(0)));
+  EXPECT_THAT('a', Not(AllArgs(Eq('b'))));
+}
+
+class AllArgsHelper {
+ public:
+  AllArgsHelper() = default;
+
+  MOCK_METHOD2(Helper, int(char x, int y));
+
+ private:
+  AllArgsHelper(const AllArgsHelper&) = delete;
+  AllArgsHelper& operator=(const AllArgsHelper&) = delete;
+};
+
+TEST(AllArgsTest, WorksInWithClause) {
+  AllArgsHelper helper;
+  ON_CALL(helper, Helper(_, _)).With(AllArgs(Lt())).WillByDefault(Return(1));
+  EXPECT_CALL(helper, Helper(_, _));
+  EXPECT_CALL(helper, Helper(_, _)).With(AllArgs(Gt())).WillOnce(Return(2));
+
+  EXPECT_EQ(1, helper.Helper('\1', 2));
+  EXPECT_EQ(2, helper.Helper('a', 1));
+}
+
+class OptionalMatchersHelper {
+ public:
+  OptionalMatchersHelper() = default;
+
+  MOCK_METHOD0(NoArgs, int());
+
+  MOCK_METHOD1(OneArg, int(int y));
+
+  MOCK_METHOD2(TwoArgs, int(char x, int y));
+
+  MOCK_METHOD1(Overloaded, int(char x));
+  MOCK_METHOD2(Overloaded, int(char x, int y));
+
+ private:
+  OptionalMatchersHelper(const OptionalMatchersHelper&) = delete;
+  OptionalMatchersHelper& operator=(const OptionalMatchersHelper&) = delete;
+};
+
+TEST(AllArgsTest, WorksWithoutMatchers) {
+  OptionalMatchersHelper helper;
+
+  ON_CALL(helper, NoArgs).WillByDefault(Return(10));
+  ON_CALL(helper, OneArg).WillByDefault(Return(20));
+  ON_CALL(helper, TwoArgs).WillByDefault(Return(30));
+
+  EXPECT_EQ(10, helper.NoArgs());
+  EXPECT_EQ(20, helper.OneArg(1));
+  EXPECT_EQ(30, helper.TwoArgs('\1', 2));
+
+  EXPECT_CALL(helper, NoArgs).Times(1);
+  EXPECT_CALL(helper, OneArg).WillOnce(Return(100));
+  EXPECT_CALL(helper, OneArg(17)).WillOnce(Return(200));
+  EXPECT_CALL(helper, TwoArgs).Times(0);
+
+  EXPECT_EQ(10, helper.NoArgs());
+  EXPECT_EQ(100, helper.OneArg(1));
+  EXPECT_EQ(200, helper.OneArg(17));
+}
+
+// Tests floating-point matchers.
+template <typename RawType>
+class FloatingPointTest : public testing::Test {
+ protected:
+  typedef testing::internal::FloatingPoint<RawType> Floating;
+  typedef typename Floating::Bits Bits;
+
+  FloatingPointTest()
+      : max_ulps_(Floating::kMaxUlps),
+        zero_bits_(Floating(0).bits()),
+        one_bits_(Floating(1).bits()),
+        infinity_bits_(Floating(Floating::Infinity()).bits()),
+        close_to_positive_zero_(
+            Floating::ReinterpretBits(zero_bits_ + max_ulps_ / 2)),
+        close_to_negative_zero_(
+            -Floating::ReinterpretBits(zero_bits_ + max_ulps_ - max_ulps_ / 2)),
+        further_from_negative_zero_(-Floating::ReinterpretBits(
+            zero_bits_ + max_ulps_ + 1 - max_ulps_ / 2)),
+        close_to_one_(Floating::ReinterpretBits(one_bits_ + max_ulps_)),
+        further_from_one_(Floating::ReinterpretBits(one_bits_ + max_ulps_ + 1)),
+        infinity_(Floating::Infinity()),
+        close_to_infinity_(
+            Floating::ReinterpretBits(infinity_bits_ - max_ulps_)),
+        further_from_infinity_(
+            Floating::ReinterpretBits(infinity_bits_ - max_ulps_ - 1)),
+        max_(std::numeric_limits<RawType>::max()),
+        nan1_(Floating::ReinterpretBits(Floating::kExponentBitMask | 1)),
+        nan2_(Floating::ReinterpretBits(Floating::kExponentBitMask | 200)) {}
+
+  void TestSize() { EXPECT_EQ(sizeof(RawType), sizeof(Bits)); }
+
+  // A battery of tests for FloatingEqMatcher::Matches.
+  // matcher_maker is a pointer to a function which creates a FloatingEqMatcher.
+  void TestMatches(
+      testing::internal::FloatingEqMatcher<RawType> (*matcher_maker)(RawType)) {
+    Matcher<RawType> m1 = matcher_maker(0.0);
+    EXPECT_TRUE(m1.Matches(-0.0));
+    EXPECT_TRUE(m1.Matches(close_to_positive_zero_));
+    EXPECT_TRUE(m1.Matches(close_to_negative_zero_));
+    EXPECT_FALSE(m1.Matches(1.0));
+
+    Matcher<RawType> m2 = matcher_maker(close_to_positive_zero_);
+    EXPECT_FALSE(m2.Matches(further_from_negative_zero_));
+
+    Matcher<RawType> m3 = matcher_maker(1.0);
+    EXPECT_TRUE(m3.Matches(close_to_one_));
+    EXPECT_FALSE(m3.Matches(further_from_one_));
+
+    // Test commutativity: matcher_maker(0.0).Matches(1.0) was tested above.
+    EXPECT_FALSE(m3.Matches(0.0));
+
+    Matcher<RawType> m4 = matcher_maker(-infinity_);
+    EXPECT_TRUE(m4.Matches(-close_to_infinity_));
+
+    Matcher<RawType> m5 = matcher_maker(infinity_);
+    EXPECT_TRUE(m5.Matches(close_to_infinity_));
+
+    // This is interesting as the representations of infinity_ and nan1_
+    // are only 1 DLP apart.
+    EXPECT_FALSE(m5.Matches(nan1_));
+
+    // matcher_maker can produce a Matcher<const RawType&>, which is needed in
+    // some cases.
+    Matcher<const RawType&> m6 = matcher_maker(0.0);
+    EXPECT_TRUE(m6.Matches(-0.0));
+    EXPECT_TRUE(m6.Matches(close_to_positive_zero_));
+    EXPECT_FALSE(m6.Matches(1.0));
+
+    // matcher_maker can produce a Matcher<RawType&>, which is needed in some
+    // cases.
+    Matcher<RawType&> m7 = matcher_maker(0.0);
+    RawType x = 0.0;
+    EXPECT_TRUE(m7.Matches(x));
+    x = 0.01f;
+    EXPECT_FALSE(m7.Matches(x));
+  }
+
+  // Pre-calculated numbers to be used by the tests.
+
+  const Bits max_ulps_;
+
+  const Bits zero_bits_;      // The bits that represent 0.0.
+  const Bits one_bits_;       // The bits that represent 1.0.
+  const Bits infinity_bits_;  // The bits that represent +infinity.
+
+  // Some numbers close to 0.0.
+  const RawType close_to_positive_zero_;
+  const RawType close_to_negative_zero_;
+  const RawType further_from_negative_zero_;
+
+  // Some numbers close to 1.0.
+  const RawType close_to_one_;
+  const RawType further_from_one_;
+
+  // Some numbers close to +infinity.
+  const RawType infinity_;
+  const RawType close_to_infinity_;
+  const RawType further_from_infinity_;
+
+  // Maximum representable value that's not infinity.
+  const RawType max_;
+
+  // Some NaNs.
+  const RawType nan1_;
+  const RawType nan2_;
+};
+
+// Tests floating-point matchers with fixed epsilons.
+template <typename RawType>
+class FloatingPointNearTest : public FloatingPointTest<RawType> {
+ protected:
+  typedef FloatingPointTest<RawType> ParentType;
+
+  // A battery of tests for FloatingEqMatcher::Matches with a fixed epsilon.
+  // matcher_maker is a pointer to a function which creates a FloatingEqMatcher.
+  void TestNearMatches(testing::internal::FloatingEqMatcher<RawType> (
+      *matcher_maker)(RawType, RawType)) {
+    Matcher<RawType> m1 = matcher_maker(0.0, 0.0);
+    EXPECT_TRUE(m1.Matches(0.0));
+    EXPECT_TRUE(m1.Matches(-0.0));
+    EXPECT_FALSE(m1.Matches(ParentType::close_to_positive_zero_));
+    EXPECT_FALSE(m1.Matches(ParentType::close_to_negative_zero_));
+    EXPECT_FALSE(m1.Matches(1.0));
+
+    Matcher<RawType> m2 = matcher_maker(0.0, 1.0);
+    EXPECT_TRUE(m2.Matches(0.0));
+    EXPECT_TRUE(m2.Matches(-0.0));
+    EXPECT_TRUE(m2.Matches(1.0));
+    EXPECT_TRUE(m2.Matches(-1.0));
+    EXPECT_FALSE(m2.Matches(ParentType::close_to_one_));
+    EXPECT_FALSE(m2.Matches(-ParentType::close_to_one_));
+
+    // Check that inf matches inf, regardless of the of the specified max
+    // absolute error.
+    Matcher<RawType> m3 = matcher_maker(ParentType::infinity_, 0.0);
+    EXPECT_TRUE(m3.Matches(ParentType::infinity_));
+    EXPECT_FALSE(m3.Matches(ParentType::close_to_infinity_));
+    EXPECT_FALSE(m3.Matches(-ParentType::infinity_));
+
+    Matcher<RawType> m4 = matcher_maker(-ParentType::infinity_, 0.0);
+    EXPECT_TRUE(m4.Matches(-ParentType::infinity_));
+    EXPECT_FALSE(m4.Matches(-ParentType::close_to_infinity_));
+    EXPECT_FALSE(m4.Matches(ParentType::infinity_));
+
+    // Test various overflow scenarios.
+    Matcher<RawType> m5 = matcher_maker(ParentType::max_, ParentType::max_);
+    EXPECT_TRUE(m5.Matches(ParentType::max_));
+    EXPECT_FALSE(m5.Matches(-ParentType::max_));
+
+    Matcher<RawType> m6 = matcher_maker(-ParentType::max_, ParentType::max_);
+    EXPECT_FALSE(m6.Matches(ParentType::max_));
+    EXPECT_TRUE(m6.Matches(-ParentType::max_));
+
+    Matcher<RawType> m7 = matcher_maker(ParentType::max_, 0);
+    EXPECT_TRUE(m7.Matches(ParentType::max_));
+    EXPECT_FALSE(m7.Matches(-ParentType::max_));
+
+    Matcher<RawType> m8 = matcher_maker(-ParentType::max_, 0);
+    EXPECT_FALSE(m8.Matches(ParentType::max_));
+    EXPECT_TRUE(m8.Matches(-ParentType::max_));
+
+    // The difference between max() and -max() normally overflows to infinity,
+    // but it should still match if the max_abs_error is also infinity.
+    Matcher<RawType> m9 =
+        matcher_maker(ParentType::max_, ParentType::infinity_);
+    EXPECT_TRUE(m8.Matches(-ParentType::max_));
+
+    // matcher_maker can produce a Matcher<const RawType&>, which is needed in
+    // some cases.
+    Matcher<const RawType&> m10 = matcher_maker(0.0, 1.0);
+    EXPECT_TRUE(m10.Matches(-0.0));
+    EXPECT_TRUE(m10.Matches(ParentType::close_to_positive_zero_));
+    EXPECT_FALSE(m10.Matches(ParentType::close_to_one_));
+
+    // matcher_maker can produce a Matcher<RawType&>, which is needed in some
+    // cases.
+    Matcher<RawType&> m11 = matcher_maker(0.0, 1.0);
+    RawType x = 0.0;
+    EXPECT_TRUE(m11.Matches(x));
+    x = 1.0f;
+    EXPECT_TRUE(m11.Matches(x));
+    x = -1.0f;
+    EXPECT_TRUE(m11.Matches(x));
+    x = 1.1f;
+    EXPECT_FALSE(m11.Matches(x));
+    x = -1.1f;
+    EXPECT_FALSE(m11.Matches(x));
+  }
+};
+
+// Instantiate FloatingPointTest for testing floats.
+typedef FloatingPointTest<float> FloatTest;
+
+TEST_F(FloatTest, FloatEqApproximatelyMatchesFloats) { TestMatches(&FloatEq); }
+
+TEST_F(FloatTest, NanSensitiveFloatEqApproximatelyMatchesFloats) {
+  TestMatches(&NanSensitiveFloatEq);
+}
+
+TEST_F(FloatTest, FloatEqCannotMatchNaN) {
+  // FloatEq never matches NaN.
+  Matcher<float> m = FloatEq(nan1_);
+  EXPECT_FALSE(m.Matches(nan1_));
+  EXPECT_FALSE(m.Matches(nan2_));
+  EXPECT_FALSE(m.Matches(1.0));
+}
+
+TEST_F(FloatTest, NanSensitiveFloatEqCanMatchNaN) {
+  // NanSensitiveFloatEq will match NaN.
+  Matcher<float> m = NanSensitiveFloatEq(nan1_);
+  EXPECT_TRUE(m.Matches(nan1_));
+  EXPECT_TRUE(m.Matches(nan2_));
+  EXPECT_FALSE(m.Matches(1.0));
+}
+
+TEST_F(FloatTest, FloatEqCanDescribeSelf) {
+  Matcher<float> m1 = FloatEq(2.0f);
+  EXPECT_EQ("is approximately 2", Describe(m1));
+  EXPECT_EQ("isn't approximately 2", DescribeNegation(m1));
+
+  Matcher<float> m2 = FloatEq(0.5f);
+  EXPECT_EQ("is approximately 0.5", Describe(m2));
+  EXPECT_EQ("isn't approximately 0.5", DescribeNegation(m2));
+
+  Matcher<float> m3 = FloatEq(nan1_);
+  EXPECT_EQ("never matches", Describe(m3));
+  EXPECT_EQ("is anything", DescribeNegation(m3));
+}
+
+TEST_F(FloatTest, NanSensitiveFloatEqCanDescribeSelf) {
+  Matcher<float> m1 = NanSensitiveFloatEq(2.0f);
+  EXPECT_EQ("is approximately 2", Describe(m1));
+  EXPECT_EQ("isn't approximately 2", DescribeNegation(m1));
+
+  Matcher<float> m2 = NanSensitiveFloatEq(0.5f);
+  EXPECT_EQ("is approximately 0.5", Describe(m2));
+  EXPECT_EQ("isn't approximately 0.5", DescribeNegation(m2));
+
+  Matcher<float> m3 = NanSensitiveFloatEq(nan1_);
+  EXPECT_EQ("is NaN", Describe(m3));
+  EXPECT_EQ("isn't NaN", DescribeNegation(m3));
+}
+
+// Instantiate FloatingPointTest for testing floats with a user-specified
+// max absolute error.
+typedef FloatingPointNearTest<float> FloatNearTest;
+
+TEST_F(FloatNearTest, FloatNearMatches) { TestNearMatches(&FloatNear); }
+
+TEST_F(FloatNearTest, NanSensitiveFloatNearApproximatelyMatchesFloats) {
+  TestNearMatches(&NanSensitiveFloatNear);
+}
+
+TEST_F(FloatNearTest, FloatNearCanDescribeSelf) {
+  Matcher<float> m1 = FloatNear(2.0f, 0.5f);
+  EXPECT_EQ("is approximately 2 (absolute error <= 0.5)", Describe(m1));
+  EXPECT_EQ("isn't approximately 2 (absolute error > 0.5)",
+            DescribeNegation(m1));
+
+  Matcher<float> m2 = FloatNear(0.5f, 0.5f);
+  EXPECT_EQ("is approximately 0.5 (absolute error <= 0.5)", Describe(m2));
+  EXPECT_EQ("isn't approximately 0.5 (absolute error > 0.5)",
+            DescribeNegation(m2));
+
+  Matcher<float> m3 = FloatNear(nan1_, 0.0);
+  EXPECT_EQ("never matches", Describe(m3));
+  EXPECT_EQ("is anything", DescribeNegation(m3));
+}
+
+TEST_F(FloatNearTest, NanSensitiveFloatNearCanDescribeSelf) {
+  Matcher<float> m1 = NanSensitiveFloatNear(2.0f, 0.5f);
+  EXPECT_EQ("is approximately 2 (absolute error <= 0.5)", Describe(m1));
+  EXPECT_EQ("isn't approximately 2 (absolute error > 0.5)",
+            DescribeNegation(m1));
+
+  Matcher<float> m2 = NanSensitiveFloatNear(0.5f, 0.5f);
+  EXPECT_EQ("is approximately 0.5 (absolute error <= 0.5)", Describe(m2));
+  EXPECT_EQ("isn't approximately 0.5 (absolute error > 0.5)",
+            DescribeNegation(m2));
+
+  Matcher<float> m3 = NanSensitiveFloatNear(nan1_, 0.1f);
+  EXPECT_EQ("is NaN", Describe(m3));
+  EXPECT_EQ("isn't NaN", DescribeNegation(m3));
+}
+
+TEST_F(FloatNearTest, FloatNearCannotMatchNaN) {
+  // FloatNear never matches NaN.
+  Matcher<float> m = FloatNear(ParentType::nan1_, 0.1f);
+  EXPECT_FALSE(m.Matches(nan1_));
+  EXPECT_FALSE(m.Matches(nan2_));
+  EXPECT_FALSE(m.Matches(1.0));
+}
+
+TEST_F(FloatNearTest, NanSensitiveFloatNearCanMatchNaN) {
+  // NanSensitiveFloatNear will match NaN.
+  Matcher<float> m = NanSensitiveFloatNear(nan1_, 0.1f);
+  EXPECT_TRUE(m.Matches(nan1_));
+  EXPECT_TRUE(m.Matches(nan2_));
+  EXPECT_FALSE(m.Matches(1.0));
+}
+
+// Instantiate FloatingPointTest for testing doubles.
+typedef FloatingPointTest<double> DoubleTest;
+
+TEST_F(DoubleTest, DoubleEqApproximatelyMatchesDoubles) {
+  TestMatches(&DoubleEq);
+}
+
+TEST_F(DoubleTest, NanSensitiveDoubleEqApproximatelyMatchesDoubles) {
+  TestMatches(&NanSensitiveDoubleEq);
+}
+
+TEST_F(DoubleTest, DoubleEqCannotMatchNaN) {
+  // DoubleEq never matches NaN.
+  Matcher<double> m = DoubleEq(nan1_);
+  EXPECT_FALSE(m.Matches(nan1_));
+  EXPECT_FALSE(m.Matches(nan2_));
+  EXPECT_FALSE(m.Matches(1.0));
+}
+
+TEST_F(DoubleTest, NanSensitiveDoubleEqCanMatchNaN) {
+  // NanSensitiveDoubleEq will match NaN.
+  Matcher<double> m = NanSensitiveDoubleEq(nan1_);
+  EXPECT_TRUE(m.Matches(nan1_));
+  EXPECT_TRUE(m.Matches(nan2_));
+  EXPECT_FALSE(m.Matches(1.0));
+}
+
+TEST_F(DoubleTest, DoubleEqCanDescribeSelf) {
+  Matcher<double> m1 = DoubleEq(2.0);
+  EXPECT_EQ("is approximately 2", Describe(m1));
+  EXPECT_EQ("isn't approximately 2", DescribeNegation(m1));
+
+  Matcher<double> m2 = DoubleEq(0.5);
+  EXPECT_EQ("is approximately 0.5", Describe(m2));
+  EXPECT_EQ("isn't approximately 0.5", DescribeNegation(m2));
+
+  Matcher<double> m3 = DoubleEq(nan1_);
+  EXPECT_EQ("never matches", Describe(m3));
+  EXPECT_EQ("is anything", DescribeNegation(m3));
+}
+
+TEST_F(DoubleTest, NanSensitiveDoubleEqCanDescribeSelf) {
+  Matcher<double> m1 = NanSensitiveDoubleEq(2.0);
+  EXPECT_EQ("is approximately 2", Describe(m1));
+  EXPECT_EQ("isn't approximately 2", DescribeNegation(m1));
+
+  Matcher<double> m2 = NanSensitiveDoubleEq(0.5);
+  EXPECT_EQ("is approximately 0.5", Describe(m2));
+  EXPECT_EQ("isn't approximately 0.5", DescribeNegation(m2));
+
+  Matcher<double> m3 = NanSensitiveDoubleEq(nan1_);
+  EXPECT_EQ("is NaN", Describe(m3));
+  EXPECT_EQ("isn't NaN", DescribeNegation(m3));
+}
+
+// Instantiate FloatingPointTest for testing floats with a user-specified
+// max absolute error.
+typedef FloatingPointNearTest<double> DoubleNearTest;
+
+TEST_F(DoubleNearTest, DoubleNearMatches) { TestNearMatches(&DoubleNear); }
+
+TEST_F(DoubleNearTest, NanSensitiveDoubleNearApproximatelyMatchesDoubles) {
+  TestNearMatches(&NanSensitiveDoubleNear);
+}
+
+TEST_F(DoubleNearTest, DoubleNearCanDescribeSelf) {
+  Matcher<double> m1 = DoubleNear(2.0, 0.5);
+  EXPECT_EQ("is approximately 2 (absolute error <= 0.5)", Describe(m1));
+  EXPECT_EQ("isn't approximately 2 (absolute error > 0.5)",
+            DescribeNegation(m1));
+
+  Matcher<double> m2 = DoubleNear(0.5, 0.5);
+  EXPECT_EQ("is approximately 0.5 (absolute error <= 0.5)", Describe(m2));
+  EXPECT_EQ("isn't approximately 0.5 (absolute error > 0.5)",
+            DescribeNegation(m2));
+
+  Matcher<double> m3 = DoubleNear(nan1_, 0.0);
+  EXPECT_EQ("never matches", Describe(m3));
+  EXPECT_EQ("is anything", DescribeNegation(m3));
+}
+
+TEST_F(DoubleNearTest, ExplainsResultWhenMatchFails) {
+  EXPECT_EQ("", Explain(DoubleNear(2.0, 0.1), 2.05));
+  EXPECT_EQ("which is 0.2 from 2", Explain(DoubleNear(2.0, 0.1), 2.2));
+  EXPECT_EQ("which is -0.3 from 2", Explain(DoubleNear(2.0, 0.1), 1.7));
+
+  const std::string explanation =
+      Explain(DoubleNear(2.1, 1e-10), 2.1 + 1.2e-10);
+  // Different C++ implementations may print floating-point numbers
+  // slightly differently.
+  EXPECT_TRUE(explanation == "which is 1.2e-10 from 2.1" ||  // GCC
+              explanation == "which is 1.2e-010 from 2.1")   // MSVC
+      << " where explanation is \"" << explanation << "\".";
+}
+
+TEST_F(DoubleNearTest, NanSensitiveDoubleNearCanDescribeSelf) {
+  Matcher<double> m1 = NanSensitiveDoubleNear(2.0, 0.5);
+  EXPECT_EQ("is approximately 2 (absolute error <= 0.5)", Describe(m1));
+  EXPECT_EQ("isn't approximately 2 (absolute error > 0.5)",
+            DescribeNegation(m1));
+
+  Matcher<double> m2 = NanSensitiveDoubleNear(0.5, 0.5);
+  EXPECT_EQ("is approximately 0.5 (absolute error <= 0.5)", Describe(m2));
+  EXPECT_EQ("isn't approximately 0.5 (absolute error > 0.5)",
+            DescribeNegation(m2));
+
+  Matcher<double> m3 = NanSensitiveDoubleNear(nan1_, 0.1);
+  EXPECT_EQ("is NaN", Describe(m3));
+  EXPECT_EQ("isn't NaN", DescribeNegation(m3));
+}
+
+TEST_F(DoubleNearTest, DoubleNearCannotMatchNaN) {
+  // DoubleNear never matches NaN.
+  Matcher<double> m = DoubleNear(ParentType::nan1_, 0.1);
+  EXPECT_FALSE(m.Matches(nan1_));
+  EXPECT_FALSE(m.Matches(nan2_));
+  EXPECT_FALSE(m.Matches(1.0));
+}
+
+TEST_F(DoubleNearTest, NanSensitiveDoubleNearCanMatchNaN) {
+  // NanSensitiveDoubleNear will match NaN.
+  Matcher<double> m = NanSensitiveDoubleNear(nan1_, 0.1);
+  EXPECT_TRUE(m.Matches(nan1_));
+  EXPECT_TRUE(m.Matches(nan2_));
+  EXPECT_FALSE(m.Matches(1.0));
+}
+
+TEST(NotTest, WorksOnMoveOnlyType) {
+  std::unique_ptr<int> p(new int(3));
+  EXPECT_THAT(p, Pointee(Eq(3)));
+  EXPECT_THAT(p, Not(Pointee(Eq(2))));
+}
+
+TEST(AllOfTest, HugeMatcher) {
+  // Verify that using AllOf with many arguments doesn't cause
+  // the compiler to exceed template instantiation depth limit.
+  EXPECT_THAT(0, testing::AllOf(_, _, _, _, _, _, _, _, _,
+                                testing::AllOf(_, _, _, _, _, _, _, _, _, _)));
+}
+
+TEST(AnyOfTest, HugeMatcher) {
+  // Verify that using AnyOf with many arguments doesn't cause
+  // the compiler to exceed template instantiation depth limit.
+  EXPECT_THAT(0, testing::AnyOf(_, _, _, _, _, _, _, _, _,
+                                testing::AnyOf(_, _, _, _, _, _, _, _, _, _)));
+}
+
+namespace adl_test {
+
+// Verifies that the implementation of ::testing::AllOf and ::testing::AnyOf
+// don't issue unqualified recursive calls.  If they do, the argument dependent
+// name lookup will cause AllOf/AnyOf in the 'adl_test' namespace to be found
+// as a candidate and the compilation will break due to an ambiguous overload.
+
+// The matcher must be in the same namespace as AllOf/AnyOf to make argument
+// dependent lookup find those.
+MATCHER(M, "") {
+  (void)arg;
+  return true;
+}
+
+template <typename T1, typename T2>
+bool AllOf(const T1& /*t1*/, const T2& /*t2*/) {
+  return true;
+}
+
+TEST(AllOfTest, DoesNotCallAllOfUnqualified) {
+  EXPECT_THAT(42,
+              testing::AllOf(M(), M(), M(), M(), M(), M(), M(), M(), M(), M()));
+}
+
+template <typename T1, typename T2>
+bool AnyOf(const T1&, const T2&) {
+  return true;
+}
+
+TEST(AnyOfTest, DoesNotCallAnyOfUnqualified) {
+  EXPECT_THAT(42,
+              testing::AnyOf(M(), M(), M(), M(), M(), M(), M(), M(), M(), M()));
+}
+
+}  // namespace adl_test
+
+TEST(AllOfTest, WorksOnMoveOnlyType) {
+  std::unique_ptr<int> p(new int(3));
+  EXPECT_THAT(p, AllOf(Pointee(Eq(3)), Pointee(Gt(0)), Pointee(Lt(5))));
+  EXPECT_THAT(p, Not(AllOf(Pointee(Eq(3)), Pointee(Gt(0)), Pointee(Lt(3)))));
+}
+
+TEST(AnyOfTest, WorksOnMoveOnlyType) {
+  std::unique_ptr<int> p(new int(3));
+  EXPECT_THAT(p, AnyOf(Pointee(Eq(5)), Pointee(Lt(0)), Pointee(Lt(5))));
+  EXPECT_THAT(p, Not(AnyOf(Pointee(Eq(5)), Pointee(Lt(0)), Pointee(Gt(5)))));
+}
+
+}  // namespace
+}  // namespace gmock_matchers_test
+}  // namespace testing
+
+GTEST_DISABLE_MSC_WARNINGS_POP_()  // 4244 4100
diff --git a/third_party/googletest/googlemock/test/gmock-matchers-comparisons_test.cc b/third_party/googletest/googlemock/test/gmock-matchers-comparisons_test.cc
new file mode 100644
index 0000000..b2ce99e
--- /dev/null
+++ b/third_party/googletest/googlemock/test/gmock-matchers-comparisons_test.cc
@@ -0,0 +1,2361 @@
+// Copyright 2007, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Google Mock - a framework for writing C++ mock classes.
+//
+// This file tests some commonly used argument matchers.
+
+#include <functional>
+#include <memory>
+#include <string>
+#include <tuple>
+#include <vector>
+
+#include "test/gmock-matchers_test.h"
+
+// Silence warning C4244: 'initializing': conversion from 'int' to 'short',
+// possible loss of data and C4100, unreferenced local parameter
+GTEST_DISABLE_MSC_WARNINGS_PUSH_(4244 4100)
+
+
+namespace testing {
+namespace gmock_matchers_test {
+namespace {
+
+INSTANTIATE_GTEST_MATCHER_TEST_P(MonotonicMatcherTest);
+
+TEST_P(MonotonicMatcherTestP, IsPrintable) {
+  stringstream ss;
+  ss << GreaterThan(5);
+  EXPECT_EQ("is > 5", ss.str());
+}
+
+TEST(MatchResultListenerTest, StreamingWorks) {
+  StringMatchResultListener listener;
+  listener << "hi" << 5;
+  EXPECT_EQ("hi5", listener.str());
+
+  listener.Clear();
+  EXPECT_EQ("", listener.str());
+
+  listener << 42;
+  EXPECT_EQ("42", listener.str());
+
+  // Streaming shouldn't crash when the underlying ostream is NULL.
+  DummyMatchResultListener dummy;
+  dummy << "hi" << 5;
+}
+
+TEST(MatchResultListenerTest, CanAccessUnderlyingStream) {
+  EXPECT_TRUE(DummyMatchResultListener().stream() == nullptr);
+  EXPECT_TRUE(StreamMatchResultListener(nullptr).stream() == nullptr);
+
+  EXPECT_EQ(&std::cout, StreamMatchResultListener(&std::cout).stream());
+}
+
+TEST(MatchResultListenerTest, IsInterestedWorks) {
+  EXPECT_TRUE(StringMatchResultListener().IsInterested());
+  EXPECT_TRUE(StreamMatchResultListener(&std::cout).IsInterested());
+
+  EXPECT_FALSE(DummyMatchResultListener().IsInterested());
+  EXPECT_FALSE(StreamMatchResultListener(nullptr).IsInterested());
+}
+
+// Makes sure that the MatcherInterface<T> interface doesn't
+// change.
+class EvenMatcherImpl : public MatcherInterface<int> {
+ public:
+  bool MatchAndExplain(int x,
+                       MatchResultListener* /* listener */) const override {
+    return x % 2 == 0;
+  }
+
+  void DescribeTo(ostream* os) const override { *os << "is an even number"; }
+
+  // We deliberately don't define DescribeNegationTo() and
+  // ExplainMatchResultTo() here, to make sure the definition of these
+  // two methods is optional.
+};
+
+// Makes sure that the MatcherInterface API doesn't change.
+TEST(MatcherInterfaceTest, CanBeImplementedUsingPublishedAPI) {
+  EvenMatcherImpl m;
+}
+
+// Tests implementing a monomorphic matcher using MatchAndExplain().
+
+class NewEvenMatcherImpl : public MatcherInterface<int> {
+ public:
+  bool MatchAndExplain(int x, MatchResultListener* listener) const override {
+    const bool match = x % 2 == 0;
+    // Verifies that we can stream to a listener directly.
+    *listener << "value % " << 2;
+    if (listener->stream() != nullptr) {
+      // Verifies that we can stream to a listener's underlying stream
+      // too.
+      *listener->stream() << " == " << (x % 2);
+    }
+    return match;
+  }
+
+  void DescribeTo(ostream* os) const override { *os << "is an even number"; }
+};
+
+TEST(MatcherInterfaceTest, CanBeImplementedUsingNewAPI) {
+  Matcher<int> m = MakeMatcher(new NewEvenMatcherImpl);
+  EXPECT_TRUE(m.Matches(2));
+  EXPECT_FALSE(m.Matches(3));
+  EXPECT_EQ("value % 2 == 0", Explain(m, 2));
+  EXPECT_EQ("value % 2 == 1", Explain(m, 3));
+}
+
+INSTANTIATE_GTEST_MATCHER_TEST_P(MatcherTest);
+
+// Tests default-constructing a matcher.
+TEST(MatcherTest, CanBeDefaultConstructed) { Matcher<double> m; }
+
+// Tests that Matcher<T> can be constructed from a MatcherInterface<T>*.
+TEST(MatcherTest, CanBeConstructedFromMatcherInterface) {
+  const MatcherInterface<int>* impl = new EvenMatcherImpl;
+  Matcher<int> m(impl);
+  EXPECT_TRUE(m.Matches(4));
+  EXPECT_FALSE(m.Matches(5));
+}
+
+// Tests that value can be used in place of Eq(value).
+TEST(MatcherTest, CanBeImplicitlyConstructedFromValue) {
+  Matcher<int> m1 = 5;
+  EXPECT_TRUE(m1.Matches(5));
+  EXPECT_FALSE(m1.Matches(6));
+}
+
+// Tests that NULL can be used in place of Eq(NULL).
+TEST(MatcherTest, CanBeImplicitlyConstructedFromNULL) {
+  Matcher<int*> m1 = nullptr;
+  EXPECT_TRUE(m1.Matches(nullptr));
+  int n = 0;
+  EXPECT_FALSE(m1.Matches(&n));
+}
+
+// Tests that matchers can be constructed from a variable that is not properly
+// defined. This should be illegal, but many users rely on this accidentally.
+struct Undefined {
+  virtual ~Undefined() = 0;
+  static const int kInt = 1;
+};
+
+TEST(MatcherTest, CanBeConstructedFromUndefinedVariable) {
+  Matcher<int> m1 = Undefined::kInt;
+  EXPECT_TRUE(m1.Matches(1));
+  EXPECT_FALSE(m1.Matches(2));
+}
+
+// Test that a matcher parameterized with an abstract class compiles.
+TEST(MatcherTest, CanAcceptAbstractClass) { Matcher<const Undefined&> m = _; }
+
+// Tests that matchers are copyable.
+TEST(MatcherTest, IsCopyable) {
+  // Tests the copy constructor.
+  Matcher<bool> m1 = Eq(false);
+  EXPECT_TRUE(m1.Matches(false));
+  EXPECT_FALSE(m1.Matches(true));
+
+  // Tests the assignment operator.
+  m1 = Eq(true);
+  EXPECT_TRUE(m1.Matches(true));
+  EXPECT_FALSE(m1.Matches(false));
+}
+
+// Tests that Matcher<T>::DescribeTo() calls
+// MatcherInterface<T>::DescribeTo().
+TEST(MatcherTest, CanDescribeItself) {
+  EXPECT_EQ("is an even number", Describe(Matcher<int>(new EvenMatcherImpl)));
+}
+
+// Tests Matcher<T>::MatchAndExplain().
+TEST_P(MatcherTestP, MatchAndExplain) {
+  Matcher<int> m = GreaterThan(0);
+  StringMatchResultListener listener1;
+  EXPECT_TRUE(m.MatchAndExplain(42, &listener1));
+  EXPECT_EQ("which is 42 more than 0", listener1.str());
+
+  StringMatchResultListener listener2;
+  EXPECT_FALSE(m.MatchAndExplain(-9, &listener2));
+  EXPECT_EQ("which is 9 less than 0", listener2.str());
+}
+
+// Tests that a C-string literal can be implicitly converted to a
+// Matcher<std::string> or Matcher<const std::string&>.
+TEST(StringMatcherTest, CanBeImplicitlyConstructedFromCStringLiteral) {
+  Matcher<std::string> m1 = "hi";
+  EXPECT_TRUE(m1.Matches("hi"));
+  EXPECT_FALSE(m1.Matches("hello"));
+
+  Matcher<const std::string&> m2 = "hi";
+  EXPECT_TRUE(m2.Matches("hi"));
+  EXPECT_FALSE(m2.Matches("hello"));
+}
+
+// Tests that a string object can be implicitly converted to a
+// Matcher<std::string> or Matcher<const std::string&>.
+TEST(StringMatcherTest, CanBeImplicitlyConstructedFromString) {
+  Matcher<std::string> m1 = std::string("hi");
+  EXPECT_TRUE(m1.Matches("hi"));
+  EXPECT_FALSE(m1.Matches("hello"));
+
+  Matcher<const std::string&> m2 = std::string("hi");
+  EXPECT_TRUE(m2.Matches("hi"));
+  EXPECT_FALSE(m2.Matches("hello"));
+}
+
+#if GTEST_INTERNAL_HAS_STRING_VIEW
+// Tests that a C-string literal can be implicitly converted to a
+// Matcher<StringView> or Matcher<const StringView&>.
+TEST(StringViewMatcherTest, CanBeImplicitlyConstructedFromCStringLiteral) {
+  Matcher<internal::StringView> m1 = "cats";
+  EXPECT_TRUE(m1.Matches("cats"));
+  EXPECT_FALSE(m1.Matches("dogs"));
+
+  Matcher<const internal::StringView&> m2 = "cats";
+  EXPECT_TRUE(m2.Matches("cats"));
+  EXPECT_FALSE(m2.Matches("dogs"));
+}
+
+// Tests that a std::string object can be implicitly converted to a
+// Matcher<StringView> or Matcher<const StringView&>.
+TEST(StringViewMatcherTest, CanBeImplicitlyConstructedFromString) {
+  Matcher<internal::StringView> m1 = std::string("cats");
+  EXPECT_TRUE(m1.Matches("cats"));
+  EXPECT_FALSE(m1.Matches("dogs"));
+
+  Matcher<const internal::StringView&> m2 = std::string("cats");
+  EXPECT_TRUE(m2.Matches("cats"));
+  EXPECT_FALSE(m2.Matches("dogs"));
+}
+
+// Tests that a StringView object can be implicitly converted to a
+// Matcher<StringView> or Matcher<const StringView&>.
+TEST(StringViewMatcherTest, CanBeImplicitlyConstructedFromStringView) {
+  Matcher<internal::StringView> m1 = internal::StringView("cats");
+  EXPECT_TRUE(m1.Matches("cats"));
+  EXPECT_FALSE(m1.Matches("dogs"));
+
+  Matcher<const internal::StringView&> m2 = internal::StringView("cats");
+  EXPECT_TRUE(m2.Matches("cats"));
+  EXPECT_FALSE(m2.Matches("dogs"));
+}
+#endif  // GTEST_INTERNAL_HAS_STRING_VIEW
+
+// Tests that a std::reference_wrapper<std::string> object can be implicitly
+// converted to a Matcher<std::string> or Matcher<const std::string&> via Eq().
+TEST(StringMatcherTest,
+     CanBeImplicitlyConstructedFromEqReferenceWrapperString) {
+  std::string value = "cats";
+  Matcher<std::string> m1 = Eq(std::ref(value));
+  EXPECT_TRUE(m1.Matches("cats"));
+  EXPECT_FALSE(m1.Matches("dogs"));
+
+  Matcher<const std::string&> m2 = Eq(std::ref(value));
+  EXPECT_TRUE(m2.Matches("cats"));
+  EXPECT_FALSE(m2.Matches("dogs"));
+}
+
+// Tests that MakeMatcher() constructs a Matcher<T> from a
+// MatcherInterface* without requiring the user to explicitly
+// write the type.
+TEST(MakeMatcherTest, ConstructsMatcherFromMatcherInterface) {
+  const MatcherInterface<int>* dummy_impl = new EvenMatcherImpl;
+  Matcher<int> m = MakeMatcher(dummy_impl);
+}
+
+// Tests that MakePolymorphicMatcher() can construct a polymorphic
+// matcher from its implementation using the old API.
+const int g_bar = 1;
+class ReferencesBarOrIsZeroImpl {
+ public:
+  template <typename T>
+  bool MatchAndExplain(const T& x, MatchResultListener* /* listener */) const {
+    const void* p = &x;
+    return p == &g_bar || x == 0;
+  }
+
+  void DescribeTo(ostream* os) const { *os << "g_bar or zero"; }
+
+  void DescribeNegationTo(ostream* os) const {
+    *os << "doesn't reference g_bar and is not zero";
+  }
+};
+
+// This function verifies that MakePolymorphicMatcher() returns a
+// PolymorphicMatcher<T> where T is the argument's type.
+PolymorphicMatcher<ReferencesBarOrIsZeroImpl> ReferencesBarOrIsZero() {
+  return MakePolymorphicMatcher(ReferencesBarOrIsZeroImpl());
+}
+
+TEST(MakePolymorphicMatcherTest, ConstructsMatcherUsingOldAPI) {
+  // Using a polymorphic matcher to match a reference type.
+  Matcher<const int&> m1 = ReferencesBarOrIsZero();
+  EXPECT_TRUE(m1.Matches(0));
+  // Verifies that the identity of a by-reference argument is preserved.
+  EXPECT_TRUE(m1.Matches(g_bar));
+  EXPECT_FALSE(m1.Matches(1));
+  EXPECT_EQ("g_bar or zero", Describe(m1));
+
+  // Using a polymorphic matcher to match a value type.
+  Matcher<double> m2 = ReferencesBarOrIsZero();
+  EXPECT_TRUE(m2.Matches(0.0));
+  EXPECT_FALSE(m2.Matches(0.1));
+  EXPECT_EQ("g_bar or zero", Describe(m2));
+}
+
+// Tests implementing a polymorphic matcher using MatchAndExplain().
+
+class PolymorphicIsEvenImpl {
+ public:
+  void DescribeTo(ostream* os) const { *os << "is even"; }
+
+  void DescribeNegationTo(ostream* os) const { *os << "is odd"; }
+
+  template <typename T>
+  bool MatchAndExplain(const T& x, MatchResultListener* listener) const {
+    // Verifies that we can stream to the listener directly.
+    *listener << "% " << 2;
+    if (listener->stream() != nullptr) {
+      // Verifies that we can stream to the listener's underlying stream
+      // too.
+      *listener->stream() << " == " << (x % 2);
+    }
+    return (x % 2) == 0;
+  }
+};
+
+PolymorphicMatcher<PolymorphicIsEvenImpl> PolymorphicIsEven() {
+  return MakePolymorphicMatcher(PolymorphicIsEvenImpl());
+}
+
+TEST(MakePolymorphicMatcherTest, ConstructsMatcherUsingNewAPI) {
+  // Using PolymorphicIsEven() as a Matcher<int>.
+  const Matcher<int> m1 = PolymorphicIsEven();
+  EXPECT_TRUE(m1.Matches(42));
+  EXPECT_FALSE(m1.Matches(43));
+  EXPECT_EQ("is even", Describe(m1));
+
+  const Matcher<int> not_m1 = Not(m1);
+  EXPECT_EQ("is odd", Describe(not_m1));
+
+  EXPECT_EQ("% 2 == 0", Explain(m1, 42));
+
+  // Using PolymorphicIsEven() as a Matcher<char>.
+  const Matcher<char> m2 = PolymorphicIsEven();
+  EXPECT_TRUE(m2.Matches('\x42'));
+  EXPECT_FALSE(m2.Matches('\x43'));
+  EXPECT_EQ("is even", Describe(m2));
+
+  const Matcher<char> not_m2 = Not(m2);
+  EXPECT_EQ("is odd", Describe(not_m2));
+
+  EXPECT_EQ("% 2 == 0", Explain(m2, '\x42'));
+}
+
+INSTANTIATE_GTEST_MATCHER_TEST_P(MatcherCastTest);
+
+// Tests that MatcherCast<T>(m) works when m is a polymorphic matcher.
+TEST_P(MatcherCastTestP, FromPolymorphicMatcher) {
+  Matcher<int16_t> m;
+  if (use_gtest_matcher_) {
+    m = MatcherCast<int16_t>(GtestGreaterThan(int64_t{5}));
+  } else {
+    m = MatcherCast<int16_t>(Gt(int64_t{5}));
+  }
+  EXPECT_TRUE(m.Matches(6));
+  EXPECT_FALSE(m.Matches(4));
+}
+
+// For testing casting matchers between compatible types.
+class IntValue {
+ public:
+  // An int can be statically (although not implicitly) cast to a
+  // IntValue.
+  explicit IntValue(int a_value) : value_(a_value) {}
+
+  int value() const { return value_; }
+
+ private:
+  int value_;
+};
+
+// For testing casting matchers between compatible types.
+bool IsPositiveIntValue(const IntValue& foo) { return foo.value() > 0; }
+
+// Tests that MatcherCast<T>(m) works when m is a Matcher<U> where T
+// can be statically converted to U.
+TEST(MatcherCastTest, FromCompatibleType) {
+  Matcher<double> m1 = Eq(2.0);
+  Matcher<int> m2 = MatcherCast<int>(m1);
+  EXPECT_TRUE(m2.Matches(2));
+  EXPECT_FALSE(m2.Matches(3));
+
+  Matcher<IntValue> m3 = Truly(IsPositiveIntValue);
+  Matcher<int> m4 = MatcherCast<int>(m3);
+  // In the following, the arguments 1 and 0 are statically converted
+  // to IntValue objects, and then tested by the IsPositiveIntValue()
+  // predicate.
+  EXPECT_TRUE(m4.Matches(1));
+  EXPECT_FALSE(m4.Matches(0));
+}
+
+// Tests that MatcherCast<T>(m) works when m is a Matcher<const T&>.
+TEST(MatcherCastTest, FromConstReferenceToNonReference) {
+  Matcher<const int&> m1 = Eq(0);
+  Matcher<int> m2 = MatcherCast<int>(m1);
+  EXPECT_TRUE(m2.Matches(0));
+  EXPECT_FALSE(m2.Matches(1));
+}
+
+// Tests that MatcherCast<T>(m) works when m is a Matcher<T&>.
+TEST(MatcherCastTest, FromReferenceToNonReference) {
+  Matcher<int&> m1 = Eq(0);
+  Matcher<int> m2 = MatcherCast<int>(m1);
+  EXPECT_TRUE(m2.Matches(0));
+  EXPECT_FALSE(m2.Matches(1));
+}
+
+// Tests that MatcherCast<const T&>(m) works when m is a Matcher<T>.
+TEST(MatcherCastTest, FromNonReferenceToConstReference) {
+  Matcher<int> m1 = Eq(0);
+  Matcher<const int&> m2 = MatcherCast<const int&>(m1);
+  EXPECT_TRUE(m2.Matches(0));
+  EXPECT_FALSE(m2.Matches(1));
+}
+
+// Tests that MatcherCast<T&>(m) works when m is a Matcher<T>.
+TEST(MatcherCastTest, FromNonReferenceToReference) {
+  Matcher<int> m1 = Eq(0);
+  Matcher<int&> m2 = MatcherCast<int&>(m1);
+  int n = 0;
+  EXPECT_TRUE(m2.Matches(n));
+  n = 1;
+  EXPECT_FALSE(m2.Matches(n));
+}
+
+// Tests that MatcherCast<T>(m) works when m is a Matcher<T>.
+TEST(MatcherCastTest, FromSameType) {
+  Matcher<int> m1 = Eq(0);
+  Matcher<int> m2 = MatcherCast<int>(m1);
+  EXPECT_TRUE(m2.Matches(0));
+  EXPECT_FALSE(m2.Matches(1));
+}
+
+// Tests that MatcherCast<T>(m) works when m is a value of the same type as the
+// value type of the Matcher.
+TEST(MatcherCastTest, FromAValue) {
+  Matcher<int> m = MatcherCast<int>(42);
+  EXPECT_TRUE(m.Matches(42));
+  EXPECT_FALSE(m.Matches(239));
+}
+
+// Tests that MatcherCast<T>(m) works when m is a value of the type implicitly
+// convertible to the value type of the Matcher.
+TEST(MatcherCastTest, FromAnImplicitlyConvertibleValue) {
+  const int kExpected = 'c';
+  Matcher<int> m = MatcherCast<int>('c');
+  EXPECT_TRUE(m.Matches(kExpected));
+  EXPECT_FALSE(m.Matches(kExpected + 1));
+}
+
+struct NonImplicitlyConstructibleTypeWithOperatorEq {
+  friend bool operator==(
+      const NonImplicitlyConstructibleTypeWithOperatorEq& /* ignored */,
+      int rhs) {
+    return 42 == rhs;
+  }
+  friend bool operator==(
+      int lhs,
+      const NonImplicitlyConstructibleTypeWithOperatorEq& /* ignored */) {
+    return lhs == 42;
+  }
+};
+
+// Tests that MatcherCast<T>(m) works when m is a neither a matcher nor
+// implicitly convertible to the value type of the Matcher, but the value type
+// of the matcher has operator==() overload accepting m.
+TEST(MatcherCastTest, NonImplicitlyConstructibleTypeWithOperatorEq) {
+  Matcher<NonImplicitlyConstructibleTypeWithOperatorEq> m1 =
+      MatcherCast<NonImplicitlyConstructibleTypeWithOperatorEq>(42);
+  EXPECT_TRUE(m1.Matches(NonImplicitlyConstructibleTypeWithOperatorEq()));
+
+  Matcher<NonImplicitlyConstructibleTypeWithOperatorEq> m2 =
+      MatcherCast<NonImplicitlyConstructibleTypeWithOperatorEq>(239);
+  EXPECT_FALSE(m2.Matches(NonImplicitlyConstructibleTypeWithOperatorEq()));
+
+  // When updating the following lines please also change the comment to
+  // namespace convertible_from_any.
+  Matcher<int> m3 =
+      MatcherCast<int>(NonImplicitlyConstructibleTypeWithOperatorEq());
+  EXPECT_TRUE(m3.Matches(42));
+  EXPECT_FALSE(m3.Matches(239));
+}
+
+// ConvertibleFromAny does not work with MSVC. resulting in
+// error C2440: 'initializing': cannot convert from 'Eq' to 'M'
+// No constructor could take the source type, or constructor overload
+// resolution was ambiguous
+
+#if !defined _MSC_VER
+
+// The below ConvertibleFromAny struct is implicitly constructible from anything
+// and when in the same namespace can interact with other tests. In particular,
+// if it is in the same namespace as other tests and one removes
+//   NonImplicitlyConstructibleTypeWithOperatorEq::operator==(int lhs, ...);
+// then the corresponding test still compiles (and it should not!) by implicitly
+// converting NonImplicitlyConstructibleTypeWithOperatorEq to ConvertibleFromAny
+// in m3.Matcher().
+namespace convertible_from_any {
+// Implicitly convertible from any type.
+struct ConvertibleFromAny {
+  ConvertibleFromAny(int a_value) : value(a_value) {}
+  template <typename T>
+  ConvertibleFromAny(const T& /*a_value*/) : value(-1) {
+    ADD_FAILURE() << "Conversion constructor called";
+  }
+  int value;
+};
+
+bool operator==(const ConvertibleFromAny& a, const ConvertibleFromAny& b) {
+  return a.value == b.value;
+}
+
+ostream& operator<<(ostream& os, const ConvertibleFromAny& a) {
+  return os << a.value;
+}
+
+TEST(MatcherCastTest, ConversionConstructorIsUsed) {
+  Matcher<ConvertibleFromAny> m = MatcherCast<ConvertibleFromAny>(1);
+  EXPECT_TRUE(m.Matches(ConvertibleFromAny(1)));
+  EXPECT_FALSE(m.Matches(ConvertibleFromAny(2)));
+}
+
+TEST(MatcherCastTest, FromConvertibleFromAny) {
+  Matcher<ConvertibleFromAny> m =
+      MatcherCast<ConvertibleFromAny>(Eq(ConvertibleFromAny(1)));
+  EXPECT_TRUE(m.Matches(ConvertibleFromAny(1)));
+  EXPECT_FALSE(m.Matches(ConvertibleFromAny(2)));
+}
+}  // namespace convertible_from_any
+
+#endif  // !defined _MSC_VER
+
+struct IntReferenceWrapper {
+  IntReferenceWrapper(const int& a_value) : value(&a_value) {}
+  const int* value;
+};
+
+bool operator==(const IntReferenceWrapper& a, const IntReferenceWrapper& b) {
+  return a.value == b.value;
+}
+
+TEST(MatcherCastTest, ValueIsNotCopied) {
+  int n = 42;
+  Matcher<IntReferenceWrapper> m = MatcherCast<IntReferenceWrapper>(n);
+  // Verify that the matcher holds a reference to n, not to its temporary copy.
+  EXPECT_TRUE(m.Matches(n));
+}
+
+class Base {
+ public:
+  virtual ~Base() = default;
+  Base() = default;
+
+ private:
+  Base(const Base&) = delete;
+  Base& operator=(const Base&) = delete;
+};
+
+class Derived : public Base {
+ public:
+  Derived() : Base() {}
+  int i;
+};
+
+class OtherDerived : public Base {};
+
+INSTANTIATE_GTEST_MATCHER_TEST_P(SafeMatcherCastTest);
+
+// Tests that SafeMatcherCast<T>(m) works when m is a polymorphic matcher.
+TEST_P(SafeMatcherCastTestP, FromPolymorphicMatcher) {
+  Matcher<char> m2;
+  if (use_gtest_matcher_) {
+    m2 = SafeMatcherCast<char>(GtestGreaterThan(32));
+  } else {
+    m2 = SafeMatcherCast<char>(Gt(32));
+  }
+  EXPECT_TRUE(m2.Matches('A'));
+  EXPECT_FALSE(m2.Matches('\n'));
+}
+
+// Tests that SafeMatcherCast<T>(m) works when m is a Matcher<U> where
+// T and U are arithmetic types and T can be losslessly converted to
+// U.
+TEST(SafeMatcherCastTest, FromLosslesslyConvertibleArithmeticType) {
+  Matcher<double> m1 = DoubleEq(1.0);
+  Matcher<float> m2 = SafeMatcherCast<float>(m1);
+  EXPECT_TRUE(m2.Matches(1.0f));
+  EXPECT_FALSE(m2.Matches(2.0f));
+
+  Matcher<char> m3 = SafeMatcherCast<char>(TypedEq<int>('a'));
+  EXPECT_TRUE(m3.Matches('a'));
+  EXPECT_FALSE(m3.Matches('b'));
+}
+
+// Tests that SafeMatcherCast<T>(m) works when m is a Matcher<U> where T and U
+// are pointers or references to a derived and a base class, correspondingly.
+TEST(SafeMatcherCastTest, FromBaseClass) {
+  Derived d, d2;
+  Matcher<Base*> m1 = Eq(&d);
+  Matcher<Derived*> m2 = SafeMatcherCast<Derived*>(m1);
+  EXPECT_TRUE(m2.Matches(&d));
+  EXPECT_FALSE(m2.Matches(&d2));
+
+  Matcher<Base&> m3 = Ref(d);
+  Matcher<Derived&> m4 = SafeMatcherCast<Derived&>(m3);
+  EXPECT_TRUE(m4.Matches(d));
+  EXPECT_FALSE(m4.Matches(d2));
+}
+
+// Tests that SafeMatcherCast<T&>(m) works when m is a Matcher<const T&>.
+TEST(SafeMatcherCastTest, FromConstReferenceToReference) {
+  int n = 0;
+  Matcher<const int&> m1 = Ref(n);
+  Matcher<int&> m2 = SafeMatcherCast<int&>(m1);
+  int n1 = 0;
+  EXPECT_TRUE(m2.Matches(n));
+  EXPECT_FALSE(m2.Matches(n1));
+}
+
+// Tests that MatcherCast<const T&>(m) works when m is a Matcher<T>.
+TEST(SafeMatcherCastTest, FromNonReferenceToConstReference) {
+  Matcher<std::unique_ptr<int>> m1 = IsNull();
+  Matcher<const std::unique_ptr<int>&> m2 =
+      SafeMatcherCast<const std::unique_ptr<int>&>(m1);
+  EXPECT_TRUE(m2.Matches(std::unique_ptr<int>()));
+  EXPECT_FALSE(m2.Matches(std::unique_ptr<int>(new int)));
+}
+
+// Tests that SafeMatcherCast<T&>(m) works when m is a Matcher<T>.
+TEST(SafeMatcherCastTest, FromNonReferenceToReference) {
+  Matcher<int> m1 = Eq(0);
+  Matcher<int&> m2 = SafeMatcherCast<int&>(m1);
+  int n = 0;
+  EXPECT_TRUE(m2.Matches(n));
+  n = 1;
+  EXPECT_FALSE(m2.Matches(n));
+}
+
+// Tests that SafeMatcherCast<T>(m) works when m is a Matcher<T>.
+TEST(SafeMatcherCastTest, FromSameType) {
+  Matcher<int> m1 = Eq(0);
+  Matcher<int> m2 = SafeMatcherCast<int>(m1);
+  EXPECT_TRUE(m2.Matches(0));
+  EXPECT_FALSE(m2.Matches(1));
+}
+
+#if !defined _MSC_VER
+
+namespace convertible_from_any {
+TEST(SafeMatcherCastTest, ConversionConstructorIsUsed) {
+  Matcher<ConvertibleFromAny> m = SafeMatcherCast<ConvertibleFromAny>(1);
+  EXPECT_TRUE(m.Matches(ConvertibleFromAny(1)));
+  EXPECT_FALSE(m.Matches(ConvertibleFromAny(2)));
+}
+
+TEST(SafeMatcherCastTest, FromConvertibleFromAny) {
+  Matcher<ConvertibleFromAny> m =
+      SafeMatcherCast<ConvertibleFromAny>(Eq(ConvertibleFromAny(1)));
+  EXPECT_TRUE(m.Matches(ConvertibleFromAny(1)));
+  EXPECT_FALSE(m.Matches(ConvertibleFromAny(2)));
+}
+}  // namespace convertible_from_any
+
+#endif  // !defined _MSC_VER
+
+TEST(SafeMatcherCastTest, ValueIsNotCopied) {
+  int n = 42;
+  Matcher<IntReferenceWrapper> m = SafeMatcherCast<IntReferenceWrapper>(n);
+  // Verify that the matcher holds a reference to n, not to its temporary copy.
+  EXPECT_TRUE(m.Matches(n));
+}
+
+TEST(ExpectThat, TakesLiterals) {
+  EXPECT_THAT(1, 1);
+  EXPECT_THAT(1.0, 1.0);
+  EXPECT_THAT(std::string(), "");
+}
+
+TEST(ExpectThat, TakesFunctions) {
+  struct Helper {
+    static void Func() {}
+  };
+  void (*func)() = Helper::Func;
+  EXPECT_THAT(func, Helper::Func);
+  EXPECT_THAT(func, &Helper::Func);
+}
+
+// Tests that A<T>() matches any value of type T.
+TEST(ATest, MatchesAnyValue) {
+  // Tests a matcher for a value type.
+  Matcher<double> m1 = A<double>();
+  EXPECT_TRUE(m1.Matches(91.43));
+  EXPECT_TRUE(m1.Matches(-15.32));
+
+  // Tests a matcher for a reference type.
+  int a = 2;
+  int b = -6;
+  Matcher<int&> m2 = A<int&>();
+  EXPECT_TRUE(m2.Matches(a));
+  EXPECT_TRUE(m2.Matches(b));
+}
+
+TEST(ATest, WorksForDerivedClass) {
+  Base base;
+  Derived derived;
+  EXPECT_THAT(&base, A<Base*>());
+  // This shouldn't compile: EXPECT_THAT(&base, A<Derived*>());
+  EXPECT_THAT(&derived, A<Base*>());
+  EXPECT_THAT(&derived, A<Derived*>());
+}
+
+// Tests that A<T>() describes itself properly.
+TEST(ATest, CanDescribeSelf) { EXPECT_EQ("is anything", Describe(A<bool>())); }
+
+// Tests that An<T>() matches any value of type T.
+TEST(AnTest, MatchesAnyValue) {
+  // Tests a matcher for a value type.
+  Matcher<int> m1 = An<int>();
+  EXPECT_TRUE(m1.Matches(9143));
+  EXPECT_TRUE(m1.Matches(-1532));
+
+  // Tests a matcher for a reference type.
+  int a = 2;
+  int b = -6;
+  Matcher<int&> m2 = An<int&>();
+  EXPECT_TRUE(m2.Matches(a));
+  EXPECT_TRUE(m2.Matches(b));
+}
+
+// Tests that An<T>() describes itself properly.
+TEST(AnTest, CanDescribeSelf) { EXPECT_EQ("is anything", Describe(An<int>())); }
+
+// Tests that _ can be used as a matcher for any type and matches any
+// value of that type.
+TEST(UnderscoreTest, MatchesAnyValue) {
+  // Uses _ as a matcher for a value type.
+  Matcher<int> m1 = _;
+  EXPECT_TRUE(m1.Matches(123));
+  EXPECT_TRUE(m1.Matches(-242));
+
+  // Uses _ as a matcher for a reference type.
+  bool a = false;
+  const bool b = true;
+  Matcher<const bool&> m2 = _;
+  EXPECT_TRUE(m2.Matches(a));
+  EXPECT_TRUE(m2.Matches(b));
+}
+
+// Tests that _ describes itself properly.
+TEST(UnderscoreTest, CanDescribeSelf) {
+  Matcher<int> m = _;
+  EXPECT_EQ("is anything", Describe(m));
+}
+
+// Tests that Eq(x) matches any value equal to x.
+TEST(EqTest, MatchesEqualValue) {
+  // 2 C-strings with same content but different addresses.
+  const char a1[] = "hi";
+  const char a2[] = "hi";
+
+  Matcher<const char*> m1 = Eq(a1);
+  EXPECT_TRUE(m1.Matches(a1));
+  EXPECT_FALSE(m1.Matches(a2));
+}
+
+// Tests that Eq(v) describes itself properly.
+
+class Unprintable {
+ public:
+  Unprintable() : c_('a') {}
+
+  bool operator==(const Unprintable& /* rhs */) const { return true; }
+  // -Wunused-private-field: dummy accessor for `c_`.
+  char dummy_c() { return c_; }
+
+ private:
+  char c_;
+};
+
+TEST(EqTest, CanDescribeSelf) {
+  Matcher<Unprintable> m = Eq(Unprintable());
+  EXPECT_EQ("is equal to 1-byte object <61>", Describe(m));
+}
+
+// Tests that Eq(v) can be used to match any type that supports
+// comparing with type T, where T is v's type.
+TEST(EqTest, IsPolymorphic) {
+  Matcher<int> m1 = Eq(1);
+  EXPECT_TRUE(m1.Matches(1));
+  EXPECT_FALSE(m1.Matches(2));
+
+  Matcher<char> m2 = Eq(1);
+  EXPECT_TRUE(m2.Matches('\1'));
+  EXPECT_FALSE(m2.Matches('a'));
+}
+
+// Tests that TypedEq<T>(v) matches values of type T that's equal to v.
+TEST(TypedEqTest, ChecksEqualityForGivenType) {
+  Matcher<char> m1 = TypedEq<char>('a');
+  EXPECT_TRUE(m1.Matches('a'));
+  EXPECT_FALSE(m1.Matches('b'));
+
+  Matcher<int> m2 = TypedEq<int>(6);
+  EXPECT_TRUE(m2.Matches(6));
+  EXPECT_FALSE(m2.Matches(7));
+}
+
+// Tests that TypedEq(v) describes itself properly.
+TEST(TypedEqTest, CanDescribeSelf) {
+  EXPECT_EQ("is equal to 2", Describe(TypedEq<int>(2)));
+}
+
+// Tests that TypedEq<T>(v) has type Matcher<T>.
+
+// Type<T>::IsTypeOf(v) compiles if and only if the type of value v is T, where
+// T is a "bare" type (i.e. not in the form of const U or U&).  If v's type is
+// not T, the compiler will generate a message about "undefined reference".
+template <typename T>
+struct Type {
+  static bool IsTypeOf(const T& /* v */) { return true; }
+
+  template <typename T2>
+  static void IsTypeOf(T2 v);
+};
+
+TEST(TypedEqTest, HasSpecifiedType) {
+  // Verifies that the type of TypedEq<T>(v) is Matcher<T>.
+  Type<Matcher<int>>::IsTypeOf(TypedEq<int>(5));
+  Type<Matcher<double>>::IsTypeOf(TypedEq<double>(5));
+}
+
+// Tests that Ge(v) matches anything >= v.
+TEST(GeTest, ImplementsGreaterThanOrEqual) {
+  Matcher<int> m1 = Ge(0);
+  EXPECT_TRUE(m1.Matches(1));
+  EXPECT_TRUE(m1.Matches(0));
+  EXPECT_FALSE(m1.Matches(-1));
+}
+
+// Tests that Ge(v) describes itself properly.
+TEST(GeTest, CanDescribeSelf) {
+  Matcher<int> m = Ge(5);
+  EXPECT_EQ("is >= 5", Describe(m));
+}
+
+// Tests that Gt(v) matches anything > v.
+TEST(GtTest, ImplementsGreaterThan) {
+  Matcher<double> m1 = Gt(0);
+  EXPECT_TRUE(m1.Matches(1.0));
+  EXPECT_FALSE(m1.Matches(0.0));
+  EXPECT_FALSE(m1.Matches(-1.0));
+}
+
+// Tests that Gt(v) describes itself properly.
+TEST(GtTest, CanDescribeSelf) {
+  Matcher<int> m = Gt(5);
+  EXPECT_EQ("is > 5", Describe(m));
+}
+
+// Tests that Le(v) matches anything <= v.
+TEST(LeTest, ImplementsLessThanOrEqual) {
+  Matcher<char> m1 = Le('b');
+  EXPECT_TRUE(m1.Matches('a'));
+  EXPECT_TRUE(m1.Matches('b'));
+  EXPECT_FALSE(m1.Matches('c'));
+}
+
+// Tests that Le(v) describes itself properly.
+TEST(LeTest, CanDescribeSelf) {
+  Matcher<int> m = Le(5);
+  EXPECT_EQ("is <= 5", Describe(m));
+}
+
+// Tests that Lt(v) matches anything < v.
+TEST(LtTest, ImplementsLessThan) {
+  Matcher<const std::string&> m1 = Lt("Hello");
+  EXPECT_TRUE(m1.Matches("Abc"));
+  EXPECT_FALSE(m1.Matches("Hello"));
+  EXPECT_FALSE(m1.Matches("Hello, world!"));
+}
+
+// Tests that Lt(v) describes itself properly.
+TEST(LtTest, CanDescribeSelf) {
+  Matcher<int> m = Lt(5);
+  EXPECT_EQ("is < 5", Describe(m));
+}
+
+// Tests that Ne(v) matches anything != v.
+TEST(NeTest, ImplementsNotEqual) {
+  Matcher<int> m1 = Ne(0);
+  EXPECT_TRUE(m1.Matches(1));
+  EXPECT_TRUE(m1.Matches(-1));
+  EXPECT_FALSE(m1.Matches(0));
+}
+
+// Tests that Ne(v) describes itself properly.
+TEST(NeTest, CanDescribeSelf) {
+  Matcher<int> m = Ne(5);
+  EXPECT_EQ("isn't equal to 5", Describe(m));
+}
+
+class MoveOnly {
+ public:
+  explicit MoveOnly(int i) : i_(i) {}
+  MoveOnly(const MoveOnly&) = delete;
+  MoveOnly(MoveOnly&&) = default;
+  MoveOnly& operator=(const MoveOnly&) = delete;
+  MoveOnly& operator=(MoveOnly&&) = default;
+
+  bool operator==(const MoveOnly& other) const { return i_ == other.i_; }
+  bool operator!=(const MoveOnly& other) const { return i_ != other.i_; }
+  bool operator<(const MoveOnly& other) const { return i_ < other.i_; }
+  bool operator<=(const MoveOnly& other) const { return i_ <= other.i_; }
+  bool operator>(const MoveOnly& other) const { return i_ > other.i_; }
+  bool operator>=(const MoveOnly& other) const { return i_ >= other.i_; }
+
+ private:
+  int i_;
+};
+
+struct MoveHelper {
+  MOCK_METHOD1(Call, void(MoveOnly));
+};
+
+// Disable this test in VS 2015 (version 14), where it fails when SEH is enabled
+#if defined(_MSC_VER) && (_MSC_VER < 1910)
+TEST(ComparisonBaseTest, DISABLED_WorksWithMoveOnly) {
+#else
+TEST(ComparisonBaseTest, WorksWithMoveOnly) {
+#endif
+  MoveOnly m{0};
+  MoveHelper helper;
+
+  EXPECT_CALL(helper, Call(Eq(ByRef(m))));
+  helper.Call(MoveOnly(0));
+  EXPECT_CALL(helper, Call(Ne(ByRef(m))));
+  helper.Call(MoveOnly(1));
+  EXPECT_CALL(helper, Call(Le(ByRef(m))));
+  helper.Call(MoveOnly(0));
+  EXPECT_CALL(helper, Call(Lt(ByRef(m))));
+  helper.Call(MoveOnly(-1));
+  EXPECT_CALL(helper, Call(Ge(ByRef(m))));
+  helper.Call(MoveOnly(0));
+  EXPECT_CALL(helper, Call(Gt(ByRef(m))));
+  helper.Call(MoveOnly(1));
+}
+
+TEST(IsEmptyTest, MatchesContainer) {
+  const Matcher<std::vector<int>> m = IsEmpty();
+  std::vector<int> a = {};
+  std::vector<int> b = {1};
+  EXPECT_TRUE(m.Matches(a));
+  EXPECT_FALSE(m.Matches(b));
+}
+
+TEST(IsEmptyTest, MatchesStdString) {
+  const Matcher<std::string> m = IsEmpty();
+  std::string a = "z";
+  std::string b = "";
+  EXPECT_FALSE(m.Matches(a));
+  EXPECT_TRUE(m.Matches(b));
+}
+
+TEST(IsEmptyTest, MatchesCString) {
+  const Matcher<const char*> m = IsEmpty();
+  const char a[] = "";
+  const char b[] = "x";
+  EXPECT_TRUE(m.Matches(a));
+  EXPECT_FALSE(m.Matches(b));
+}
+
+// Tests that IsNull() matches any NULL pointer of any type.
+TEST(IsNullTest, MatchesNullPointer) {
+  Matcher<int*> m1 = IsNull();
+  int* p1 = nullptr;
+  int n = 0;
+  EXPECT_TRUE(m1.Matches(p1));
+  EXPECT_FALSE(m1.Matches(&n));
+
+  Matcher<const char*> m2 = IsNull();
+  const char* p2 = nullptr;
+  EXPECT_TRUE(m2.Matches(p2));
+  EXPECT_FALSE(m2.Matches("hi"));
+
+  Matcher<void*> m3 = IsNull();
+  void* p3 = nullptr;
+  EXPECT_TRUE(m3.Matches(p3));
+  EXPECT_FALSE(m3.Matches(reinterpret_cast<void*>(0xbeef)));
+}
+
+TEST(IsNullTest, StdFunction) {
+  const Matcher<std::function<void()>> m = IsNull();
+
+  EXPECT_TRUE(m.Matches(std::function<void()>()));
+  EXPECT_FALSE(m.Matches([] {}));
+}
+
+// Tests that IsNull() describes itself properly.
+TEST(IsNullTest, CanDescribeSelf) {
+  Matcher<int*> m = IsNull();
+  EXPECT_EQ("is NULL", Describe(m));
+  EXPECT_EQ("isn't NULL", DescribeNegation(m));
+}
+
+// Tests that NotNull() matches any non-NULL pointer of any type.
+TEST(NotNullTest, MatchesNonNullPointer) {
+  Matcher<int*> m1 = NotNull();
+  int* p1 = nullptr;
+  int n = 0;
+  EXPECT_FALSE(m1.Matches(p1));
+  EXPECT_TRUE(m1.Matches(&n));
+
+  Matcher<const char*> m2 = NotNull();
+  const char* p2 = nullptr;
+  EXPECT_FALSE(m2.Matches(p2));
+  EXPECT_TRUE(m2.Matches("hi"));
+}
+
+TEST(NotNullTest, LinkedPtr) {
+  const Matcher<std::shared_ptr<int>> m = NotNull();
+  const std::shared_ptr<int> null_p;
+  const std::shared_ptr<int> non_null_p(new int);
+
+  EXPECT_FALSE(m.Matches(null_p));
+  EXPECT_TRUE(m.Matches(non_null_p));
+}
+
+TEST(NotNullTest, ReferenceToConstLinkedPtr) {
+  const Matcher<const std::shared_ptr<double>&> m = NotNull();
+  const std::shared_ptr<double> null_p;
+  const std::shared_ptr<double> non_null_p(new double);
+
+  EXPECT_FALSE(m.Matches(null_p));
+  EXPECT_TRUE(m.Matches(non_null_p));
+}
+
+TEST(NotNullTest, StdFunction) {
+  const Matcher<std::function<void()>> m = NotNull();
+
+  EXPECT_TRUE(m.Matches([] {}));
+  EXPECT_FALSE(m.Matches(std::function<void()>()));
+}
+
+// Tests that NotNull() describes itself properly.
+TEST(NotNullTest, CanDescribeSelf) {
+  Matcher<int*> m = NotNull();
+  EXPECT_EQ("isn't NULL", Describe(m));
+}
+
+// Tests that Ref(variable) matches an argument that references
+// 'variable'.
+TEST(RefTest, MatchesSameVariable) {
+  int a = 0;
+  int b = 0;
+  Matcher<int&> m = Ref(a);
+  EXPECT_TRUE(m.Matches(a));
+  EXPECT_FALSE(m.Matches(b));
+}
+
+// Tests that Ref(variable) describes itself properly.
+TEST(RefTest, CanDescribeSelf) {
+  int n = 5;
+  Matcher<int&> m = Ref(n);
+  stringstream ss;
+  ss << "references the variable @" << &n << " 5";
+  EXPECT_EQ(ss.str(), Describe(m));
+}
+
+// Test that Ref(non_const_varialbe) can be used as a matcher for a
+// const reference.
+TEST(RefTest, CanBeUsedAsMatcherForConstReference) {
+  int a = 0;
+  int b = 0;
+  Matcher<const int&> m = Ref(a);
+  EXPECT_TRUE(m.Matches(a));
+  EXPECT_FALSE(m.Matches(b));
+}
+
+// Tests that Ref(variable) is covariant, i.e. Ref(derived) can be
+// used wherever Ref(base) can be used (Ref(derived) is a sub-type
+// of Ref(base), but not vice versa.
+
+TEST(RefTest, IsCovariant) {
+  Base base, base2;
+  Derived derived;
+  Matcher<const Base&> m1 = Ref(base);
+  EXPECT_TRUE(m1.Matches(base));
+  EXPECT_FALSE(m1.Matches(base2));
+  EXPECT_FALSE(m1.Matches(derived));
+
+  m1 = Ref(derived);
+  EXPECT_TRUE(m1.Matches(derived));
+  EXPECT_FALSE(m1.Matches(base));
+  EXPECT_FALSE(m1.Matches(base2));
+}
+
+TEST(RefTest, ExplainsResult) {
+  int n = 0;
+  EXPECT_THAT(Explain(Matcher<const int&>(Ref(n)), n),
+              StartsWith("which is located @"));
+
+  int m = 0;
+  EXPECT_THAT(Explain(Matcher<const int&>(Ref(n)), m),
+              StartsWith("which is located @"));
+}
+
+// Tests string comparison matchers.
+
+template <typename T = std::string>
+std::string FromStringLike(internal::StringLike<T> str) {
+  return std::string(str);
+}
+
+TEST(StringLike, TestConversions) {
+  EXPECT_EQ("foo", FromStringLike("foo"));
+  EXPECT_EQ("foo", FromStringLike(std::string("foo")));
+#if GTEST_INTERNAL_HAS_STRING_VIEW
+  EXPECT_EQ("foo", FromStringLike(internal::StringView("foo")));
+#endif  // GTEST_INTERNAL_HAS_STRING_VIEW
+
+  // Non deducible types.
+  EXPECT_EQ("", FromStringLike({}));
+  EXPECT_EQ("foo", FromStringLike({'f', 'o', 'o'}));
+  const char buf[] = "foo";
+  EXPECT_EQ("foo", FromStringLike({buf, buf + 3}));
+}
+
+TEST(StrEqTest, MatchesEqualString) {
+  Matcher<const char*> m = StrEq(std::string("Hello"));
+  EXPECT_TRUE(m.Matches("Hello"));
+  EXPECT_FALSE(m.Matches("hello"));
+  EXPECT_FALSE(m.Matches(nullptr));
+
+  Matcher<const std::string&> m2 = StrEq("Hello");
+  EXPECT_TRUE(m2.Matches("Hello"));
+  EXPECT_FALSE(m2.Matches("Hi"));
+
+#if GTEST_INTERNAL_HAS_STRING_VIEW
+  Matcher<const internal::StringView&> m3 =
+      StrEq(internal::StringView("Hello"));
+  EXPECT_TRUE(m3.Matches(internal::StringView("Hello")));
+  EXPECT_FALSE(m3.Matches(internal::StringView("hello")));
+  EXPECT_FALSE(m3.Matches(internal::StringView()));
+
+  Matcher<const internal::StringView&> m_empty = StrEq("");
+  EXPECT_TRUE(m_empty.Matches(internal::StringView("")));
+  EXPECT_TRUE(m_empty.Matches(internal::StringView()));
+  EXPECT_FALSE(m_empty.Matches(internal::StringView("hello")));
+#endif  // GTEST_INTERNAL_HAS_STRING_VIEW
+}
+
+TEST(StrEqTest, CanDescribeSelf) {
+  Matcher<std::string> m = StrEq("Hi-\'\"?\\\a\b\f\n\r\t\v\xD3");
+  EXPECT_EQ("is equal to \"Hi-\'\\\"?\\\\\\a\\b\\f\\n\\r\\t\\v\\xD3\"",
+            Describe(m));
+
+  std::string str("01204500800");
+  str[3] = '\0';
+  Matcher<std::string> m2 = StrEq(str);
+  EXPECT_EQ("is equal to \"012\\04500800\"", Describe(m2));
+  str[0] = str[6] = str[7] = str[9] = str[10] = '\0';
+  Matcher<std::string> m3 = StrEq(str);
+  EXPECT_EQ("is equal to \"\\012\\045\\0\\08\\0\\0\"", Describe(m3));
+}
+
+TEST(StrNeTest, MatchesUnequalString) {
+  Matcher<const char*> m = StrNe("Hello");
+  EXPECT_TRUE(m.Matches(""));
+  EXPECT_TRUE(m.Matches(nullptr));
+  EXPECT_FALSE(m.Matches("Hello"));
+
+  Matcher<std::string> m2 = StrNe(std::string("Hello"));
+  EXPECT_TRUE(m2.Matches("hello"));
+  EXPECT_FALSE(m2.Matches("Hello"));
+
+#if GTEST_INTERNAL_HAS_STRING_VIEW
+  Matcher<const internal::StringView> m3 = StrNe(internal::StringView("Hello"));
+  EXPECT_TRUE(m3.Matches(internal::StringView("")));
+  EXPECT_TRUE(m3.Matches(internal::StringView()));
+  EXPECT_FALSE(m3.Matches(internal::StringView("Hello")));
+#endif  // GTEST_INTERNAL_HAS_STRING_VIEW
+}
+
+TEST(StrNeTest, CanDescribeSelf) {
+  Matcher<const char*> m = StrNe("Hi");
+  EXPECT_EQ("isn't equal to \"Hi\"", Describe(m));
+}
+
+TEST(StrCaseEqTest, MatchesEqualStringIgnoringCase) {
+  Matcher<const char*> m = StrCaseEq(std::string("Hello"));
+  EXPECT_TRUE(m.Matches("Hello"));
+  EXPECT_TRUE(m.Matches("hello"));
+  EXPECT_FALSE(m.Matches("Hi"));
+  EXPECT_FALSE(m.Matches(nullptr));
+
+  Matcher<const std::string&> m2 = StrCaseEq("Hello");
+  EXPECT_TRUE(m2.Matches("hello"));
+  EXPECT_FALSE(m2.Matches("Hi"));
+
+#if GTEST_INTERNAL_HAS_STRING_VIEW
+  Matcher<const internal::StringView&> m3 =
+      StrCaseEq(internal::StringView("Hello"));
+  EXPECT_TRUE(m3.Matches(internal::StringView("Hello")));
+  EXPECT_TRUE(m3.Matches(internal::StringView("hello")));
+  EXPECT_FALSE(m3.Matches(internal::StringView("Hi")));
+  EXPECT_FALSE(m3.Matches(internal::StringView()));
+#endif  // GTEST_INTERNAL_HAS_STRING_VIEW
+}
+
+TEST(StrCaseEqTest, MatchesEqualStringWith0IgnoringCase) {
+  std::string str1("oabocdooeoo");
+  std::string str2("OABOCDOOEOO");
+  Matcher<const std::string&> m0 = StrCaseEq(str1);
+  EXPECT_FALSE(m0.Matches(str2 + std::string(1, '\0')));
+
+  str1[3] = str2[3] = '\0';
+  Matcher<const std::string&> m1 = StrCaseEq(str1);
+  EXPECT_TRUE(m1.Matches(str2));
+
+  str1[0] = str1[6] = str1[7] = str1[10] = '\0';
+  str2[0] = str2[6] = str2[7] = str2[10] = '\0';
+  Matcher<const std::string&> m2 = StrCaseEq(str1);
+  str1[9] = str2[9] = '\0';
+  EXPECT_FALSE(m2.Matches(str2));
+
+  Matcher<const std::string&> m3 = StrCaseEq(str1);
+  EXPECT_TRUE(m3.Matches(str2));
+
+  EXPECT_FALSE(m3.Matches(str2 + "x"));
+  str2.append(1, '\0');
+  EXPECT_FALSE(m3.Matches(str2));
+  EXPECT_FALSE(m3.Matches(std::string(str2, 0, 9)));
+}
+
+TEST(StrCaseEqTest, CanDescribeSelf) {
+  Matcher<std::string> m = StrCaseEq("Hi");
+  EXPECT_EQ("is equal to (ignoring case) \"Hi\"", Describe(m));
+}
+
+TEST(StrCaseNeTest, MatchesUnequalStringIgnoringCase) {
+  Matcher<const char*> m = StrCaseNe("Hello");
+  EXPECT_TRUE(m.Matches("Hi"));
+  EXPECT_TRUE(m.Matches(nullptr));
+  EXPECT_FALSE(m.Matches("Hello"));
+  EXPECT_FALSE(m.Matches("hello"));
+
+  Matcher<std::string> m2 = StrCaseNe(std::string("Hello"));
+  EXPECT_TRUE(m2.Matches(""));
+  EXPECT_FALSE(m2.Matches("Hello"));
+
+#if GTEST_INTERNAL_HAS_STRING_VIEW
+  Matcher<const internal::StringView> m3 =
+      StrCaseNe(internal::StringView("Hello"));
+  EXPECT_TRUE(m3.Matches(internal::StringView("Hi")));
+  EXPECT_TRUE(m3.Matches(internal::StringView()));
+  EXPECT_FALSE(m3.Matches(internal::StringView("Hello")));
+  EXPECT_FALSE(m3.Matches(internal::StringView("hello")));
+#endif  // GTEST_INTERNAL_HAS_STRING_VIEW
+}
+
+TEST(StrCaseNeTest, CanDescribeSelf) {
+  Matcher<const char*> m = StrCaseNe("Hi");
+  EXPECT_EQ("isn't equal to (ignoring case) \"Hi\"", Describe(m));
+}
+
+// Tests that HasSubstr() works for matching string-typed values.
+TEST(HasSubstrTest, WorksForStringClasses) {
+  const Matcher<std::string> m1 = HasSubstr("foo");
+  EXPECT_TRUE(m1.Matches(std::string("I love food.")));
+  EXPECT_FALSE(m1.Matches(std::string("tofo")));
+
+  const Matcher<const std::string&> m2 = HasSubstr("foo");
+  EXPECT_TRUE(m2.Matches(std::string("I love food.")));
+  EXPECT_FALSE(m2.Matches(std::string("tofo")));
+
+  const Matcher<std::string> m_empty = HasSubstr("");
+  EXPECT_TRUE(m_empty.Matches(std::string()));
+  EXPECT_TRUE(m_empty.Matches(std::string("not empty")));
+}
+
+// Tests that HasSubstr() works for matching C-string-typed values.
+TEST(HasSubstrTest, WorksForCStrings) {
+  const Matcher<char*> m1 = HasSubstr("foo");
+  EXPECT_TRUE(m1.Matches(const_cast<char*>("I love food.")));
+  EXPECT_FALSE(m1.Matches(const_cast<char*>("tofo")));
+  EXPECT_FALSE(m1.Matches(nullptr));
+
+  const Matcher<const char*> m2 = HasSubstr("foo");
+  EXPECT_TRUE(m2.Matches("I love food."));
+  EXPECT_FALSE(m2.Matches("tofo"));
+  EXPECT_FALSE(m2.Matches(nullptr));
+
+  const Matcher<const char*> m_empty = HasSubstr("");
+  EXPECT_TRUE(m_empty.Matches("not empty"));
+  EXPECT_TRUE(m_empty.Matches(""));
+  EXPECT_FALSE(m_empty.Matches(nullptr));
+}
+
+#if GTEST_INTERNAL_HAS_STRING_VIEW
+// Tests that HasSubstr() works for matching StringView-typed values.
+TEST(HasSubstrTest, WorksForStringViewClasses) {
+  const Matcher<internal::StringView> m1 =
+      HasSubstr(internal::StringView("foo"));
+  EXPECT_TRUE(m1.Matches(internal::StringView("I love food.")));
+  EXPECT_FALSE(m1.Matches(internal::StringView("tofo")));
+  EXPECT_FALSE(m1.Matches(internal::StringView()));
+
+  const Matcher<const internal::StringView&> m2 = HasSubstr("foo");
+  EXPECT_TRUE(m2.Matches(internal::StringView("I love food.")));
+  EXPECT_FALSE(m2.Matches(internal::StringView("tofo")));
+  EXPECT_FALSE(m2.Matches(internal::StringView()));
+
+  const Matcher<const internal::StringView&> m3 = HasSubstr("");
+  EXPECT_TRUE(m3.Matches(internal::StringView("foo")));
+  EXPECT_TRUE(m3.Matches(internal::StringView("")));
+  EXPECT_TRUE(m3.Matches(internal::StringView()));
+}
+#endif  // GTEST_INTERNAL_HAS_STRING_VIEW
+
+// Tests that HasSubstr(s) describes itself properly.
+TEST(HasSubstrTest, CanDescribeSelf) {
+  Matcher<std::string> m = HasSubstr("foo\n\"");
+  EXPECT_EQ("has substring \"foo\\n\\\"\"", Describe(m));
+}
+
+INSTANTIATE_GTEST_MATCHER_TEST_P(KeyTest);
+
+TEST(KeyTest, CanDescribeSelf) {
+  Matcher<const pair<std::string, int>&> m = Key("foo");
+  EXPECT_EQ("has a key that is equal to \"foo\"", Describe(m));
+  EXPECT_EQ("doesn't have a key that is equal to \"foo\"", DescribeNegation(m));
+}
+
+TEST_P(KeyTestP, ExplainsResult) {
+  Matcher<pair<int, bool>> m = Key(GreaterThan(10));
+  EXPECT_EQ("whose first field is a value which is 5 less than 10",
+            Explain(m, make_pair(5, true)));
+  EXPECT_EQ("whose first field is a value which is 5 more than 10",
+            Explain(m, make_pair(15, true)));
+}
+
+TEST(KeyTest, MatchesCorrectly) {
+  pair<int, std::string> p(25, "foo");
+  EXPECT_THAT(p, Key(25));
+  EXPECT_THAT(p, Not(Key(42)));
+  EXPECT_THAT(p, Key(Ge(20)));
+  EXPECT_THAT(p, Not(Key(Lt(25))));
+}
+
+TEST(KeyTest, WorksWithMoveOnly) {
+  pair<std::unique_ptr<int>, std::unique_ptr<int>> p;
+  EXPECT_THAT(p, Key(Eq(nullptr)));
+}
+
+INSTANTIATE_GTEST_MATCHER_TEST_P(PairTest);
+
+template <size_t I>
+struct Tag {};
+
+struct PairWithGet {
+  int member_1;
+  std::string member_2;
+  using first_type = int;
+  using second_type = std::string;
+
+  const int& GetImpl(Tag<0>) const { return member_1; }
+  const std::string& GetImpl(Tag<1>) const { return member_2; }
+};
+template <size_t I>
+auto get(const PairWithGet& value) -> decltype(value.GetImpl(Tag<I>())) {
+  return value.GetImpl(Tag<I>());
+}
+TEST(PairTest, MatchesPairWithGetCorrectly) {
+  PairWithGet p{25, "foo"};
+  EXPECT_THAT(p, Key(25));
+  EXPECT_THAT(p, Not(Key(42)));
+  EXPECT_THAT(p, Key(Ge(20)));
+  EXPECT_THAT(p, Not(Key(Lt(25))));
+
+  std::vector<PairWithGet> v = {{11, "Foo"}, {29, "gMockIsBestMock"}};
+  EXPECT_THAT(v, Contains(Key(29)));
+}
+
+TEST(KeyTest, SafelyCastsInnerMatcher) {
+  Matcher<int> is_positive = Gt(0);
+  Matcher<int> is_negative = Lt(0);
+  pair<char, bool> p('a', true);
+  EXPECT_THAT(p, Key(is_positive));
+  EXPECT_THAT(p, Not(Key(is_negative)));
+}
+
+TEST(KeyTest, InsideContainsUsingMap) {
+  map<int, char> container;
+  container.insert(make_pair(1, 'a'));
+  container.insert(make_pair(2, 'b'));
+  container.insert(make_pair(4, 'c'));
+  EXPECT_THAT(container, Contains(Key(1)));
+  EXPECT_THAT(container, Not(Contains(Key(3))));
+}
+
+TEST(KeyTest, InsideContainsUsingMultimap) {
+  multimap<int, char> container;
+  container.insert(make_pair(1, 'a'));
+  container.insert(make_pair(2, 'b'));
+  container.insert(make_pair(4, 'c'));
+
+  EXPECT_THAT(container, Not(Contains(Key(25))));
+  container.insert(make_pair(25, 'd'));
+  EXPECT_THAT(container, Contains(Key(25)));
+  container.insert(make_pair(25, 'e'));
+  EXPECT_THAT(container, Contains(Key(25)));
+
+  EXPECT_THAT(container, Contains(Key(1)));
+  EXPECT_THAT(container, Not(Contains(Key(3))));
+}
+
+TEST(PairTest, Typing) {
+  // Test verifies the following type conversions can be compiled.
+  Matcher<const pair<const char*, int>&> m1 = Pair("foo", 42);
+  Matcher<const pair<const char*, int>> m2 = Pair("foo", 42);
+  Matcher<pair<const char*, int>> m3 = Pair("foo", 42);
+
+  Matcher<pair<int, const std::string>> m4 = Pair(25, "42");
+  Matcher<pair<const std::string, int>> m5 = Pair("25", 42);
+}
+
+TEST(PairTest, CanDescribeSelf) {
+  Matcher<const pair<std::string, int>&> m1 = Pair("foo", 42);
+  EXPECT_EQ(
+      "has a first field that is equal to \"foo\""
+      ", and has a second field that is equal to 42",
+      Describe(m1));
+  EXPECT_EQ(
+      "has a first field that isn't equal to \"foo\""
+      ", or has a second field that isn't equal to 42",
+      DescribeNegation(m1));
+  // Double and triple negation (1 or 2 times not and description of negation).
+  Matcher<const pair<int, int>&> m2 = Not(Pair(Not(13), 42));
+  EXPECT_EQ(
+      "has a first field that isn't equal to 13"
+      ", and has a second field that is equal to 42",
+      DescribeNegation(m2));
+}
+
+TEST_P(PairTestP, CanExplainMatchResultTo) {
+  // If neither field matches, Pair() should explain about the first
+  // field.
+  const Matcher<pair<int, int>> m = Pair(GreaterThan(0), GreaterThan(0));
+  EXPECT_EQ("whose first field does not match, which is 1 less than 0",
+            Explain(m, make_pair(-1, -2)));
+
+  // If the first field matches but the second doesn't, Pair() should
+  // explain about the second field.
+  EXPECT_EQ("whose second field does not match, which is 2 less than 0",
+            Explain(m, make_pair(1, -2)));
+
+  // If the first field doesn't match but the second does, Pair()
+  // should explain about the first field.
+  EXPECT_EQ("whose first field does not match, which is 1 less than 0",
+            Explain(m, make_pair(-1, 2)));
+
+  // If both fields match, Pair() should explain about them both.
+  EXPECT_EQ(
+      "whose both fields match, where the first field is a value "
+      "which is 1 more than 0, and the second field is a value "
+      "which is 2 more than 0",
+      Explain(m, make_pair(1, 2)));
+
+  // If only the first match has an explanation, only this explanation should
+  // be printed.
+  const Matcher<pair<int, int>> explain_first = Pair(GreaterThan(0), 0);
+  EXPECT_EQ(
+      "whose both fields match, where the first field is a value "
+      "which is 1 more than 0",
+      Explain(explain_first, make_pair(1, 0)));
+
+  // If only the second match has an explanation, only this explanation should
+  // be printed.
+  const Matcher<pair<int, int>> explain_second = Pair(0, GreaterThan(0));
+  EXPECT_EQ(
+      "whose both fields match, where the second field is a value "
+      "which is 1 more than 0",
+      Explain(explain_second, make_pair(0, 1)));
+}
+
+TEST(PairTest, MatchesCorrectly) {
+  pair<int, std::string> p(25, "foo");
+
+  // Both fields match.
+  EXPECT_THAT(p, Pair(25, "foo"));
+  EXPECT_THAT(p, Pair(Ge(20), HasSubstr("o")));
+
+  // 'first' doesn't match, but 'second' matches.
+  EXPECT_THAT(p, Not(Pair(42, "foo")));
+  EXPECT_THAT(p, Not(Pair(Lt(25), "foo")));
+
+  // 'first' matches, but 'second' doesn't match.
+  EXPECT_THAT(p, Not(Pair(25, "bar")));
+  EXPECT_THAT(p, Not(Pair(25, Not("foo"))));
+
+  // Neither field matches.
+  EXPECT_THAT(p, Not(Pair(13, "bar")));
+  EXPECT_THAT(p, Not(Pair(Lt(13), HasSubstr("a"))));
+}
+
+TEST(PairTest, WorksWithMoveOnly) {
+  pair<std::unique_ptr<int>, std::unique_ptr<int>> p;
+  p.second = std::make_unique<int>(7);
+  EXPECT_THAT(p, Pair(Eq(nullptr), Ne(nullptr)));
+}
+
+TEST(PairTest, SafelyCastsInnerMatchers) {
+  Matcher<int> is_positive = Gt(0);
+  Matcher<int> is_negative = Lt(0);
+  pair<char, bool> p('a', true);
+  EXPECT_THAT(p, Pair(is_positive, _));
+  EXPECT_THAT(p, Not(Pair(is_negative, _)));
+  EXPECT_THAT(p, Pair(_, is_positive));
+  EXPECT_THAT(p, Not(Pair(_, is_negative)));
+}
+
+TEST(PairTest, InsideContainsUsingMap) {
+  map<int, char> container;
+  container.insert(make_pair(1, 'a'));
+  container.insert(make_pair(2, 'b'));
+  container.insert(make_pair(4, 'c'));
+  EXPECT_THAT(container, Contains(Pair(1, 'a')));
+  EXPECT_THAT(container, Contains(Pair(1, _)));
+  EXPECT_THAT(container, Contains(Pair(_, 'a')));
+  EXPECT_THAT(container, Not(Contains(Pair(3, _))));
+}
+
+INSTANTIATE_GTEST_MATCHER_TEST_P(FieldsAreTest);
+
+TEST(FieldsAreTest, MatchesCorrectly) {
+  std::tuple<int, std::string, double> p(25, "foo", .5);
+
+  // All fields match.
+  EXPECT_THAT(p, FieldsAre(25, "foo", .5));
+  EXPECT_THAT(p, FieldsAre(Ge(20), HasSubstr("o"), DoubleEq(.5)));
+
+  // Some don't match.
+  EXPECT_THAT(p, Not(FieldsAre(26, "foo", .5)));
+  EXPECT_THAT(p, Not(FieldsAre(25, "fo", .5)));
+  EXPECT_THAT(p, Not(FieldsAre(25, "foo", .6)));
+}
+
+TEST(FieldsAreTest, CanDescribeSelf) {
+  Matcher<const pair<std::string, int>&> m1 = FieldsAre("foo", 42);
+  EXPECT_EQ(
+      "has field #0 that is equal to \"foo\""
+      ", and has field #1 that is equal to 42",
+      Describe(m1));
+  EXPECT_EQ(
+      "has field #0 that isn't equal to \"foo\""
+      ", or has field #1 that isn't equal to 42",
+      DescribeNegation(m1));
+}
+
+TEST_P(FieldsAreTestP, CanExplainMatchResultTo) {
+  // The first one that fails is the one that gives the error.
+  Matcher<std::tuple<int, int, int>> m =
+      FieldsAre(GreaterThan(0), GreaterThan(0), GreaterThan(0));
+
+  EXPECT_EQ("whose field #0 does not match, which is 1 less than 0",
+            Explain(m, std::make_tuple(-1, -2, -3)));
+  EXPECT_EQ("whose field #1 does not match, which is 2 less than 0",
+            Explain(m, std::make_tuple(1, -2, -3)));
+  EXPECT_EQ("whose field #2 does not match, which is 3 less than 0",
+            Explain(m, std::make_tuple(1, 2, -3)));
+
+  // If they all match, we get a long explanation of success.
+  EXPECT_EQ(
+      "whose all elements match, "
+      "where field #0 is a value which is 1 more than 0"
+      ", and field #1 is a value which is 2 more than 0"
+      ", and field #2 is a value which is 3 more than 0",
+      Explain(m, std::make_tuple(1, 2, 3)));
+
+  // Only print those that have an explanation.
+  m = FieldsAre(GreaterThan(0), 0, GreaterThan(0));
+  EXPECT_EQ(
+      "whose all elements match, "
+      "where field #0 is a value which is 1 more than 0"
+      ", and field #2 is a value which is 3 more than 0",
+      Explain(m, std::make_tuple(1, 0, 3)));
+
+  // If only one has an explanation, then print that one.
+  m = FieldsAre(0, GreaterThan(0), 0);
+  EXPECT_EQ(
+      "whose all elements match, "
+      "where field #1 is a value which is 1 more than 0",
+      Explain(m, std::make_tuple(0, 1, 0)));
+}
+
+#if defined(__cpp_structured_bindings) && __cpp_structured_bindings >= 201606
+TEST(FieldsAreTest, StructuredBindings) {
+  // testing::FieldsAre can also match aggregates and such with C++17 and up.
+  struct MyType {
+    int i;
+    std::string str;
+  };
+  EXPECT_THAT((MyType{17, "foo"}), FieldsAre(Eq(17), HasSubstr("oo")));
+
+  // Test all the supported arities.
+  struct MyVarType1 {
+    int a;
+  };
+  EXPECT_THAT(MyVarType1{}, FieldsAre(0));
+  struct MyVarType2 {
+    int a, b;
+  };
+  EXPECT_THAT(MyVarType2{}, FieldsAre(0, 0));
+  struct MyVarType3 {
+    int a, b, c;
+  };
+  EXPECT_THAT(MyVarType3{}, FieldsAre(0, 0, 0));
+  struct MyVarType4 {
+    int a, b, c, d;
+  };
+  EXPECT_THAT(MyVarType4{}, FieldsAre(0, 0, 0, 0));
+  struct MyVarType5 {
+    int a, b, c, d, e;
+  };
+  EXPECT_THAT(MyVarType5{}, FieldsAre(0, 0, 0, 0, 0));
+  struct MyVarType6 {
+    int a, b, c, d, e, f;
+  };
+  EXPECT_THAT(MyVarType6{}, FieldsAre(0, 0, 0, 0, 0, 0));
+  struct MyVarType7 {
+    int a, b, c, d, e, f, g;
+  };
+  EXPECT_THAT(MyVarType7{}, FieldsAre(0, 0, 0, 0, 0, 0, 0));
+  struct MyVarType8 {
+    int a, b, c, d, e, f, g, h;
+  };
+  EXPECT_THAT(MyVarType8{}, FieldsAre(0, 0, 0, 0, 0, 0, 0, 0));
+  struct MyVarType9 {
+    int a, b, c, d, e, f, g, h, i;
+  };
+  EXPECT_THAT(MyVarType9{}, FieldsAre(0, 0, 0, 0, 0, 0, 0, 0, 0));
+  struct MyVarType10 {
+    int a, b, c, d, e, f, g, h, i, j;
+  };
+  EXPECT_THAT(MyVarType10{}, FieldsAre(0, 0, 0, 0, 0, 0, 0, 0, 0, 0));
+  struct MyVarType11 {
+    int a, b, c, d, e, f, g, h, i, j, k;
+  };
+  EXPECT_THAT(MyVarType11{}, FieldsAre(0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0));
+  struct MyVarType12 {
+    int a, b, c, d, e, f, g, h, i, j, k, l;
+  };
+  EXPECT_THAT(MyVarType12{}, FieldsAre(0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0));
+  struct MyVarType13 {
+    int a, b, c, d, e, f, g, h, i, j, k, l, m;
+  };
+  EXPECT_THAT(MyVarType13{}, FieldsAre(0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0));
+  struct MyVarType14 {
+    int a, b, c, d, e, f, g, h, i, j, k, l, m, n;
+  };
+  EXPECT_THAT(MyVarType14{},
+              FieldsAre(0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0));
+  struct MyVarType15 {
+    int a, b, c, d, e, f, g, h, i, j, k, l, m, n, o;
+  };
+  EXPECT_THAT(MyVarType15{},
+              FieldsAre(0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0));
+  struct MyVarType16 {
+    int a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p;
+  };
+  EXPECT_THAT(MyVarType16{},
+              FieldsAre(0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0));
+  struct MyVarType17 {
+    int a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p, q;
+  };
+  EXPECT_THAT(MyVarType17{},
+              FieldsAre(0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0));
+  struct MyVarType18 {
+    int a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p, q, r;
+  };
+  EXPECT_THAT(MyVarType18{},
+              FieldsAre(0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0));
+  struct MyVarType19 {
+    int a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p, q, r, s;
+  };
+  EXPECT_THAT(MyVarType19{}, FieldsAre(0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+                                       0, 0, 0, 0, 0));
+}
+#endif
+
+TEST(PairTest, UseGetInsteadOfMembers) {
+  PairWithGet pair{7, "ABC"};
+  EXPECT_THAT(pair, Pair(7, "ABC"));
+  EXPECT_THAT(pair, Pair(Ge(7), HasSubstr("AB")));
+  EXPECT_THAT(pair, Not(Pair(Lt(7), "ABC")));
+
+  std::vector<PairWithGet> v = {{11, "Foo"}, {29, "gMockIsBestMock"}};
+  EXPECT_THAT(v,
+              ElementsAre(Pair(11, std::string("Foo")), Pair(Ge(10), Not(""))));
+}
+
+// Tests StartsWith(s).
+
+TEST(StartsWithTest, MatchesStringWithGivenPrefix) {
+  const Matcher<const char*> m1 = StartsWith(std::string(""));
+  EXPECT_TRUE(m1.Matches("Hi"));
+  EXPECT_TRUE(m1.Matches(""));
+  EXPECT_FALSE(m1.Matches(nullptr));
+
+  const Matcher<const std::string&> m2 = StartsWith("Hi");
+  EXPECT_TRUE(m2.Matches("Hi"));
+  EXPECT_TRUE(m2.Matches("Hi Hi!"));
+  EXPECT_TRUE(m2.Matches("High"));
+  EXPECT_FALSE(m2.Matches("H"));
+  EXPECT_FALSE(m2.Matches(" Hi"));
+
+#if GTEST_INTERNAL_HAS_STRING_VIEW
+  const Matcher<internal::StringView> m_empty =
+      StartsWith(internal::StringView(""));
+  EXPECT_TRUE(m_empty.Matches(internal::StringView()));
+  EXPECT_TRUE(m_empty.Matches(internal::StringView("")));
+  EXPECT_TRUE(m_empty.Matches(internal::StringView("not empty")));
+#endif  // GTEST_INTERNAL_HAS_STRING_VIEW
+}
+
+TEST(StartsWithTest, CanDescribeSelf) {
+  Matcher<const std::string> m = StartsWith("Hi");
+  EXPECT_EQ("starts with \"Hi\"", Describe(m));
+}
+
+// Tests EndsWith(s).
+
+TEST(EndsWithTest, MatchesStringWithGivenSuffix) {
+  const Matcher<const char*> m1 = EndsWith("");
+  EXPECT_TRUE(m1.Matches("Hi"));
+  EXPECT_TRUE(m1.Matches(""));
+  EXPECT_FALSE(m1.Matches(nullptr));
+
+  const Matcher<const std::string&> m2 = EndsWith(std::string("Hi"));
+  EXPECT_TRUE(m2.Matches("Hi"));
+  EXPECT_TRUE(m2.Matches("Wow Hi Hi"));
+  EXPECT_TRUE(m2.Matches("Super Hi"));
+  EXPECT_FALSE(m2.Matches("i"));
+  EXPECT_FALSE(m2.Matches("Hi "));
+
+#if GTEST_INTERNAL_HAS_STRING_VIEW
+  const Matcher<const internal::StringView&> m4 =
+      EndsWith(internal::StringView(""));
+  EXPECT_TRUE(m4.Matches("Hi"));
+  EXPECT_TRUE(m4.Matches(""));
+  EXPECT_TRUE(m4.Matches(internal::StringView()));
+  EXPECT_TRUE(m4.Matches(internal::StringView("")));
+#endif  // GTEST_INTERNAL_HAS_STRING_VIEW
+}
+
+TEST(EndsWithTest, CanDescribeSelf) {
+  Matcher<const std::string> m = EndsWith("Hi");
+  EXPECT_EQ("ends with \"Hi\"", Describe(m));
+}
+
+// Tests WhenBase64Unescaped.
+
+TEST(WhenBase64UnescapedTest, MatchesUnescapedBase64Strings) {
+  const Matcher<const char*> m1 = WhenBase64Unescaped(EndsWith("!"));
+  EXPECT_FALSE(m1.Matches("invalid base64"));
+  EXPECT_FALSE(m1.Matches("aGVsbG8gd29ybGQ="));  // hello world
+  EXPECT_TRUE(m1.Matches("aGVsbG8gd29ybGQh"));   // hello world!
+  EXPECT_TRUE(m1.Matches("+/-_IQ"));             // \xfb\xff\xbf!
+
+  const Matcher<const std::string&> m2 = WhenBase64Unescaped(EndsWith("!"));
+  EXPECT_FALSE(m2.Matches("invalid base64"));
+  EXPECT_FALSE(m2.Matches("aGVsbG8gd29ybGQ="));  // hello world
+  EXPECT_TRUE(m2.Matches("aGVsbG8gd29ybGQh"));   // hello world!
+  EXPECT_TRUE(m2.Matches("+/-_IQ"));             // \xfb\xff\xbf!
+
+#if GTEST_INTERNAL_HAS_STRING_VIEW
+  const Matcher<const internal::StringView&> m3 =
+      WhenBase64Unescaped(EndsWith("!"));
+  EXPECT_FALSE(m3.Matches("invalid base64"));
+  EXPECT_FALSE(m3.Matches("aGVsbG8gd29ybGQ="));  // hello world
+  EXPECT_TRUE(m3.Matches("aGVsbG8gd29ybGQh"));   // hello world!
+  EXPECT_TRUE(m3.Matches("+/-_IQ"));             // \xfb\xff\xbf!
+#endif  // GTEST_INTERNAL_HAS_STRING_VIEW
+}
+
+TEST(WhenBase64UnescapedTest, CanDescribeSelf) {
+  const Matcher<const char*> m = WhenBase64Unescaped(EndsWith("!"));
+  EXPECT_EQ("matches after Base64Unescape ends with \"!\"", Describe(m));
+}
+
+// Tests MatchesRegex().
+
+TEST(MatchesRegexTest, MatchesStringMatchingGivenRegex) {
+  const Matcher<const char*> m1 = MatchesRegex("a.*z");
+  EXPECT_TRUE(m1.Matches("az"));
+  EXPECT_TRUE(m1.Matches("abcz"));
+  EXPECT_FALSE(m1.Matches(nullptr));
+
+  const Matcher<const std::string&> m2 = MatchesRegex(new RE("a.*z"));
+  EXPECT_TRUE(m2.Matches("azbz"));
+  EXPECT_FALSE(m2.Matches("az1"));
+  EXPECT_FALSE(m2.Matches("1az"));
+
+#if GTEST_INTERNAL_HAS_STRING_VIEW
+  const Matcher<const internal::StringView&> m3 = MatchesRegex("a.*z");
+  EXPECT_TRUE(m3.Matches(internal::StringView("az")));
+  EXPECT_TRUE(m3.Matches(internal::StringView("abcz")));
+  EXPECT_FALSE(m3.Matches(internal::StringView("1az")));
+  EXPECT_FALSE(m3.Matches(internal::StringView()));
+  const Matcher<const internal::StringView&> m4 =
+      MatchesRegex(internal::StringView(""));
+  EXPECT_TRUE(m4.Matches(internal::StringView("")));
+  EXPECT_TRUE(m4.Matches(internal::StringView()));
+#endif  // GTEST_INTERNAL_HAS_STRING_VIEW
+}
+
+TEST(MatchesRegexTest, CanDescribeSelf) {
+  Matcher<const std::string> m1 = MatchesRegex(std::string("Hi.*"));
+  EXPECT_EQ("matches regular expression \"Hi.*\"", Describe(m1));
+
+  Matcher<const char*> m2 = MatchesRegex(new RE("a.*"));
+  EXPECT_EQ("matches regular expression \"a.*\"", Describe(m2));
+
+#if GTEST_INTERNAL_HAS_STRING_VIEW
+  Matcher<const internal::StringView> m3 = MatchesRegex(new RE("0.*"));
+  EXPECT_EQ("matches regular expression \"0.*\"", Describe(m3));
+#endif  // GTEST_INTERNAL_HAS_STRING_VIEW
+}
+
+// Tests ContainsRegex().
+
+TEST(ContainsRegexTest, MatchesStringContainingGivenRegex) {
+  const Matcher<const char*> m1 = ContainsRegex(std::string("a.*z"));
+  EXPECT_TRUE(m1.Matches("az"));
+  EXPECT_TRUE(m1.Matches("0abcz1"));
+  EXPECT_FALSE(m1.Matches(nullptr));
+
+  const Matcher<const std::string&> m2 = ContainsRegex(new RE("a.*z"));
+  EXPECT_TRUE(m2.Matches("azbz"));
+  EXPECT_TRUE(m2.Matches("az1"));
+  EXPECT_FALSE(m2.Matches("1a"));
+
+#if GTEST_INTERNAL_HAS_STRING_VIEW
+  const Matcher<const internal::StringView&> m3 = ContainsRegex(new RE("a.*z"));
+  EXPECT_TRUE(m3.Matches(internal::StringView("azbz")));
+  EXPECT_TRUE(m3.Matches(internal::StringView("az1")));
+  EXPECT_FALSE(m3.Matches(internal::StringView("1a")));
+  EXPECT_FALSE(m3.Matches(internal::StringView()));
+  const Matcher<const internal::StringView&> m4 =
+      ContainsRegex(internal::StringView(""));
+  EXPECT_TRUE(m4.Matches(internal::StringView("")));
+  EXPECT_TRUE(m4.Matches(internal::StringView()));
+#endif  // GTEST_INTERNAL_HAS_STRING_VIEW
+}
+
+TEST(ContainsRegexTest, CanDescribeSelf) {
+  Matcher<const std::string> m1 = ContainsRegex("Hi.*");
+  EXPECT_EQ("contains regular expression \"Hi.*\"", Describe(m1));
+
+  Matcher<const char*> m2 = ContainsRegex(new RE("a.*"));
+  EXPECT_EQ("contains regular expression \"a.*\"", Describe(m2));
+
+#if GTEST_INTERNAL_HAS_STRING_VIEW
+  Matcher<const internal::StringView> m3 = ContainsRegex(new RE("0.*"));
+  EXPECT_EQ("contains regular expression \"0.*\"", Describe(m3));
+#endif  // GTEST_INTERNAL_HAS_STRING_VIEW
+}
+
+// Tests for wide strings.
+#if GTEST_HAS_STD_WSTRING
+TEST(StdWideStrEqTest, MatchesEqual) {
+  Matcher<const wchar_t*> m = StrEq(::std::wstring(L"Hello"));
+  EXPECT_TRUE(m.Matches(L"Hello"));
+  EXPECT_FALSE(m.Matches(L"hello"));
+  EXPECT_FALSE(m.Matches(nullptr));
+
+  Matcher<const ::std::wstring&> m2 = StrEq(L"Hello");
+  EXPECT_TRUE(m2.Matches(L"Hello"));
+  EXPECT_FALSE(m2.Matches(L"Hi"));
+
+  Matcher<const ::std::wstring&> m3 = StrEq(L"\xD3\x576\x8D3\xC74D");
+  EXPECT_TRUE(m3.Matches(L"\xD3\x576\x8D3\xC74D"));
+  EXPECT_FALSE(m3.Matches(L"\xD3\x576\x8D3\xC74E"));
+
+  ::std::wstring str(L"01204500800");
+  str[3] = L'\0';
+  Matcher<const ::std::wstring&> m4 = StrEq(str);
+  EXPECT_TRUE(m4.Matches(str));
+  str[0] = str[6] = str[7] = str[9] = str[10] = L'\0';
+  Matcher<const ::std::wstring&> m5 = StrEq(str);
+  EXPECT_TRUE(m5.Matches(str));
+}
+
+TEST(StdWideStrEqTest, CanDescribeSelf) {
+  Matcher<::std::wstring> m = StrEq(L"Hi-\'\"?\\\a\b\f\n\r\t\v");
+  EXPECT_EQ("is equal to L\"Hi-\'\\\"?\\\\\\a\\b\\f\\n\\r\\t\\v\"",
+            Describe(m));
+
+  Matcher<::std::wstring> m2 = StrEq(L"\xD3\x576\x8D3\xC74D");
+  EXPECT_EQ("is equal to L\"\\xD3\\x576\\x8D3\\xC74D\"", Describe(m2));
+
+  ::std::wstring str(L"01204500800");
+  str[3] = L'\0';
+  Matcher<const ::std::wstring&> m4 = StrEq(str);
+  EXPECT_EQ("is equal to L\"012\\04500800\"", Describe(m4));
+  str[0] = str[6] = str[7] = str[9] = str[10] = L'\0';
+  Matcher<const ::std::wstring&> m5 = StrEq(str);
+  EXPECT_EQ("is equal to L\"\\012\\045\\0\\08\\0\\0\"", Describe(m5));
+}
+
+TEST(StdWideStrNeTest, MatchesUnequalString) {
+  Matcher<const wchar_t*> m = StrNe(L"Hello");
+  EXPECT_TRUE(m.Matches(L""));
+  EXPECT_TRUE(m.Matches(nullptr));
+  EXPECT_FALSE(m.Matches(L"Hello"));
+
+  Matcher<::std::wstring> m2 = StrNe(::std::wstring(L"Hello"));
+  EXPECT_TRUE(m2.Matches(L"hello"));
+  EXPECT_FALSE(m2.Matches(L"Hello"));
+}
+
+TEST(StdWideStrNeTest, CanDescribeSelf) {
+  Matcher<const wchar_t*> m = StrNe(L"Hi");
+  EXPECT_EQ("isn't equal to L\"Hi\"", Describe(m));
+}
+
+TEST(StdWideStrCaseEqTest, MatchesEqualStringIgnoringCase) {
+  Matcher<const wchar_t*> m = StrCaseEq(::std::wstring(L"Hello"));
+  EXPECT_TRUE(m.Matches(L"Hello"));
+  EXPECT_TRUE(m.Matches(L"hello"));
+  EXPECT_FALSE(m.Matches(L"Hi"));
+  EXPECT_FALSE(m.Matches(nullptr));
+
+  Matcher<const ::std::wstring&> m2 = StrCaseEq(L"Hello");
+  EXPECT_TRUE(m2.Matches(L"hello"));
+  EXPECT_FALSE(m2.Matches(L"Hi"));
+}
+
+TEST(StdWideStrCaseEqTest, MatchesEqualStringWith0IgnoringCase) {
+  ::std::wstring str1(L"oabocdooeoo");
+  ::std::wstring str2(L"OABOCDOOEOO");
+  Matcher<const ::std::wstring&> m0 = StrCaseEq(str1);
+  EXPECT_FALSE(m0.Matches(str2 + ::std::wstring(1, L'\0')));
+
+  str1[3] = str2[3] = L'\0';
+  Matcher<const ::std::wstring&> m1 = StrCaseEq(str1);
+  EXPECT_TRUE(m1.Matches(str2));
+
+  str1[0] = str1[6] = str1[7] = str1[10] = L'\0';
+  str2[0] = str2[6] = str2[7] = str2[10] = L'\0';
+  Matcher<const ::std::wstring&> m2 = StrCaseEq(str1);
+  str1[9] = str2[9] = L'\0';
+  EXPECT_FALSE(m2.Matches(str2));
+
+  Matcher<const ::std::wstring&> m3 = StrCaseEq(str1);
+  EXPECT_TRUE(m3.Matches(str2));
+
+  EXPECT_FALSE(m3.Matches(str2 + L"x"));
+  str2.append(1, L'\0');
+  EXPECT_FALSE(m3.Matches(str2));
+  EXPECT_FALSE(m3.Matches(::std::wstring(str2, 0, 9)));
+}
+
+TEST(StdWideStrCaseEqTest, CanDescribeSelf) {
+  Matcher<::std::wstring> m = StrCaseEq(L"Hi");
+  EXPECT_EQ("is equal to (ignoring case) L\"Hi\"", Describe(m));
+}
+
+TEST(StdWideStrCaseNeTest, MatchesUnequalStringIgnoringCase) {
+  Matcher<const wchar_t*> m = StrCaseNe(L"Hello");
+  EXPECT_TRUE(m.Matches(L"Hi"));
+  EXPECT_TRUE(m.Matches(nullptr));
+  EXPECT_FALSE(m.Matches(L"Hello"));
+  EXPECT_FALSE(m.Matches(L"hello"));
+
+  Matcher<::std::wstring> m2 = StrCaseNe(::std::wstring(L"Hello"));
+  EXPECT_TRUE(m2.Matches(L""));
+  EXPECT_FALSE(m2.Matches(L"Hello"));
+}
+
+TEST(StdWideStrCaseNeTest, CanDescribeSelf) {
+  Matcher<const wchar_t*> m = StrCaseNe(L"Hi");
+  EXPECT_EQ("isn't equal to (ignoring case) L\"Hi\"", Describe(m));
+}
+
+// Tests that HasSubstr() works for matching wstring-typed values.
+TEST(StdWideHasSubstrTest, WorksForStringClasses) {
+  const Matcher<::std::wstring> m1 = HasSubstr(L"foo");
+  EXPECT_TRUE(m1.Matches(::std::wstring(L"I love food.")));
+  EXPECT_FALSE(m1.Matches(::std::wstring(L"tofo")));
+
+  const Matcher<const ::std::wstring&> m2 = HasSubstr(L"foo");
+  EXPECT_TRUE(m2.Matches(::std::wstring(L"I love food.")));
+  EXPECT_FALSE(m2.Matches(::std::wstring(L"tofo")));
+}
+
+// Tests that HasSubstr() works for matching C-wide-string-typed values.
+TEST(StdWideHasSubstrTest, WorksForCStrings) {
+  const Matcher<wchar_t*> m1 = HasSubstr(L"foo");
+  EXPECT_TRUE(m1.Matches(const_cast<wchar_t*>(L"I love food.")));
+  EXPECT_FALSE(m1.Matches(const_cast<wchar_t*>(L"tofo")));
+  EXPECT_FALSE(m1.Matches(nullptr));
+
+  const Matcher<const wchar_t*> m2 = HasSubstr(L"foo");
+  EXPECT_TRUE(m2.Matches(L"I love food."));
+  EXPECT_FALSE(m2.Matches(L"tofo"));
+  EXPECT_FALSE(m2.Matches(nullptr));
+}
+
+// Tests that HasSubstr(s) describes itself properly.
+TEST(StdWideHasSubstrTest, CanDescribeSelf) {
+  Matcher<::std::wstring> m = HasSubstr(L"foo\n\"");
+  EXPECT_EQ("has substring L\"foo\\n\\\"\"", Describe(m));
+}
+
+// Tests StartsWith(s).
+
+TEST(StdWideStartsWithTest, MatchesStringWithGivenPrefix) {
+  const Matcher<const wchar_t*> m1 = StartsWith(::std::wstring(L""));
+  EXPECT_TRUE(m1.Matches(L"Hi"));
+  EXPECT_TRUE(m1.Matches(L""));
+  EXPECT_FALSE(m1.Matches(nullptr));
+
+  const Matcher<const ::std::wstring&> m2 = StartsWith(L"Hi");
+  EXPECT_TRUE(m2.Matches(L"Hi"));
+  EXPECT_TRUE(m2.Matches(L"Hi Hi!"));
+  EXPECT_TRUE(m2.Matches(L"High"));
+  EXPECT_FALSE(m2.Matches(L"H"));
+  EXPECT_FALSE(m2.Matches(L" Hi"));
+}
+
+TEST(StdWideStartsWithTest, CanDescribeSelf) {
+  Matcher<const ::std::wstring> m = StartsWith(L"Hi");
+  EXPECT_EQ("starts with L\"Hi\"", Describe(m));
+}
+
+// Tests EndsWith(s).
+
+TEST(StdWideEndsWithTest, MatchesStringWithGivenSuffix) {
+  const Matcher<const wchar_t*> m1 = EndsWith(L"");
+  EXPECT_TRUE(m1.Matches(L"Hi"));
+  EXPECT_TRUE(m1.Matches(L""));
+  EXPECT_FALSE(m1.Matches(nullptr));
+
+  const Matcher<const ::std::wstring&> m2 = EndsWith(::std::wstring(L"Hi"));
+  EXPECT_TRUE(m2.Matches(L"Hi"));
+  EXPECT_TRUE(m2.Matches(L"Wow Hi Hi"));
+  EXPECT_TRUE(m2.Matches(L"Super Hi"));
+  EXPECT_FALSE(m2.Matches(L"i"));
+  EXPECT_FALSE(m2.Matches(L"Hi "));
+}
+
+TEST(StdWideEndsWithTest, CanDescribeSelf) {
+  Matcher<const ::std::wstring> m = EndsWith(L"Hi");
+  EXPECT_EQ("ends with L\"Hi\"", Describe(m));
+}
+
+#endif  // GTEST_HAS_STD_WSTRING
+
+TEST(ExplainMatchResultTest, WorksWithPolymorphicMatcher) {
+  StringMatchResultListener listener1;
+  EXPECT_TRUE(ExplainMatchResult(PolymorphicIsEven(), 42, &listener1));
+  EXPECT_EQ("% 2 == 0", listener1.str());
+
+  StringMatchResultListener listener2;
+  EXPECT_FALSE(ExplainMatchResult(Ge(42), 1.5, &listener2));
+  EXPECT_EQ("", listener2.str());
+}
+
+TEST(ExplainMatchResultTest, WorksWithMonomorphicMatcher) {
+  const Matcher<int> is_even = PolymorphicIsEven();
+  StringMatchResultListener listener1;
+  EXPECT_TRUE(ExplainMatchResult(is_even, 42, &listener1));
+  EXPECT_EQ("% 2 == 0", listener1.str());
+
+  const Matcher<const double&> is_zero = Eq(0);
+  StringMatchResultListener listener2;
+  EXPECT_FALSE(ExplainMatchResult(is_zero, 1.5, &listener2));
+  EXPECT_EQ("", listener2.str());
+}
+
+MATCHER(ConstructNoArg, "") { return true; }
+MATCHER_P(Construct1Arg, arg1, "") { return true; }
+MATCHER_P2(Construct2Args, arg1, arg2, "") { return true; }
+
+TEST(MatcherConstruct, ExplicitVsImplicit) {
+  {
+    // No arg constructor can be constructed with empty brace.
+    ConstructNoArgMatcher m = {};
+    (void)m;
+    // And with no args
+    ConstructNoArgMatcher m2;
+    (void)m2;
+  }
+  {
+    // The one arg constructor has an explicit constructor.
+    // This is to prevent the implicit conversion.
+    using M = Construct1ArgMatcherP<int>;
+    EXPECT_TRUE((std::is_constructible<M, int>::value));
+    EXPECT_FALSE((std::is_convertible<int, M>::value));
+  }
+  {
+    // Multiple arg matchers can be constructed with an implicit construction.
+    Construct2ArgsMatcherP2<int, double> m = {1, 2.2};
+    (void)m;
+  }
+}
+
+MATCHER_P(Really, inner_matcher, "") {
+  return ExplainMatchResult(inner_matcher, arg, result_listener);
+}
+
+TEST(ExplainMatchResultTest, WorksInsideMATCHER) {
+  EXPECT_THAT(0, Really(Eq(0)));
+}
+
+TEST(DescribeMatcherTest, WorksWithValue) {
+  EXPECT_EQ("is equal to 42", DescribeMatcher<int>(42));
+  EXPECT_EQ("isn't equal to 42", DescribeMatcher<int>(42, true));
+}
+
+TEST(DescribeMatcherTest, WorksWithMonomorphicMatcher) {
+  const Matcher<int> monomorphic = Le(0);
+  EXPECT_EQ("is <= 0", DescribeMatcher<int>(monomorphic));
+  EXPECT_EQ("isn't <= 0", DescribeMatcher<int>(monomorphic, true));
+}
+
+TEST(DescribeMatcherTest, WorksWithPolymorphicMatcher) {
+  EXPECT_EQ("is even", DescribeMatcher<int>(PolymorphicIsEven()));
+  EXPECT_EQ("is odd", DescribeMatcher<int>(PolymorphicIsEven(), true));
+}
+
+MATCHER_P(FieldIIs, inner_matcher, "") {
+  return ExplainMatchResult(inner_matcher, arg.i, result_listener);
+}
+
+#if GTEST_HAS_RTTI
+TEST(WhenDynamicCastToTest, SameType) {
+  Derived derived;
+  derived.i = 4;
+
+  // Right type. A pointer is passed down.
+  Base* as_base_ptr = &derived;
+  EXPECT_THAT(as_base_ptr, WhenDynamicCastTo<Derived*>(Not(IsNull())));
+  EXPECT_THAT(as_base_ptr, WhenDynamicCastTo<Derived*>(Pointee(FieldIIs(4))));
+  EXPECT_THAT(as_base_ptr,
+              Not(WhenDynamicCastTo<Derived*>(Pointee(FieldIIs(5)))));
+}
+
+TEST(WhenDynamicCastToTest, WrongTypes) {
+  Base base;
+  Derived derived;
+  OtherDerived other_derived;
+
+  // Wrong types. NULL is passed.
+  EXPECT_THAT(&base, Not(WhenDynamicCastTo<Derived*>(Pointee(_))));
+  EXPECT_THAT(&base, WhenDynamicCastTo<Derived*>(IsNull()));
+  Base* as_base_ptr = &derived;
+  EXPECT_THAT(as_base_ptr, Not(WhenDynamicCastTo<OtherDerived*>(Pointee(_))));
+  EXPECT_THAT(as_base_ptr, WhenDynamicCastTo<OtherDerived*>(IsNull()));
+  as_base_ptr = &other_derived;
+  EXPECT_THAT(as_base_ptr, Not(WhenDynamicCastTo<Derived*>(Pointee(_))));
+  EXPECT_THAT(as_base_ptr, WhenDynamicCastTo<Derived*>(IsNull()));
+}
+
+TEST(WhenDynamicCastToTest, AlreadyNull) {
+  // Already NULL.
+  Base* as_base_ptr = nullptr;
+  EXPECT_THAT(as_base_ptr, WhenDynamicCastTo<Derived*>(IsNull()));
+}
+
+struct AmbiguousCastTypes {
+  class VirtualDerived : public virtual Base {};
+  class DerivedSub1 : public VirtualDerived {};
+  class DerivedSub2 : public VirtualDerived {};
+  class ManyDerivedInHierarchy : public DerivedSub1, public DerivedSub2 {};
+};
+
+TEST(WhenDynamicCastToTest, AmbiguousCast) {
+  AmbiguousCastTypes::DerivedSub1 sub1;
+  AmbiguousCastTypes::ManyDerivedInHierarchy many_derived;
+  // Multiply derived from Base. dynamic_cast<> returns NULL.
+  Base* as_base_ptr =
+      static_cast<AmbiguousCastTypes::DerivedSub1*>(&many_derived);
+  EXPECT_THAT(as_base_ptr,
+              WhenDynamicCastTo<AmbiguousCastTypes::VirtualDerived*>(IsNull()));
+  as_base_ptr = &sub1;
+  EXPECT_THAT(
+      as_base_ptr,
+      WhenDynamicCastTo<AmbiguousCastTypes::VirtualDerived*>(Not(IsNull())));
+}
+
+TEST(WhenDynamicCastToTest, Describe) {
+  Matcher<Base*> matcher = WhenDynamicCastTo<Derived*>(Pointee(_));
+  const std::string prefix =
+      "when dynamic_cast to " + internal::GetTypeName<Derived*>() + ", ";
+  EXPECT_EQ(prefix + "points to a value that is anything", Describe(matcher));
+  EXPECT_EQ(prefix + "does not point to a value that is anything",
+            DescribeNegation(matcher));
+}
+
+TEST(WhenDynamicCastToTest, Explain) {
+  Matcher<Base*> matcher = WhenDynamicCastTo<Derived*>(Pointee(_));
+  Base* null = nullptr;
+  EXPECT_THAT(Explain(matcher, null), HasSubstr("NULL"));
+  Derived derived;
+  EXPECT_TRUE(matcher.Matches(&derived));
+  EXPECT_THAT(Explain(matcher, &derived), HasSubstr("which points to "));
+
+  // With references, the matcher itself can fail. Test for that one.
+  Matcher<const Base&> ref_matcher = WhenDynamicCastTo<const OtherDerived&>(_);
+  EXPECT_THAT(Explain(ref_matcher, derived),
+              HasSubstr("which cannot be dynamic_cast"));
+}
+
+TEST(WhenDynamicCastToTest, GoodReference) {
+  Derived derived;
+  derived.i = 4;
+  Base& as_base_ref = derived;
+  EXPECT_THAT(as_base_ref, WhenDynamicCastTo<const Derived&>(FieldIIs(4)));
+  EXPECT_THAT(as_base_ref, WhenDynamicCastTo<const Derived&>(Not(FieldIIs(5))));
+}
+
+TEST(WhenDynamicCastToTest, BadReference) {
+  Derived derived;
+  Base& as_base_ref = derived;
+  EXPECT_THAT(as_base_ref, Not(WhenDynamicCastTo<const OtherDerived&>(_)));
+}
+#endif  // GTEST_HAS_RTTI
+
+class DivisibleByImpl {
+ public:
+  explicit DivisibleByImpl(int a_divider) : divider_(a_divider) {}
+
+  // For testing using ExplainMatchResultTo() with polymorphic matchers.
+  template <typename T>
+  bool MatchAndExplain(const T& n, MatchResultListener* listener) const {
+    *listener << "which is " << (n % divider_) << " modulo " << divider_;
+    return (n % divider_) == 0;
+  }
+
+  void DescribeTo(ostream* os) const { *os << "is divisible by " << divider_; }
+
+  void DescribeNegationTo(ostream* os) const {
+    *os << "is not divisible by " << divider_;
+  }
+
+  void set_divider(int a_divider) { divider_ = a_divider; }
+  int divider() const { return divider_; }
+
+ private:
+  int divider_;
+};
+
+PolymorphicMatcher<DivisibleByImpl> DivisibleBy(int n) {
+  return MakePolymorphicMatcher(DivisibleByImpl(n));
+}
+
+// Tests that when AllOf() fails, only the first failing matcher is
+// asked to explain why.
+TEST(ExplainMatchResultTest, AllOf_False_False) {
+  const Matcher<int> m = AllOf(DivisibleBy(4), DivisibleBy(3));
+  EXPECT_EQ("which is 1 modulo 4", Explain(m, 5));
+}
+
+// Tests that when AllOf() fails, only the first failing matcher is
+// asked to explain why.
+TEST(ExplainMatchResultTest, AllOf_False_True) {
+  const Matcher<int> m = AllOf(DivisibleBy(4), DivisibleBy(3));
+  EXPECT_EQ("which is 2 modulo 4", Explain(m, 6));
+}
+
+// Tests that when AllOf() fails, only the first failing matcher is
+// asked to explain why.
+TEST(ExplainMatchResultTest, AllOf_True_False) {
+  const Matcher<int> m = AllOf(Ge(1), DivisibleBy(3));
+  EXPECT_EQ("which is 2 modulo 3", Explain(m, 5));
+}
+
+// Tests that when AllOf() succeeds, all matchers are asked to explain
+// why.
+TEST(ExplainMatchResultTest, AllOf_True_True) {
+  const Matcher<int> m = AllOf(DivisibleBy(2), DivisibleBy(3));
+  EXPECT_EQ("which is 0 modulo 2, and which is 0 modulo 3", Explain(m, 6));
+}
+
+TEST(ExplainMatchResultTest, AllOf_True_True_2) {
+  const Matcher<int> m = AllOf(Ge(2), Le(3));
+  EXPECT_EQ("", Explain(m, 2));
+}
+
+INSTANTIATE_GTEST_MATCHER_TEST_P(ExplainmatcherResultTest);
+
+TEST_P(ExplainmatcherResultTestP, MonomorphicMatcher) {
+  const Matcher<int> m = GreaterThan(5);
+  EXPECT_EQ("which is 1 more than 5", Explain(m, 6));
+}
+
+// Tests PolymorphicMatcher::mutable_impl().
+TEST(PolymorphicMatcherTest, CanAccessMutableImpl) {
+  PolymorphicMatcher<DivisibleByImpl> m(DivisibleByImpl(42));
+  DivisibleByImpl& impl = m.mutable_impl();
+  EXPECT_EQ(42, impl.divider());
+
+  impl.set_divider(0);
+  EXPECT_EQ(0, m.mutable_impl().divider());
+}
+
+// Tests PolymorphicMatcher::impl().
+TEST(PolymorphicMatcherTest, CanAccessImpl) {
+  const PolymorphicMatcher<DivisibleByImpl> m(DivisibleByImpl(42));
+  const DivisibleByImpl& impl = m.impl();
+  EXPECT_EQ(42, impl.divider());
+}
+
+}  // namespace
+}  // namespace gmock_matchers_test
+}  // namespace testing
+
+GTEST_DISABLE_MSC_WARNINGS_POP_()  // 4244 4100
diff --git a/third_party/googletest/googlemock/test/gmock-matchers-containers_test.cc b/third_party/googletest/googlemock/test/gmock-matchers-containers_test.cc
new file mode 100644
index 0000000..38fd9a5
--- /dev/null
+++ b/third_party/googletest/googlemock/test/gmock-matchers-containers_test.cc
@@ -0,0 +1,3137 @@
+// Copyright 2007, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Google Mock - a framework for writing C++ mock classes.
+//
+// This file tests some commonly used argument matchers.
+
+#include <algorithm>
+#include <array>
+#include <deque>
+#include <forward_list>
+#include <iterator>
+#include <list>
+#include <memory>
+#include <ostream>
+#include <string>
+#include <tuple>
+#include <vector>
+
+#include "gtest/gtest.h"
+
+// Silence warning C4244: 'initializing': conversion from 'int' to 'short',
+// possible loss of data and C4100, unreferenced local parameter
+GTEST_DISABLE_MSC_WARNINGS_PUSH_(4244 4100)
+
+#include "test/gmock-matchers_test.h"
+
+namespace testing {
+namespace gmock_matchers_test {
+namespace {
+
+std::vector<std::unique_ptr<int>> MakeUniquePtrs(const std::vector<int>& ints) {
+  std::vector<std::unique_ptr<int>> pointers;
+  for (int i : ints) pointers.emplace_back(new int(i));
+  return pointers;
+}
+
+std::string OfType(const std::string& type_name) {
+#if GTEST_HAS_RTTI
+  return IsReadableTypeName(type_name) ? " (of type " + type_name + ")" : "";
+#else
+  return "";
+#endif
+}
+
+TEST(ContainsTest, WorksWithMoveOnly) {
+  ContainerHelper helper;
+  EXPECT_CALL(helper, Call(Contains(Pointee(2))));
+  helper.Call(MakeUniquePtrs({1, 2}));
+}
+
+INSTANTIATE_GTEST_MATCHER_TEST_P(ElementsAreTest);
+
+// Tests the variadic version of the ElementsAreMatcher
+TEST(ElementsAreTest, HugeMatcher) {
+  vector<int> test_vector{1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12};
+
+  EXPECT_THAT(test_vector,
+              ElementsAre(Eq(1), Eq(2), Lt(13), Eq(4), Eq(5), Eq(6), Eq(7),
+                          Eq(8), Eq(9), Eq(10), Gt(1), Eq(12)));
+}
+
+// Tests the variadic version of the UnorderedElementsAreMatcher
+TEST(ElementsAreTest, HugeMatcherStr) {
+  vector<std::string> test_vector{
+      "literal_string", "", "", "", "", "", "", "", "", "", "", ""};
+
+  EXPECT_THAT(test_vector, UnorderedElementsAre("literal_string", _, _, _, _, _,
+                                                _, _, _, _, _, _));
+}
+
+// Tests the variadic version of the UnorderedElementsAreMatcher
+TEST(ElementsAreTest, HugeMatcherUnordered) {
+  vector<int> test_vector{2, 1, 8, 5, 4, 6, 7, 3, 9, 12, 11, 10};
+
+  EXPECT_THAT(test_vector, UnorderedElementsAre(
+                               Eq(2), Eq(1), Gt(7), Eq(5), Eq(4), Eq(6), Eq(7),
+                               Eq(3), Eq(9), Eq(12), Eq(11), Ne(122)));
+}
+
+// Tests that ASSERT_THAT() and EXPECT_THAT() work when the value
+// matches the matcher.
+TEST(MatcherAssertionTest, WorksWhenMatcherIsSatisfied) {
+  ASSERT_THAT(5, Ge(2)) << "This should succeed.";
+  ASSERT_THAT("Foo", EndsWith("oo"));
+  EXPECT_THAT(2, AllOf(Le(7), Ge(0))) << "This should succeed too.";
+  EXPECT_THAT("Hello", StartsWith("Hell"));
+}
+
+// Tests that ASSERT_THAT() and EXPECT_THAT() work when the value
+// doesn't match the matcher.
+TEST(MatcherAssertionTest, WorksWhenMatcherIsNotSatisfied) {
+  // 'n' must be static as it is used in an EXPECT_FATAL_FAILURE(),
+  // which cannot reference auto variables.
+  static unsigned short n;  // NOLINT
+  n = 5;
+
+  EXPECT_FATAL_FAILURE(ASSERT_THAT(n, Gt(10)),
+                       "Value of: n\n"
+                       "Expected: is > 10\n"
+                       "  Actual: 5" +
+                           OfType("unsigned short"));
+  n = 0;
+  EXPECT_NONFATAL_FAILURE(EXPECT_THAT(n, AllOf(Le(7), Ge(5))),
+                          "Value of: n\n"
+                          "Expected: (is <= 7) and (is >= 5)\n"
+                          "  Actual: 0" +
+                              OfType("unsigned short"));
+}
+
+// Tests that ASSERT_THAT() and EXPECT_THAT() work when the argument
+// has a reference type.
+TEST(MatcherAssertionTest, WorksForByRefArguments) {
+  // We use a static variable here as EXPECT_FATAL_FAILURE() cannot
+  // reference auto variables.
+  static int n;
+  n = 0;
+  EXPECT_THAT(n, AllOf(Le(7), Ref(n)));
+  EXPECT_FATAL_FAILURE(ASSERT_THAT(n, Not(Ref(n))),
+                       "Value of: n\n"
+                       "Expected: does not reference the variable @");
+  // Tests the "Actual" part.
+  EXPECT_FATAL_FAILURE(ASSERT_THAT(n, Not(Ref(n))),
+                       "Actual: 0" + OfType("int") + ", which is located @");
+}
+
+// Tests that ASSERT_THAT() and EXPECT_THAT() work when the matcher is
+// monomorphic.
+TEST(MatcherAssertionTest, WorksForMonomorphicMatcher) {
+  Matcher<const char*> starts_with_he = StartsWith("he");
+  ASSERT_THAT("hello", starts_with_he);
+
+  Matcher<const std::string&> ends_with_ok = EndsWith("ok");
+  ASSERT_THAT("book", ends_with_ok);
+  const std::string bad = "bad";
+  EXPECT_NONFATAL_FAILURE(EXPECT_THAT(bad, ends_with_ok),
+                          "Value of: bad\n"
+                          "Expected: ends with \"ok\"\n"
+                          "  Actual: \"bad\"");
+  Matcher<int> is_greater_than_5 = Gt(5);
+  EXPECT_NONFATAL_FAILURE(EXPECT_THAT(5, is_greater_than_5),
+                          "Value of: 5\n"
+                          "Expected: is > 5\n"
+                          "  Actual: 5" +
+                              OfType("int"));
+}
+
+TEST(PointeeTest, RawPointer) {
+  const Matcher<int*> m = Pointee(Ge(0));
+
+  int n = 1;
+  EXPECT_TRUE(m.Matches(&n));
+  n = -1;
+  EXPECT_FALSE(m.Matches(&n));
+  EXPECT_FALSE(m.Matches(nullptr));
+}
+
+TEST(PointeeTest, RawPointerToConst) {
+  const Matcher<const double*> m = Pointee(Ge(0));
+
+  double x = 1;
+  EXPECT_TRUE(m.Matches(&x));
+  x = -1;
+  EXPECT_FALSE(m.Matches(&x));
+  EXPECT_FALSE(m.Matches(nullptr));
+}
+
+TEST(PointeeTest, ReferenceToConstRawPointer) {
+  const Matcher<int* const&> m = Pointee(Ge(0));
+
+  int n = 1;
+  EXPECT_TRUE(m.Matches(&n));
+  n = -1;
+  EXPECT_FALSE(m.Matches(&n));
+  EXPECT_FALSE(m.Matches(nullptr));
+}
+
+TEST(PointeeTest, ReferenceToNonConstRawPointer) {
+  const Matcher<double*&> m = Pointee(Ge(0));
+
+  double x = 1.0;
+  double* p = &x;
+  EXPECT_TRUE(m.Matches(p));
+  x = -1;
+  EXPECT_FALSE(m.Matches(p));
+  p = nullptr;
+  EXPECT_FALSE(m.Matches(p));
+}
+
+TEST(PointeeTest, SmartPointer) {
+  const Matcher<std::unique_ptr<int>> m = Pointee(Ge(0));
+
+  std::unique_ptr<int> n(new int(1));
+  EXPECT_TRUE(m.Matches(n));
+}
+
+TEST(PointeeTest, SmartPointerToConst) {
+  const Matcher<std::unique_ptr<const int>> m = Pointee(Ge(0));
+
+  // There's no implicit conversion from unique_ptr<int> to const
+  // unique_ptr<const int>, so we must pass a unique_ptr<const int> into the
+  // matcher.
+  std::unique_ptr<const int> n(new int(1));
+  EXPECT_TRUE(m.Matches(n));
+}
+
+TEST(PointerTest, RawPointer) {
+  int n = 1;
+  const Matcher<int*> m = Pointer(Eq(&n));
+
+  EXPECT_TRUE(m.Matches(&n));
+
+  int* p = nullptr;
+  EXPECT_FALSE(m.Matches(p));
+  EXPECT_FALSE(m.Matches(nullptr));
+}
+
+TEST(PointerTest, RawPointerToConst) {
+  int n = 1;
+  const Matcher<const int*> m = Pointer(Eq(&n));
+
+  EXPECT_TRUE(m.Matches(&n));
+
+  int* p = nullptr;
+  EXPECT_FALSE(m.Matches(p));
+  EXPECT_FALSE(m.Matches(nullptr));
+}
+
+TEST(PointerTest, SmartPointer) {
+  std::unique_ptr<int> n(new int(10));
+  int* raw_n = n.get();
+  const Matcher<std::unique_ptr<int>> m = Pointer(Eq(raw_n));
+
+  EXPECT_TRUE(m.Matches(n));
+}
+
+TEST(PointerTest, SmartPointerToConst) {
+  std::unique_ptr<const int> n(new int(10));
+  const int* raw_n = n.get();
+  const Matcher<std::unique_ptr<const int>> m = Pointer(Eq(raw_n));
+
+  // There's no implicit conversion from unique_ptr<int> to const
+  // unique_ptr<const int>, so we must pass a unique_ptr<const int> into the
+  // matcher.
+  std::unique_ptr<const int> p(new int(10));
+  EXPECT_FALSE(m.Matches(p));
+}
+
+// Minimal const-propagating pointer.
+template <typename T>
+class ConstPropagatingPtr {
+ public:
+  typedef T element_type;
+
+  ConstPropagatingPtr() : val_() {}
+  explicit ConstPropagatingPtr(T* t) : val_(t) {}
+  ConstPropagatingPtr(const ConstPropagatingPtr& other) : val_(other.val_) {}
+
+  T* get() { return val_; }
+  T& operator*() { return *val_; }
+  // Most smart pointers return non-const T* and T& from the next methods.
+  const T* get() const { return val_; }
+  const T& operator*() const { return *val_; }
+
+ private:
+  T* val_;
+};
+
+INSTANTIATE_GTEST_MATCHER_TEST_P(PointeeTest);
+
+TEST(PointeeTest, WorksWithConstPropagatingPointers) {
+  const Matcher<ConstPropagatingPtr<int>> m = Pointee(Lt(5));
+  int three = 3;
+  const ConstPropagatingPtr<int> co(&three);
+  ConstPropagatingPtr<int> o(&three);
+  EXPECT_TRUE(m.Matches(o));
+  EXPECT_TRUE(m.Matches(co));
+  *o = 6;
+  EXPECT_FALSE(m.Matches(o));
+  EXPECT_FALSE(m.Matches(ConstPropagatingPtr<int>()));
+}
+
+TEST(PointeeTest, NeverMatchesNull) {
+  const Matcher<const char*> m = Pointee(_);
+  EXPECT_FALSE(m.Matches(nullptr));
+}
+
+// Tests that we can write Pointee(value) instead of Pointee(Eq(value)).
+TEST(PointeeTest, MatchesAgainstAValue) {
+  const Matcher<int*> m = Pointee(5);
+
+  int n = 5;
+  EXPECT_TRUE(m.Matches(&n));
+  n = -1;
+  EXPECT_FALSE(m.Matches(&n));
+  EXPECT_FALSE(m.Matches(nullptr));
+}
+
+TEST(PointeeTest, CanDescribeSelf) {
+  const Matcher<int*> m = Pointee(Gt(3));
+  EXPECT_EQ("points to a value that is > 3", Describe(m));
+  EXPECT_EQ("does not point to a value that is > 3", DescribeNegation(m));
+}
+
+TEST_P(PointeeTestP, CanExplainMatchResult) {
+  const Matcher<const std::string*> m = Pointee(StartsWith("Hi"));
+
+  EXPECT_EQ("", Explain(m, static_cast<const std::string*>(nullptr)));
+
+  const Matcher<long*> m2 = Pointee(GreaterThan(1));  // NOLINT
+  long n = 3;                                         // NOLINT
+  EXPECT_EQ("which points to 3" + OfType("long") + ", which is 2 more than 1",
+            Explain(m2, &n));
+}
+
+TEST(PointeeTest, AlwaysExplainsPointee) {
+  const Matcher<int*> m = Pointee(0);
+  int n = 42;
+  EXPECT_EQ("which points to 42" + OfType("int"), Explain(m, &n));
+}
+
+// An uncopyable class.
+class Uncopyable {
+ public:
+  Uncopyable() : value_(-1) {}
+  explicit Uncopyable(int a_value) : value_(a_value) {}
+
+  int value() const { return value_; }
+  void set_value(int i) { value_ = i; }
+
+ private:
+  int value_;
+  Uncopyable(const Uncopyable&) = delete;
+  Uncopyable& operator=(const Uncopyable&) = delete;
+};
+
+// Returns true if and only if x.value() is positive.
+bool ValueIsPositive(const Uncopyable& x) { return x.value() > 0; }
+
+MATCHER_P(UncopyableIs, inner_matcher, "") {
+  return ExplainMatchResult(inner_matcher, arg.value(), result_listener);
+}
+
+// A user-defined struct for testing Field().
+struct AStruct {
+  AStruct() : x(0), y(1.0), z(5), p(nullptr) {}
+  AStruct(const AStruct& rhs)
+      : x(rhs.x), y(rhs.y), z(rhs.z.value()), p(rhs.p) {}
+
+  int x;           // A non-const field.
+  const double y;  // A const field.
+  Uncopyable z;    // An uncopyable field.
+  const char* p;   // A pointer field.
+};
+
+// A derived struct for testing Field().
+struct DerivedStruct : public AStruct {
+  char ch;
+};
+
+INSTANTIATE_GTEST_MATCHER_TEST_P(FieldTest);
+
+// Tests that Field(&Foo::field, ...) works when field is non-const.
+TEST(FieldTest, WorksForNonConstField) {
+  Matcher<AStruct> m = Field(&AStruct::x, Ge(0));
+  Matcher<AStruct> m_with_name = Field("x", &AStruct::x, Ge(0));
+
+  AStruct a;
+  EXPECT_TRUE(m.Matches(a));
+  EXPECT_TRUE(m_with_name.Matches(a));
+  a.x = -1;
+  EXPECT_FALSE(m.Matches(a));
+  EXPECT_FALSE(m_with_name.Matches(a));
+}
+
+// Tests that Field(&Foo::field, ...) works when field is const.
+TEST(FieldTest, WorksForConstField) {
+  AStruct a;
+
+  Matcher<AStruct> m = Field(&AStruct::y, Ge(0.0));
+  Matcher<AStruct> m_with_name = Field("y", &AStruct::y, Ge(0.0));
+  EXPECT_TRUE(m.Matches(a));
+  EXPECT_TRUE(m_with_name.Matches(a));
+  m = Field(&AStruct::y, Le(0.0));
+  m_with_name = Field("y", &AStruct::y, Le(0.0));
+  EXPECT_FALSE(m.Matches(a));
+  EXPECT_FALSE(m_with_name.Matches(a));
+}
+
+// Tests that Field(&Foo::field, ...) works when field is not copyable.
+TEST(FieldTest, WorksForUncopyableField) {
+  AStruct a;
+
+  Matcher<AStruct> m = Field(&AStruct::z, Truly(ValueIsPositive));
+  EXPECT_TRUE(m.Matches(a));
+  m = Field(&AStruct::z, Not(Truly(ValueIsPositive)));
+  EXPECT_FALSE(m.Matches(a));
+}
+
+// Tests that Field(&Foo::field, ...) works when field is a pointer.
+TEST(FieldTest, WorksForPointerField) {
+  // Matching against NULL.
+  Matcher<AStruct> m = Field(&AStruct::p, static_cast<const char*>(nullptr));
+  AStruct a;
+  EXPECT_TRUE(m.Matches(a));
+  a.p = "hi";
+  EXPECT_FALSE(m.Matches(a));
+
+  // Matching a pointer that is not NULL.
+  m = Field(&AStruct::p, StartsWith("hi"));
+  a.p = "hill";
+  EXPECT_TRUE(m.Matches(a));
+  a.p = "hole";
+  EXPECT_FALSE(m.Matches(a));
+}
+
+// Tests that Field() works when the object is passed by reference.
+TEST(FieldTest, WorksForByRefArgument) {
+  Matcher<const AStruct&> m = Field(&AStruct::x, Ge(0));
+
+  AStruct a;
+  EXPECT_TRUE(m.Matches(a));
+  a.x = -1;
+  EXPECT_FALSE(m.Matches(a));
+}
+
+// Tests that Field(&Foo::field, ...) works when the argument's type
+// is a sub-type of Foo.
+TEST(FieldTest, WorksForArgumentOfSubType) {
+  // Note that the matcher expects DerivedStruct but we say AStruct
+  // inside Field().
+  Matcher<const DerivedStruct&> m = Field(&AStruct::x, Ge(0));
+
+  DerivedStruct d;
+  EXPECT_TRUE(m.Matches(d));
+  d.x = -1;
+  EXPECT_FALSE(m.Matches(d));
+}
+
+// Tests that Field(&Foo::field, m) works when field's type and m's
+// argument type are compatible but not the same.
+TEST(FieldTest, WorksForCompatibleMatcherType) {
+  // The field is an int, but the inner matcher expects a signed char.
+  Matcher<const AStruct&> m = Field(&AStruct::x, Matcher<signed char>(Ge(0)));
+
+  AStruct a;
+  EXPECT_TRUE(m.Matches(a));
+  a.x = -1;
+  EXPECT_FALSE(m.Matches(a));
+}
+
+// Tests that Field() can describe itself.
+TEST(FieldTest, CanDescribeSelf) {
+  Matcher<const AStruct&> m = Field(&AStruct::x, Ge(0));
+
+  EXPECT_EQ("is an object whose given field is >= 0", Describe(m));
+  EXPECT_EQ("is an object whose given field isn't >= 0", DescribeNegation(m));
+}
+
+TEST(FieldTest, CanDescribeSelfWithFieldName) {
+  Matcher<const AStruct&> m = Field("field_name", &AStruct::x, Ge(0));
+
+  EXPECT_EQ("is an object whose field `field_name` is >= 0", Describe(m));
+  EXPECT_EQ("is an object whose field `field_name` isn't >= 0",
+            DescribeNegation(m));
+}
+
+// Tests that Field() can explain the match result.
+TEST_P(FieldTestP, CanExplainMatchResult) {
+  Matcher<const AStruct&> m = Field(&AStruct::x, Ge(0));
+
+  AStruct a;
+  a.x = 1;
+  EXPECT_EQ("whose given field is 1" + OfType("int"), Explain(m, a));
+
+  m = Field(&AStruct::x, GreaterThan(0));
+  EXPECT_EQ(
+      "whose given field is 1" + OfType("int") + ", which is 1 more than 0",
+      Explain(m, a));
+}
+
+TEST_P(FieldTestP, CanExplainMatchResultWithFieldName) {
+  Matcher<const AStruct&> m = Field("field_name", &AStruct::x, Ge(0));
+
+  AStruct a;
+  a.x = 1;
+  EXPECT_EQ("whose field `field_name` is 1" + OfType("int"), Explain(m, a));
+
+  m = Field("field_name", &AStruct::x, GreaterThan(0));
+  EXPECT_EQ("whose field `field_name` is 1" + OfType("int") +
+                ", which is 1 more than 0",
+            Explain(m, a));
+}
+
+INSTANTIATE_GTEST_MATCHER_TEST_P(FieldForPointerTest);
+
+// Tests that Field() works when the argument is a pointer to const.
+TEST(FieldForPointerTest, WorksForPointerToConst) {
+  Matcher<const AStruct*> m = Field(&AStruct::x, Ge(0));
+
+  AStruct a;
+  EXPECT_TRUE(m.Matches(&a));
+  a.x = -1;
+  EXPECT_FALSE(m.Matches(&a));
+}
+
+// Tests that Field() works when the argument is a pointer to non-const.
+TEST(FieldForPointerTest, WorksForPointerToNonConst) {
+  Matcher<AStruct*> m = Field(&AStruct::x, Ge(0));
+
+  AStruct a;
+  EXPECT_TRUE(m.Matches(&a));
+  a.x = -1;
+  EXPECT_FALSE(m.Matches(&a));
+}
+
+// Tests that Field() works when the argument is a reference to a const pointer.
+TEST(FieldForPointerTest, WorksForReferenceToConstPointer) {
+  Matcher<AStruct* const&> m = Field(&AStruct::x, Ge(0));
+
+  AStruct a;
+  EXPECT_TRUE(m.Matches(&a));
+  a.x = -1;
+  EXPECT_FALSE(m.Matches(&a));
+}
+
+// Tests that Field() does not match the NULL pointer.
+TEST(FieldForPointerTest, DoesNotMatchNull) {
+  Matcher<const AStruct*> m = Field(&AStruct::x, _);
+  EXPECT_FALSE(m.Matches(nullptr));
+}
+
+// Tests that Field(&Foo::field, ...) works when the argument's type
+// is a sub-type of const Foo*.
+TEST(FieldForPointerTest, WorksForArgumentOfSubType) {
+  // Note that the matcher expects DerivedStruct but we say AStruct
+  // inside Field().
+  Matcher<DerivedStruct*> m = Field(&AStruct::x, Ge(0));
+
+  DerivedStruct d;
+  EXPECT_TRUE(m.Matches(&d));
+  d.x = -1;
+  EXPECT_FALSE(m.Matches(&d));
+}
+
+// Tests that Field() can describe itself when used to match a pointer.
+TEST(FieldForPointerTest, CanDescribeSelf) {
+  Matcher<const AStruct*> m = Field(&AStruct::x, Ge(0));
+
+  EXPECT_EQ("is an object whose given field is >= 0", Describe(m));
+  EXPECT_EQ("is an object whose given field isn't >= 0", DescribeNegation(m));
+}
+
+TEST(FieldForPointerTest, CanDescribeSelfWithFieldName) {
+  Matcher<const AStruct*> m = Field("field_name", &AStruct::x, Ge(0));
+
+  EXPECT_EQ("is an object whose field `field_name` is >= 0", Describe(m));
+  EXPECT_EQ("is an object whose field `field_name` isn't >= 0",
+            DescribeNegation(m));
+}
+
+// Tests that Field() can explain the result of matching a pointer.
+TEST_P(FieldForPointerTestP, CanExplainMatchResult) {
+  Matcher<const AStruct*> m = Field(&AStruct::x, Ge(0));
+
+  AStruct a;
+  a.x = 1;
+  EXPECT_EQ("", Explain(m, static_cast<const AStruct*>(nullptr)));
+  EXPECT_EQ("which points to an object whose given field is 1" + OfType("int"),
+            Explain(m, &a));
+
+  m = Field(&AStruct::x, GreaterThan(0));
+  EXPECT_EQ("which points to an object whose given field is 1" + OfType("int") +
+                ", which is 1 more than 0",
+            Explain(m, &a));
+}
+
+TEST_P(FieldForPointerTestP, CanExplainMatchResultWithFieldName) {
+  Matcher<const AStruct*> m = Field("field_name", &AStruct::x, Ge(0));
+
+  AStruct a;
+  a.x = 1;
+  EXPECT_EQ("", Explain(m, static_cast<const AStruct*>(nullptr)));
+  EXPECT_EQ(
+      "which points to an object whose field `field_name` is 1" + OfType("int"),
+      Explain(m, &a));
+
+  m = Field("field_name", &AStruct::x, GreaterThan(0));
+  EXPECT_EQ("which points to an object whose field `field_name` is 1" +
+                OfType("int") + ", which is 1 more than 0",
+            Explain(m, &a));
+}
+
+// A user-defined class for testing Property().
+class AClass {
+ public:
+  AClass() : n_(0) {}
+
+  // A getter that returns a non-reference.
+  int n() const { return n_; }
+
+  void set_n(int new_n) { n_ = new_n; }
+
+  // A getter that returns a reference to const.
+  const std::string& s() const { return s_; }
+
+  const std::string& s_ref() const& { return s_; }
+
+  void set_s(const std::string& new_s) { s_ = new_s; }
+
+  // A getter that returns a reference to non-const.
+  double& x() const { return x_; }
+
+ private:
+  int n_;
+  std::string s_;
+
+  static double x_;
+};
+
+double AClass::x_ = 0.0;
+
+// A derived class for testing Property().
+class DerivedClass : public AClass {
+ public:
+  int k() const { return k_; }
+
+ private:
+  int k_;
+};
+
+INSTANTIATE_GTEST_MATCHER_TEST_P(PropertyTest);
+
+// Tests that Property(&Foo::property, ...) works when property()
+// returns a non-reference.
+TEST(PropertyTest, WorksForNonReferenceProperty) {
+  Matcher<const AClass&> m = Property(&AClass::n, Ge(0));
+  Matcher<const AClass&> m_with_name = Property("n", &AClass::n, Ge(0));
+
+  AClass a;
+  a.set_n(1);
+  EXPECT_TRUE(m.Matches(a));
+  EXPECT_TRUE(m_with_name.Matches(a));
+
+  a.set_n(-1);
+  EXPECT_FALSE(m.Matches(a));
+  EXPECT_FALSE(m_with_name.Matches(a));
+}
+
+// Tests that Property(&Foo::property, ...) works when property()
+// returns a reference to const.
+TEST(PropertyTest, WorksForReferenceToConstProperty) {
+  Matcher<const AClass&> m = Property(&AClass::s, StartsWith("hi"));
+  Matcher<const AClass&> m_with_name =
+      Property("s", &AClass::s, StartsWith("hi"));
+
+  AClass a;
+  a.set_s("hill");
+  EXPECT_TRUE(m.Matches(a));
+  EXPECT_TRUE(m_with_name.Matches(a));
+
+  a.set_s("hole");
+  EXPECT_FALSE(m.Matches(a));
+  EXPECT_FALSE(m_with_name.Matches(a));
+}
+
+// Tests that Property(&Foo::property, ...) works when property() is
+// ref-qualified.
+TEST(PropertyTest, WorksForRefQualifiedProperty) {
+  Matcher<const AClass&> m = Property(&AClass::s_ref, StartsWith("hi"));
+  Matcher<const AClass&> m_with_name =
+      Property("s", &AClass::s_ref, StartsWith("hi"));
+
+  AClass a;
+  a.set_s("hill");
+  EXPECT_TRUE(m.Matches(a));
+  EXPECT_TRUE(m_with_name.Matches(a));
+
+  a.set_s("hole");
+  EXPECT_FALSE(m.Matches(a));
+  EXPECT_FALSE(m_with_name.Matches(a));
+}
+
+// Tests that Property(&Foo::property, ...) works when property()
+// returns a reference to non-const.
+TEST(PropertyTest, WorksForReferenceToNonConstProperty) {
+  double x = 0.0;
+  AClass a;
+
+  Matcher<const AClass&> m = Property(&AClass::x, Ref(x));
+  EXPECT_FALSE(m.Matches(a));
+
+  m = Property(&AClass::x, Not(Ref(x)));
+  EXPECT_TRUE(m.Matches(a));
+}
+
+// Tests that Property(&Foo::property, ...) works when the argument is
+// passed by value.
+TEST(PropertyTest, WorksForByValueArgument) {
+  Matcher<AClass> m = Property(&AClass::s, StartsWith("hi"));
+
+  AClass a;
+  a.set_s("hill");
+  EXPECT_TRUE(m.Matches(a));
+
+  a.set_s("hole");
+  EXPECT_FALSE(m.Matches(a));
+}
+
+// Tests that Property(&Foo::property, ...) works when the argument's
+// type is a sub-type of Foo.
+TEST(PropertyTest, WorksForArgumentOfSubType) {
+  // The matcher expects a DerivedClass, but inside the Property() we
+  // say AClass.
+  Matcher<const DerivedClass&> m = Property(&AClass::n, Ge(0));
+
+  DerivedClass d;
+  d.set_n(1);
+  EXPECT_TRUE(m.Matches(d));
+
+  d.set_n(-1);
+  EXPECT_FALSE(m.Matches(d));
+}
+
+// Tests that Property(&Foo::property, m) works when property()'s type
+// and m's argument type are compatible but different.
+TEST(PropertyTest, WorksForCompatibleMatcherType) {
+  // n() returns an int but the inner matcher expects a signed char.
+  Matcher<const AClass&> m = Property(&AClass::n, Matcher<signed char>(Ge(0)));
+
+  Matcher<const AClass&> m_with_name =
+      Property("n", &AClass::n, Matcher<signed char>(Ge(0)));
+
+  AClass a;
+  EXPECT_TRUE(m.Matches(a));
+  EXPECT_TRUE(m_with_name.Matches(a));
+  a.set_n(-1);
+  EXPECT_FALSE(m.Matches(a));
+  EXPECT_FALSE(m_with_name.Matches(a));
+}
+
+// Tests that Property() can describe itself.
+TEST(PropertyTest, CanDescribeSelf) {
+  Matcher<const AClass&> m = Property(&AClass::n, Ge(0));
+
+  EXPECT_EQ("is an object whose given property is >= 0", Describe(m));
+  EXPECT_EQ("is an object whose given property isn't >= 0",
+            DescribeNegation(m));
+}
+
+TEST(PropertyTest, CanDescribeSelfWithPropertyName) {
+  Matcher<const AClass&> m = Property("fancy_name", &AClass::n, Ge(0));
+
+  EXPECT_EQ("is an object whose property `fancy_name` is >= 0", Describe(m));
+  EXPECT_EQ("is an object whose property `fancy_name` isn't >= 0",
+            DescribeNegation(m));
+}
+
+// Tests that Property() can explain the match result.
+TEST_P(PropertyTestP, CanExplainMatchResult) {
+  Matcher<const AClass&> m = Property(&AClass::n, Ge(0));
+
+  AClass a;
+  a.set_n(1);
+  EXPECT_EQ("whose given property is 1" + OfType("int"), Explain(m, a));
+
+  m = Property(&AClass::n, GreaterThan(0));
+  EXPECT_EQ(
+      "whose given property is 1" + OfType("int") + ", which is 1 more than 0",
+      Explain(m, a));
+}
+
+TEST_P(PropertyTestP, CanExplainMatchResultWithPropertyName) {
+  Matcher<const AClass&> m = Property("fancy_name", &AClass::n, Ge(0));
+
+  AClass a;
+  a.set_n(1);
+  EXPECT_EQ("whose property `fancy_name` is 1" + OfType("int"), Explain(m, a));
+
+  m = Property("fancy_name", &AClass::n, GreaterThan(0));
+  EXPECT_EQ("whose property `fancy_name` is 1" + OfType("int") +
+                ", which is 1 more than 0",
+            Explain(m, a));
+}
+
+INSTANTIATE_GTEST_MATCHER_TEST_P(PropertyForPointerTest);
+
+// Tests that Property() works when the argument is a pointer to const.
+TEST(PropertyForPointerTest, WorksForPointerToConst) {
+  Matcher<const AClass*> m = Property(&AClass::n, Ge(0));
+
+  AClass a;
+  a.set_n(1);
+  EXPECT_TRUE(m.Matches(&a));
+
+  a.set_n(-1);
+  EXPECT_FALSE(m.Matches(&a));
+}
+
+// Tests that Property() works when the argument is a pointer to non-const.
+TEST(PropertyForPointerTest, WorksForPointerToNonConst) {
+  Matcher<AClass*> m = Property(&AClass::s, StartsWith("hi"));
+
+  AClass a;
+  a.set_s("hill");
+  EXPECT_TRUE(m.Matches(&a));
+
+  a.set_s("hole");
+  EXPECT_FALSE(m.Matches(&a));
+}
+
+// Tests that Property() works when the argument is a reference to a
+// const pointer.
+TEST(PropertyForPointerTest, WorksForReferenceToConstPointer) {
+  Matcher<AClass* const&> m = Property(&AClass::s, StartsWith("hi"));
+
+  AClass a;
+  a.set_s("hill");
+  EXPECT_TRUE(m.Matches(&a));
+
+  a.set_s("hole");
+  EXPECT_FALSE(m.Matches(&a));
+}
+
+// Tests that Property() does not match the NULL pointer.
+TEST(PropertyForPointerTest, WorksForReferenceToNonConstProperty) {
+  Matcher<const AClass*> m = Property(&AClass::x, _);
+  EXPECT_FALSE(m.Matches(nullptr));
+}
+
+// Tests that Property(&Foo::property, ...) works when the argument's
+// type is a sub-type of const Foo*.
+TEST(PropertyForPointerTest, WorksForArgumentOfSubType) {
+  // The matcher expects a DerivedClass, but inside the Property() we
+  // say AClass.
+  Matcher<const DerivedClass*> m = Property(&AClass::n, Ge(0));
+
+  DerivedClass d;
+  d.set_n(1);
+  EXPECT_TRUE(m.Matches(&d));
+
+  d.set_n(-1);
+  EXPECT_FALSE(m.Matches(&d));
+}
+
+// Tests that Property() can describe itself when used to match a pointer.
+TEST(PropertyForPointerTest, CanDescribeSelf) {
+  Matcher<const AClass*> m = Property(&AClass::n, Ge(0));
+
+  EXPECT_EQ("is an object whose given property is >= 0", Describe(m));
+  EXPECT_EQ("is an object whose given property isn't >= 0",
+            DescribeNegation(m));
+}
+
+TEST(PropertyForPointerTest, CanDescribeSelfWithPropertyDescription) {
+  Matcher<const AClass*> m = Property("fancy_name", &AClass::n, Ge(0));
+
+  EXPECT_EQ("is an object whose property `fancy_name` is >= 0", Describe(m));
+  EXPECT_EQ("is an object whose property `fancy_name` isn't >= 0",
+            DescribeNegation(m));
+}
+
+// Tests that Property() can explain the result of matching a pointer.
+TEST_P(PropertyForPointerTestP, CanExplainMatchResult) {
+  Matcher<const AClass*> m = Property(&AClass::n, Ge(0));
+
+  AClass a;
+  a.set_n(1);
+  EXPECT_EQ("", Explain(m, static_cast<const AClass*>(nullptr)));
+  EXPECT_EQ(
+      "which points to an object whose given property is 1" + OfType("int"),
+      Explain(m, &a));
+
+  m = Property(&AClass::n, GreaterThan(0));
+  EXPECT_EQ("which points to an object whose given property is 1" +
+                OfType("int") + ", which is 1 more than 0",
+            Explain(m, &a));
+}
+
+TEST_P(PropertyForPointerTestP, CanExplainMatchResultWithPropertyName) {
+  Matcher<const AClass*> m = Property("fancy_name", &AClass::n, Ge(0));
+
+  AClass a;
+  a.set_n(1);
+  EXPECT_EQ("", Explain(m, static_cast<const AClass*>(nullptr)));
+  EXPECT_EQ("which points to an object whose property `fancy_name` is 1" +
+                OfType("int"),
+            Explain(m, &a));
+
+  m = Property("fancy_name", &AClass::n, GreaterThan(0));
+  EXPECT_EQ("which points to an object whose property `fancy_name` is 1" +
+                OfType("int") + ", which is 1 more than 0",
+            Explain(m, &a));
+}
+
+// Tests ResultOf.
+
+// Tests that ResultOf(f, ...) compiles and works as expected when f is a
+// function pointer.
+std::string IntToStringFunction(int input) {
+  return input == 1 ? "foo" : "bar";
+}
+
+INSTANTIATE_GTEST_MATCHER_TEST_P(ResultOfTest);
+
+TEST(ResultOfTest, WorksForFunctionPointers) {
+  Matcher<int> matcher = ResultOf(&IntToStringFunction, Eq(std::string("foo")));
+
+  EXPECT_TRUE(matcher.Matches(1));
+  EXPECT_FALSE(matcher.Matches(2));
+}
+
+// Tests that ResultOf() can describe itself.
+TEST(ResultOfTest, CanDescribeItself) {
+  Matcher<int> matcher = ResultOf(&IntToStringFunction, StrEq("foo"));
+
+  EXPECT_EQ(
+      "is mapped by the given callable to a value that "
+      "is equal to \"foo\"",
+      Describe(matcher));
+  EXPECT_EQ(
+      "is mapped by the given callable to a value that "
+      "isn't equal to \"foo\"",
+      DescribeNegation(matcher));
+}
+
+// Tests that ResultOf() can describe itself when provided a result description.
+TEST(ResultOfTest, CanDescribeItselfWithResultDescription) {
+  Matcher<int> matcher =
+      ResultOf("string conversion", &IntToStringFunction, StrEq("foo"));
+
+  EXPECT_EQ("whose string conversion is equal to \"foo\"", Describe(matcher));
+  EXPECT_EQ("whose string conversion isn't equal to \"foo\"",
+            DescribeNegation(matcher));
+}
+
+// Tests that ResultOf() can explain the match result.
+int IntFunction(int input) { return input == 42 ? 80 : 90; }
+
+TEST_P(ResultOfTestP, CanExplainMatchResult) {
+  Matcher<int> matcher = ResultOf(&IntFunction, Ge(85));
+  EXPECT_EQ("which is mapped by the given callable to 90" + OfType("int"),
+            Explain(matcher, 36));
+
+  matcher = ResultOf(&IntFunction, GreaterThan(85));
+  EXPECT_EQ("which is mapped by the given callable to 90" + OfType("int") +
+                ", which is 5 more than 85",
+            Explain(matcher, 36));
+}
+
+TEST_P(ResultOfTestP, CanExplainMatchResultWithResultDescription) {
+  Matcher<int> matcher = ResultOf("magic int conversion", &IntFunction, Ge(85));
+  EXPECT_EQ("whose magic int conversion is 90" + OfType("int"),
+            Explain(matcher, 36));
+
+  matcher = ResultOf("magic int conversion", &IntFunction, GreaterThan(85));
+  EXPECT_EQ("whose magic int conversion is 90" + OfType("int") +
+                ", which is 5 more than 85",
+            Explain(matcher, 36));
+}
+
+// Tests that ResultOf(f, ...) compiles and works as expected when f(x)
+// returns a non-reference.
+TEST(ResultOfTest, WorksForNonReferenceResults) {
+  Matcher<int> matcher = ResultOf(&IntFunction, Eq(80));
+
+  EXPECT_TRUE(matcher.Matches(42));
+  EXPECT_FALSE(matcher.Matches(36));
+}
+
+// Tests that ResultOf(f, ...) compiles and works as expected when f(x)
+// returns a reference to non-const.
+double& DoubleFunction(double& input) { return input; }  // NOLINT
+
+Uncopyable& RefUncopyableFunction(Uncopyable& obj) {  // NOLINT
+  return obj;
+}
+
+TEST(ResultOfTest, WorksForReferenceToNonConstResults) {
+  double x = 3.14;
+  double x2 = x;
+  Matcher<double&> matcher = ResultOf(&DoubleFunction, Ref(x));
+
+  EXPECT_TRUE(matcher.Matches(x));
+  EXPECT_FALSE(matcher.Matches(x2));
+
+  // Test that ResultOf works with uncopyable objects
+  Uncopyable obj(0);
+  Uncopyable obj2(0);
+  Matcher<Uncopyable&> matcher2 = ResultOf(&RefUncopyableFunction, Ref(obj));
+
+  EXPECT_TRUE(matcher2.Matches(obj));
+  EXPECT_FALSE(matcher2.Matches(obj2));
+}
+
+// Tests that ResultOf(f, ...) compiles and works as expected when f(x)
+// returns a reference to const.
+const std::string& StringFunction(const std::string& input) { return input; }
+
+TEST(ResultOfTest, WorksForReferenceToConstResults) {
+  std::string s = "foo";
+  std::string s2 = s;
+  Matcher<const std::string&> matcher = ResultOf(&StringFunction, Ref(s));
+
+  EXPECT_TRUE(matcher.Matches(s));
+  EXPECT_FALSE(matcher.Matches(s2));
+}
+
+// Tests that ResultOf(f, m) works when f(x) and m's
+// argument types are compatible but different.
+TEST(ResultOfTest, WorksForCompatibleMatcherTypes) {
+  // IntFunction() returns int but the inner matcher expects a signed char.
+  Matcher<int> matcher = ResultOf(IntFunction, Matcher<signed char>(Ge(85)));
+
+  EXPECT_TRUE(matcher.Matches(36));
+  EXPECT_FALSE(matcher.Matches(42));
+}
+
+// Tests that the program aborts when ResultOf is passed
+// a NULL function pointer.
+TEST(ResultOfDeathTest, DiesOnNullFunctionPointers) {
+  EXPECT_DEATH_IF_SUPPORTED(
+      ResultOf(static_cast<std::string (*)(int dummy)>(nullptr),
+               Eq(std::string("foo"))),
+      "NULL function pointer is passed into ResultOf\\(\\)\\.");
+}
+
+// Tests that ResultOf(f, ...) compiles and works as expected when f is a
+// function reference.
+TEST(ResultOfTest, WorksForFunctionReferences) {
+  Matcher<int> matcher = ResultOf(IntToStringFunction, StrEq("foo"));
+  EXPECT_TRUE(matcher.Matches(1));
+  EXPECT_FALSE(matcher.Matches(2));
+}
+
+// Tests that ResultOf(f, ...) compiles and works as expected when f is a
+// function object.
+struct Functor {
+  std::string operator()(int input) const { return IntToStringFunction(input); }
+};
+
+TEST(ResultOfTest, WorksForFunctors) {
+  Matcher<int> matcher = ResultOf(Functor(), Eq(std::string("foo")));
+
+  EXPECT_TRUE(matcher.Matches(1));
+  EXPECT_FALSE(matcher.Matches(2));
+}
+
+// Tests that ResultOf(f, ...) compiles and works as expected when f is a
+// functor with more than one operator() defined. ResultOf() must work
+// for each defined operator().
+struct PolymorphicFunctor {
+  typedef int result_type;
+  int operator()(int n) { return n; }
+  int operator()(const char* s) { return static_cast<int>(strlen(s)); }
+  std::string operator()(int* p) { return p ? "good ptr" : "null"; }
+};
+
+TEST(ResultOfTest, WorksForPolymorphicFunctors) {
+  Matcher<int> matcher_int = ResultOf(PolymorphicFunctor(), Ge(5));
+
+  EXPECT_TRUE(matcher_int.Matches(10));
+  EXPECT_FALSE(matcher_int.Matches(2));
+
+  Matcher<const char*> matcher_string = ResultOf(PolymorphicFunctor(), Ge(5));
+
+  EXPECT_TRUE(matcher_string.Matches("long string"));
+  EXPECT_FALSE(matcher_string.Matches("shrt"));
+}
+
+TEST(ResultOfTest, WorksForPolymorphicFunctorsIgnoringResultType) {
+  Matcher<int*> matcher = ResultOf(PolymorphicFunctor(), "good ptr");
+
+  int n = 0;
+  EXPECT_TRUE(matcher.Matches(&n));
+  EXPECT_FALSE(matcher.Matches(nullptr));
+}
+
+TEST(ResultOfTest, WorksForLambdas) {
+  Matcher<int> matcher = ResultOf(
+      [](int str_len) {
+        return std::string(static_cast<size_t>(str_len), 'x');
+      },
+      "xxx");
+  EXPECT_TRUE(matcher.Matches(3));
+  EXPECT_FALSE(matcher.Matches(1));
+}
+
+TEST(ResultOfTest, WorksForNonCopyableArguments) {
+  Matcher<std::unique_ptr<int>> matcher = ResultOf(
+      [](const std::unique_ptr<int>& str_len) {
+        return std::string(static_cast<size_t>(*str_len), 'x');
+      },
+      "xxx");
+  EXPECT_TRUE(matcher.Matches(std::unique_ptr<int>(new int(3))));
+  EXPECT_FALSE(matcher.Matches(std::unique_ptr<int>(new int(1))));
+}
+
+const int* ReferencingFunction(const int& n) { return &n; }
+
+struct ReferencingFunctor {
+  typedef const int* result_type;
+  result_type operator()(const int& n) { return &n; }
+};
+
+TEST(ResultOfTest, WorksForReferencingCallables) {
+  const int n = 1;
+  const int n2 = 1;
+  Matcher<const int&> matcher2 = ResultOf(ReferencingFunction, Eq(&n));
+  EXPECT_TRUE(matcher2.Matches(n));
+  EXPECT_FALSE(matcher2.Matches(n2));
+
+  Matcher<const int&> matcher3 = ResultOf(ReferencingFunctor(), Eq(&n));
+  EXPECT_TRUE(matcher3.Matches(n));
+  EXPECT_FALSE(matcher3.Matches(n2));
+}
+
+TEST(SizeIsTest, ImplementsSizeIs) {
+  vector<int> container;
+  EXPECT_THAT(container, SizeIs(0));
+  EXPECT_THAT(container, Not(SizeIs(1)));
+  container.push_back(0);
+  EXPECT_THAT(container, Not(SizeIs(0)));
+  EXPECT_THAT(container, SizeIs(1));
+  container.push_back(0);
+  EXPECT_THAT(container, Not(SizeIs(0)));
+  EXPECT_THAT(container, SizeIs(2));
+}
+
+TEST(SizeIsTest, WorksWithMap) {
+  map<std::string, int> container;
+  EXPECT_THAT(container, SizeIs(0));
+  EXPECT_THAT(container, Not(SizeIs(1)));
+  container.insert(make_pair("foo", 1));
+  EXPECT_THAT(container, Not(SizeIs(0)));
+  EXPECT_THAT(container, SizeIs(1));
+  container.insert(make_pair("bar", 2));
+  EXPECT_THAT(container, Not(SizeIs(0)));
+  EXPECT_THAT(container, SizeIs(2));
+}
+
+TEST(SizeIsTest, WorksWithReferences) {
+  vector<int> container;
+  Matcher<const vector<int>&> m = SizeIs(1);
+  EXPECT_THAT(container, Not(m));
+  container.push_back(0);
+  EXPECT_THAT(container, m);
+}
+
+TEST(SizeIsTest, WorksWithMoveOnly) {
+  ContainerHelper helper;
+  EXPECT_CALL(helper, Call(SizeIs(3)));
+  helper.Call(MakeUniquePtrs({1, 2, 3}));
+}
+
+// SizeIs should work for any type that provides a size() member function.
+// For example, a size_type member type should not need to be provided.
+struct MinimalistCustomType {
+  int size() const { return 1; }
+};
+TEST(SizeIsTest, WorksWithMinimalistCustomType) {
+  MinimalistCustomType container;
+  EXPECT_THAT(container, SizeIs(1));
+  EXPECT_THAT(container, Not(SizeIs(0)));
+}
+
+TEST(SizeIsTest, CanDescribeSelf) {
+  Matcher<vector<int>> m = SizeIs(2);
+  EXPECT_EQ("has a size that is equal to 2", Describe(m));
+  EXPECT_EQ("has a size that isn't equal to 2", DescribeNegation(m));
+}
+
+TEST(SizeIsTest, ExplainsResult) {
+  Matcher<vector<int>> m1 = SizeIs(2);
+  Matcher<vector<int>> m2 = SizeIs(Lt(2u));
+  Matcher<vector<int>> m3 = SizeIs(AnyOf(0, 3));
+  Matcher<vector<int>> m4 = SizeIs(Gt(1u));
+  vector<int> container;
+  EXPECT_EQ("whose size 0 doesn't match", Explain(m1, container));
+  EXPECT_EQ("whose size 0 matches", Explain(m2, container));
+  EXPECT_EQ("whose size 0 matches", Explain(m3, container));
+  EXPECT_EQ("whose size 0 doesn't match", Explain(m4, container));
+  container.push_back(0);
+  container.push_back(0);
+  EXPECT_EQ("whose size 2 matches", Explain(m1, container));
+  EXPECT_EQ("whose size 2 doesn't match", Explain(m2, container));
+  EXPECT_EQ("whose size 2 doesn't match", Explain(m3, container));
+  EXPECT_EQ("whose size 2 matches", Explain(m4, container));
+}
+
+TEST(WhenSortedByTest, WorksForEmptyContainer) {
+  const vector<int> numbers;
+  EXPECT_THAT(numbers, WhenSortedBy(less<int>(), ElementsAre()));
+  EXPECT_THAT(numbers, Not(WhenSortedBy(less<int>(), ElementsAre(1))));
+}
+
+TEST(WhenSortedByTest, WorksForNonEmptyContainer) {
+  vector<unsigned> numbers;
+  numbers.push_back(3);
+  numbers.push_back(1);
+  numbers.push_back(2);
+  numbers.push_back(2);
+  EXPECT_THAT(numbers,
+              WhenSortedBy(greater<unsigned>(), ElementsAre(3, 2, 2, 1)));
+  EXPECT_THAT(numbers,
+              Not(WhenSortedBy(greater<unsigned>(), ElementsAre(1, 2, 2, 3))));
+}
+
+TEST(WhenSortedByTest, WorksForNonVectorContainer) {
+  list<std::string> words;
+  words.push_back("say");
+  words.push_back("hello");
+  words.push_back("world");
+  EXPECT_THAT(words, WhenSortedBy(less<std::string>(),
+                                  ElementsAre("hello", "say", "world")));
+  EXPECT_THAT(words, Not(WhenSortedBy(less<std::string>(),
+                                      ElementsAre("say", "hello", "world"))));
+}
+
+TEST(WhenSortedByTest, WorksForNativeArray) {
+  const int numbers[] = {1, 3, 2, 4};
+  const int sorted_numbers[] = {1, 2, 3, 4};
+  EXPECT_THAT(numbers, WhenSortedBy(less<int>(), ElementsAre(1, 2, 3, 4)));
+  EXPECT_THAT(numbers,
+              WhenSortedBy(less<int>(), ElementsAreArray(sorted_numbers)));
+  EXPECT_THAT(numbers, Not(WhenSortedBy(less<int>(), ElementsAre(1, 3, 2, 4))));
+}
+
+TEST(WhenSortedByTest, CanDescribeSelf) {
+  const Matcher<vector<int>> m = WhenSortedBy(less<int>(), ElementsAre(1, 2));
+  EXPECT_EQ(
+      "(when sorted) has 2 elements where\n"
+      "element #0 is equal to 1,\n"
+      "element #1 is equal to 2",
+      Describe(m));
+  EXPECT_EQ(
+      "(when sorted) doesn't have 2 elements, or\n"
+      "element #0 isn't equal to 1, or\n"
+      "element #1 isn't equal to 2",
+      DescribeNegation(m));
+}
+
+TEST(WhenSortedByTest, ExplainsMatchResult) {
+  const int a[] = {2, 1};
+  EXPECT_EQ("which is { 1, 2 } when sorted, whose element #0 doesn't match",
+            Explain(WhenSortedBy(less<int>(), ElementsAre(2, 3)), a));
+  EXPECT_EQ("which is { 1, 2 } when sorted",
+            Explain(WhenSortedBy(less<int>(), ElementsAre(1, 2)), a));
+}
+
+// WhenSorted() is a simple wrapper on WhenSortedBy().  Hence we don't
+// need to test it as exhaustively as we test the latter.
+
+TEST(WhenSortedTest, WorksForEmptyContainer) {
+  const vector<int> numbers;
+  EXPECT_THAT(numbers, WhenSorted(ElementsAre()));
+  EXPECT_THAT(numbers, Not(WhenSorted(ElementsAre(1))));
+}
+
+TEST(WhenSortedTest, WorksForNonEmptyContainer) {
+  list<std::string> words;
+  words.push_back("3");
+  words.push_back("1");
+  words.push_back("2");
+  words.push_back("2");
+  EXPECT_THAT(words, WhenSorted(ElementsAre("1", "2", "2", "3")));
+  EXPECT_THAT(words, Not(WhenSorted(ElementsAre("3", "1", "2", "2"))));
+}
+
+TEST(WhenSortedTest, WorksForMapTypes) {
+  map<std::string, int> word_counts;
+  word_counts["and"] = 1;
+  word_counts["the"] = 1;
+  word_counts["buffalo"] = 2;
+  EXPECT_THAT(word_counts,
+              WhenSorted(ElementsAre(Pair("and", 1), Pair("buffalo", 2),
+                                     Pair("the", 1))));
+  EXPECT_THAT(word_counts,
+              Not(WhenSorted(ElementsAre(Pair("and", 1), Pair("the", 1),
+                                         Pair("buffalo", 2)))));
+}
+
+TEST(WhenSortedTest, WorksForMultiMapTypes) {
+  multimap<int, int> ifib;
+  ifib.insert(make_pair(8, 6));
+  ifib.insert(make_pair(2, 3));
+  ifib.insert(make_pair(1, 1));
+  ifib.insert(make_pair(3, 4));
+  ifib.insert(make_pair(1, 2));
+  ifib.insert(make_pair(5, 5));
+  EXPECT_THAT(ifib,
+              WhenSorted(ElementsAre(Pair(1, 1), Pair(1, 2), Pair(2, 3),
+                                     Pair(3, 4), Pair(5, 5), Pair(8, 6))));
+  EXPECT_THAT(ifib,
+              Not(WhenSorted(ElementsAre(Pair(8, 6), Pair(2, 3), Pair(1, 1),
+                                         Pair(3, 4), Pair(1, 2), Pair(5, 5)))));
+}
+
+TEST(WhenSortedTest, WorksForPolymorphicMatcher) {
+  std::deque<int> d;
+  d.push_back(2);
+  d.push_back(1);
+  EXPECT_THAT(d, WhenSorted(ElementsAre(1, 2)));
+  EXPECT_THAT(d, Not(WhenSorted(ElementsAre(2, 1))));
+}
+
+TEST(WhenSortedTest, WorksForVectorConstRefMatcher) {
+  std::deque<int> d;
+  d.push_back(2);
+  d.push_back(1);
+  Matcher<const std::vector<int>&> vector_match = ElementsAre(1, 2);
+  EXPECT_THAT(d, WhenSorted(vector_match));
+  Matcher<const std::vector<int>&> not_vector_match = ElementsAre(2, 1);
+  EXPECT_THAT(d, Not(WhenSorted(not_vector_match)));
+}
+
+// Deliberately bare pseudo-container.
+// Offers only begin() and end() accessors, yielding InputIterator.
+template <typename T>
+class Streamlike {
+ private:
+  class ConstIter;
+
+ public:
+  typedef ConstIter const_iterator;
+  typedef T value_type;
+
+  template <typename InIter>
+  Streamlike(InIter first, InIter last) : remainder_(first, last) {}
+
+  const_iterator begin() const {
+    return const_iterator(this, remainder_.begin());
+  }
+  const_iterator end() const { return const_iterator(this, remainder_.end()); }
+
+ private:
+  class ConstIter {
+   public:
+    using iterator_category = std::input_iterator_tag;
+    using value_type = T;
+    using difference_type = ptrdiff_t;
+    using pointer = const value_type*;
+    using reference = const value_type&;
+
+    ConstIter(const Streamlike* s, typename std::list<value_type>::iterator pos)
+        : s_(s), pos_(pos) {}
+
+    const value_type& operator*() const { return *pos_; }
+    const value_type* operator->() const { return &*pos_; }
+    ConstIter& operator++() {
+      s_->remainder_.erase(pos_++);
+      return *this;
+    }
+
+    // *iter++ is required to work (see std::istreambuf_iterator).
+    // (void)iter++ is also required to work.
+    class PostIncrProxy {
+     public:
+      explicit PostIncrProxy(const value_type& value) : value_(value) {}
+      value_type operator*() const { return value_; }
+
+     private:
+      value_type value_;
+    };
+    PostIncrProxy operator++(int) {
+      PostIncrProxy proxy(**this);
+      ++(*this);
+      return proxy;
+    }
+
+    friend bool operator==(const ConstIter& a, const ConstIter& b) {
+      return a.s_ == b.s_ && a.pos_ == b.pos_;
+    }
+    friend bool operator!=(const ConstIter& a, const ConstIter& b) {
+      return !(a == b);
+    }
+
+   private:
+    const Streamlike* s_;
+    typename std::list<value_type>::iterator pos_;
+  };
+
+  friend std::ostream& operator<<(std::ostream& os, const Streamlike& s) {
+    os << "[";
+    typedef typename std::list<value_type>::const_iterator Iter;
+    const char* sep = "";
+    for (Iter it = s.remainder_.begin(); it != s.remainder_.end(); ++it) {
+      os << sep << *it;
+      sep = ",";
+    }
+    os << "]";
+    return os;
+  }
+
+  mutable std::list<value_type> remainder_;  // modified by iteration
+};
+
+TEST(StreamlikeTest, Iteration) {
+  const int a[5] = {2, 1, 4, 5, 3};
+  Streamlike<int> s(a, a + 5);
+  Streamlike<int>::const_iterator it = s.begin();
+  const int* ip = a;
+  while (it != s.end()) {
+    SCOPED_TRACE(ip - a);
+    EXPECT_EQ(*ip++, *it++);
+  }
+}
+
+INSTANTIATE_GTEST_MATCHER_TEST_P(BeginEndDistanceIsTest);
+
+TEST(BeginEndDistanceIsTest, WorksWithForwardList) {
+  std::forward_list<int> container;
+  EXPECT_THAT(container, BeginEndDistanceIs(0));
+  EXPECT_THAT(container, Not(BeginEndDistanceIs(1)));
+  container.push_front(0);
+  EXPECT_THAT(container, Not(BeginEndDistanceIs(0)));
+  EXPECT_THAT(container, BeginEndDistanceIs(1));
+  container.push_front(0);
+  EXPECT_THAT(container, Not(BeginEndDistanceIs(0)));
+  EXPECT_THAT(container, BeginEndDistanceIs(2));
+}
+
+TEST(BeginEndDistanceIsTest, WorksWithNonStdList) {
+  const int a[5] = {1, 2, 3, 4, 5};
+  Streamlike<int> s(a, a + 5);
+  EXPECT_THAT(s, BeginEndDistanceIs(5));
+}
+
+TEST(BeginEndDistanceIsTest, CanDescribeSelf) {
+  Matcher<vector<int>> m = BeginEndDistanceIs(2);
+  EXPECT_EQ("distance between begin() and end() is equal to 2", Describe(m));
+  EXPECT_EQ("distance between begin() and end() isn't equal to 2",
+            DescribeNegation(m));
+}
+
+TEST(BeginEndDistanceIsTest, WorksWithMoveOnly) {
+  ContainerHelper helper;
+  EXPECT_CALL(helper, Call(BeginEndDistanceIs(2)));
+  helper.Call(MakeUniquePtrs({1, 2}));
+}
+
+TEST_P(BeginEndDistanceIsTestP, ExplainsResult) {
+  Matcher<vector<int>> m1 = BeginEndDistanceIs(2);
+  Matcher<vector<int>> m2 = BeginEndDistanceIs(Lt(2));
+  Matcher<vector<int>> m3 = BeginEndDistanceIs(AnyOf(0, 3));
+  Matcher<vector<int>> m4 = BeginEndDistanceIs(GreaterThan(1));
+  vector<int> container;
+  EXPECT_EQ("whose distance between begin() and end() 0 doesn't match",
+            Explain(m1, container));
+  EXPECT_EQ("whose distance between begin() and end() 0 matches",
+            Explain(m2, container));
+  EXPECT_EQ("whose distance between begin() and end() 0 matches",
+            Explain(m3, container));
+  EXPECT_EQ(
+      "whose distance between begin() and end() 0 doesn't match, which is 1 "
+      "less than 1",
+      Explain(m4, container));
+  container.push_back(0);
+  container.push_back(0);
+  EXPECT_EQ("whose distance between begin() and end() 2 matches",
+            Explain(m1, container));
+  EXPECT_EQ("whose distance between begin() and end() 2 doesn't match",
+            Explain(m2, container));
+  EXPECT_EQ("whose distance between begin() and end() 2 doesn't match",
+            Explain(m3, container));
+  EXPECT_EQ(
+      "whose distance between begin() and end() 2 matches, which is 1 more "
+      "than 1",
+      Explain(m4, container));
+}
+
+TEST(WhenSortedTest, WorksForStreamlike) {
+  // Streamlike 'container' provides only minimal iterator support.
+  // Its iterators are tagged with input_iterator_tag.
+  const int a[5] = {2, 1, 4, 5, 3};
+  Streamlike<int> s(std::begin(a), std::end(a));
+  EXPECT_THAT(s, WhenSorted(ElementsAre(1, 2, 3, 4, 5)));
+  EXPECT_THAT(s, Not(WhenSorted(ElementsAre(2, 1, 4, 5, 3))));
+}
+
+TEST(WhenSortedTest, WorksForVectorConstRefMatcherOnStreamlike) {
+  const int a[] = {2, 1, 4, 5, 3};
+  Streamlike<int> s(std::begin(a), std::end(a));
+  Matcher<const std::vector<int>&> vector_match = ElementsAre(1, 2, 3, 4, 5);
+  EXPECT_THAT(s, WhenSorted(vector_match));
+  EXPECT_THAT(s, Not(WhenSorted(ElementsAre(2, 1, 4, 5, 3))));
+}
+
+TEST(IsSupersetOfTest, WorksForNativeArray) {
+  const int subset[] = {1, 4};
+  const int superset[] = {1, 2, 4};
+  const int disjoint[] = {1, 0, 3};
+  EXPECT_THAT(subset, IsSupersetOf(subset));
+  EXPECT_THAT(subset, Not(IsSupersetOf(superset)));
+  EXPECT_THAT(superset, IsSupersetOf(subset));
+  EXPECT_THAT(subset, Not(IsSupersetOf(disjoint)));
+  EXPECT_THAT(disjoint, Not(IsSupersetOf(subset)));
+}
+
+TEST(IsSupersetOfTest, WorksWithDuplicates) {
+  const int not_enough[] = {1, 2};
+  const int enough[] = {1, 1, 2};
+  const int expected[] = {1, 1};
+  EXPECT_THAT(not_enough, Not(IsSupersetOf(expected)));
+  EXPECT_THAT(enough, IsSupersetOf(expected));
+}
+
+TEST(IsSupersetOfTest, WorksForEmpty) {
+  vector<int> numbers;
+  vector<int> expected;
+  EXPECT_THAT(numbers, IsSupersetOf(expected));
+  expected.push_back(1);
+  EXPECT_THAT(numbers, Not(IsSupersetOf(expected)));
+  expected.clear();
+  numbers.push_back(1);
+  numbers.push_back(2);
+  EXPECT_THAT(numbers, IsSupersetOf(expected));
+  expected.push_back(1);
+  EXPECT_THAT(numbers, IsSupersetOf(expected));
+  expected.push_back(2);
+  EXPECT_THAT(numbers, IsSupersetOf(expected));
+  expected.push_back(3);
+  EXPECT_THAT(numbers, Not(IsSupersetOf(expected)));
+}
+
+TEST(IsSupersetOfTest, WorksForStreamlike) {
+  const int a[5] = {1, 2, 3, 4, 5};
+  Streamlike<int> s(std::begin(a), std::end(a));
+
+  vector<int> expected;
+  expected.push_back(1);
+  expected.push_back(2);
+  expected.push_back(5);
+  EXPECT_THAT(s, IsSupersetOf(expected));
+
+  expected.push_back(0);
+  EXPECT_THAT(s, Not(IsSupersetOf(expected)));
+}
+
+TEST(IsSupersetOfTest, TakesStlContainer) {
+  const int actual[] = {3, 1, 2};
+
+  ::std::list<int> expected;
+  expected.push_back(1);
+  expected.push_back(3);
+  EXPECT_THAT(actual, IsSupersetOf(expected));
+
+  expected.push_back(4);
+  EXPECT_THAT(actual, Not(IsSupersetOf(expected)));
+}
+
+TEST(IsSupersetOfTest, Describe) {
+  typedef std::vector<int> IntVec;
+  IntVec expected;
+  expected.push_back(111);
+  expected.push_back(222);
+  expected.push_back(333);
+  EXPECT_THAT(
+      Describe<IntVec>(IsSupersetOf(expected)),
+      Eq("a surjection from elements to requirements exists such that:\n"
+         " - an element is equal to 111\n"
+         " - an element is equal to 222\n"
+         " - an element is equal to 333"));
+}
+
+TEST(IsSupersetOfTest, DescribeNegation) {
+  typedef std::vector<int> IntVec;
+  IntVec expected;
+  expected.push_back(111);
+  expected.push_back(222);
+  expected.push_back(333);
+  EXPECT_THAT(
+      DescribeNegation<IntVec>(IsSupersetOf(expected)),
+      Eq("no surjection from elements to requirements exists such that:\n"
+         " - an element is equal to 111\n"
+         " - an element is equal to 222\n"
+         " - an element is equal to 333"));
+}
+
+TEST(IsSupersetOfTest, MatchAndExplain) {
+  std::vector<int> v;
+  v.push_back(2);
+  v.push_back(3);
+  std::vector<int> expected;
+  expected.push_back(1);
+  expected.push_back(2);
+  StringMatchResultListener listener;
+  ASSERT_FALSE(ExplainMatchResult(IsSupersetOf(expected), v, &listener))
+      << listener.str();
+  EXPECT_THAT(listener.str(),
+              Eq("where the following matchers don't match any elements:\n"
+                 "matcher #0: is equal to 1"));
+
+  v.push_back(1);
+  listener.Clear();
+  ASSERT_TRUE(ExplainMatchResult(IsSupersetOf(expected), v, &listener))
+      << listener.str();
+  EXPECT_THAT(listener.str(), Eq("where:\n"
+                                 " - element #0 is matched by matcher #1,\n"
+                                 " - element #2 is matched by matcher #0"));
+}
+
+TEST(IsSupersetOfTest, WorksForRhsInitializerList) {
+  const int numbers[] = {1, 3, 6, 2, 4, 5};
+  EXPECT_THAT(numbers, IsSupersetOf({1, 2}));
+  EXPECT_THAT(numbers, Not(IsSupersetOf({3, 0})));
+}
+
+TEST(IsSupersetOfTest, WorksWithMoveOnly) {
+  ContainerHelper helper;
+  EXPECT_CALL(helper, Call(IsSupersetOf({Pointee(1)})));
+  helper.Call(MakeUniquePtrs({1, 2}));
+  EXPECT_CALL(helper, Call(Not(IsSupersetOf({Pointee(1), Pointee(2)}))));
+  helper.Call(MakeUniquePtrs({2}));
+}
+
+TEST(IsSubsetOfTest, WorksForNativeArray) {
+  const int subset[] = {1, 4};
+  const int superset[] = {1, 2, 4};
+  const int disjoint[] = {1, 0, 3};
+  EXPECT_THAT(subset, IsSubsetOf(subset));
+  EXPECT_THAT(subset, IsSubsetOf(superset));
+  EXPECT_THAT(superset, Not(IsSubsetOf(subset)));
+  EXPECT_THAT(subset, Not(IsSubsetOf(disjoint)));
+  EXPECT_THAT(disjoint, Not(IsSubsetOf(subset)));
+}
+
+TEST(IsSubsetOfTest, WorksWithDuplicates) {
+  const int not_enough[] = {1, 2};
+  const int enough[] = {1, 1, 2};
+  const int actual[] = {1, 1};
+  EXPECT_THAT(actual, Not(IsSubsetOf(not_enough)));
+  EXPECT_THAT(actual, IsSubsetOf(enough));
+}
+
+TEST(IsSubsetOfTest, WorksForEmpty) {
+  vector<int> numbers;
+  vector<int> expected;
+  EXPECT_THAT(numbers, IsSubsetOf(expected));
+  expected.push_back(1);
+  EXPECT_THAT(numbers, IsSubsetOf(expected));
+  expected.clear();
+  numbers.push_back(1);
+  numbers.push_back(2);
+  EXPECT_THAT(numbers, Not(IsSubsetOf(expected)));
+  expected.push_back(1);
+  EXPECT_THAT(numbers, Not(IsSubsetOf(expected)));
+  expected.push_back(2);
+  EXPECT_THAT(numbers, IsSubsetOf(expected));
+  expected.push_back(3);
+  EXPECT_THAT(numbers, IsSubsetOf(expected));
+}
+
+TEST(IsSubsetOfTest, WorksForStreamlike) {
+  const int a[5] = {1, 2};
+  Streamlike<int> s(std::begin(a), std::end(a));
+
+  vector<int> expected;
+  expected.push_back(1);
+  EXPECT_THAT(s, Not(IsSubsetOf(expected)));
+  expected.push_back(2);
+  expected.push_back(5);
+  EXPECT_THAT(s, IsSubsetOf(expected));
+}
+
+TEST(IsSubsetOfTest, TakesStlContainer) {
+  const int actual[] = {3, 1, 2};
+
+  ::std::list<int> expected;
+  expected.push_back(1);
+  expected.push_back(3);
+  EXPECT_THAT(actual, Not(IsSubsetOf(expected)));
+
+  expected.push_back(2);
+  expected.push_back(4);
+  EXPECT_THAT(actual, IsSubsetOf(expected));
+}
+
+TEST(IsSubsetOfTest, Describe) {
+  typedef std::vector<int> IntVec;
+  IntVec expected;
+  expected.push_back(111);
+  expected.push_back(222);
+  expected.push_back(333);
+
+  EXPECT_THAT(
+      Describe<IntVec>(IsSubsetOf(expected)),
+      Eq("an injection from elements to requirements exists such that:\n"
+         " - an element is equal to 111\n"
+         " - an element is equal to 222\n"
+         " - an element is equal to 333"));
+}
+
+TEST(IsSubsetOfTest, DescribeNegation) {
+  typedef std::vector<int> IntVec;
+  IntVec expected;
+  expected.push_back(111);
+  expected.push_back(222);
+  expected.push_back(333);
+  EXPECT_THAT(
+      DescribeNegation<IntVec>(IsSubsetOf(expected)),
+      Eq("no injection from elements to requirements exists such that:\n"
+         " - an element is equal to 111\n"
+         " - an element is equal to 222\n"
+         " - an element is equal to 333"));
+}
+
+TEST(IsSubsetOfTest, MatchAndExplain) {
+  std::vector<int> v;
+  v.push_back(2);
+  v.push_back(3);
+  std::vector<int> expected;
+  expected.push_back(1);
+  expected.push_back(2);
+  StringMatchResultListener listener;
+  ASSERT_FALSE(ExplainMatchResult(IsSubsetOf(expected), v, &listener))
+      << listener.str();
+  EXPECT_THAT(listener.str(),
+              Eq("where the following elements don't match any matchers:\n"
+                 "element #1: 3"));
+
+  expected.push_back(3);
+  listener.Clear();
+  ASSERT_TRUE(ExplainMatchResult(IsSubsetOf(expected), v, &listener))
+      << listener.str();
+  EXPECT_THAT(listener.str(), Eq("where:\n"
+                                 " - element #0 is matched by matcher #1,\n"
+                                 " - element #1 is matched by matcher #2"));
+}
+
+TEST(IsSubsetOfTest, WorksForRhsInitializerList) {
+  const int numbers[] = {1, 2, 3};
+  EXPECT_THAT(numbers, IsSubsetOf({1, 2, 3, 4}));
+  EXPECT_THAT(numbers, Not(IsSubsetOf({1, 2})));
+}
+
+TEST(IsSubsetOfTest, WorksWithMoveOnly) {
+  ContainerHelper helper;
+  EXPECT_CALL(helper, Call(IsSubsetOf({Pointee(1), Pointee(2)})));
+  helper.Call(MakeUniquePtrs({1}));
+  EXPECT_CALL(helper, Call(Not(IsSubsetOf({Pointee(1)}))));
+  helper.Call(MakeUniquePtrs({2}));
+}
+
+// Tests using ElementsAre() and ElementsAreArray() with stream-like
+// "containers".
+
+TEST(ElemensAreStreamTest, WorksForStreamlike) {
+  const int a[5] = {1, 2, 3, 4, 5};
+  Streamlike<int> s(std::begin(a), std::end(a));
+  EXPECT_THAT(s, ElementsAre(1, 2, 3, 4, 5));
+  EXPECT_THAT(s, Not(ElementsAre(2, 1, 4, 5, 3)));
+}
+
+TEST(ElemensAreArrayStreamTest, WorksForStreamlike) {
+  const int a[5] = {1, 2, 3, 4, 5};
+  Streamlike<int> s(std::begin(a), std::end(a));
+
+  vector<int> expected;
+  expected.push_back(1);
+  expected.push_back(2);
+  expected.push_back(3);
+  expected.push_back(4);
+  expected.push_back(5);
+  EXPECT_THAT(s, ElementsAreArray(expected));
+
+  expected[3] = 0;
+  EXPECT_THAT(s, Not(ElementsAreArray(expected)));
+}
+
+TEST(ElementsAreTest, WorksWithUncopyable) {
+  Uncopyable objs[2];
+  objs[0].set_value(-3);
+  objs[1].set_value(1);
+  EXPECT_THAT(objs, ElementsAre(UncopyableIs(-3), Truly(ValueIsPositive)));
+}
+
+TEST(ElementsAreTest, WorksWithMoveOnly) {
+  ContainerHelper helper;
+  EXPECT_CALL(helper, Call(ElementsAre(Pointee(1), Pointee(2))));
+  helper.Call(MakeUniquePtrs({1, 2}));
+
+  EXPECT_CALL(helper, Call(ElementsAreArray({Pointee(3), Pointee(4)})));
+  helper.Call(MakeUniquePtrs({3, 4}));
+}
+
+TEST(ElementsAreTest, TakesStlContainer) {
+  const int actual[] = {3, 1, 2};
+
+  ::std::list<int> expected;
+  expected.push_back(3);
+  expected.push_back(1);
+  expected.push_back(2);
+  EXPECT_THAT(actual, ElementsAreArray(expected));
+
+  expected.push_back(4);
+  EXPECT_THAT(actual, Not(ElementsAreArray(expected)));
+}
+
+// Tests for UnorderedElementsAreArray()
+
+TEST(UnorderedElementsAreArrayTest, SucceedsWhenExpected) {
+  const int a[] = {0, 1, 2, 3, 4};
+  std::vector<int> s(std::begin(a), std::end(a));
+  do {
+    StringMatchResultListener listener;
+    EXPECT_TRUE(ExplainMatchResult(UnorderedElementsAreArray(a), s, &listener))
+        << listener.str();
+  } while (std::next_permutation(s.begin(), s.end()));
+}
+
+TEST(UnorderedElementsAreArrayTest, VectorBool) {
+  const bool a[] = {false, true, false, true, true};
+  const bool b[] = {true, false, true, true, false};
+  std::vector<bool> expected(std::begin(a), std::end(a));
+  std::vector<bool> actual(std::begin(b), std::end(b));
+  StringMatchResultListener listener;
+  EXPECT_TRUE(ExplainMatchResult(UnorderedElementsAreArray(expected), actual,
+                                 &listener))
+      << listener.str();
+}
+
+TEST(UnorderedElementsAreArrayTest, WorksForStreamlike) {
+  // Streamlike 'container' provides only minimal iterator support.
+  // Its iterators are tagged with input_iterator_tag, and it has no
+  // size() or empty() methods.
+  const int a[5] = {2, 1, 4, 5, 3};
+  Streamlike<int> s(std::begin(a), std::end(a));
+
+  ::std::vector<int> expected;
+  expected.push_back(1);
+  expected.push_back(2);
+  expected.push_back(3);
+  expected.push_back(4);
+  expected.push_back(5);
+  EXPECT_THAT(s, UnorderedElementsAreArray(expected));
+
+  expected.push_back(6);
+  EXPECT_THAT(s, Not(UnorderedElementsAreArray(expected)));
+}
+
+TEST(UnorderedElementsAreArrayTest, TakesStlContainer) {
+  const int actual[] = {3, 1, 2};
+
+  ::std::list<int> expected;
+  expected.push_back(1);
+  expected.push_back(2);
+  expected.push_back(3);
+  EXPECT_THAT(actual, UnorderedElementsAreArray(expected));
+
+  expected.push_back(4);
+  EXPECT_THAT(actual, Not(UnorderedElementsAreArray(expected)));
+}
+
+TEST(UnorderedElementsAreArrayTest, TakesInitializerList) {
+  const int a[5] = {2, 1, 4, 5, 3};
+  EXPECT_THAT(a, UnorderedElementsAreArray({1, 2, 3, 4, 5}));
+  EXPECT_THAT(a, Not(UnorderedElementsAreArray({1, 2, 3, 4, 6})));
+}
+
+TEST(UnorderedElementsAreArrayTest, TakesInitializerListOfCStrings) {
+  const std::string a[5] = {"a", "b", "c", "d", "e"};
+  EXPECT_THAT(a, UnorderedElementsAreArray({"a", "b", "c", "d", "e"}));
+  EXPECT_THAT(a, Not(UnorderedElementsAreArray({"a", "b", "c", "d", "ef"})));
+}
+
+TEST(UnorderedElementsAreArrayTest, TakesInitializerListOfSameTypedMatchers) {
+  const int a[5] = {2, 1, 4, 5, 3};
+  EXPECT_THAT(a,
+              UnorderedElementsAreArray({Eq(1), Eq(2), Eq(3), Eq(4), Eq(5)}));
+  EXPECT_THAT(
+      a, Not(UnorderedElementsAreArray({Eq(1), Eq(2), Eq(3), Eq(4), Eq(6)})));
+}
+
+TEST(UnorderedElementsAreArrayTest,
+     TakesInitializerListOfDifferentTypedMatchers) {
+  const int a[5] = {2, 1, 4, 5, 3};
+  // The compiler cannot infer the type of the initializer list if its
+  // elements have different types.  We must explicitly specify the
+  // unified element type in this case.
+  EXPECT_THAT(a, UnorderedElementsAreArray<Matcher<int>>(
+                     {Eq(1), Ne(-2), Ge(3), Le(4), Eq(5)}));
+  EXPECT_THAT(a, Not(UnorderedElementsAreArray<Matcher<int>>(
+                     {Eq(1), Ne(-2), Ge(3), Le(4), Eq(6)})));
+}
+
+TEST(UnorderedElementsAreArrayTest, WorksWithMoveOnly) {
+  ContainerHelper helper;
+  EXPECT_CALL(helper,
+              Call(UnorderedElementsAreArray({Pointee(1), Pointee(2)})));
+  helper.Call(MakeUniquePtrs({2, 1}));
+}
+
+class UnorderedElementsAreTest : public testing::Test {
+ protected:
+  typedef std::vector<int> IntVec;
+};
+
+TEST_F(UnorderedElementsAreTest, WorksWithUncopyable) {
+  Uncopyable objs[2];
+  objs[0].set_value(-3);
+  objs[1].set_value(1);
+  EXPECT_THAT(objs,
+              UnorderedElementsAre(Truly(ValueIsPositive), UncopyableIs(-3)));
+}
+
+TEST_F(UnorderedElementsAreTest, SucceedsWhenExpected) {
+  const int a[] = {1, 2, 3};
+  std::vector<int> s(std::begin(a), std::end(a));
+  do {
+    StringMatchResultListener listener;
+    EXPECT_TRUE(ExplainMatchResult(UnorderedElementsAre(1, 2, 3), s, &listener))
+        << listener.str();
+  } while (std::next_permutation(s.begin(), s.end()));
+}
+
+TEST_F(UnorderedElementsAreTest, FailsWhenAnElementMatchesNoMatcher) {
+  const int a[] = {1, 2, 3};
+  std::vector<int> s(std::begin(a), std::end(a));
+  std::vector<Matcher<int>> mv;
+  mv.push_back(1);
+  mv.push_back(2);
+  mv.push_back(2);
+  // The element with value '3' matches nothing: fail fast.
+  StringMatchResultListener listener;
+  EXPECT_FALSE(ExplainMatchResult(UnorderedElementsAreArray(mv), s, &listener))
+      << listener.str();
+}
+
+TEST_F(UnorderedElementsAreTest, WorksForStreamlike) {
+  // Streamlike 'container' provides only minimal iterator support.
+  // Its iterators are tagged with input_iterator_tag, and it has no
+  // size() or empty() methods.
+  const int a[5] = {2, 1, 4, 5, 3};
+  Streamlike<int> s(std::begin(a), std::end(a));
+
+  EXPECT_THAT(s, UnorderedElementsAre(1, 2, 3, 4, 5));
+  EXPECT_THAT(s, Not(UnorderedElementsAre(2, 2, 3, 4, 5)));
+}
+
+TEST_F(UnorderedElementsAreTest, WorksWithMoveOnly) {
+  ContainerHelper helper;
+  EXPECT_CALL(helper, Call(UnorderedElementsAre(Pointee(1), Pointee(2))));
+  helper.Call(MakeUniquePtrs({2, 1}));
+}
+
+// One naive implementation of the matcher runs in O(N!) time, which is too
+// slow for many real-world inputs. This test shows that our matcher can match
+// 100 inputs very quickly (a few milliseconds).  An O(100!) is 10^158
+// iterations and obviously effectively incomputable.
+// [ RUN      ] UnorderedElementsAreTest.Performance
+// [       OK ] UnorderedElementsAreTest.Performance (4 ms)
+TEST_F(UnorderedElementsAreTest, Performance) {
+  std::vector<int> s;
+  std::vector<Matcher<int>> mv;
+  for (int i = 0; i < 100; ++i) {
+    s.push_back(i);
+    mv.push_back(_);
+  }
+  mv[50] = Eq(0);
+  StringMatchResultListener listener;
+  EXPECT_TRUE(ExplainMatchResult(UnorderedElementsAreArray(mv), s, &listener))
+      << listener.str();
+}
+
+// Another variant of 'Performance' with similar expectations.
+// [ RUN      ] UnorderedElementsAreTest.PerformanceHalfStrict
+// [       OK ] UnorderedElementsAreTest.PerformanceHalfStrict (4 ms)
+TEST_F(UnorderedElementsAreTest, PerformanceHalfStrict) {
+  std::vector<int> s;
+  std::vector<Matcher<int>> mv;
+  for (int i = 0; i < 100; ++i) {
+    s.push_back(i);
+    if (i & 1) {
+      mv.push_back(_);
+    } else {
+      mv.push_back(i);
+    }
+  }
+  StringMatchResultListener listener;
+  EXPECT_TRUE(ExplainMatchResult(UnorderedElementsAreArray(mv), s, &listener))
+      << listener.str();
+}
+
+TEST_F(UnorderedElementsAreTest, FailMessageCountWrong) {
+  std::vector<int> v;
+  v.push_back(4);
+  StringMatchResultListener listener;
+  EXPECT_FALSE(ExplainMatchResult(UnorderedElementsAre(1, 2, 3), v, &listener))
+      << listener.str();
+  EXPECT_THAT(listener.str(), Eq("which has 1 element"));
+}
+
+TEST_F(UnorderedElementsAreTest, FailMessageCountWrongZero) {
+  std::vector<int> v;
+  StringMatchResultListener listener;
+  EXPECT_FALSE(ExplainMatchResult(UnorderedElementsAre(1, 2, 3), v, &listener))
+      << listener.str();
+  EXPECT_THAT(listener.str(), Eq(""));
+}
+
+TEST_F(UnorderedElementsAreTest, FailMessageUnmatchedMatchers) {
+  std::vector<int> v;
+  v.push_back(1);
+  v.push_back(1);
+  StringMatchResultListener listener;
+  EXPECT_FALSE(ExplainMatchResult(UnorderedElementsAre(1, 2), v, &listener))
+      << listener.str();
+  EXPECT_THAT(listener.str(),
+              Eq("where the following matchers don't match any elements:\n"
+                 "matcher #1: is equal to 2"));
+}
+
+TEST_F(UnorderedElementsAreTest, FailMessageUnmatchedElements) {
+  std::vector<int> v;
+  v.push_back(1);
+  v.push_back(2);
+  StringMatchResultListener listener;
+  EXPECT_FALSE(ExplainMatchResult(UnorderedElementsAre(1, 1), v, &listener))
+      << listener.str();
+  EXPECT_THAT(listener.str(),
+              Eq("where the following elements don't match any matchers:\n"
+                 "element #1: 2"));
+}
+
+TEST_F(UnorderedElementsAreTest, FailMessageUnmatchedMatcherAndElement) {
+  std::vector<int> v;
+  v.push_back(2);
+  v.push_back(3);
+  StringMatchResultListener listener;
+  EXPECT_FALSE(ExplainMatchResult(UnorderedElementsAre(1, 2), v, &listener))
+      << listener.str();
+  EXPECT_THAT(listener.str(),
+              Eq("where"
+                 " the following matchers don't match any elements:\n"
+                 "matcher #0: is equal to 1\n"
+                 "and"
+                 " where"
+                 " the following elements don't match any matchers:\n"
+                 "element #1: 3"));
+}
+
+// Test helper for formatting element, matcher index pairs in expectations.
+static std::string EMString(int element, int matcher) {
+  stringstream ss;
+  ss << "(element #" << element << ", matcher #" << matcher << ")";
+  return ss.str();
+}
+
+TEST_F(UnorderedElementsAreTest, FailMessageImperfectMatchOnly) {
+  // A situation where all elements and matchers have a match
+  // associated with them, but the max matching is not perfect.
+  std::vector<std::string> v;
+  v.push_back("a");
+  v.push_back("b");
+  v.push_back("c");
+  StringMatchResultListener listener;
+  EXPECT_FALSE(ExplainMatchResult(
+      UnorderedElementsAre("a", "a", AnyOf("b", "c")), v, &listener))
+      << listener.str();
+
+  std::string prefix =
+      "where no permutation of the elements can satisfy all matchers, "
+      "and the closest match is 2 of 3 matchers with the "
+      "pairings:\n";
+
+  // We have to be a bit loose here, because there are 4 valid max matches.
+  EXPECT_THAT(
+      listener.str(),
+      AnyOf(
+          prefix + "{\n  " + EMString(0, 0) + ",\n  " + EMString(1, 2) + "\n}",
+          prefix + "{\n  " + EMString(0, 1) + ",\n  " + EMString(1, 2) + "\n}",
+          prefix + "{\n  " + EMString(0, 0) + ",\n  " + EMString(2, 2) + "\n}",
+          prefix + "{\n  " + EMString(0, 1) + ",\n  " + EMString(2, 2) +
+              "\n}"));
+}
+
+TEST_F(UnorderedElementsAreTest, Describe) {
+  EXPECT_THAT(Describe<IntVec>(UnorderedElementsAre()), Eq("is empty"));
+  EXPECT_THAT(Describe<IntVec>(UnorderedElementsAre(345)),
+              Eq("has 1 element and that element is equal to 345"));
+  EXPECT_THAT(Describe<IntVec>(UnorderedElementsAre(111, 222, 333)),
+              Eq("has 3 elements and there exists some permutation "
+                 "of elements such that:\n"
+                 " - element #0 is equal to 111, and\n"
+                 " - element #1 is equal to 222, and\n"
+                 " - element #2 is equal to 333"));
+}
+
+TEST_F(UnorderedElementsAreTest, DescribeNegation) {
+  EXPECT_THAT(DescribeNegation<IntVec>(UnorderedElementsAre()),
+              Eq("isn't empty"));
+  EXPECT_THAT(
+      DescribeNegation<IntVec>(UnorderedElementsAre(345)),
+      Eq("doesn't have 1 element, or has 1 element that isn't equal to 345"));
+  EXPECT_THAT(DescribeNegation<IntVec>(UnorderedElementsAre(123, 234, 345)),
+              Eq("doesn't have 3 elements, or there exists no permutation "
+                 "of elements such that:\n"
+                 " - element #0 is equal to 123, and\n"
+                 " - element #1 is equal to 234, and\n"
+                 " - element #2 is equal to 345"));
+}
+
+// Tests Each().
+
+INSTANTIATE_GTEST_MATCHER_TEST_P(EachTest);
+
+TEST_P(EachTestP, ExplainsMatchResultCorrectly) {
+  set<int> a;  // empty
+
+  Matcher<set<int>> m = Each(2);
+  EXPECT_EQ("", Explain(m, a));
+
+  Matcher<const int(&)[1]> n = Each(1);  // NOLINT
+
+  const int b[1] = {1};
+  EXPECT_EQ("", Explain(n, b));
+
+  n = Each(3);
+  EXPECT_EQ("whose element #0 doesn't match", Explain(n, b));
+
+  a.insert(1);
+  a.insert(2);
+  a.insert(3);
+  m = Each(GreaterThan(0));
+  EXPECT_EQ("", Explain(m, a));
+
+  m = Each(GreaterThan(10));
+  EXPECT_EQ("whose element #0 doesn't match, which is 9 less than 10",
+            Explain(m, a));
+}
+
+TEST(EachTest, DescribesItselfCorrectly) {
+  Matcher<vector<int>> m = Each(1);
+  EXPECT_EQ("only contains elements that is equal to 1", Describe(m));
+
+  Matcher<vector<int>> m2 = Not(m);
+  EXPECT_EQ("contains some element that isn't equal to 1", Describe(m2));
+}
+
+TEST(EachTest, MatchesVectorWhenAllElementsMatch) {
+  vector<int> some_vector;
+  EXPECT_THAT(some_vector, Each(1));
+  some_vector.push_back(3);
+  EXPECT_THAT(some_vector, Not(Each(1)));
+  EXPECT_THAT(some_vector, Each(3));
+  some_vector.push_back(1);
+  some_vector.push_back(2);
+  EXPECT_THAT(some_vector, Not(Each(3)));
+  EXPECT_THAT(some_vector, Each(Lt(3.5)));
+
+  vector<std::string> another_vector;
+  another_vector.push_back("fee");
+  EXPECT_THAT(another_vector, Each(std::string("fee")));
+  another_vector.push_back("fie");
+  another_vector.push_back("foe");
+  another_vector.push_back("fum");
+  EXPECT_THAT(another_vector, Not(Each(std::string("fee"))));
+}
+
+TEST(EachTest, MatchesMapWhenAllElementsMatch) {
+  map<const char*, int> my_map;
+  const char* bar = "a string";
+  my_map[bar] = 2;
+  EXPECT_THAT(my_map, Each(make_pair(bar, 2)));
+
+  map<std::string, int> another_map;
+  EXPECT_THAT(another_map, Each(make_pair(std::string("fee"), 1)));
+  another_map["fee"] = 1;
+  EXPECT_THAT(another_map, Each(make_pair(std::string("fee"), 1)));
+  another_map["fie"] = 2;
+  another_map["foe"] = 3;
+  another_map["fum"] = 4;
+  EXPECT_THAT(another_map, Not(Each(make_pair(std::string("fee"), 1))));
+  EXPECT_THAT(another_map, Not(Each(make_pair(std::string("fum"), 1))));
+  EXPECT_THAT(another_map, Each(Pair(_, Gt(0))));
+}
+
+TEST(EachTest, AcceptsMatcher) {
+  const int a[] = {1, 2, 3};
+  EXPECT_THAT(a, Each(Gt(0)));
+  EXPECT_THAT(a, Not(Each(Gt(1))));
+}
+
+TEST(EachTest, WorksForNativeArrayAsTuple) {
+  const int a[] = {1, 2};
+  const int* const pointer = a;
+  EXPECT_THAT(std::make_tuple(pointer, 2), Each(Gt(0)));
+  EXPECT_THAT(std::make_tuple(pointer, 2), Not(Each(Gt(1))));
+}
+
+TEST(EachTest, WorksWithMoveOnly) {
+  ContainerHelper helper;
+  EXPECT_CALL(helper, Call(Each(Pointee(Gt(0)))));
+  helper.Call(MakeUniquePtrs({1, 2}));
+}
+
+// For testing Pointwise().
+class IsHalfOfMatcher {
+ public:
+  template <typename T1, typename T2>
+  bool MatchAndExplain(const std::tuple<T1, T2>& a_pair,
+                       MatchResultListener* listener) const {
+    if (std::get<0>(a_pair) == std::get<1>(a_pair) / 2) {
+      *listener << "where the second is " << std::get<1>(a_pair);
+      return true;
+    } else {
+      *listener << "where the second/2 is " << std::get<1>(a_pair) / 2;
+      return false;
+    }
+  }
+
+  void DescribeTo(ostream* os) const {
+    *os << "are a pair where the first is half of the second";
+  }
+
+  void DescribeNegationTo(ostream* os) const {
+    *os << "are a pair where the first isn't half of the second";
+  }
+};
+
+PolymorphicMatcher<IsHalfOfMatcher> IsHalfOf() {
+  return MakePolymorphicMatcher(IsHalfOfMatcher());
+}
+
+TEST(PointwiseTest, DescribesSelf) {
+  vector<int> rhs;
+  rhs.push_back(1);
+  rhs.push_back(2);
+  rhs.push_back(3);
+  const Matcher<const vector<int>&> m = Pointwise(IsHalfOf(), rhs);
+  EXPECT_EQ(
+      "contains 3 values, where each value and its corresponding value "
+      "in { 1, 2, 3 } are a pair where the first is half of the second",
+      Describe(m));
+  EXPECT_EQ(
+      "doesn't contain exactly 3 values, or contains a value x at some "
+      "index i where x and the i-th value of { 1, 2, 3 } are a pair "
+      "where the first isn't half of the second",
+      DescribeNegation(m));
+}
+
+TEST(PointwiseTest, MakesCopyOfRhs) {
+  list<signed char> rhs;
+  rhs.push_back(2);
+  rhs.push_back(4);
+
+  int lhs[] = {1, 2};
+  const Matcher<const int(&)[2]> m = Pointwise(IsHalfOf(), rhs);
+  EXPECT_THAT(lhs, m);
+
+  // Changing rhs now shouldn't affect m, which made a copy of rhs.
+  rhs.push_back(6);
+  EXPECT_THAT(lhs, m);
+}
+
+TEST(PointwiseTest, WorksForLhsNativeArray) {
+  const int lhs[] = {1, 2, 3};
+  vector<int> rhs;
+  rhs.push_back(2);
+  rhs.push_back(4);
+  rhs.push_back(6);
+  EXPECT_THAT(lhs, Pointwise(Lt(), rhs));
+  EXPECT_THAT(lhs, Not(Pointwise(Gt(), rhs)));
+}
+
+TEST(PointwiseTest, WorksForRhsNativeArray) {
+  const int rhs[] = {1, 2, 3};
+  vector<int> lhs;
+  lhs.push_back(2);
+  lhs.push_back(4);
+  lhs.push_back(6);
+  EXPECT_THAT(lhs, Pointwise(Gt(), rhs));
+  EXPECT_THAT(lhs, Not(Pointwise(Lt(), rhs)));
+}
+
+// Test is effective only with sanitizers.
+TEST(PointwiseTest, WorksForVectorOfBool) {
+  vector<bool> rhs(3, false);
+  rhs[1] = true;
+  vector<bool> lhs = rhs;
+  EXPECT_THAT(lhs, Pointwise(Eq(), rhs));
+  rhs[0] = true;
+  EXPECT_THAT(lhs, Not(Pointwise(Eq(), rhs)));
+}
+
+TEST(PointwiseTest, WorksForRhsInitializerList) {
+  const vector<int> lhs{2, 4, 6};
+  EXPECT_THAT(lhs, Pointwise(Gt(), {1, 2, 3}));
+  EXPECT_THAT(lhs, Not(Pointwise(Lt(), {3, 3, 7})));
+}
+
+TEST(PointwiseTest, RejectsWrongSize) {
+  const double lhs[2] = {1, 2};
+  const int rhs[1] = {0};
+  EXPECT_THAT(lhs, Not(Pointwise(Gt(), rhs)));
+  EXPECT_EQ("which contains 2 values", Explain(Pointwise(Gt(), rhs), lhs));
+
+  const int rhs2[3] = {0, 1, 2};
+  EXPECT_THAT(lhs, Not(Pointwise(Gt(), rhs2)));
+}
+
+TEST(PointwiseTest, RejectsWrongContent) {
+  const double lhs[3] = {1, 2, 3};
+  const int rhs[3] = {2, 6, 4};
+  EXPECT_THAT(lhs, Not(Pointwise(IsHalfOf(), rhs)));
+  EXPECT_EQ(
+      "where the value pair (2, 6) at index #1 don't match, "
+      "where the second/2 is 3",
+      Explain(Pointwise(IsHalfOf(), rhs), lhs));
+}
+
+TEST(PointwiseTest, AcceptsCorrectContent) {
+  const double lhs[3] = {1, 2, 3};
+  const int rhs[3] = {2, 4, 6};
+  EXPECT_THAT(lhs, Pointwise(IsHalfOf(), rhs));
+  EXPECT_EQ("", Explain(Pointwise(IsHalfOf(), rhs), lhs));
+}
+
+TEST(PointwiseTest, AllowsMonomorphicInnerMatcher) {
+  const double lhs[3] = {1, 2, 3};
+  const int rhs[3] = {2, 4, 6};
+  const Matcher<std::tuple<const double&, const int&>> m1 = IsHalfOf();
+  EXPECT_THAT(lhs, Pointwise(m1, rhs));
+  EXPECT_EQ("", Explain(Pointwise(m1, rhs), lhs));
+
+  // This type works as a std::tuple<const double&, const int&> can be
+  // implicitly cast to std::tuple<double, int>.
+  const Matcher<std::tuple<double, int>> m2 = IsHalfOf();
+  EXPECT_THAT(lhs, Pointwise(m2, rhs));
+  EXPECT_EQ("", Explain(Pointwise(m2, rhs), lhs));
+}
+
+MATCHER(PointeeEquals, "Points to an equal value") {
+  return ExplainMatchResult(::testing::Pointee(::testing::get<1>(arg)),
+                            ::testing::get<0>(arg), result_listener);
+}
+
+TEST(PointwiseTest, WorksWithMoveOnly) {
+  ContainerHelper helper;
+  EXPECT_CALL(helper, Call(Pointwise(PointeeEquals(), std::vector<int>{1, 2})));
+  helper.Call(MakeUniquePtrs({1, 2}));
+}
+
+TEST(UnorderedPointwiseTest, DescribesSelf) {
+  vector<int> rhs;
+  rhs.push_back(1);
+  rhs.push_back(2);
+  rhs.push_back(3);
+  const Matcher<const vector<int>&> m = UnorderedPointwise(IsHalfOf(), rhs);
+  EXPECT_EQ(
+      "has 3 elements and there exists some permutation of elements such "
+      "that:\n"
+      " - element #0 and 1 are a pair where the first is half of the second, "
+      "and\n"
+      " - element #1 and 2 are a pair where the first is half of the second, "
+      "and\n"
+      " - element #2 and 3 are a pair where the first is half of the second",
+      Describe(m));
+  EXPECT_EQ(
+      "doesn't have 3 elements, or there exists no permutation of elements "
+      "such that:\n"
+      " - element #0 and 1 are a pair where the first is half of the second, "
+      "and\n"
+      " - element #1 and 2 are a pair where the first is half of the second, "
+      "and\n"
+      " - element #2 and 3 are a pair where the first is half of the second",
+      DescribeNegation(m));
+}
+
+TEST(UnorderedPointwiseTest, MakesCopyOfRhs) {
+  list<signed char> rhs;
+  rhs.push_back(2);
+  rhs.push_back(4);
+
+  int lhs[] = {2, 1};
+  const Matcher<const int(&)[2]> m = UnorderedPointwise(IsHalfOf(), rhs);
+  EXPECT_THAT(lhs, m);
+
+  // Changing rhs now shouldn't affect m, which made a copy of rhs.
+  rhs.push_back(6);
+  EXPECT_THAT(lhs, m);
+}
+
+TEST(UnorderedPointwiseTest, WorksForLhsNativeArray) {
+  const int lhs[] = {1, 2, 3};
+  vector<int> rhs;
+  rhs.push_back(4);
+  rhs.push_back(6);
+  rhs.push_back(2);
+  EXPECT_THAT(lhs, UnorderedPointwise(Lt(), rhs));
+  EXPECT_THAT(lhs, Not(UnorderedPointwise(Gt(), rhs)));
+}
+
+TEST(UnorderedPointwiseTest, WorksForRhsNativeArray) {
+  const int rhs[] = {1, 2, 3};
+  vector<int> lhs;
+  lhs.push_back(4);
+  lhs.push_back(2);
+  lhs.push_back(6);
+  EXPECT_THAT(lhs, UnorderedPointwise(Gt(), rhs));
+  EXPECT_THAT(lhs, Not(UnorderedPointwise(Lt(), rhs)));
+}
+
+TEST(UnorderedPointwiseTest, WorksForRhsInitializerList) {
+  const vector<int> lhs{2, 4, 6};
+  EXPECT_THAT(lhs, UnorderedPointwise(Gt(), {5, 1, 3}));
+  EXPECT_THAT(lhs, Not(UnorderedPointwise(Lt(), {1, 1, 7})));
+}
+
+TEST(UnorderedPointwiseTest, RejectsWrongSize) {
+  const double lhs[2] = {1, 2};
+  const int rhs[1] = {0};
+  EXPECT_THAT(lhs, Not(UnorderedPointwise(Gt(), rhs)));
+  EXPECT_EQ("which has 2 elements",
+            Explain(UnorderedPointwise(Gt(), rhs), lhs));
+
+  const int rhs2[3] = {0, 1, 2};
+  EXPECT_THAT(lhs, Not(UnorderedPointwise(Gt(), rhs2)));
+}
+
+TEST(UnorderedPointwiseTest, RejectsWrongContent) {
+  const double lhs[3] = {1, 2, 3};
+  const int rhs[3] = {2, 6, 6};
+  EXPECT_THAT(lhs, Not(UnorderedPointwise(IsHalfOf(), rhs)));
+  EXPECT_EQ(
+      "where the following elements don't match any matchers:\n"
+      "element #1: 2",
+      Explain(UnorderedPointwise(IsHalfOf(), rhs), lhs));
+}
+
+TEST(UnorderedPointwiseTest, AcceptsCorrectContentInSameOrder) {
+  const double lhs[3] = {1, 2, 3};
+  const int rhs[3] = {2, 4, 6};
+  EXPECT_THAT(lhs, UnorderedPointwise(IsHalfOf(), rhs));
+}
+
+TEST(UnorderedPointwiseTest, AcceptsCorrectContentInDifferentOrder) {
+  const double lhs[3] = {1, 2, 3};
+  const int rhs[3] = {6, 4, 2};
+  EXPECT_THAT(lhs, UnorderedPointwise(IsHalfOf(), rhs));
+}
+
+TEST(UnorderedPointwiseTest, AllowsMonomorphicInnerMatcher) {
+  const double lhs[3] = {1, 2, 3};
+  const int rhs[3] = {4, 6, 2};
+  const Matcher<std::tuple<const double&, const int&>> m1 = IsHalfOf();
+  EXPECT_THAT(lhs, UnorderedPointwise(m1, rhs));
+
+  // This type works as a std::tuple<const double&, const int&> can be
+  // implicitly cast to std::tuple<double, int>.
+  const Matcher<std::tuple<double, int>> m2 = IsHalfOf();
+  EXPECT_THAT(lhs, UnorderedPointwise(m2, rhs));
+}
+
+TEST(UnorderedPointwiseTest, WorksWithMoveOnly) {
+  ContainerHelper helper;
+  EXPECT_CALL(helper, Call(UnorderedPointwise(PointeeEquals(),
+                                              std::vector<int>{1, 2})));
+  helper.Call(MakeUniquePtrs({2, 1}));
+}
+
+TEST(PointeeTest, WorksOnMoveOnlyType) {
+  std::unique_ptr<int> p(new int(3));
+  EXPECT_THAT(p, Pointee(Eq(3)));
+  EXPECT_THAT(p, Not(Pointee(Eq(2))));
+}
+
+class PredicateFormatterFromMatcherTest : public ::testing::Test {
+ protected:
+  enum Behavior { kInitialSuccess, kAlwaysFail, kFlaky };
+
+  // A matcher that can return different results when used multiple times on the
+  // same input. No real matcher should do this; but this lets us test that we
+  // detect such behavior and fail appropriately.
+  class MockMatcher : public MatcherInterface<Behavior> {
+   public:
+    bool MatchAndExplain(Behavior behavior,
+                         MatchResultListener* listener) const override {
+      *listener << "[MatchAndExplain]";
+      switch (behavior) {
+        case kInitialSuccess:
+          // The first call to MatchAndExplain should use a "not interested"
+          // listener; so this is expected to return |true|. There should be no
+          // subsequent calls.
+          return !listener->IsInterested();
+
+        case kAlwaysFail:
+          return false;
+
+        case kFlaky:
+          // The first call to MatchAndExplain should use a "not interested"
+          // listener; so this will return |false|. Subsequent calls should have
+          // an "interested" listener; so this will return |true|, thus
+          // simulating a flaky matcher.
+          return listener->IsInterested();
+      }
+
+      GTEST_LOG_(FATAL) << "This should never be reached";
+      return false;
+    }
+
+    void DescribeTo(ostream* os) const override { *os << "[DescribeTo]"; }
+
+    void DescribeNegationTo(ostream* os) const override {
+      *os << "[DescribeNegationTo]";
+    }
+  };
+
+  AssertionResult RunPredicateFormatter(Behavior behavior) {
+    auto matcher = MakeMatcher(new MockMatcher);
+    PredicateFormatterFromMatcher<Matcher<Behavior>> predicate_formatter(
+        matcher);
+    return predicate_formatter("dummy-name", behavior);
+  }
+};
+
+TEST_F(PredicateFormatterFromMatcherTest, ShortCircuitOnSuccess) {
+  AssertionResult result = RunPredicateFormatter(kInitialSuccess);
+  EXPECT_TRUE(result);  // Implicit cast to bool.
+  std::string expect;
+  EXPECT_EQ(expect, result.message());
+}
+
+TEST_F(PredicateFormatterFromMatcherTest, NoShortCircuitOnFailure) {
+  AssertionResult result = RunPredicateFormatter(kAlwaysFail);
+  EXPECT_FALSE(result);  // Implicit cast to bool.
+  std::string expect =
+      "Value of: dummy-name\nExpected: [DescribeTo]\n"
+      "  Actual: 1" +
+      OfType(internal::GetTypeName<Behavior>()) + ", [MatchAndExplain]";
+  EXPECT_EQ(expect, result.message());
+}
+
+TEST_F(PredicateFormatterFromMatcherTest, DetectsFlakyShortCircuit) {
+  AssertionResult result = RunPredicateFormatter(kFlaky);
+  EXPECT_FALSE(result);  // Implicit cast to bool.
+  std::string expect =
+      "Value of: dummy-name\nExpected: [DescribeTo]\n"
+      "  The matcher failed on the initial attempt; but passed when rerun to "
+      "generate the explanation.\n"
+      "  Actual: 2" +
+      OfType(internal::GetTypeName<Behavior>()) + ", [MatchAndExplain]";
+  EXPECT_EQ(expect, result.message());
+}
+
+// Tests for ElementsAre().
+
+TEST(ElementsAreTest, CanDescribeExpectingNoElement) {
+  Matcher<const vector<int>&> m = ElementsAre();
+  EXPECT_EQ("is empty", Describe(m));
+}
+
+TEST(ElementsAreTest, CanDescribeExpectingOneElement) {
+  Matcher<vector<int>> m = ElementsAre(Gt(5));
+  EXPECT_EQ("has 1 element that is > 5", Describe(m));
+}
+
+TEST(ElementsAreTest, CanDescribeExpectingManyElements) {
+  Matcher<list<std::string>> m = ElementsAre(StrEq("one"), "two");
+  EXPECT_EQ(
+      "has 2 elements where\n"
+      "element #0 is equal to \"one\",\n"
+      "element #1 is equal to \"two\"",
+      Describe(m));
+}
+
+TEST(ElementsAreTest, CanDescribeNegationOfExpectingNoElement) {
+  Matcher<vector<int>> m = ElementsAre();
+  EXPECT_EQ("isn't empty", DescribeNegation(m));
+}
+
+TEST(ElementsAreTest, CanDescribeNegationOfExpectingOneElement) {
+  Matcher<const list<int>&> m = ElementsAre(Gt(5));
+  EXPECT_EQ(
+      "doesn't have 1 element, or\n"
+      "element #0 isn't > 5",
+      DescribeNegation(m));
+}
+
+TEST(ElementsAreTest, CanDescribeNegationOfExpectingManyElements) {
+  Matcher<const list<std::string>&> m = ElementsAre("one", "two");
+  EXPECT_EQ(
+      "doesn't have 2 elements, or\n"
+      "element #0 isn't equal to \"one\", or\n"
+      "element #1 isn't equal to \"two\"",
+      DescribeNegation(m));
+}
+
+TEST(ElementsAreTest, DoesNotExplainTrivialMatch) {
+  Matcher<const list<int>&> m = ElementsAre(1, Ne(2));
+
+  list<int> test_list;
+  test_list.push_back(1);
+  test_list.push_back(3);
+  EXPECT_EQ("", Explain(m, test_list));  // No need to explain anything.
+}
+
+TEST_P(ElementsAreTestP, ExplainsNonTrivialMatch) {
+  Matcher<const vector<int>&> m =
+      ElementsAre(GreaterThan(1), 0, GreaterThan(2));
+
+  const int a[] = {10, 0, 100};
+  vector<int> test_vector(std::begin(a), std::end(a));
+  EXPECT_EQ(
+      "whose element #0 matches, which is 9 more than 1,\n"
+      "and whose element #2 matches, which is 98 more than 2",
+      Explain(m, test_vector));
+}
+
+TEST(ElementsAreTest, CanExplainMismatchWrongSize) {
+  Matcher<const list<int>&> m = ElementsAre(1, 3);
+
+  list<int> test_list;
+  // No need to explain when the container is empty.
+  EXPECT_EQ("", Explain(m, test_list));
+
+  test_list.push_back(1);
+  EXPECT_EQ("which has 1 element", Explain(m, test_list));
+}
+
+TEST_P(ElementsAreTestP, CanExplainMismatchRightSize) {
+  Matcher<const vector<int>&> m = ElementsAre(1, GreaterThan(5));
+
+  vector<int> v;
+  v.push_back(2);
+  v.push_back(1);
+  EXPECT_EQ("whose element #0 doesn't match", Explain(m, v));
+
+  v[0] = 1;
+  EXPECT_EQ("whose element #1 doesn't match, which is 4 less than 5",
+            Explain(m, v));
+}
+
+TEST(ElementsAreTest, MatchesOneElementVector) {
+  vector<std::string> test_vector;
+  test_vector.push_back("test string");
+
+  EXPECT_THAT(test_vector, ElementsAre(StrEq("test string")));
+}
+
+TEST(ElementsAreTest, MatchesOneElementList) {
+  list<std::string> test_list;
+  test_list.push_back("test string");
+
+  EXPECT_THAT(test_list, ElementsAre("test string"));
+}
+
+TEST(ElementsAreTest, MatchesThreeElementVector) {
+  vector<std::string> test_vector;
+  test_vector.push_back("one");
+  test_vector.push_back("two");
+  test_vector.push_back("three");
+
+  EXPECT_THAT(test_vector, ElementsAre("one", StrEq("two"), _));
+}
+
+TEST(ElementsAreTest, MatchesOneElementEqMatcher) {
+  vector<int> test_vector;
+  test_vector.push_back(4);
+
+  EXPECT_THAT(test_vector, ElementsAre(Eq(4)));
+}
+
+TEST(ElementsAreTest, MatchesOneElementAnyMatcher) {
+  vector<int> test_vector;
+  test_vector.push_back(4);
+
+  EXPECT_THAT(test_vector, ElementsAre(_));
+}
+
+TEST(ElementsAreTest, MatchesOneElementValue) {
+  vector<int> test_vector;
+  test_vector.push_back(4);
+
+  EXPECT_THAT(test_vector, ElementsAre(4));
+}
+
+TEST(ElementsAreTest, MatchesThreeElementsMixedMatchers) {
+  vector<int> test_vector;
+  test_vector.push_back(1);
+  test_vector.push_back(2);
+  test_vector.push_back(3);
+
+  EXPECT_THAT(test_vector, ElementsAre(1, Eq(2), _));
+}
+
+TEST(ElementsAreTest, MatchesTenElementVector) {
+  const int a[] = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9};
+  vector<int> test_vector(std::begin(a), std::end(a));
+
+  EXPECT_THAT(test_vector,
+              // The element list can contain values and/or matchers
+              // of different types.
+              ElementsAre(0, Ge(0), _, 3, 4, Ne(2), Eq(6), 7, 8, _));
+}
+
+TEST(ElementsAreTest, DoesNotMatchWrongSize) {
+  vector<std::string> test_vector;
+  test_vector.push_back("test string");
+  test_vector.push_back("test string");
+
+  Matcher<vector<std::string>> m = ElementsAre(StrEq("test string"));
+  EXPECT_FALSE(m.Matches(test_vector));
+}
+
+TEST(ElementsAreTest, DoesNotMatchWrongValue) {
+  vector<std::string> test_vector;
+  test_vector.push_back("other string");
+
+  Matcher<vector<std::string>> m = ElementsAre(StrEq("test string"));
+  EXPECT_FALSE(m.Matches(test_vector));
+}
+
+TEST(ElementsAreTest, DoesNotMatchWrongOrder) {
+  vector<std::string> test_vector;
+  test_vector.push_back("one");
+  test_vector.push_back("three");
+  test_vector.push_back("two");
+
+  Matcher<vector<std::string>> m =
+      ElementsAre(StrEq("one"), StrEq("two"), StrEq("three"));
+  EXPECT_FALSE(m.Matches(test_vector));
+}
+
+TEST(ElementsAreTest, WorksForNestedContainer) {
+  constexpr std::array<const char*, 2> strings = {{"Hi", "world"}};
+
+  vector<list<char>> nested;
+  for (const auto& s : strings) {
+    nested.emplace_back(s, s + strlen(s));
+  }
+
+  EXPECT_THAT(nested, ElementsAre(ElementsAre('H', Ne('e')),
+                                  ElementsAre('w', 'o', _, _, 'd')));
+  EXPECT_THAT(nested, Not(ElementsAre(ElementsAre('H', 'e'),
+                                      ElementsAre('w', 'o', _, _, 'd'))));
+}
+
+TEST(ElementsAreTest, WorksWithByRefElementMatchers) {
+  int a[] = {0, 1, 2};
+  vector<int> v(std::begin(a), std::end(a));
+
+  EXPECT_THAT(v, ElementsAre(Ref(v[0]), Ref(v[1]), Ref(v[2])));
+  EXPECT_THAT(v, Not(ElementsAre(Ref(v[0]), Ref(v[1]), Ref(a[2]))));
+}
+
+TEST(ElementsAreTest, WorksWithContainerPointerUsingPointee) {
+  int a[] = {0, 1, 2};
+  vector<int> v(std::begin(a), std::end(a));
+
+  EXPECT_THAT(&v, Pointee(ElementsAre(0, 1, _)));
+  EXPECT_THAT(&v, Not(Pointee(ElementsAre(0, _, 3))));
+}
+
+TEST(ElementsAreTest, WorksWithNativeArrayPassedByReference) {
+  int array[] = {0, 1, 2};
+  EXPECT_THAT(array, ElementsAre(0, 1, _));
+  EXPECT_THAT(array, Not(ElementsAre(1, _, _)));
+  EXPECT_THAT(array, Not(ElementsAre(0, _)));
+}
+
+class NativeArrayPassedAsPointerAndSize {
+ public:
+  NativeArrayPassedAsPointerAndSize() = default;
+
+  MOCK_METHOD(void, Helper, (int* array, int size));
+
+ private:
+  NativeArrayPassedAsPointerAndSize(const NativeArrayPassedAsPointerAndSize&) =
+      delete;
+  NativeArrayPassedAsPointerAndSize& operator=(
+      const NativeArrayPassedAsPointerAndSize&) = delete;
+};
+
+TEST(ElementsAreTest, WorksWithNativeArrayPassedAsPointerAndSize) {
+  int array[] = {0, 1};
+  ::std::tuple<int*, size_t> array_as_tuple(array, 2);
+  EXPECT_THAT(array_as_tuple, ElementsAre(0, 1));
+  EXPECT_THAT(array_as_tuple, Not(ElementsAre(0)));
+
+  NativeArrayPassedAsPointerAndSize helper;
+  EXPECT_CALL(helper, Helper(_, _)).With(ElementsAre(0, 1));
+  helper.Helper(array, 2);
+}
+
+TEST(ElementsAreTest, WorksWithTwoDimensionalNativeArray) {
+  const char a2[][3] = {"hi", "lo"};
+  EXPECT_THAT(a2, ElementsAre(ElementsAre('h', 'i', '\0'),
+                              ElementsAre('l', 'o', '\0')));
+  EXPECT_THAT(a2, ElementsAre(StrEq("hi"), StrEq("lo")));
+  EXPECT_THAT(a2, ElementsAre(Not(ElementsAre('h', 'o', '\0')),
+                              ElementsAre('l', 'o', '\0')));
+}
+
+TEST(ElementsAreTest, AcceptsStringLiteral) {
+  std::string array[] = {"hi", "one", "two"};
+  EXPECT_THAT(array, ElementsAre("hi", "one", "two"));
+  EXPECT_THAT(array, Not(ElementsAre("hi", "one", "too")));
+}
+
+// Declared here with the size unknown.  Defined AFTER the following test.
+extern const char kHi[];
+
+TEST(ElementsAreTest, AcceptsArrayWithUnknownSize) {
+  // The size of kHi is not known in this test, but ElementsAre() should
+  // still accept it.
+
+  std::string array1[] = {"hi"};
+  EXPECT_THAT(array1, ElementsAre(kHi));
+
+  std::string array2[] = {"ho"};
+  EXPECT_THAT(array2, Not(ElementsAre(kHi)));
+}
+
+const char kHi[] = "hi";
+
+TEST(ElementsAreTest, MakesCopyOfArguments) {
+  int x = 1;
+  int y = 2;
+  // This should make a copy of x and y.
+  ::testing::internal::ElementsAreMatcher<std::tuple<int, int>>
+      polymorphic_matcher = ElementsAre(x, y);
+  // Changing x and y now shouldn't affect the meaning of the above matcher.
+  x = y = 0;
+  const int array1[] = {1, 2};
+  EXPECT_THAT(array1, polymorphic_matcher);
+  const int array2[] = {0, 0};
+  EXPECT_THAT(array2, Not(polymorphic_matcher));
+}
+
+// Tests for ElementsAreArray().  Since ElementsAreArray() shares most
+// of the implementation with ElementsAre(), we don't test it as
+// thoroughly here.
+
+TEST(ElementsAreArrayTest, CanBeCreatedWithValueArray) {
+  const int a[] = {1, 2, 3};
+
+  vector<int> test_vector(std::begin(a), std::end(a));
+  EXPECT_THAT(test_vector, ElementsAreArray(a));
+
+  test_vector[2] = 0;
+  EXPECT_THAT(test_vector, Not(ElementsAreArray(a)));
+}
+
+TEST(ElementsAreArrayTest, CanBeCreatedWithArraySize) {
+  std::array<const char*, 3> a = {{"one", "two", "three"}};
+
+  vector<std::string> test_vector(std::begin(a), std::end(a));
+  EXPECT_THAT(test_vector, ElementsAreArray(a.data(), a.size()));
+
+  const char** p = a.data();
+  test_vector[0] = "1";
+  EXPECT_THAT(test_vector, Not(ElementsAreArray(p, a.size())));
+}
+
+TEST(ElementsAreArrayTest, CanBeCreatedWithoutArraySize) {
+  const char* a[] = {"one", "two", "three"};
+
+  vector<std::string> test_vector(std::begin(a), std::end(a));
+  EXPECT_THAT(test_vector, ElementsAreArray(a));
+
+  test_vector[0] = "1";
+  EXPECT_THAT(test_vector, Not(ElementsAreArray(a)));
+}
+
+TEST(ElementsAreArrayTest, CanBeCreatedWithMatcherArray) {
+  const Matcher<std::string> kMatcherArray[] = {StrEq("one"), StrEq("two"),
+                                                StrEq("three")};
+
+  vector<std::string> test_vector;
+  test_vector.push_back("one");
+  test_vector.push_back("two");
+  test_vector.push_back("three");
+  EXPECT_THAT(test_vector, ElementsAreArray(kMatcherArray));
+
+  test_vector.push_back("three");
+  EXPECT_THAT(test_vector, Not(ElementsAreArray(kMatcherArray)));
+}
+
+TEST(ElementsAreArrayTest, CanBeCreatedWithVector) {
+  const int a[] = {1, 2, 3};
+  vector<int> test_vector(std::begin(a), std::end(a));
+  const vector<int> expected(std::begin(a), std::end(a));
+  EXPECT_THAT(test_vector, ElementsAreArray(expected));
+  test_vector.push_back(4);
+  EXPECT_THAT(test_vector, Not(ElementsAreArray(expected)));
+}
+
+TEST(ElementsAreArrayTest, TakesInitializerList) {
+  const int a[5] = {1, 2, 3, 4, 5};
+  EXPECT_THAT(a, ElementsAreArray({1, 2, 3, 4, 5}));
+  EXPECT_THAT(a, Not(ElementsAreArray({1, 2, 3, 5, 4})));
+  EXPECT_THAT(a, Not(ElementsAreArray({1, 2, 3, 4, 6})));
+}
+
+TEST(ElementsAreArrayTest, TakesInitializerListOfCStrings) {
+  const std::string a[5] = {"a", "b", "c", "d", "e"};
+  EXPECT_THAT(a, ElementsAreArray({"a", "b", "c", "d", "e"}));
+  EXPECT_THAT(a, Not(ElementsAreArray({"a", "b", "c", "e", "d"})));
+  EXPECT_THAT(a, Not(ElementsAreArray({"a", "b", "c", "d", "ef"})));
+}
+
+TEST(ElementsAreArrayTest, TakesInitializerListOfSameTypedMatchers) {
+  const int a[5] = {1, 2, 3, 4, 5};
+  EXPECT_THAT(a, ElementsAreArray({Eq(1), Eq(2), Eq(3), Eq(4), Eq(5)}));
+  EXPECT_THAT(a, Not(ElementsAreArray({Eq(1), Eq(2), Eq(3), Eq(4), Eq(6)})));
+}
+
+TEST(ElementsAreArrayTest, TakesInitializerListOfDifferentTypedMatchers) {
+  const int a[5] = {1, 2, 3, 4, 5};
+  // The compiler cannot infer the type of the initializer list if its
+  // elements have different types.  We must explicitly specify the
+  // unified element type in this case.
+  EXPECT_THAT(
+      a, ElementsAreArray<Matcher<int>>({Eq(1), Ne(-2), Ge(3), Le(4), Eq(5)}));
+  EXPECT_THAT(a, Not(ElementsAreArray<Matcher<int>>(
+                     {Eq(1), Ne(-2), Ge(3), Le(4), Eq(6)})));
+}
+
+TEST(ElementsAreArrayTest, CanBeCreatedWithMatcherVector) {
+  const int a[] = {1, 2, 3};
+  const Matcher<int> kMatchers[] = {Eq(1), Eq(2), Eq(3)};
+  vector<int> test_vector(std::begin(a), std::end(a));
+  const vector<Matcher<int>> expected(std::begin(kMatchers),
+                                      std::end(kMatchers));
+  EXPECT_THAT(test_vector, ElementsAreArray(expected));
+  test_vector.push_back(4);
+  EXPECT_THAT(test_vector, Not(ElementsAreArray(expected)));
+}
+
+TEST(ElementsAreArrayTest, CanBeCreatedWithIteratorRange) {
+  const int a[] = {1, 2, 3};
+  const vector<int> test_vector(std::begin(a), std::end(a));
+  const vector<int> expected(std::begin(a), std::end(a));
+  EXPECT_THAT(test_vector, ElementsAreArray(expected.begin(), expected.end()));
+  // Pointers are iterators, too.
+  EXPECT_THAT(test_vector, ElementsAreArray(std::begin(a), std::end(a)));
+  // The empty range of NULL pointers should also be okay.
+  int* const null_int = nullptr;
+  EXPECT_THAT(test_vector, Not(ElementsAreArray(null_int, null_int)));
+  EXPECT_THAT((vector<int>()), ElementsAreArray(null_int, null_int));
+}
+
+// Since ElementsAre() and ElementsAreArray() share much of the
+// implementation, we only do a test for native arrays here.
+TEST(ElementsAreArrayTest, WorksWithNativeArray) {
+  ::std::string a[] = {"hi", "ho"};
+  ::std::string b[] = {"hi", "ho"};
+
+  EXPECT_THAT(a, ElementsAreArray(b));
+  EXPECT_THAT(a, ElementsAreArray(b, 2));
+  EXPECT_THAT(a, Not(ElementsAreArray(b, 1)));
+}
+
+TEST(ElementsAreArrayTest, SourceLifeSpan) {
+  const int a[] = {1, 2, 3};
+  vector<int> test_vector(std::begin(a), std::end(a));
+  vector<int> expect(std::begin(a), std::end(a));
+  ElementsAreArrayMatcher<int> matcher_maker =
+      ElementsAreArray(expect.begin(), expect.end());
+  EXPECT_THAT(test_vector, matcher_maker);
+  // Changing in place the values that initialized matcher_maker should not
+  // affect matcher_maker anymore. It should have made its own copy of them.
+  for (int& i : expect) {
+    i += 10;
+  }
+  EXPECT_THAT(test_vector, matcher_maker);
+  test_vector.push_back(3);
+  EXPECT_THAT(test_vector, Not(matcher_maker));
+}
+
+// Tests Contains().
+
+INSTANTIATE_GTEST_MATCHER_TEST_P(ContainsTest);
+
+TEST(ContainsTest, ListMatchesWhenElementIsInContainer) {
+  list<int> some_list;
+  some_list.push_back(3);
+  some_list.push_back(1);
+  some_list.push_back(2);
+  some_list.push_back(3);
+  EXPECT_THAT(some_list, Contains(1));
+  EXPECT_THAT(some_list, Contains(Gt(2.5)));
+  EXPECT_THAT(some_list, Contains(Eq(2.0f)));
+
+  list<std::string> another_list;
+  another_list.push_back("fee");
+  another_list.push_back("fie");
+  another_list.push_back("foe");
+  another_list.push_back("fum");
+  EXPECT_THAT(another_list, Contains(std::string("fee")));
+}
+
+TEST(ContainsTest, ListDoesNotMatchWhenElementIsNotInContainer) {
+  list<int> some_list;
+  some_list.push_back(3);
+  some_list.push_back(1);
+  EXPECT_THAT(some_list, Not(Contains(4)));
+}
+
+TEST(ContainsTest, SetMatchesWhenElementIsInContainer) {
+  set<int> some_set;
+  some_set.insert(3);
+  some_set.insert(1);
+  some_set.insert(2);
+  EXPECT_THAT(some_set, Contains(Eq(1.0)));
+  EXPECT_THAT(some_set, Contains(Eq(3.0f)));
+  EXPECT_THAT(some_set, Contains(2));
+
+  set<std::string> another_set;
+  another_set.insert("fee");
+  another_set.insert("fie");
+  another_set.insert("foe");
+  another_set.insert("fum");
+  EXPECT_THAT(another_set, Contains(Eq(std::string("fum"))));
+}
+
+TEST(ContainsTest, SetDoesNotMatchWhenElementIsNotInContainer) {
+  set<int> some_set;
+  some_set.insert(3);
+  some_set.insert(1);
+  EXPECT_THAT(some_set, Not(Contains(4)));
+
+  set<std::string> c_string_set;
+  c_string_set.insert("hello");
+  EXPECT_THAT(c_string_set, Not(Contains(std::string("goodbye"))));
+}
+
+TEST_P(ContainsTestP, ExplainsMatchResultCorrectly) {
+  const int a[2] = {1, 2};
+  Matcher<const int(&)[2]> m = Contains(2);
+  EXPECT_EQ("whose element #1 matches", Explain(m, a));
+
+  m = Contains(3);
+  EXPECT_EQ("", Explain(m, a));
+
+  m = Contains(GreaterThan(0));
+  EXPECT_EQ("whose element #0 matches, which is 1 more than 0", Explain(m, a));
+
+  m = Contains(GreaterThan(10));
+  EXPECT_EQ("", Explain(m, a));
+}
+
+TEST(ContainsTest, DescribesItselfCorrectly) {
+  Matcher<vector<int>> m = Contains(1);
+  EXPECT_EQ("contains at least one element that is equal to 1", Describe(m));
+
+  Matcher<vector<int>> m2 = Not(m);
+  EXPECT_EQ("doesn't contain any element that is equal to 1", Describe(m2));
+}
+
+TEST(ContainsTest, MapMatchesWhenElementIsInContainer) {
+  map<std::string, int> my_map;
+  const char* bar = "a string";
+  my_map[bar] = 2;
+  EXPECT_THAT(my_map, Contains(pair<const char* const, int>(bar, 2)));
+
+  map<std::string, int> another_map;
+  another_map["fee"] = 1;
+  another_map["fie"] = 2;
+  another_map["foe"] = 3;
+  another_map["fum"] = 4;
+  EXPECT_THAT(another_map,
+              Contains(pair<const std::string, int>(std::string("fee"), 1)));
+  EXPECT_THAT(another_map, Contains(pair<const std::string, int>("fie", 2)));
+}
+
+TEST(ContainsTest, MapDoesNotMatchWhenElementIsNotInContainer) {
+  map<int, int> some_map;
+  some_map[1] = 11;
+  some_map[2] = 22;
+  EXPECT_THAT(some_map, Not(Contains(pair<const int, int>(2, 23))));
+}
+
+TEST(ContainsTest, ArrayMatchesWhenElementIsInContainer) {
+  const char* string_array[] = {"fee", "fie", "foe", "fum"};
+  EXPECT_THAT(string_array, Contains(Eq(std::string("fum"))));
+}
+
+TEST(ContainsTest, ArrayDoesNotMatchWhenElementIsNotInContainer) {
+  int int_array[] = {1, 2, 3, 4};
+  EXPECT_THAT(int_array, Not(Contains(5)));
+}
+
+TEST(ContainsTest, AcceptsMatcher) {
+  const int a[] = {1, 2, 3};
+  EXPECT_THAT(a, Contains(Gt(2)));
+  EXPECT_THAT(a, Not(Contains(Gt(4))));
+}
+
+TEST(ContainsTest, WorksForNativeArrayAsTuple) {
+  const int a[] = {1, 2};
+  const int* const pointer = a;
+  EXPECT_THAT(std::make_tuple(pointer, 2), Contains(1));
+  EXPECT_THAT(std::make_tuple(pointer, 2), Not(Contains(Gt(3))));
+}
+
+TEST(ContainsTest, WorksForTwoDimensionalNativeArray) {
+  int a[][3] = {{1, 2, 3}, {4, 5, 6}};
+  EXPECT_THAT(a, Contains(ElementsAre(4, 5, 6)));
+  EXPECT_THAT(a, Contains(Contains(5)));
+  EXPECT_THAT(a, Not(Contains(ElementsAre(3, 4, 5))));
+  EXPECT_THAT(a, Contains(Not(Contains(5))));
+}
+
+}  // namespace
+}  // namespace gmock_matchers_test
+}  // namespace testing
+
+GTEST_DISABLE_MSC_WARNINGS_POP_()  // 4244 4100
diff --git a/third_party/googletest/googlemock/test/gmock-matchers-misc_test.cc b/third_party/googletest/googlemock/test/gmock-matchers-misc_test.cc
new file mode 100644
index 0000000..b8f6458
--- /dev/null
+++ b/third_party/googletest/googlemock/test/gmock-matchers-misc_test.cc
@@ -0,0 +1,1823 @@
+// Copyright 2007, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Google Mock - a framework for writing C++ mock classes.
+//
+// This file tests some commonly used argument matchers.
+
+#include <array>
+#include <memory>
+#include <ostream>
+#include <string>
+#include <tuple>
+#include <utility>
+#include <vector>
+
+#include "gtest/gtest.h"
+
+// Silence warning C4244: 'initializing': conversion from 'int' to 'short',
+// possible loss of data and C4100, unreferenced local parameter
+GTEST_DISABLE_MSC_WARNINGS_PUSH_(4244 4100)
+
+#include "test/gmock-matchers_test.h"
+
+namespace testing {
+namespace gmock_matchers_test {
+namespace {
+
+TEST(AddressTest, NonConst) {
+  int n = 1;
+  const Matcher<int> m = Address(Eq(&n));
+
+  EXPECT_TRUE(m.Matches(n));
+
+  int other = 5;
+
+  EXPECT_FALSE(m.Matches(other));
+
+  int& n_ref = n;
+
+  EXPECT_TRUE(m.Matches(n_ref));
+}
+
+TEST(AddressTest, Const) {
+  const int n = 1;
+  const Matcher<int> m = Address(Eq(&n));
+
+  EXPECT_TRUE(m.Matches(n));
+
+  int other = 5;
+
+  EXPECT_FALSE(m.Matches(other));
+}
+
+TEST(AddressTest, MatcherDoesntCopy) {
+  std::unique_ptr<int> n(new int(1));
+  const Matcher<std::unique_ptr<int>> m = Address(Eq(&n));
+
+  EXPECT_TRUE(m.Matches(n));
+}
+
+TEST(AddressTest, Describe) {
+  Matcher<int> matcher = Address(_);
+  EXPECT_EQ("has address that is anything", Describe(matcher));
+  EXPECT_EQ("does not have address that is anything",
+            DescribeNegation(matcher));
+}
+
+// The following two tests verify that values without a public copy
+// ctor can be used as arguments to matchers like Eq(), Ge(), and etc
+// with the help of ByRef().
+
+class NotCopyable {
+ public:
+  explicit NotCopyable(int a_value) : value_(a_value) {}
+
+  int value() const { return value_; }
+
+  bool operator==(const NotCopyable& rhs) const {
+    return value() == rhs.value();
+  }
+
+  bool operator>=(const NotCopyable& rhs) const {
+    return value() >= rhs.value();
+  }
+
+ private:
+  int value_;
+
+  NotCopyable(const NotCopyable&) = delete;
+  NotCopyable& operator=(const NotCopyable&) = delete;
+};
+
+TEST(ByRefTest, AllowsNotCopyableConstValueInMatchers) {
+  const NotCopyable const_value1(1);
+  const Matcher<const NotCopyable&> m = Eq(ByRef(const_value1));
+
+  const NotCopyable n1(1), n2(2);
+  EXPECT_TRUE(m.Matches(n1));
+  EXPECT_FALSE(m.Matches(n2));
+}
+
+TEST(ByRefTest, AllowsNotCopyableValueInMatchers) {
+  NotCopyable value2(2);
+  const Matcher<NotCopyable&> m = Ge(ByRef(value2));
+
+  NotCopyable n1(1), n2(2);
+  EXPECT_FALSE(m.Matches(n1));
+  EXPECT_TRUE(m.Matches(n2));
+}
+
+TEST(IsEmptyTest, ImplementsIsEmpty) {
+  vector<int> container;
+  EXPECT_THAT(container, IsEmpty());
+  container.push_back(0);
+  EXPECT_THAT(container, Not(IsEmpty()));
+  container.push_back(1);
+  EXPECT_THAT(container, Not(IsEmpty()));
+}
+
+TEST(IsEmptyTest, WorksWithString) {
+  std::string text;
+  EXPECT_THAT(text, IsEmpty());
+  text = "foo";
+  EXPECT_THAT(text, Not(IsEmpty()));
+  text = std::string("\0", 1);
+  EXPECT_THAT(text, Not(IsEmpty()));
+}
+
+TEST(IsEmptyTest, CanDescribeSelf) {
+  Matcher<vector<int>> m = IsEmpty();
+  EXPECT_EQ("is empty", Describe(m));
+  EXPECT_EQ("isn't empty", DescribeNegation(m));
+}
+
+TEST(IsEmptyTest, ExplainsResult) {
+  Matcher<vector<int>> m = IsEmpty();
+  vector<int> container;
+  EXPECT_EQ("", Explain(m, container));
+  container.push_back(0);
+  EXPECT_EQ("whose size is 1", Explain(m, container));
+}
+
+TEST(IsEmptyTest, WorksWithMoveOnly) {
+  ContainerHelper helper;
+  EXPECT_CALL(helper, Call(IsEmpty()));
+  helper.Call({});
+}
+
+TEST(IsTrueTest, IsTrueIsFalse) {
+  EXPECT_THAT(true, IsTrue());
+  EXPECT_THAT(false, IsFalse());
+  EXPECT_THAT(true, Not(IsFalse()));
+  EXPECT_THAT(false, Not(IsTrue()));
+  EXPECT_THAT(0, Not(IsTrue()));
+  EXPECT_THAT(0, IsFalse());
+  EXPECT_THAT(nullptr, Not(IsTrue()));
+  EXPECT_THAT(nullptr, IsFalse());
+  EXPECT_THAT(-1, IsTrue());
+  EXPECT_THAT(-1, Not(IsFalse()));
+  EXPECT_THAT(1, IsTrue());
+  EXPECT_THAT(1, Not(IsFalse()));
+  EXPECT_THAT(2, IsTrue());
+  EXPECT_THAT(2, Not(IsFalse()));
+  int a = 42;
+  EXPECT_THAT(a, IsTrue());
+  EXPECT_THAT(a, Not(IsFalse()));
+  EXPECT_THAT(&a, IsTrue());
+  EXPECT_THAT(&a, Not(IsFalse()));
+  EXPECT_THAT(false, Not(IsTrue()));
+  EXPECT_THAT(true, Not(IsFalse()));
+  EXPECT_THAT(std::true_type(), IsTrue());
+  EXPECT_THAT(std::true_type(), Not(IsFalse()));
+  EXPECT_THAT(std::false_type(), IsFalse());
+  EXPECT_THAT(std::false_type(), Not(IsTrue()));
+  EXPECT_THAT(nullptr, Not(IsTrue()));
+  EXPECT_THAT(nullptr, IsFalse());
+  std::unique_ptr<int> null_unique;
+  std::unique_ptr<int> nonnull_unique(new int(0));
+  EXPECT_THAT(null_unique, Not(IsTrue()));
+  EXPECT_THAT(null_unique, IsFalse());
+  EXPECT_THAT(nonnull_unique, IsTrue());
+  EXPECT_THAT(nonnull_unique, Not(IsFalse()));
+}
+
+#ifdef GTEST_HAS_TYPED_TEST
+// Tests ContainerEq with different container types, and
+// different element types.
+
+template <typename T>
+class ContainerEqTest : public testing::Test {};
+
+typedef testing::Types<set<int>, vector<size_t>, multiset<size_t>, list<int>>
+    ContainerEqTestTypes;
+
+TYPED_TEST_SUITE(ContainerEqTest, ContainerEqTestTypes);
+
+// Tests that the filled container is equal to itself.
+TYPED_TEST(ContainerEqTest, EqualsSelf) {
+  static const int vals[] = {1, 1, 2, 3, 5, 8};
+  TypeParam my_set(vals, vals + 6);
+  const Matcher<TypeParam> m = ContainerEq(my_set);
+  EXPECT_TRUE(m.Matches(my_set));
+  EXPECT_EQ("", Explain(m, my_set));
+}
+
+// Tests that missing values are reported.
+TYPED_TEST(ContainerEqTest, ValueMissing) {
+  static const int vals[] = {1, 1, 2, 3, 5, 8};
+  static const int test_vals[] = {2, 1, 8, 5};
+  TypeParam my_set(vals, vals + 6);
+  TypeParam test_set(test_vals, test_vals + 4);
+  const Matcher<TypeParam> m = ContainerEq(my_set);
+  EXPECT_FALSE(m.Matches(test_set));
+  EXPECT_EQ("which doesn't have these expected elements: 3",
+            Explain(m, test_set));
+}
+
+// Tests that added values are reported.
+TYPED_TEST(ContainerEqTest, ValueAdded) {
+  static const int vals[] = {1, 1, 2, 3, 5, 8};
+  static const int test_vals[] = {1, 2, 3, 5, 8, 46};
+  TypeParam my_set(vals, vals + 6);
+  TypeParam test_set(test_vals, test_vals + 6);
+  const Matcher<const TypeParam&> m = ContainerEq(my_set);
+  EXPECT_FALSE(m.Matches(test_set));
+  EXPECT_EQ("which has these unexpected elements: 46", Explain(m, test_set));
+}
+
+// Tests that added and missing values are reported together.
+TYPED_TEST(ContainerEqTest, ValueAddedAndRemoved) {
+  static const int vals[] = {1, 1, 2, 3, 5, 8};
+  static const int test_vals[] = {1, 2, 3, 8, 46};
+  TypeParam my_set(vals, vals + 6);
+  TypeParam test_set(test_vals, test_vals + 5);
+  const Matcher<TypeParam> m = ContainerEq(my_set);
+  EXPECT_FALSE(m.Matches(test_set));
+  EXPECT_EQ(
+      "which has these unexpected elements: 46,\n"
+      "and doesn't have these expected elements: 5",
+      Explain(m, test_set));
+}
+
+// Tests duplicated value -- expect no explanation.
+TYPED_TEST(ContainerEqTest, DuplicateDifference) {
+  static const int vals[] = {1, 1, 2, 3, 5, 8};
+  static const int test_vals[] = {1, 2, 3, 5, 8};
+  TypeParam my_set(vals, vals + 6);
+  TypeParam test_set(test_vals, test_vals + 5);
+  const Matcher<const TypeParam&> m = ContainerEq(my_set);
+  // Depending on the container, match may be true or false
+  // But in any case there should be no explanation.
+  EXPECT_EQ("", Explain(m, test_set));
+}
+#endif  // GTEST_HAS_TYPED_TEST
+
+// Tests that multiple missing values are reported.
+// Using just vector here, so order is predictable.
+TEST(ContainerEqExtraTest, MultipleValuesMissing) {
+  static const int vals[] = {1, 1, 2, 3, 5, 8};
+  static const int test_vals[] = {2, 1, 5};
+  vector<int> my_set(vals, vals + 6);
+  vector<int> test_set(test_vals, test_vals + 3);
+  const Matcher<vector<int>> m = ContainerEq(my_set);
+  EXPECT_FALSE(m.Matches(test_set));
+  EXPECT_EQ("which doesn't have these expected elements: 3, 8",
+            Explain(m, test_set));
+}
+
+// Tests that added values are reported.
+// Using just vector here, so order is predictable.
+TEST(ContainerEqExtraTest, MultipleValuesAdded) {
+  static const int vals[] = {1, 1, 2, 3, 5, 8};
+  static const int test_vals[] = {1, 2, 92, 3, 5, 8, 46};
+  list<size_t> my_set(vals, vals + 6);
+  list<size_t> test_set(test_vals, test_vals + 7);
+  const Matcher<const list<size_t>&> m = ContainerEq(my_set);
+  EXPECT_FALSE(m.Matches(test_set));
+  EXPECT_EQ("which has these unexpected elements: 92, 46",
+            Explain(m, test_set));
+}
+
+// Tests that added and missing values are reported together.
+TEST(ContainerEqExtraTest, MultipleValuesAddedAndRemoved) {
+  static const int vals[] = {1, 1, 2, 3, 5, 8};
+  static const int test_vals[] = {1, 2, 3, 92, 46};
+  list<size_t> my_set(vals, vals + 6);
+  list<size_t> test_set(test_vals, test_vals + 5);
+  const Matcher<const list<size_t>> m = ContainerEq(my_set);
+  EXPECT_FALSE(m.Matches(test_set));
+  EXPECT_EQ(
+      "which has these unexpected elements: 92, 46,\n"
+      "and doesn't have these expected elements: 5, 8",
+      Explain(m, test_set));
+}
+
+// Tests to see that duplicate elements are detected,
+// but (as above) not reported in the explanation.
+TEST(ContainerEqExtraTest, MultiSetOfIntDuplicateDifference) {
+  static const int vals[] = {1, 1, 2, 3, 5, 8};
+  static const int test_vals[] = {1, 2, 3, 5, 8};
+  vector<int> my_set(vals, vals + 6);
+  vector<int> test_set(test_vals, test_vals + 5);
+  const Matcher<vector<int>> m = ContainerEq(my_set);
+  EXPECT_TRUE(m.Matches(my_set));
+  EXPECT_FALSE(m.Matches(test_set));
+  // There is nothing to report when both sets contain all the same values.
+  EXPECT_EQ("", Explain(m, test_set));
+}
+
+// Tests that ContainerEq works for non-trivial associative containers,
+// like maps.
+TEST(ContainerEqExtraTest, WorksForMaps) {
+  map<int, std::string> my_map;
+  my_map[0] = "a";
+  my_map[1] = "b";
+
+  map<int, std::string> test_map;
+  test_map[0] = "aa";
+  test_map[1] = "b";
+
+  const Matcher<const map<int, std::string>&> m = ContainerEq(my_map);
+  EXPECT_TRUE(m.Matches(my_map));
+  EXPECT_FALSE(m.Matches(test_map));
+
+  EXPECT_EQ(
+      "which has these unexpected elements: (0, \"aa\"),\n"
+      "and doesn't have these expected elements: (0, \"a\")",
+      Explain(m, test_map));
+}
+
+TEST(ContainerEqExtraTest, WorksForNativeArray) {
+  int a1[] = {1, 2, 3};
+  int a2[] = {1, 2, 3};
+  int b[] = {1, 2, 4};
+
+  EXPECT_THAT(a1, ContainerEq(a2));
+  EXPECT_THAT(a1, Not(ContainerEq(b)));
+}
+
+TEST(ContainerEqExtraTest, WorksForTwoDimensionalNativeArray) {
+  const char a1[][3] = {"hi", "lo"};
+  const char a2[][3] = {"hi", "lo"};
+  const char b[][3] = {"lo", "hi"};
+
+  // Tests using ContainerEq() in the first dimension.
+  EXPECT_THAT(a1, ContainerEq(a2));
+  EXPECT_THAT(a1, Not(ContainerEq(b)));
+
+  // Tests using ContainerEq() in the second dimension.
+  EXPECT_THAT(a1, ElementsAre(ContainerEq(a2[0]), ContainerEq(a2[1])));
+  EXPECT_THAT(a1, ElementsAre(Not(ContainerEq(b[0])), ContainerEq(a2[1])));
+}
+
+TEST(ContainerEqExtraTest, WorksForNativeArrayAsTuple) {
+  const int a1[] = {1, 2, 3};
+  const int a2[] = {1, 2, 3};
+  const int b[] = {1, 2, 3, 4};
+
+  const int* const p1 = a1;
+  EXPECT_THAT(std::make_tuple(p1, 3), ContainerEq(a2));
+  EXPECT_THAT(std::make_tuple(p1, 3), Not(ContainerEq(b)));
+
+  const int c[] = {1, 3, 2};
+  EXPECT_THAT(std::make_tuple(p1, 3), Not(ContainerEq(c)));
+}
+
+TEST(ContainerEqExtraTest, CopiesNativeArrayParameter) {
+  std::string a1[][3] = {{"hi", "hello", "ciao"}, {"bye", "see you", "ciao"}};
+
+  std::string a2[][3] = {{"hi", "hello", "ciao"}, {"bye", "see you", "ciao"}};
+
+  const Matcher<const std::string(&)[2][3]> m = ContainerEq(a2);
+  EXPECT_THAT(a1, m);
+
+  a2[0][0] = "ha";
+  EXPECT_THAT(a1, m);
+}
+
+namespace {
+
+// Used as a check on the more complex max flow method used in the
+// real testing::internal::FindMaxBipartiteMatching. This method is
+// compatible but runs in worst-case factorial time, so we only
+// use it in testing for small problem sizes.
+template <typename Graph>
+class BacktrackingMaxBPMState {
+ public:
+  // Does not take ownership of 'g'.
+  explicit BacktrackingMaxBPMState(const Graph* g) : graph_(g) {}
+
+  ElementMatcherPairs Compute() {
+    if (graph_->LhsSize() == 0 || graph_->RhsSize() == 0) {
+      return best_so_far_;
+    }
+    lhs_used_.assign(graph_->LhsSize(), kUnused);
+    rhs_used_.assign(graph_->RhsSize(), kUnused);
+    for (size_t irhs = 0; irhs < graph_->RhsSize(); ++irhs) {
+      matches_.clear();
+      RecurseInto(irhs);
+      if (best_so_far_.size() == graph_->RhsSize()) break;
+    }
+    return best_so_far_;
+  }
+
+ private:
+  static const size_t kUnused = static_cast<size_t>(-1);
+
+  void PushMatch(size_t lhs, size_t rhs) {
+    matches_.push_back(ElementMatcherPair(lhs, rhs));
+    lhs_used_[lhs] = rhs;
+    rhs_used_[rhs] = lhs;
+    if (matches_.size() > best_so_far_.size()) {
+      best_so_far_ = matches_;
+    }
+  }
+
+  void PopMatch() {
+    const ElementMatcherPair& back = matches_.back();
+    lhs_used_[back.first] = kUnused;
+    rhs_used_[back.second] = kUnused;
+    matches_.pop_back();
+  }
+
+  bool RecurseInto(size_t irhs) {
+    if (rhs_used_[irhs] != kUnused) {
+      return true;
+    }
+    for (size_t ilhs = 0; ilhs < graph_->LhsSize(); ++ilhs) {
+      if (lhs_used_[ilhs] != kUnused) {
+        continue;
+      }
+      if (!graph_->HasEdge(ilhs, irhs)) {
+        continue;
+      }
+      PushMatch(ilhs, irhs);
+      if (best_so_far_.size() == graph_->RhsSize()) {
+        return false;
+      }
+      for (size_t mi = irhs + 1; mi < graph_->RhsSize(); ++mi) {
+        if (!RecurseInto(mi)) return false;
+      }
+      PopMatch();
+    }
+    return true;
+  }
+
+  const Graph* graph_;  // not owned
+  std::vector<size_t> lhs_used_;
+  std::vector<size_t> rhs_used_;
+  ElementMatcherPairs matches_;
+  ElementMatcherPairs best_so_far_;
+};
+
+template <typename Graph>
+const size_t BacktrackingMaxBPMState<Graph>::kUnused;
+
+}  // namespace
+
+// Implement a simple backtracking algorithm to determine if it is possible
+// to find one element per matcher, without reusing elements.
+template <typename Graph>
+ElementMatcherPairs FindBacktrackingMaxBPM(const Graph& g) {
+  return BacktrackingMaxBPMState<Graph>(&g).Compute();
+}
+
+class BacktrackingBPMTest : public ::testing::Test {};
+
+// Tests the MaxBipartiteMatching algorithm with square matrices.
+// The single int param is the # of nodes on each of the left and right sides.
+class BipartiteTest : public ::testing::TestWithParam<size_t> {};
+
+// Verify all match graphs up to some moderate number of edges.
+TEST_P(BipartiteTest, Exhaustive) {
+  size_t nodes = GetParam();
+  MatchMatrix graph(nodes, nodes);
+  do {
+    ElementMatcherPairs matches = internal::FindMaxBipartiteMatching(graph);
+    EXPECT_EQ(FindBacktrackingMaxBPM(graph).size(), matches.size())
+        << "graph: " << graph.DebugString();
+    // Check that all elements of matches are in the graph.
+    // Check that elements of first and second are unique.
+    std::vector<bool> seen_element(graph.LhsSize());
+    std::vector<bool> seen_matcher(graph.RhsSize());
+    SCOPED_TRACE(PrintToString(matches));
+    for (size_t i = 0; i < matches.size(); ++i) {
+      size_t ilhs = matches[i].first;
+      size_t irhs = matches[i].second;
+      EXPECT_TRUE(graph.HasEdge(ilhs, irhs));
+      EXPECT_FALSE(seen_element[ilhs]);
+      EXPECT_FALSE(seen_matcher[irhs]);
+      seen_element[ilhs] = true;
+      seen_matcher[irhs] = true;
+    }
+  } while (graph.NextGraph());
+}
+
+INSTANTIATE_TEST_SUITE_P(AllGraphs, BipartiteTest,
+                         ::testing::Range(size_t{0}, size_t{5}));
+
+// Parameterized by a pair interpreted as (LhsSize, RhsSize).
+class BipartiteNonSquareTest
+    : public ::testing::TestWithParam<std::pair<size_t, size_t>> {};
+
+TEST_F(BipartiteNonSquareTest, SimpleBacktracking) {
+  //   .......
+  // 0:-----\ :
+  // 1:---\ | :
+  // 2:---\ | :
+  // 3:-\ | | :
+  //  :.......:
+  //    0 1 2
+  MatchMatrix g(4, 3);
+  constexpr std::array<std::array<size_t, 2>, 4> kEdges = {
+      {{{0, 2}}, {{1, 1}}, {{2, 1}}, {{3, 0}}}};
+  for (size_t i = 0; i < kEdges.size(); ++i) {
+    g.SetEdge(kEdges[i][0], kEdges[i][1], true);
+  }
+  EXPECT_THAT(FindBacktrackingMaxBPM(g),
+              ElementsAre(Pair(3, 0), Pair(AnyOf(1, 2), 1), Pair(0, 2)))
+      << g.DebugString();
+}
+
+// Verify a few nonsquare matrices.
+TEST_P(BipartiteNonSquareTest, Exhaustive) {
+  size_t nlhs = GetParam().first;
+  size_t nrhs = GetParam().second;
+  MatchMatrix graph(nlhs, nrhs);
+  do {
+    EXPECT_EQ(FindBacktrackingMaxBPM(graph).size(),
+              internal::FindMaxBipartiteMatching(graph).size())
+        << "graph: " << graph.DebugString()
+        << "\nbacktracking: " << PrintToString(FindBacktrackingMaxBPM(graph))
+        << "\nmax flow: "
+        << PrintToString(internal::FindMaxBipartiteMatching(graph));
+  } while (graph.NextGraph());
+}
+
+INSTANTIATE_TEST_SUITE_P(
+    AllGraphs, BipartiteNonSquareTest,
+    testing::Values(std::make_pair(1, 2), std::make_pair(2, 1),
+                    std::make_pair(3, 2), std::make_pair(2, 3),
+                    std::make_pair(4, 1), std::make_pair(1, 4),
+                    std::make_pair(4, 3), std::make_pair(3, 4)));
+
+class BipartiteRandomTest
+    : public ::testing::TestWithParam<std::pair<int, int>> {};
+
+// Verifies a large sample of larger graphs.
+TEST_P(BipartiteRandomTest, LargerNets) {
+  int nodes = GetParam().first;
+  int iters = GetParam().second;
+  MatchMatrix graph(static_cast<size_t>(nodes), static_cast<size_t>(nodes));
+
+  auto seed = static_cast<uint32_t>(GTEST_FLAG_GET(random_seed));
+  if (seed == 0) {
+    seed = static_cast<uint32_t>(time(nullptr));
+  }
+
+  for (; iters > 0; --iters, ++seed) {
+    srand(static_cast<unsigned int>(seed));
+    graph.Randomize();
+    EXPECT_EQ(FindBacktrackingMaxBPM(graph).size(),
+              internal::FindMaxBipartiteMatching(graph).size())
+        << " graph: " << graph.DebugString()
+        << "\nTo reproduce the failure, rerun the test with the flag"
+           " --"
+        << GTEST_FLAG_PREFIX_ << "random_seed=" << seed;
+  }
+}
+
+// Test argument is a std::pair<int, int> representing (nodes, iters).
+INSTANTIATE_TEST_SUITE_P(Samples, BipartiteRandomTest,
+                         testing::Values(std::make_pair(5, 10000),
+                                         std::make_pair(6, 5000),
+                                         std::make_pair(7, 2000),
+                                         std::make_pair(8, 500),
+                                         std::make_pair(9, 100)));
+
+// Tests IsReadableTypeName().
+
+TEST(IsReadableTypeNameTest, ReturnsTrueForShortNames) {
+  EXPECT_TRUE(IsReadableTypeName("int"));
+  EXPECT_TRUE(IsReadableTypeName("const unsigned char*"));
+  EXPECT_TRUE(IsReadableTypeName("MyMap<int, void*>"));
+  EXPECT_TRUE(IsReadableTypeName("void (*)(int, bool)"));
+}
+
+TEST(IsReadableTypeNameTest, ReturnsTrueForLongNonTemplateNonFunctionNames) {
+  EXPECT_TRUE(IsReadableTypeName("my_long_namespace::MyClassName"));
+  EXPECT_TRUE(IsReadableTypeName("int [5][6][7][8][9][10][11]"));
+  EXPECT_TRUE(IsReadableTypeName("my_namespace::MyOuterClass::MyInnerClass"));
+}
+
+TEST(IsReadableTypeNameTest, ReturnsFalseForLongTemplateNames) {
+  EXPECT_FALSE(
+      IsReadableTypeName("basic_string<char, std::char_traits<char> >"));
+  EXPECT_FALSE(IsReadableTypeName("std::vector<int, std::alloc_traits<int> >"));
+}
+
+TEST(IsReadableTypeNameTest, ReturnsFalseForLongFunctionTypeNames) {
+  EXPECT_FALSE(IsReadableTypeName("void (&)(int, bool, char, float)"));
+}
+
+// Tests FormatMatcherDescription().
+
+TEST(FormatMatcherDescriptionTest, WorksForEmptyDescription) {
+  EXPECT_EQ("is even",
+            FormatMatcherDescription(false, "IsEven", {}, Strings()));
+  EXPECT_EQ("not (is even)",
+            FormatMatcherDescription(true, "IsEven", {}, Strings()));
+
+  EXPECT_EQ("equals (a: 5)",
+            FormatMatcherDescription(false, "Equals", {"a"}, {"5"}));
+
+  EXPECT_EQ(
+      "is in range (a: 5, b: 8)",
+      FormatMatcherDescription(false, "IsInRange", {"a", "b"}, {"5", "8"}));
+}
+
+INSTANTIATE_GTEST_MATCHER_TEST_P(MatcherTupleTest);
+
+TEST_P(MatcherTupleTestP, ExplainsMatchFailure) {
+  stringstream ss1;
+  ExplainMatchFailureTupleTo(
+      std::make_tuple(Matcher<char>(Eq('a')), GreaterThan(5)),
+      std::make_tuple('a', 10), &ss1);
+  EXPECT_EQ("", ss1.str());  // Successful match.
+
+  stringstream ss2;
+  ExplainMatchFailureTupleTo(
+      std::make_tuple(GreaterThan(5), Matcher<char>(Eq('a'))),
+      std::make_tuple(2, 'b'), &ss2);
+  EXPECT_EQ(
+      "  Expected arg #0: is > 5\n"
+      "           Actual: 2, which is 3 less than 5\n"
+      "  Expected arg #1: is equal to 'a' (97, 0x61)\n"
+      "           Actual: 'b' (98, 0x62)\n",
+      ss2.str());  // Failed match where both arguments need explanation.
+
+  stringstream ss3;
+  ExplainMatchFailureTupleTo(
+      std::make_tuple(GreaterThan(5), Matcher<char>(Eq('a'))),
+      std::make_tuple(2, 'a'), &ss3);
+  EXPECT_EQ(
+      "  Expected arg #0: is > 5\n"
+      "           Actual: 2, which is 3 less than 5\n",
+      ss3.str());  // Failed match where only one argument needs
+                   // explanation.
+}
+
+// Sample optional type implementation with minimal requirements for use with
+// Optional matcher.
+template <typename T>
+class SampleOptional {
+ public:
+  using value_type = T;
+  explicit SampleOptional(T value)
+      : value_(std::move(value)), has_value_(true) {}
+  SampleOptional() : value_(), has_value_(false) {}
+  operator bool() const { return has_value_; }
+  const T& operator*() const { return value_; }
+
+ private:
+  T value_;
+  bool has_value_;
+};
+
+TEST(OptionalTest, DescribesSelf) {
+  const Matcher<SampleOptional<int>> m = Optional(Eq(1));
+  EXPECT_EQ("value is equal to 1", Describe(m));
+}
+
+TEST(OptionalTest, ExplainsSelf) {
+  const Matcher<SampleOptional<int>> m = Optional(Eq(1));
+  EXPECT_EQ("whose value 1 matches", Explain(m, SampleOptional<int>(1)));
+  EXPECT_EQ("whose value 2 doesn't match", Explain(m, SampleOptional<int>(2)));
+}
+
+TEST(OptionalTest, MatchesNonEmptyOptional) {
+  const Matcher<SampleOptional<int>> m1 = Optional(1);
+  const Matcher<SampleOptional<int>> m2 = Optional(Eq(2));
+  const Matcher<SampleOptional<int>> m3 = Optional(Lt(3));
+  SampleOptional<int> opt(1);
+  EXPECT_TRUE(m1.Matches(opt));
+  EXPECT_FALSE(m2.Matches(opt));
+  EXPECT_TRUE(m3.Matches(opt));
+}
+
+TEST(OptionalTest, DoesNotMatchNullopt) {
+  const Matcher<SampleOptional<int>> m = Optional(1);
+  SampleOptional<int> empty;
+  EXPECT_FALSE(m.Matches(empty));
+}
+
+TEST(OptionalTest, WorksWithMoveOnly) {
+  Matcher<SampleOptional<std::unique_ptr<int>>> m = Optional(Eq(nullptr));
+  EXPECT_TRUE(m.Matches(SampleOptional<std::unique_ptr<int>>(nullptr)));
+}
+
+class SampleVariantIntString {
+ public:
+  SampleVariantIntString(int i) : i_(i), has_int_(true) {}
+  SampleVariantIntString(const std::string& s) : s_(s), has_int_(false) {}
+
+  template <typename T>
+  friend bool holds_alternative(const SampleVariantIntString& value) {
+    return value.has_int_ == std::is_same<T, int>::value;
+  }
+
+  template <typename T>
+  friend const T& get(const SampleVariantIntString& value) {
+    return value.get_impl(static_cast<T*>(nullptr));
+  }
+
+ private:
+  const int& get_impl(int*) const { return i_; }
+  const std::string& get_impl(std::string*) const { return s_; }
+
+  int i_;
+  std::string s_;
+  bool has_int_;
+};
+
+TEST(VariantTest, DescribesSelf) {
+  const Matcher<SampleVariantIntString> m = VariantWith<int>(Eq(1));
+  EXPECT_THAT(Describe(m), ContainsRegex("is a variant<> with value of type "
+                                         "'.*' and the value is equal to 1"));
+}
+
+TEST(VariantTest, ExplainsSelf) {
+  const Matcher<SampleVariantIntString> m = VariantWith<int>(Eq(1));
+  EXPECT_THAT(Explain(m, SampleVariantIntString(1)),
+              ContainsRegex("whose value 1"));
+  EXPECT_THAT(Explain(m, SampleVariantIntString("A")),
+              HasSubstr("whose value is not of type '"));
+  EXPECT_THAT(Explain(m, SampleVariantIntString(2)),
+              "whose value 2 doesn't match");
+}
+
+TEST(VariantTest, FullMatch) {
+  Matcher<SampleVariantIntString> m = VariantWith<int>(Eq(1));
+  EXPECT_TRUE(m.Matches(SampleVariantIntString(1)));
+
+  m = VariantWith<std::string>(Eq("1"));
+  EXPECT_TRUE(m.Matches(SampleVariantIntString("1")));
+}
+
+TEST(VariantTest, TypeDoesNotMatch) {
+  Matcher<SampleVariantIntString> m = VariantWith<int>(Eq(1));
+  EXPECT_FALSE(m.Matches(SampleVariantIntString("1")));
+
+  m = VariantWith<std::string>(Eq("1"));
+  EXPECT_FALSE(m.Matches(SampleVariantIntString(1)));
+}
+
+TEST(VariantTest, InnerDoesNotMatch) {
+  Matcher<SampleVariantIntString> m = VariantWith<int>(Eq(1));
+  EXPECT_FALSE(m.Matches(SampleVariantIntString(2)));
+
+  m = VariantWith<std::string>(Eq("1"));
+  EXPECT_FALSE(m.Matches(SampleVariantIntString("2")));
+}
+
+class SampleAnyType {
+ public:
+  explicit SampleAnyType(int i) : index_(0), i_(i) {}
+  explicit SampleAnyType(const std::string& s) : index_(1), s_(s) {}
+
+  template <typename T>
+  friend const T* any_cast(const SampleAnyType* any) {
+    return any->get_impl(static_cast<T*>(nullptr));
+  }
+
+ private:
+  int index_;
+  int i_;
+  std::string s_;
+
+  const int* get_impl(int*) const { return index_ == 0 ? &i_ : nullptr; }
+  const std::string* get_impl(std::string*) const {
+    return index_ == 1 ? &s_ : nullptr;
+  }
+};
+
+TEST(AnyWithTest, FullMatch) {
+  Matcher<SampleAnyType> m = AnyWith<int>(Eq(1));
+  EXPECT_TRUE(m.Matches(SampleAnyType(1)));
+}
+
+TEST(AnyWithTest, TestBadCastType) {
+  Matcher<SampleAnyType> m = AnyWith<std::string>(Eq("fail"));
+  EXPECT_FALSE(m.Matches(SampleAnyType(1)));
+}
+
+TEST(AnyWithTest, TestUseInContainers) {
+  std::vector<SampleAnyType> a;
+  a.emplace_back(1);
+  a.emplace_back(2);
+  a.emplace_back(3);
+  EXPECT_THAT(
+      a, ElementsAreArray({AnyWith<int>(1), AnyWith<int>(2), AnyWith<int>(3)}));
+
+  std::vector<SampleAnyType> b;
+  b.emplace_back("hello");
+  b.emplace_back("merhaba");
+  b.emplace_back("salut");
+  EXPECT_THAT(b, ElementsAreArray({AnyWith<std::string>("hello"),
+                                   AnyWith<std::string>("merhaba"),
+                                   AnyWith<std::string>("salut")}));
+}
+TEST(AnyWithTest, TestCompare) {
+  EXPECT_THAT(SampleAnyType(1), AnyWith<int>(Gt(0)));
+}
+
+TEST(AnyWithTest, DescribesSelf) {
+  const Matcher<const SampleAnyType&> m = AnyWith<int>(Eq(1));
+  EXPECT_THAT(Describe(m), ContainsRegex("is an 'any' type with value of type "
+                                         "'.*' and the value is equal to 1"));
+}
+
+TEST(AnyWithTest, ExplainsSelf) {
+  const Matcher<const SampleAnyType&> m = AnyWith<int>(Eq(1));
+
+  EXPECT_THAT(Explain(m, SampleAnyType(1)), ContainsRegex("whose value 1"));
+  EXPECT_THAT(Explain(m, SampleAnyType("A")),
+              HasSubstr("whose value is not of type '"));
+  EXPECT_THAT(Explain(m, SampleAnyType(2)), "whose value 2 doesn't match");
+}
+
+// Tests Args<k0, ..., kn>(m).
+
+TEST(ArgsTest, AcceptsZeroTemplateArg) {
+  const std::tuple<int, bool> t(5, true);
+  EXPECT_THAT(t, Args<>(Eq(std::tuple<>())));
+  EXPECT_THAT(t, Not(Args<>(Ne(std::tuple<>()))));
+}
+
+TEST(ArgsTest, AcceptsOneTemplateArg) {
+  const std::tuple<int, bool> t(5, true);
+  EXPECT_THAT(t, Args<0>(Eq(std::make_tuple(5))));
+  EXPECT_THAT(t, Args<1>(Eq(std::make_tuple(true))));
+  EXPECT_THAT(t, Not(Args<1>(Eq(std::make_tuple(false)))));
+}
+
+TEST(ArgsTest, AcceptsTwoTemplateArgs) {
+  const std::tuple<short, int, long> t(short{4}, 5, 6L);  // NOLINT
+
+  EXPECT_THAT(t, (Args<0, 1>(Lt())));
+  EXPECT_THAT(t, (Args<1, 2>(Lt())));
+  EXPECT_THAT(t, Not(Args<0, 2>(Gt())));
+}
+
+TEST(ArgsTest, AcceptsRepeatedTemplateArgs) {
+  const std::tuple<short, int, long> t(short{4}, 5, 6L);  // NOLINT
+  EXPECT_THAT(t, (Args<0, 0>(Eq())));
+  EXPECT_THAT(t, Not(Args<1, 1>(Ne())));
+}
+
+TEST(ArgsTest, AcceptsDecreasingTemplateArgs) {
+  const std::tuple<short, int, long> t(short{4}, 5, 6L);  // NOLINT
+  EXPECT_THAT(t, (Args<2, 0>(Gt())));
+  EXPECT_THAT(t, Not(Args<2, 1>(Lt())));
+}
+
+MATCHER(SumIsZero, "") {
+  return std::get<0>(arg) + std::get<1>(arg) + std::get<2>(arg) == 0;
+}
+
+TEST(ArgsTest, AcceptsMoreTemplateArgsThanArityOfOriginalTuple) {
+  EXPECT_THAT(std::make_tuple(-1, 2), (Args<0, 0, 1>(SumIsZero())));
+  EXPECT_THAT(std::make_tuple(1, 2), Not(Args<0, 0, 1>(SumIsZero())));
+}
+
+TEST(ArgsTest, CanBeNested) {
+  const std::tuple<short, int, long, int> t(short{4}, 5, 6L, 6);  // NOLINT
+  EXPECT_THAT(t, (Args<1, 2, 3>(Args<1, 2>(Eq()))));
+  EXPECT_THAT(t, (Args<0, 1, 3>(Args<0, 2>(Lt()))));
+}
+
+TEST(ArgsTest, CanMatchTupleByValue) {
+  typedef std::tuple<char, int, int> Tuple3;
+  const Matcher<Tuple3> m = Args<1, 2>(Lt());
+  EXPECT_TRUE(m.Matches(Tuple3('a', 1, 2)));
+  EXPECT_FALSE(m.Matches(Tuple3('b', 2, 2)));
+}
+
+TEST(ArgsTest, CanMatchTupleByReference) {
+  typedef std::tuple<char, char, int> Tuple3;
+  const Matcher<const Tuple3&> m = Args<0, 1>(Lt());
+  EXPECT_TRUE(m.Matches(Tuple3('a', 'b', 2)));
+  EXPECT_FALSE(m.Matches(Tuple3('b', 'b', 2)));
+}
+
+// Validates that arg is printed as str.
+MATCHER_P(PrintsAs, str, "") { return testing::PrintToString(arg) == str; }
+
+TEST(ArgsTest, AcceptsTenTemplateArgs) {
+  EXPECT_THAT(std::make_tuple(0, 1L, 2, 3L, 4, 5, 6, 7, 8, 9),
+              (Args<9, 8, 7, 6, 5, 4, 3, 2, 1, 0>(
+                  PrintsAs("(9, 8, 7, 6, 5, 4, 3, 2, 1, 0)"))));
+  EXPECT_THAT(std::make_tuple(0, 1L, 2, 3L, 4, 5, 6, 7, 8, 9),
+              Not(Args<9, 8, 7, 6, 5, 4, 3, 2, 1, 0>(
+                  PrintsAs("(0, 8, 7, 6, 5, 4, 3, 2, 1, 0)"))));
+}
+
+TEST(ArgsTest, DescirbesSelfCorrectly) {
+  const Matcher<std::tuple<int, bool, char>> m = Args<2, 0>(Lt());
+  EXPECT_EQ(
+      "are a tuple whose fields (#2, #0) are a pair where "
+      "the first < the second",
+      Describe(m));
+}
+
+TEST(ArgsTest, DescirbesNestedArgsCorrectly) {
+  const Matcher<const std::tuple<int, bool, char, int>&> m =
+      Args<0, 2, 3>(Args<2, 0>(Lt()));
+  EXPECT_EQ(
+      "are a tuple whose fields (#0, #2, #3) are a tuple "
+      "whose fields (#2, #0) are a pair where the first < the second",
+      Describe(m));
+}
+
+TEST(ArgsTest, DescribesNegationCorrectly) {
+  const Matcher<std::tuple<int, char>> m = Args<1, 0>(Gt());
+  EXPECT_EQ(
+      "are a tuple whose fields (#1, #0) aren't a pair "
+      "where the first > the second",
+      DescribeNegation(m));
+}
+
+TEST(ArgsTest, ExplainsMatchResultWithoutInnerExplanation) {
+  const Matcher<std::tuple<bool, int, int>> m = Args<1, 2>(Eq());
+  EXPECT_EQ("whose fields (#1, #2) are (42, 42)",
+            Explain(m, std::make_tuple(false, 42, 42)));
+  EXPECT_EQ("whose fields (#1, #2) are (42, 43)",
+            Explain(m, std::make_tuple(false, 42, 43)));
+}
+
+// For testing Args<>'s explanation.
+class LessThanMatcher : public MatcherInterface<std::tuple<char, int>> {
+ public:
+  void DescribeTo(::std::ostream* /*os*/) const override {}
+
+  bool MatchAndExplain(std::tuple<char, int> value,
+                       MatchResultListener* listener) const override {
+    const int diff = std::get<0>(value) - std::get<1>(value);
+    if (diff > 0) {
+      *listener << "where the first value is " << diff
+                << " more than the second";
+    }
+    return diff < 0;
+  }
+};
+
+Matcher<std::tuple<char, int>> LessThan() {
+  return MakeMatcher(new LessThanMatcher);
+}
+
+TEST(ArgsTest, ExplainsMatchResultWithInnerExplanation) {
+  const Matcher<std::tuple<char, int, int>> m = Args<0, 2>(LessThan());
+  EXPECT_EQ(
+      "whose fields (#0, #2) are ('a' (97, 0x61), 42), "
+      "where the first value is 55 more than the second",
+      Explain(m, std::make_tuple('a', 42, 42)));
+  EXPECT_EQ("whose fields (#0, #2) are ('\\0', 43)",
+            Explain(m, std::make_tuple('\0', 42, 43)));
+}
+
+// Tests for the MATCHER*() macro family.
+
+// Tests that a simple MATCHER() definition works.
+
+MATCHER(IsEven, "") { return (arg % 2) == 0; }
+
+TEST(MatcherMacroTest, Works) {
+  const Matcher<int> m = IsEven();
+  EXPECT_TRUE(m.Matches(6));
+  EXPECT_FALSE(m.Matches(7));
+
+  EXPECT_EQ("is even", Describe(m));
+  EXPECT_EQ("not (is even)", DescribeNegation(m));
+  EXPECT_EQ("", Explain(m, 6));
+  EXPECT_EQ("", Explain(m, 7));
+}
+
+// This also tests that the description string can reference 'negation'.
+MATCHER(IsEven2, negation ? "is odd" : "is even") {
+  if ((arg % 2) == 0) {
+    // Verifies that we can stream to result_listener, a listener
+    // supplied by the MATCHER macro implicitly.
+    *result_listener << "OK";
+    return true;
+  } else {
+    *result_listener << "% 2 == " << (arg % 2);
+    return false;
+  }
+}
+
+// This also tests that the description string can reference matcher
+// parameters.
+MATCHER_P2(EqSumOf, x, y,
+           std::string(negation ? "doesn't equal" : "equals") + " the sum of " +
+               PrintToString(x) + " and " + PrintToString(y)) {
+  if (arg == (x + y)) {
+    *result_listener << "OK";
+    return true;
+  } else {
+    // Verifies that we can stream to the underlying stream of
+    // result_listener.
+    if (result_listener->stream() != nullptr) {
+      *result_listener->stream() << "diff == " << (x + y - arg);
+    }
+    return false;
+  }
+}
+
+// Tests that the matcher description can reference 'negation' and the
+// matcher parameters.
+TEST(MatcherMacroTest, DescriptionCanReferenceNegationAndParameters) {
+  const Matcher<int> m1 = IsEven2();
+  EXPECT_EQ("is even", Describe(m1));
+  EXPECT_EQ("is odd", DescribeNegation(m1));
+
+  const Matcher<int> m2 = EqSumOf(5, 9);
+  EXPECT_EQ("equals the sum of 5 and 9", Describe(m2));
+  EXPECT_EQ("doesn't equal the sum of 5 and 9", DescribeNegation(m2));
+}
+
+// Tests explaining match result in a MATCHER* macro.
+TEST(MatcherMacroTest, CanExplainMatchResult) {
+  const Matcher<int> m1 = IsEven2();
+  EXPECT_EQ("OK", Explain(m1, 4));
+  EXPECT_EQ("% 2 == 1", Explain(m1, 5));
+
+  const Matcher<int> m2 = EqSumOf(1, 2);
+  EXPECT_EQ("OK", Explain(m2, 3));
+  EXPECT_EQ("diff == -1", Explain(m2, 4));
+}
+
+// Tests that the body of MATCHER() can reference the type of the
+// value being matched.
+
+MATCHER(IsEmptyString, "") {
+  StaticAssertTypeEq<::std::string, arg_type>();
+  return arg.empty();
+}
+
+MATCHER(IsEmptyStringByRef, "") {
+  StaticAssertTypeEq<const ::std::string&, arg_type>();
+  return arg.empty();
+}
+
+TEST(MatcherMacroTest, CanReferenceArgType) {
+  const Matcher<::std::string> m1 = IsEmptyString();
+  EXPECT_TRUE(m1.Matches(""));
+
+  const Matcher<const ::std::string&> m2 = IsEmptyStringByRef();
+  EXPECT_TRUE(m2.Matches(""));
+}
+
+// Tests that MATCHER() can be used in a namespace.
+
+namespace matcher_test {
+MATCHER(IsOdd, "") { return (arg % 2) != 0; }
+}  // namespace matcher_test
+
+TEST(MatcherMacroTest, WorksInNamespace) {
+  Matcher<int> m = matcher_test::IsOdd();
+  EXPECT_FALSE(m.Matches(4));
+  EXPECT_TRUE(m.Matches(5));
+}
+
+// Tests that Value() can be used to compose matchers.
+MATCHER(IsPositiveOdd, "") {
+  return Value(arg, matcher_test::IsOdd()) && arg > 0;
+}
+
+TEST(MatcherMacroTest, CanBeComposedUsingValue) {
+  EXPECT_THAT(3, IsPositiveOdd());
+  EXPECT_THAT(4, Not(IsPositiveOdd()));
+  EXPECT_THAT(-1, Not(IsPositiveOdd()));
+}
+
+// Tests that a simple MATCHER_P() definition works.
+
+MATCHER_P(IsGreaterThan32And, n, "") { return arg > 32 && arg > n; }
+
+TEST(MatcherPMacroTest, Works) {
+  const Matcher<int> m = IsGreaterThan32And(5);
+  EXPECT_TRUE(m.Matches(36));
+  EXPECT_FALSE(m.Matches(5));
+
+  EXPECT_EQ("is greater than 32 and (n: 5)", Describe(m));
+  EXPECT_EQ("not (is greater than 32 and (n: 5))", DescribeNegation(m));
+  EXPECT_EQ("", Explain(m, 36));
+  EXPECT_EQ("", Explain(m, 5));
+}
+
+// Tests that the description is calculated correctly from the matcher name.
+MATCHER_P(_is_Greater_Than32and_, n, "") { return arg > 32 && arg > n; }
+
+TEST(MatcherPMacroTest, GeneratesCorrectDescription) {
+  const Matcher<int> m = _is_Greater_Than32and_(5);
+
+  EXPECT_EQ("is greater than 32 and (n: 5)", Describe(m));
+  EXPECT_EQ("not (is greater than 32 and (n: 5))", DescribeNegation(m));
+  EXPECT_EQ("", Explain(m, 36));
+  EXPECT_EQ("", Explain(m, 5));
+}
+
+// Tests that a MATCHER_P matcher can be explicitly instantiated with
+// a reference parameter type.
+
+class UncopyableFoo {
+ public:
+  explicit UncopyableFoo(char value) : value_(value) { (void)value_; }
+
+  UncopyableFoo(const UncopyableFoo&) = delete;
+  void operator=(const UncopyableFoo&) = delete;
+
+ private:
+  char value_;
+};
+
+MATCHER_P(ReferencesUncopyable, variable, "") { return &arg == &variable; }
+
+TEST(MatcherPMacroTest, WorksWhenExplicitlyInstantiatedWithReference) {
+  UncopyableFoo foo1('1'), foo2('2');
+  const Matcher<const UncopyableFoo&> m =
+      ReferencesUncopyable<const UncopyableFoo&>(foo1);
+
+  EXPECT_TRUE(m.Matches(foo1));
+  EXPECT_FALSE(m.Matches(foo2));
+
+  // We don't want the address of the parameter printed, as most
+  // likely it will just annoy the user.  If the address is
+  // interesting, the user should consider passing the parameter by
+  // pointer instead.
+  EXPECT_EQ("references uncopyable (variable: 1-byte object <31>)",
+            Describe(m));
+}
+
+// Tests that the body of MATCHER_Pn() can reference the parameter
+// types.
+
+MATCHER_P3(ParamTypesAreIntLongAndChar, foo, bar, baz, "") {
+  StaticAssertTypeEq<int, foo_type>();
+  StaticAssertTypeEq<long, bar_type>();  // NOLINT
+  StaticAssertTypeEq<char, baz_type>();
+  return arg == 0;
+}
+
+TEST(MatcherPnMacroTest, CanReferenceParamTypes) {
+  EXPECT_THAT(0, ParamTypesAreIntLongAndChar(10, 20L, 'a'));
+}
+
+// Tests that a MATCHER_Pn matcher can be explicitly instantiated with
+// reference parameter types.
+
+MATCHER_P2(ReferencesAnyOf, variable1, variable2, "") {
+  return &arg == &variable1 || &arg == &variable2;
+}
+
+TEST(MatcherPnMacroTest, WorksWhenExplicitlyInstantiatedWithReferences) {
+  UncopyableFoo foo1('1'), foo2('2'), foo3('3');
+  const Matcher<const UncopyableFoo&> const_m =
+      ReferencesAnyOf<const UncopyableFoo&, const UncopyableFoo&>(foo1, foo2);
+
+  EXPECT_TRUE(const_m.Matches(foo1));
+  EXPECT_TRUE(const_m.Matches(foo2));
+  EXPECT_FALSE(const_m.Matches(foo3));
+
+  const Matcher<UncopyableFoo&> m =
+      ReferencesAnyOf<UncopyableFoo&, UncopyableFoo&>(foo1, foo2);
+
+  EXPECT_TRUE(m.Matches(foo1));
+  EXPECT_TRUE(m.Matches(foo2));
+  EXPECT_FALSE(m.Matches(foo3));
+}
+
+TEST(MatcherPnMacroTest,
+     GeneratesCorretDescriptionWhenExplicitlyInstantiatedWithReferences) {
+  UncopyableFoo foo1('1'), foo2('2');
+  const Matcher<const UncopyableFoo&> m =
+      ReferencesAnyOf<const UncopyableFoo&, const UncopyableFoo&>(foo1, foo2);
+
+  // We don't want the addresses of the parameters printed, as most
+  // likely they will just annoy the user.  If the addresses are
+  // interesting, the user should consider passing the parameters by
+  // pointers instead.
+  EXPECT_EQ(
+      "references any of (variable1: 1-byte object <31>, variable2: 1-byte "
+      "object <32>)",
+      Describe(m));
+}
+
+// Tests that a simple MATCHER_P2() definition works.
+
+MATCHER_P2(IsNotInClosedRange, low, hi, "") { return arg < low || arg > hi; }
+
+TEST(MatcherPnMacroTest, Works) {
+  const Matcher<const long&> m = IsNotInClosedRange(10, 20);  // NOLINT
+  EXPECT_TRUE(m.Matches(36L));
+  EXPECT_FALSE(m.Matches(15L));
+
+  EXPECT_EQ("is not in closed range (low: 10, hi: 20)", Describe(m));
+  EXPECT_EQ("not (is not in closed range (low: 10, hi: 20))",
+            DescribeNegation(m));
+  EXPECT_EQ("", Explain(m, 36L));
+  EXPECT_EQ("", Explain(m, 15L));
+}
+
+// Tests that MATCHER*() definitions can be overloaded on the number
+// of parameters; also tests MATCHER_Pn() where n >= 3.
+
+MATCHER(EqualsSumOf, "") { return arg == 0; }
+MATCHER_P(EqualsSumOf, a, "") { return arg == a; }
+MATCHER_P2(EqualsSumOf, a, b, "") { return arg == a + b; }
+MATCHER_P3(EqualsSumOf, a, b, c, "") { return arg == a + b + c; }
+MATCHER_P4(EqualsSumOf, a, b, c, d, "") { return arg == a + b + c + d; }
+MATCHER_P5(EqualsSumOf, a, b, c, d, e, "") { return arg == a + b + c + d + e; }
+MATCHER_P6(EqualsSumOf, a, b, c, d, e, f, "") {
+  return arg == a + b + c + d + e + f;
+}
+MATCHER_P7(EqualsSumOf, a, b, c, d, e, f, g, "") {
+  return arg == a + b + c + d + e + f + g;
+}
+MATCHER_P8(EqualsSumOf, a, b, c, d, e, f, g, h, "") {
+  return arg == a + b + c + d + e + f + g + h;
+}
+MATCHER_P9(EqualsSumOf, a, b, c, d, e, f, g, h, i, "") {
+  return arg == a + b + c + d + e + f + g + h + i;
+}
+MATCHER_P10(EqualsSumOf, a, b, c, d, e, f, g, h, i, j, "") {
+  return arg == a + b + c + d + e + f + g + h + i + j;
+}
+
+TEST(MatcherPnMacroTest, CanBeOverloadedOnNumberOfParameters) {
+  EXPECT_THAT(0, EqualsSumOf());
+  EXPECT_THAT(1, EqualsSumOf(1));
+  EXPECT_THAT(12, EqualsSumOf(10, 2));
+  EXPECT_THAT(123, EqualsSumOf(100, 20, 3));
+  EXPECT_THAT(1234, EqualsSumOf(1000, 200, 30, 4));
+  EXPECT_THAT(12345, EqualsSumOf(10000, 2000, 300, 40, 5));
+  EXPECT_THAT("abcdef",
+              EqualsSumOf(::std::string("a"), 'b', 'c', "d", "e", 'f'));
+  EXPECT_THAT("abcdefg",
+              EqualsSumOf(::std::string("a"), 'b', 'c', "d", "e", 'f', 'g'));
+  EXPECT_THAT("abcdefgh", EqualsSumOf(::std::string("a"), 'b', 'c', "d", "e",
+                                      'f', 'g', "h"));
+  EXPECT_THAT("abcdefghi", EqualsSumOf(::std::string("a"), 'b', 'c', "d", "e",
+                                       'f', 'g', "h", 'i'));
+  EXPECT_THAT("abcdefghij",
+              EqualsSumOf(::std::string("a"), 'b', 'c', "d", "e", 'f', 'g', "h",
+                          'i', ::std::string("j")));
+
+  EXPECT_THAT(1, Not(EqualsSumOf()));
+  EXPECT_THAT(-1, Not(EqualsSumOf(1)));
+  EXPECT_THAT(-12, Not(EqualsSumOf(10, 2)));
+  EXPECT_THAT(-123, Not(EqualsSumOf(100, 20, 3)));
+  EXPECT_THAT(-1234, Not(EqualsSumOf(1000, 200, 30, 4)));
+  EXPECT_THAT(-12345, Not(EqualsSumOf(10000, 2000, 300, 40, 5)));
+  EXPECT_THAT("abcdef ",
+              Not(EqualsSumOf(::std::string("a"), 'b', 'c', "d", "e", 'f')));
+  EXPECT_THAT("abcdefg ", Not(EqualsSumOf(::std::string("a"), 'b', 'c', "d",
+                                          "e", 'f', 'g')));
+  EXPECT_THAT("abcdefgh ", Not(EqualsSumOf(::std::string("a"), 'b', 'c', "d",
+                                           "e", 'f', 'g', "h")));
+  EXPECT_THAT("abcdefghi ", Not(EqualsSumOf(::std::string("a"), 'b', 'c', "d",
+                                            "e", 'f', 'g', "h", 'i')));
+  EXPECT_THAT("abcdefghij ",
+              Not(EqualsSumOf(::std::string("a"), 'b', 'c', "d", "e", 'f', 'g',
+                              "h", 'i', ::std::string("j"))));
+}
+
+// Tests that a MATCHER_Pn() definition can be instantiated with any
+// compatible parameter types.
+TEST(MatcherPnMacroTest, WorksForDifferentParameterTypes) {
+  EXPECT_THAT(123, EqualsSumOf(100L, 20, static_cast<char>(3)));
+  EXPECT_THAT("abcd", EqualsSumOf(::std::string("a"), "b", 'c', "d"));
+
+  EXPECT_THAT(124, Not(EqualsSumOf(100L, 20, static_cast<char>(3))));
+  EXPECT_THAT("abcde", Not(EqualsSumOf(::std::string("a"), "b", 'c', "d")));
+}
+
+// Tests that the matcher body can promote the parameter types.
+
+MATCHER_P2(EqConcat, prefix, suffix, "") {
+  // The following lines promote the two parameters to desired types.
+  std::string prefix_str(prefix);
+  char suffix_char = static_cast<char>(suffix);
+  return arg == prefix_str + suffix_char;
+}
+
+TEST(MatcherPnMacroTest, SimpleTypePromotion) {
+  Matcher<std::string> no_promo = EqConcat(std::string("foo"), 't');
+  Matcher<const std::string&> promo = EqConcat("foo", static_cast<int>('t'));
+  EXPECT_FALSE(no_promo.Matches("fool"));
+  EXPECT_FALSE(promo.Matches("fool"));
+  EXPECT_TRUE(no_promo.Matches("foot"));
+  EXPECT_TRUE(promo.Matches("foot"));
+}
+
+// Verifies the type of a MATCHER*.
+
+TEST(MatcherPnMacroTest, TypesAreCorrect) {
+  // EqualsSumOf() must be assignable to a EqualsSumOfMatcher variable.
+  EqualsSumOfMatcher a0 = EqualsSumOf();
+
+  // EqualsSumOf(1) must be assignable to a EqualsSumOfMatcherP variable.
+  EqualsSumOfMatcherP<int> a1 = EqualsSumOf(1);
+
+  // EqualsSumOf(p1, ..., pk) must be assignable to a EqualsSumOfMatcherPk
+  // variable, and so on.
+  EqualsSumOfMatcherP2<int, char> a2 = EqualsSumOf(1, '2');
+  EqualsSumOfMatcherP3<int, int, char> a3 = EqualsSumOf(1, 2, '3');
+  EqualsSumOfMatcherP4<int, int, int, char> a4 = EqualsSumOf(1, 2, 3, '4');
+  EqualsSumOfMatcherP5<int, int, int, int, char> a5 =
+      EqualsSumOf(1, 2, 3, 4, '5');
+  EqualsSumOfMatcherP6<int, int, int, int, int, char> a6 =
+      EqualsSumOf(1, 2, 3, 4, 5, '6');
+  EqualsSumOfMatcherP7<int, int, int, int, int, int, char> a7 =
+      EqualsSumOf(1, 2, 3, 4, 5, 6, '7');
+  EqualsSumOfMatcherP8<int, int, int, int, int, int, int, char> a8 =
+      EqualsSumOf(1, 2, 3, 4, 5, 6, 7, '8');
+  EqualsSumOfMatcherP9<int, int, int, int, int, int, int, int, char> a9 =
+      EqualsSumOf(1, 2, 3, 4, 5, 6, 7, 8, '9');
+  EqualsSumOfMatcherP10<int, int, int, int, int, int, int, int, int, char> a10 =
+      EqualsSumOf(1, 2, 3, 4, 5, 6, 7, 8, 9, '0');
+
+  // Avoid "unused variable" warnings.
+  (void)a0;
+  (void)a1;
+  (void)a2;
+  (void)a3;
+  (void)a4;
+  (void)a5;
+  (void)a6;
+  (void)a7;
+  (void)a8;
+  (void)a9;
+  (void)a10;
+}
+
+// Tests that matcher-typed parameters can be used in Value() inside a
+// MATCHER_Pn definition.
+
+// Succeeds if arg matches exactly 2 of the 3 matchers.
+MATCHER_P3(TwoOf, m1, m2, m3, "") {
+  const int count = static_cast<int>(Value(arg, m1)) +
+                    static_cast<int>(Value(arg, m2)) +
+                    static_cast<int>(Value(arg, m3));
+  return count == 2;
+}
+
+TEST(MatcherPnMacroTest, CanUseMatcherTypedParameterInValue) {
+  EXPECT_THAT(42, TwoOf(Gt(0), Lt(50), Eq(10)));
+  EXPECT_THAT(0, Not(TwoOf(Gt(-1), Lt(1), Eq(0))));
+}
+
+// Tests Contains().Times().
+
+INSTANTIATE_GTEST_MATCHER_TEST_P(ContainsTimes);
+
+TEST(ContainsTimes, ListMatchesWhenElementQuantityMatches) {
+  list<int> some_list;
+  some_list.push_back(3);
+  some_list.push_back(1);
+  some_list.push_back(2);
+  some_list.push_back(3);
+  EXPECT_THAT(some_list, Contains(3).Times(2));
+  EXPECT_THAT(some_list, Contains(2).Times(1));
+  EXPECT_THAT(some_list, Contains(Ge(2)).Times(3));
+  EXPECT_THAT(some_list, Contains(Ge(2)).Times(Gt(2)));
+  EXPECT_THAT(some_list, Contains(4).Times(0));
+  EXPECT_THAT(some_list, Contains(_).Times(4));
+  EXPECT_THAT(some_list, Not(Contains(5).Times(1)));
+  EXPECT_THAT(some_list, Contains(5).Times(_));  // Times(_) always matches
+  EXPECT_THAT(some_list, Not(Contains(3).Times(1)));
+  EXPECT_THAT(some_list, Contains(3).Times(Not(1)));
+  EXPECT_THAT(list<int>{}, Not(Contains(_)));
+}
+
+TEST_P(ContainsTimesP, ExplainsMatchResultCorrectly) {
+  const int a[2] = {1, 2};
+  Matcher<const int(&)[2]> m = Contains(2).Times(3);
+  EXPECT_EQ(
+      "whose element #1 matches but whose match quantity of 1 does not match",
+      Explain(m, a));
+
+  m = Contains(3).Times(0);
+  EXPECT_EQ("has no element that matches and whose match quantity of 0 matches",
+            Explain(m, a));
+
+  m = Contains(3).Times(4);
+  EXPECT_EQ(
+      "has no element that matches and whose match quantity of 0 does not "
+      "match",
+      Explain(m, a));
+
+  m = Contains(2).Times(4);
+  EXPECT_EQ(
+      "whose element #1 matches but whose match quantity of 1 does not "
+      "match",
+      Explain(m, a));
+
+  m = Contains(GreaterThan(0)).Times(2);
+  EXPECT_EQ("whose elements (0, 1) match and whose match quantity of 2 matches",
+            Explain(m, a));
+
+  m = Contains(GreaterThan(10)).Times(Gt(1));
+  EXPECT_EQ(
+      "has no element that matches and whose match quantity of 0 does not "
+      "match",
+      Explain(m, a));
+
+  m = Contains(GreaterThan(0)).Times(GreaterThan<size_t>(5));
+  EXPECT_EQ(
+      "whose elements (0, 1) match but whose match quantity of 2 does not "
+      "match, which is 3 less than 5",
+      Explain(m, a));
+}
+
+TEST(ContainsTimes, DescribesItselfCorrectly) {
+  Matcher<vector<int>> m = Contains(1).Times(2);
+  EXPECT_EQ("quantity of elements that match is equal to 1 is equal to 2",
+            Describe(m));
+
+  Matcher<vector<int>> m2 = Not(m);
+  EXPECT_EQ("quantity of elements that match is equal to 1 isn't equal to 2",
+            Describe(m2));
+}
+
+// Tests AllOfArray()
+
+TEST(AllOfArrayTest, BasicForms) {
+  // Iterator
+  std::vector<int> v0{};
+  std::vector<int> v1{1};
+  std::vector<int> v2{2, 3};
+  std::vector<int> v3{4, 4, 4};
+  EXPECT_THAT(0, AllOfArray(v0.begin(), v0.end()));
+  EXPECT_THAT(1, AllOfArray(v1.begin(), v1.end()));
+  EXPECT_THAT(2, Not(AllOfArray(v1.begin(), v1.end())));
+  EXPECT_THAT(3, Not(AllOfArray(v2.begin(), v2.end())));
+  EXPECT_THAT(4, AllOfArray(v3.begin(), v3.end()));
+  // Pointer +  size
+  int ar[6] = {1, 2, 3, 4, 4, 4};
+  EXPECT_THAT(0, AllOfArray(ar, 0));
+  EXPECT_THAT(1, AllOfArray(ar, 1));
+  EXPECT_THAT(2, Not(AllOfArray(ar, 1)));
+  EXPECT_THAT(3, Not(AllOfArray(ar + 1, 3)));
+  EXPECT_THAT(4, AllOfArray(ar + 3, 3));
+  // Array
+  // int ar0[0];  Not usable
+  int ar1[1] = {1};
+  int ar2[2] = {2, 3};
+  int ar3[3] = {4, 4, 4};
+  // EXPECT_THAT(0, Not(AllOfArray(ar0)));  // Cannot work
+  EXPECT_THAT(1, AllOfArray(ar1));
+  EXPECT_THAT(2, Not(AllOfArray(ar1)));
+  EXPECT_THAT(3, Not(AllOfArray(ar2)));
+  EXPECT_THAT(4, AllOfArray(ar3));
+  // Container
+  EXPECT_THAT(0, AllOfArray(v0));
+  EXPECT_THAT(1, AllOfArray(v1));
+  EXPECT_THAT(2, Not(AllOfArray(v1)));
+  EXPECT_THAT(3, Not(AllOfArray(v2)));
+  EXPECT_THAT(4, AllOfArray(v3));
+  // Initializer
+  EXPECT_THAT(0, AllOfArray<int>({}));  // Requires template arg.
+  EXPECT_THAT(1, AllOfArray({1}));
+  EXPECT_THAT(2, Not(AllOfArray({1})));
+  EXPECT_THAT(3, Not(AllOfArray({2, 3})));
+  EXPECT_THAT(4, AllOfArray({4, 4, 4}));
+}
+
+TEST(AllOfArrayTest, Matchers) {
+  // vector
+  std::vector<Matcher<int>> matchers{Ge(1), Lt(2)};
+  EXPECT_THAT(0, Not(AllOfArray(matchers)));
+  EXPECT_THAT(1, AllOfArray(matchers));
+  EXPECT_THAT(2, Not(AllOfArray(matchers)));
+  // initializer_list
+  EXPECT_THAT(0, Not(AllOfArray({Ge(0), Ge(1)})));
+  EXPECT_THAT(1, AllOfArray({Ge(0), Ge(1)}));
+}
+
+INSTANTIATE_GTEST_MATCHER_TEST_P(AnyOfArrayTest);
+
+TEST(AnyOfArrayTest, BasicForms) {
+  // Iterator
+  std::vector<int> v0{};
+  std::vector<int> v1{1};
+  std::vector<int> v2{2, 3};
+  EXPECT_THAT(0, Not(AnyOfArray(v0.begin(), v0.end())));
+  EXPECT_THAT(1, AnyOfArray(v1.begin(), v1.end()));
+  EXPECT_THAT(2, Not(AnyOfArray(v1.begin(), v1.end())));
+  EXPECT_THAT(3, AnyOfArray(v2.begin(), v2.end()));
+  EXPECT_THAT(4, Not(AnyOfArray(v2.begin(), v2.end())));
+  // Pointer +  size
+  int ar[3] = {1, 2, 3};
+  EXPECT_THAT(0, Not(AnyOfArray(ar, 0)));
+  EXPECT_THAT(1, AnyOfArray(ar, 1));
+  EXPECT_THAT(2, Not(AnyOfArray(ar, 1)));
+  EXPECT_THAT(3, AnyOfArray(ar + 1, 2));
+  EXPECT_THAT(4, Not(AnyOfArray(ar + 1, 2)));
+  // Array
+  // int ar0[0];  Not usable
+  int ar1[1] = {1};
+  int ar2[2] = {2, 3};
+  // EXPECT_THAT(0, Not(AnyOfArray(ar0)));  // Cannot work
+  EXPECT_THAT(1, AnyOfArray(ar1));
+  EXPECT_THAT(2, Not(AnyOfArray(ar1)));
+  EXPECT_THAT(3, AnyOfArray(ar2));
+  EXPECT_THAT(4, Not(AnyOfArray(ar2)));
+  // Container
+  EXPECT_THAT(0, Not(AnyOfArray(v0)));
+  EXPECT_THAT(1, AnyOfArray(v1));
+  EXPECT_THAT(2, Not(AnyOfArray(v1)));
+  EXPECT_THAT(3, AnyOfArray(v2));
+  EXPECT_THAT(4, Not(AnyOfArray(v2)));
+  // Initializer
+  EXPECT_THAT(0, Not(AnyOfArray<int>({})));  // Requires template arg.
+  EXPECT_THAT(1, AnyOfArray({1}));
+  EXPECT_THAT(2, Not(AnyOfArray({1})));
+  EXPECT_THAT(3, AnyOfArray({2, 3}));
+  EXPECT_THAT(4, Not(AnyOfArray({2, 3})));
+}
+
+TEST(AnyOfArrayTest, Matchers) {
+  // We negate test AllOfArrayTest.Matchers.
+  // vector
+  std::vector<Matcher<int>> matchers{Lt(1), Ge(2)};
+  EXPECT_THAT(0, AnyOfArray(matchers));
+  EXPECT_THAT(1, Not(AnyOfArray(matchers)));
+  EXPECT_THAT(2, AnyOfArray(matchers));
+  // initializer_list
+  EXPECT_THAT(0, AnyOfArray({Lt(0), Lt(1)}));
+  EXPECT_THAT(1, Not(AllOfArray({Lt(0), Lt(1)})));
+}
+
+TEST_P(AnyOfArrayTestP, ExplainsMatchResultCorrectly) {
+  // AnyOfArray and AllOfArray use the same underlying template-template,
+  // thus it is sufficient to test one here.
+  const std::vector<int> v0{};
+  const std::vector<int> v1{1};
+  const std::vector<int> v2{2, 3};
+  const Matcher<int> m0 = AnyOfArray(v0);
+  const Matcher<int> m1 = AnyOfArray(v1);
+  const Matcher<int> m2 = AnyOfArray(v2);
+  EXPECT_EQ("", Explain(m0, 0));
+  EXPECT_EQ("", Explain(m1, 1));
+  EXPECT_EQ("", Explain(m1, 2));
+  EXPECT_EQ("", Explain(m2, 3));
+  EXPECT_EQ("", Explain(m2, 4));
+  EXPECT_EQ("()", Describe(m0));
+  EXPECT_EQ("(is equal to 1)", Describe(m1));
+  EXPECT_EQ("(is equal to 2) or (is equal to 3)", Describe(m2));
+  EXPECT_EQ("()", DescribeNegation(m0));
+  EXPECT_EQ("(isn't equal to 1)", DescribeNegation(m1));
+  EXPECT_EQ("(isn't equal to 2) and (isn't equal to 3)", DescribeNegation(m2));
+  // Explain with matchers
+  const Matcher<int> g1 = AnyOfArray({GreaterThan(1)});
+  const Matcher<int> g2 = AnyOfArray({GreaterThan(1), GreaterThan(2)});
+  // Explains the first positive match and all prior negative matches...
+  EXPECT_EQ("which is 1 less than 1", Explain(g1, 0));
+  EXPECT_EQ("which is the same as 1", Explain(g1, 1));
+  EXPECT_EQ("which is 1 more than 1", Explain(g1, 2));
+  EXPECT_EQ("which is 1 less than 1, and which is 2 less than 2",
+            Explain(g2, 0));
+  EXPECT_EQ("which is the same as 1, and which is 1 less than 2",
+            Explain(g2, 1));
+  EXPECT_EQ("which is 1 more than 1",  // Only the first
+            Explain(g2, 2));
+}
+
+MATCHER(IsNotNull, "") { return arg != nullptr; }
+
+// Verifies that a matcher defined using MATCHER() can work on
+// move-only types.
+TEST(MatcherMacroTest, WorksOnMoveOnlyType) {
+  std::unique_ptr<int> p(new int(3));
+  EXPECT_THAT(p, IsNotNull());
+  EXPECT_THAT(std::unique_ptr<int>(), Not(IsNotNull()));
+}
+
+MATCHER_P(UniquePointee, pointee, "") { return *arg == pointee; }
+
+// Verifies that a matcher defined using MATCHER_P*() can work on
+// move-only types.
+TEST(MatcherPMacroTest, WorksOnMoveOnlyType) {
+  std::unique_ptr<int> p(new int(3));
+  EXPECT_THAT(p, UniquePointee(3));
+  EXPECT_THAT(p, Not(UniquePointee(2)));
+}
+
+MATCHER(EnsureNoUnusedButMarkedUnusedWarning, "") { return (arg % 2) == 0; }
+
+TEST(MockMethodMockFunctionTest, EnsureNoUnusedButMarkedUnusedWarning) {
+#ifdef __clang__
+#pragma clang diagnostic push
+#pragma clang diagnostic error "-Wused-but-marked-unused"
+#endif
+  // https://github.com/google/googletest/issues/4055
+  EXPECT_THAT(0, EnsureNoUnusedButMarkedUnusedWarning());
+#ifdef __clang__
+#pragma clang diagnostic pop
+#endif
+}
+
+#if GTEST_HAS_EXCEPTIONS
+
+// std::function<void()> is used below for compatibility with older copies of
+// GCC. Normally, a raw lambda is all that is needed.
+
+// Test that examples from documentation compile
+TEST(ThrowsTest, Examples) {
+  EXPECT_THAT(
+      std::function<void()>([]() { throw std::runtime_error("message"); }),
+      Throws<std::runtime_error>());
+
+  EXPECT_THAT(
+      std::function<void()>([]() { throw std::runtime_error("message"); }),
+      ThrowsMessage<std::runtime_error>(HasSubstr("message")));
+}
+
+TEST(ThrowsTest, PrintsExceptionWhat) {
+  EXPECT_THAT(
+      std::function<void()>([]() { throw std::runtime_error("ABC123XYZ"); }),
+      ThrowsMessage<std::runtime_error>(HasSubstr("ABC123XYZ")));
+}
+
+TEST(ThrowsTest, DoesNotGenerateDuplicateCatchClauseWarning) {
+  EXPECT_THAT(std::function<void()>([]() { throw std::exception(); }),
+              Throws<std::exception>());
+}
+
+TEST(ThrowsTest, CallableExecutedExactlyOnce) {
+  size_t a = 0;
+
+  EXPECT_THAT(std::function<void()>([&a]() {
+                a++;
+                throw 10;
+              }),
+              Throws<int>());
+  EXPECT_EQ(a, 1u);
+
+  EXPECT_THAT(std::function<void()>([&a]() {
+                a++;
+                throw std::runtime_error("message");
+              }),
+              Throws<std::runtime_error>());
+  EXPECT_EQ(a, 2u);
+
+  EXPECT_THAT(std::function<void()>([&a]() {
+                a++;
+                throw std::runtime_error("message");
+              }),
+              ThrowsMessage<std::runtime_error>(HasSubstr("message")));
+  EXPECT_EQ(a, 3u);
+
+  EXPECT_THAT(std::function<void()>([&a]() {
+                a++;
+                throw std::runtime_error("message");
+              }),
+              Throws<std::runtime_error>(
+                  Property(&std::runtime_error::what, HasSubstr("message"))));
+  EXPECT_EQ(a, 4u);
+}
+
+TEST(ThrowsTest, Describe) {
+  Matcher<std::function<void()>> matcher = Throws<std::runtime_error>();
+  std::stringstream ss;
+  matcher.DescribeTo(&ss);
+  auto explanation = ss.str();
+  EXPECT_THAT(explanation, HasSubstr("std::runtime_error"));
+}
+
+TEST(ThrowsTest, Success) {
+  Matcher<std::function<void()>> matcher = Throws<std::runtime_error>();
+  StringMatchResultListener listener;
+  EXPECT_TRUE(matcher.MatchAndExplain(
+      []() { throw std::runtime_error("error message"); }, &listener));
+  EXPECT_THAT(listener.str(), HasSubstr("std::runtime_error"));
+}
+
+TEST(ThrowsTest, FailWrongType) {
+  Matcher<std::function<void()>> matcher = Throws<std::runtime_error>();
+  StringMatchResultListener listener;
+  EXPECT_FALSE(matcher.MatchAndExplain(
+      []() { throw std::logic_error("error message"); }, &listener));
+  EXPECT_THAT(listener.str(), HasSubstr("std::logic_error"));
+  EXPECT_THAT(listener.str(), HasSubstr("\"error message\""));
+}
+
+TEST(ThrowsTest, FailWrongTypeNonStd) {
+  Matcher<std::function<void()>> matcher = Throws<std::runtime_error>();
+  StringMatchResultListener listener;
+  EXPECT_FALSE(matcher.MatchAndExplain([]() { throw 10; }, &listener));
+  EXPECT_THAT(listener.str(),
+              HasSubstr("throws an exception of an unknown type"));
+}
+
+TEST(ThrowsTest, FailNoThrow) {
+  Matcher<std::function<void()>> matcher = Throws<std::runtime_error>();
+  StringMatchResultListener listener;
+  EXPECT_FALSE(matcher.MatchAndExplain([]() { (void)0; }, &listener));
+  EXPECT_THAT(listener.str(), HasSubstr("does not throw any exception"));
+}
+
+class ThrowsPredicateTest
+    : public TestWithParam<Matcher<std::function<void()>>> {};
+
+TEST_P(ThrowsPredicateTest, Describe) {
+  Matcher<std::function<void()>> matcher = GetParam();
+  std::stringstream ss;
+  matcher.DescribeTo(&ss);
+  auto explanation = ss.str();
+  EXPECT_THAT(explanation, HasSubstr("std::runtime_error"));
+  EXPECT_THAT(explanation, HasSubstr("error message"));
+}
+
+TEST_P(ThrowsPredicateTest, Success) {
+  Matcher<std::function<void()>> matcher = GetParam();
+  StringMatchResultListener listener;
+  EXPECT_TRUE(matcher.MatchAndExplain(
+      []() { throw std::runtime_error("error message"); }, &listener));
+  EXPECT_THAT(listener.str(), HasSubstr("std::runtime_error"));
+}
+
+TEST_P(ThrowsPredicateTest, FailWrongType) {
+  Matcher<std::function<void()>> matcher = GetParam();
+  StringMatchResultListener listener;
+  EXPECT_FALSE(matcher.MatchAndExplain(
+      []() { throw std::logic_error("error message"); }, &listener));
+  EXPECT_THAT(listener.str(), HasSubstr("std::logic_error"));
+  EXPECT_THAT(listener.str(), HasSubstr("\"error message\""));
+}
+
+TEST_P(ThrowsPredicateTest, FailWrongTypeNonStd) {
+  Matcher<std::function<void()>> matcher = GetParam();
+  StringMatchResultListener listener;
+  EXPECT_FALSE(matcher.MatchAndExplain([]() { throw 10; }, &listener));
+  EXPECT_THAT(listener.str(),
+              HasSubstr("throws an exception of an unknown type"));
+}
+
+TEST_P(ThrowsPredicateTest, FailNoThrow) {
+  Matcher<std::function<void()>> matcher = GetParam();
+  StringMatchResultListener listener;
+  EXPECT_FALSE(matcher.MatchAndExplain([]() {}, &listener));
+  EXPECT_THAT(listener.str(), HasSubstr("does not throw any exception"));
+}
+
+INSTANTIATE_TEST_SUITE_P(
+    AllMessagePredicates, ThrowsPredicateTest,
+    Values(Matcher<std::function<void()>>(
+        ThrowsMessage<std::runtime_error>(HasSubstr("error message")))));
+
+// Tests that Throws<E1>(Matcher<E2>{}) compiles even when E2 != const E1&.
+TEST(ThrowsPredicateCompilesTest, ExceptionMatcherAcceptsBroadType) {
+  {
+    Matcher<std::function<void()>> matcher =
+        ThrowsMessage<std::runtime_error>(HasSubstr("error message"));
+    EXPECT_TRUE(
+        matcher.Matches([]() { throw std::runtime_error("error message"); }));
+    EXPECT_FALSE(
+        matcher.Matches([]() { throw std::runtime_error("wrong message"); }));
+  }
+
+  {
+    Matcher<uint64_t> inner = Eq(10);
+    Matcher<std::function<void()>> matcher = Throws<uint32_t>(inner);
+    EXPECT_TRUE(matcher.Matches([]() { throw (uint32_t)10; }));
+    EXPECT_FALSE(matcher.Matches([]() { throw (uint32_t)11; }));
+  }
+}
+
+// Tests that ThrowsMessage("message") is equivalent
+// to ThrowsMessage(Eq<std::string>("message")).
+TEST(ThrowsPredicateCompilesTest, MessageMatcherAcceptsNonMatcher) {
+  Matcher<std::function<void()>> matcher =
+      ThrowsMessage<std::runtime_error>("error message");
+  EXPECT_TRUE(
+      matcher.Matches([]() { throw std::runtime_error("error message"); }));
+  EXPECT_FALSE(matcher.Matches(
+      []() { throw std::runtime_error("wrong error message"); }));
+}
+
+#endif  // GTEST_HAS_EXCEPTIONS
+
+}  // namespace
+}  // namespace gmock_matchers_test
+}  // namespace testing
+
+GTEST_DISABLE_MSC_WARNINGS_POP_()  // 4244 4100
diff --git a/third_party/googletest/googlemock/test/gmock-matchers_test.h b/third_party/googletest/googlemock/test/gmock-matchers_test.h
new file mode 100644
index 0000000..5695607
--- /dev/null
+++ b/third_party/googletest/googlemock/test/gmock-matchers_test.h
@@ -0,0 +1,192 @@
+// Copyright 2007, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Google Mock - a framework for writing C++ mock classes.
+//
+// This file tests some commonly used argument matchers.
+
+#ifndef GOOGLEMOCK_TEST_GMOCK_MATCHERS_TEST_H_
+#define GOOGLEMOCK_TEST_GMOCK_MATCHERS_TEST_H_
+
+#include <string.h>
+#include <time.h>
+
+#include <array>
+#include <cstdint>
+#include <deque>
+#include <forward_list>
+#include <functional>
+#include <iostream>
+#include <iterator>
+#include <limits>
+#include <list>
+#include <map>
+#include <memory>
+#include <set>
+#include <sstream>
+#include <string>
+#include <type_traits>
+#include <unordered_map>
+#include <unordered_set>
+#include <utility>
+#include <vector>
+
+#include "gmock/gmock-matchers.h"
+#include "gmock/gmock-more-matchers.h"
+#include "gmock/gmock.h"
+#include "gtest/gtest-spi.h"
+#include "gtest/gtest.h"
+
+namespace testing {
+namespace gmock_matchers_test {
+
+using std::greater;
+using std::less;
+using std::list;
+using std::make_pair;
+using std::map;
+using std::multimap;
+using std::multiset;
+using std::ostream;
+using std::pair;
+using std::set;
+using std::stringstream;
+using std::vector;
+using testing::internal::DummyMatchResultListener;
+using testing::internal::ElementMatcherPair;
+using testing::internal::ElementMatcherPairs;
+using testing::internal::ElementsAreArrayMatcher;
+using testing::internal::ExplainMatchFailureTupleTo;
+using testing::internal::FloatingEqMatcher;
+using testing::internal::FormatMatcherDescription;
+using testing::internal::IsReadableTypeName;
+using testing::internal::MatchMatrix;
+using testing::internal::PredicateFormatterFromMatcher;
+using testing::internal::RE;
+using testing::internal::StreamMatchResultListener;
+using testing::internal::Strings;
+
+// Helper for testing container-valued matchers in mock method context. It is
+// important to test matchers in this context, since it requires additional type
+// deduction beyond what EXPECT_THAT does, thus making it more restrictive.
+struct ContainerHelper {
+  MOCK_METHOD1(Call, void(std::vector<std::unique_ptr<int>>));
+};
+
+// For testing ExplainMatchResultTo().
+template <typename T>
+struct GtestGreaterThanMatcher {
+  using is_gtest_matcher = void;
+
+  void DescribeTo(ostream* os) const { *os << "is > " << rhs; }
+  void DescribeNegationTo(ostream* os) const { *os << "is <= " << rhs; }
+
+  bool MatchAndExplain(T lhs, MatchResultListener* listener) const {
+    if (lhs > rhs) {
+      *listener << "which is " << (lhs - rhs) << " more than " << rhs;
+    } else if (lhs == rhs) {
+      *listener << "which is the same as " << rhs;
+    } else {
+      *listener << "which is " << (rhs - lhs) << " less than " << rhs;
+    }
+
+    return lhs > rhs;
+  }
+
+  T rhs;
+};
+
+template <typename T>
+GtestGreaterThanMatcher<typename std::decay<T>::type> GtestGreaterThan(
+    T&& rhs) {
+  return {rhs};
+}
+
+// As the matcher above, but using the base class with virtual functions.
+template <typename T>
+class GreaterThanMatcher : public MatcherInterface<T> {
+ public:
+  explicit GreaterThanMatcher(T rhs) : impl_{rhs} {}
+
+  void DescribeTo(ostream* os) const override { impl_.DescribeTo(os); }
+  void DescribeNegationTo(ostream* os) const override {
+    impl_.DescribeNegationTo(os);
+  }
+
+  bool MatchAndExplain(T lhs, MatchResultListener* listener) const override {
+    return impl_.MatchAndExplain(lhs, listener);
+  }
+
+ private:
+  const GtestGreaterThanMatcher<T> impl_;
+};
+
+// Names and instantiates a new instance of GTestMatcherTestP.
+#define INSTANTIATE_GTEST_MATCHER_TEST_P(TestSuite)                        \
+  using TestSuite##P = GTestMatcherTestP;                                  \
+  INSTANTIATE_TEST_SUITE_P(MatcherInterface, TestSuite##P, Values(false)); \
+  INSTANTIATE_TEST_SUITE_P(GtestMatcher, TestSuite##P, Values(true))
+
+class GTestMatcherTestP : public testing::TestWithParam<bool> {
+ public:
+  template <typename T>
+  Matcher<T> GreaterThan(T n) {
+    if (use_gtest_matcher_) {
+      return GtestGreaterThan(n);
+    } else {
+      return MakeMatcher(new GreaterThanMatcher<T>(n));
+    }
+  }
+  const bool use_gtest_matcher_ = GetParam();
+};
+
+// Returns the description of the given matcher.
+template <typename T>
+std::string Describe(const Matcher<T>& m) {
+  return DescribeMatcher<T>(m);
+}
+
+// Returns the description of the negation of the given matcher.
+template <typename T>
+std::string DescribeNegation(const Matcher<T>& m) {
+  return DescribeMatcher<T>(m, true);
+}
+
+// Returns the reason why x matches, or doesn't match, m.
+template <typename MatcherType, typename Value>
+std::string Explain(const MatcherType& m, const Value& x) {
+  StringMatchResultListener listener;
+  ExplainMatchResult(m, x, &listener);
+  return listener.str();
+}
+
+}  // namespace gmock_matchers_test
+}  // namespace testing
+
+#endif  // GOOGLEMOCK_TEST_GMOCK_MATCHERS_TEST_H_
diff --git a/third_party/googletest/googlemock/test/gmock-more-actions_test.cc b/third_party/googletest/googlemock/test/gmock-more-actions_test.cc
new file mode 100644
index 0000000..9980f3b
--- /dev/null
+++ b/third_party/googletest/googlemock/test/gmock-more-actions_test.cc
@@ -0,0 +1,1550 @@
+// Copyright 2007, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Google Mock - a framework for writing C++ mock classes.
+//
+// This file tests the built-in actions in gmock-actions.h.
+
+#include "gmock/gmock-more-actions.h"
+
+#include <algorithm>
+#include <functional>
+#include <iterator>
+#include <memory>
+#include <sstream>
+#include <string>
+#include <tuple>
+#include <vector>
+
+#include "gmock/gmock.h"
+#include "gtest/gtest-spi.h"
+#include "gtest/gtest.h"
+
+GTEST_DISABLE_MSC_WARNINGS_PUSH_(4577)
+
+namespace testing {
+namespace gmock_more_actions_test {
+
+using ::std::plus;
+using ::std::string;
+using testing::Action;
+using testing::DeleteArg;
+using testing::Invoke;
+using testing::ReturnArg;
+using testing::ReturnPointee;
+using testing::SaveArg;
+using testing::SaveArgPointee;
+using testing::SetArgReferee;
+using testing::Unused;
+using testing::WithArg;
+using testing::WithoutArgs;
+
+// For suppressing compiler warnings on conversion possibly losing precision.
+inline short Short(short n) { return n; }  // NOLINT
+inline char Char(char ch) { return ch; }
+
+// Sample functions and functors for testing Invoke() and etc.
+int Nullary() { return 1; }
+
+bool g_done = false;
+
+bool Unary(int x) { return x < 0; }
+
+bool ByConstRef(const std::string& s) { return s == "Hi"; }
+
+const double g_double = 0;
+bool ReferencesGlobalDouble(const double& x) { return &x == &g_double; }
+
+struct UnaryFunctor {
+  int operator()(bool x) { return x ? 1 : -1; }
+};
+
+const char* Binary(const char* input, short n) { return input + n; }  // NOLINT
+
+int Ternary(int x, char y, short z) { return x + y + z; }  // NOLINT
+
+int SumOf4(int a, int b, int c, int d) { return a + b + c + d; }
+
+int SumOfFirst2(int a, int b, Unused, Unused) { return a + b; }
+
+int SumOf5(int a, int b, int c, int d, int e) { return a + b + c + d + e; }
+
+struct SumOf5Functor {
+  int operator()(int a, int b, int c, int d, int e) {
+    return a + b + c + d + e;
+  }
+};
+
+int SumOf6(int a, int b, int c, int d, int e, int f) {
+  return a + b + c + d + e + f;
+}
+
+struct SumOf6Functor {
+  int operator()(int a, int b, int c, int d, int e, int f) {
+    return a + b + c + d + e + f;
+  }
+};
+
+std::string Concat7(const char* s1, const char* s2, const char* s3,
+                    const char* s4, const char* s5, const char* s6,
+                    const char* s7) {
+  return std::string(s1) + s2 + s3 + s4 + s5 + s6 + s7;
+}
+
+std::string Concat8(const char* s1, const char* s2, const char* s3,
+                    const char* s4, const char* s5, const char* s6,
+                    const char* s7, const char* s8) {
+  return std::string(s1) + s2 + s3 + s4 + s5 + s6 + s7 + s8;
+}
+
+std::string Concat9(const char* s1, const char* s2, const char* s3,
+                    const char* s4, const char* s5, const char* s6,
+                    const char* s7, const char* s8, const char* s9) {
+  return std::string(s1) + s2 + s3 + s4 + s5 + s6 + s7 + s8 + s9;
+}
+
+std::string Concat10(const char* s1, const char* s2, const char* s3,
+                     const char* s4, const char* s5, const char* s6,
+                     const char* s7, const char* s8, const char* s9,
+                     const char* s10) {
+  return std::string(s1) + s2 + s3 + s4 + s5 + s6 + s7 + s8 + s9 + s10;
+}
+
+class Foo {
+ public:
+  Foo() : value_(123) {}
+
+  int Nullary() const { return value_; }
+
+  short Unary(long x) { return static_cast<short>(value_ + x); }  // NOLINT
+
+  std::string Binary(const std::string& str, char c) const { return str + c; }
+
+  int Ternary(int x, bool y, char z) { return value_ + x + y * z; }
+
+  int SumOf4(int a, int b, int c, int d) const {
+    return a + b + c + d + value_;
+  }
+
+  int SumOfLast2(Unused, Unused, int a, int b) const { return a + b; }
+
+  int SumOf5(int a, int b, int c, int d, int e) { return a + b + c + d + e; }
+
+  int SumOf6(int a, int b, int c, int d, int e, int f) {
+    return a + b + c + d + e + f;
+  }
+
+  std::string Concat7(const char* s1, const char* s2, const char* s3,
+                      const char* s4, const char* s5, const char* s6,
+                      const char* s7) {
+    return std::string(s1) + s2 + s3 + s4 + s5 + s6 + s7;
+  }
+
+  std::string Concat8(const char* s1, const char* s2, const char* s3,
+                      const char* s4, const char* s5, const char* s6,
+                      const char* s7, const char* s8) {
+    return std::string(s1) + s2 + s3 + s4 + s5 + s6 + s7 + s8;
+  }
+
+  std::string Concat9(const char* s1, const char* s2, const char* s3,
+                      const char* s4, const char* s5, const char* s6,
+                      const char* s7, const char* s8, const char* s9) {
+    return std::string(s1) + s2 + s3 + s4 + s5 + s6 + s7 + s8 + s9;
+  }
+
+  std::string Concat10(const char* s1, const char* s2, const char* s3,
+                       const char* s4, const char* s5, const char* s6,
+                       const char* s7, const char* s8, const char* s9,
+                       const char* s10) {
+    return std::string(s1) + s2 + s3 + s4 + s5 + s6 + s7 + s8 + s9 + s10;
+  }
+
+ private:
+  int value_;
+};
+
+// Tests using Invoke() with a nullary function.
+TEST(InvokeTest, Nullary) {
+  Action<int()> a = Invoke(Nullary);  // NOLINT
+  EXPECT_EQ(1, a.Perform(std::make_tuple()));
+}
+
+// Tests using Invoke() with a unary function.
+TEST(InvokeTest, Unary) {
+  Action<bool(int)> a = Invoke(Unary);  // NOLINT
+  EXPECT_FALSE(a.Perform(std::make_tuple(1)));
+  EXPECT_TRUE(a.Perform(std::make_tuple(-1)));
+}
+
+// Tests using Invoke() with a binary function.
+TEST(InvokeTest, Binary) {
+  Action<const char*(const char*, short)> a = Invoke(Binary);  // NOLINT
+  const char* p = "Hello";
+  EXPECT_EQ(p + 2, a.Perform(std::make_tuple(p, Short(2))));
+}
+
+// Tests using Invoke() with a ternary function.
+TEST(InvokeTest, Ternary) {
+  Action<int(int, char, short)> a = Invoke(Ternary);  // NOLINT
+  EXPECT_EQ(6, a.Perform(std::make_tuple(1, '\2', Short(3))));
+}
+
+// Tests using Invoke() with a 4-argument function.
+TEST(InvokeTest, FunctionThatTakes4Arguments) {
+  Action<int(int, int, int, int)> a = Invoke(SumOf4);  // NOLINT
+  EXPECT_EQ(1234, a.Perform(std::make_tuple(1000, 200, 30, 4)));
+}
+
+// Tests using Invoke() with a 5-argument function.
+TEST(InvokeTest, FunctionThatTakes5Arguments) {
+  Action<int(int, int, int, int, int)> a = Invoke(SumOf5);  // NOLINT
+  EXPECT_EQ(12345, a.Perform(std::make_tuple(10000, 2000, 300, 40, 5)));
+}
+
+// Tests using Invoke() with a 6-argument function.
+TEST(InvokeTest, FunctionThatTakes6Arguments) {
+  Action<int(int, int, int, int, int, int)> a = Invoke(SumOf6);  // NOLINT
+  EXPECT_EQ(123456,
+            a.Perform(std::make_tuple(100000, 20000, 3000, 400, 50, 6)));
+}
+
+// A helper that turns the type of a C-string literal from const
+// char[N] to const char*.
+inline const char* CharPtr(const char* s) { return s; }
+
+// Tests using Invoke() with a 7-argument function.
+TEST(InvokeTest, FunctionThatTakes7Arguments) {
+  Action<std::string(const char*, const char*, const char*, const char*,
+                     const char*, const char*, const char*)>
+      a = Invoke(Concat7);
+  EXPECT_EQ("1234567",
+            a.Perform(std::make_tuple(CharPtr("1"), CharPtr("2"), CharPtr("3"),
+                                      CharPtr("4"), CharPtr("5"), CharPtr("6"),
+                                      CharPtr("7"))));
+}
+
+// Tests using Invoke() with a 8-argument function.
+TEST(InvokeTest, FunctionThatTakes8Arguments) {
+  Action<std::string(const char*, const char*, const char*, const char*,
+                     const char*, const char*, const char*, const char*)>
+      a = Invoke(Concat8);
+  EXPECT_EQ("12345678",
+            a.Perform(std::make_tuple(CharPtr("1"), CharPtr("2"), CharPtr("3"),
+                                      CharPtr("4"), CharPtr("5"), CharPtr("6"),
+                                      CharPtr("7"), CharPtr("8"))));
+}
+
+// Tests using Invoke() with a 9-argument function.
+TEST(InvokeTest, FunctionThatTakes9Arguments) {
+  Action<std::string(const char*, const char*, const char*, const char*,
+                     const char*, const char*, const char*, const char*,
+                     const char*)>
+      a = Invoke(Concat9);
+  EXPECT_EQ("123456789", a.Perform(std::make_tuple(
+                             CharPtr("1"), CharPtr("2"), CharPtr("3"),
+                             CharPtr("4"), CharPtr("5"), CharPtr("6"),
+                             CharPtr("7"), CharPtr("8"), CharPtr("9"))));
+}
+
+// Tests using Invoke() with a 10-argument function.
+TEST(InvokeTest, FunctionThatTakes10Arguments) {
+  Action<std::string(const char*, const char*, const char*, const char*,
+                     const char*, const char*, const char*, const char*,
+                     const char*, const char*)>
+      a = Invoke(Concat10);
+  EXPECT_EQ("1234567890",
+            a.Perform(std::make_tuple(CharPtr("1"), CharPtr("2"), CharPtr("3"),
+                                      CharPtr("4"), CharPtr("5"), CharPtr("6"),
+                                      CharPtr("7"), CharPtr("8"), CharPtr("9"),
+                                      CharPtr("0"))));
+}
+
+// Tests using Invoke() with functions with parameters declared as Unused.
+TEST(InvokeTest, FunctionWithUnusedParameters) {
+  Action<int(int, int, double, const std::string&)> a1 = Invoke(SumOfFirst2);
+  std::tuple<int, int, double, std::string> dummy =
+      std::make_tuple(10, 2, 5.6, std::string("hi"));
+  EXPECT_EQ(12, a1.Perform(dummy));
+
+  Action<int(int, int, bool, int*)> a2 = Invoke(SumOfFirst2);
+  EXPECT_EQ(
+      23, a2.Perform(std::make_tuple(20, 3, true, static_cast<int*>(nullptr))));
+}
+
+// Tests using Invoke() with methods with parameters declared as Unused.
+TEST(InvokeTest, MethodWithUnusedParameters) {
+  Foo foo;
+  Action<int(std::string, bool, int, int)> a1 = Invoke(&foo, &Foo::SumOfLast2);
+  EXPECT_EQ(12, a1.Perform(std::make_tuple(CharPtr("hi"), true, 10, 2)));
+
+  Action<int(char, double, int, int)> a2 = Invoke(&foo, &Foo::SumOfLast2);
+  EXPECT_EQ(23, a2.Perform(std::make_tuple('a', 2.5, 20, 3)));
+}
+
+// Tests using Invoke() with a functor.
+TEST(InvokeTest, Functor) {
+  Action<long(long, int)> a = Invoke(plus<long>());  // NOLINT
+  EXPECT_EQ(3L, a.Perform(std::make_tuple(1, 2)));
+}
+
+// Tests using Invoke(f) as an action of a compatible type.
+TEST(InvokeTest, FunctionWithCompatibleType) {
+  Action<long(int, short, char, bool)> a = Invoke(SumOf4);  // NOLINT
+  EXPECT_EQ(4321, a.Perform(std::make_tuple(4000, Short(300), Char(20), true)));
+}
+
+// Tests using Invoke() with an object pointer and a method pointer.
+
+// Tests using Invoke() with a nullary method.
+TEST(InvokeMethodTest, Nullary) {
+  Foo foo;
+  Action<int()> a = Invoke(&foo, &Foo::Nullary);  // NOLINT
+  EXPECT_EQ(123, a.Perform(std::make_tuple()));
+}
+
+// Tests using Invoke() with a unary method.
+TEST(InvokeMethodTest, Unary) {
+  Foo foo;
+  Action<short(long)> a = Invoke(&foo, &Foo::Unary);  // NOLINT
+  EXPECT_EQ(4123, a.Perform(std::make_tuple(4000)));
+}
+
+// Tests using Invoke() with a binary method.
+TEST(InvokeMethodTest, Binary) {
+  Foo foo;
+  Action<std::string(const std::string&, char)> a = Invoke(&foo, &Foo::Binary);
+  std::string s("Hell");
+  std::tuple<std::string, char> dummy = std::make_tuple(s, 'o');
+  EXPECT_EQ("Hello", a.Perform(dummy));
+}
+
+// Tests using Invoke() with a ternary method.
+TEST(InvokeMethodTest, Ternary) {
+  Foo foo;
+  Action<int(int, bool, char)> a = Invoke(&foo, &Foo::Ternary);  // NOLINT
+  EXPECT_EQ(1124, a.Perform(std::make_tuple(1000, true, Char(1))));
+}
+
+// Tests using Invoke() with a 4-argument method.
+TEST(InvokeMethodTest, MethodThatTakes4Arguments) {
+  Foo foo;
+  Action<int(int, int, int, int)> a = Invoke(&foo, &Foo::SumOf4);  // NOLINT
+  EXPECT_EQ(1357, a.Perform(std::make_tuple(1000, 200, 30, 4)));
+}
+
+// Tests using Invoke() with a 5-argument method.
+TEST(InvokeMethodTest, MethodThatTakes5Arguments) {
+  Foo foo;
+  Action<int(int, int, int, int, int)> a =
+      Invoke(&foo, &Foo::SumOf5);  // NOLINT
+  EXPECT_EQ(12345, a.Perform(std::make_tuple(10000, 2000, 300, 40, 5)));
+}
+
+// Tests using Invoke() with a 6-argument method.
+TEST(InvokeMethodTest, MethodThatTakes6Arguments) {
+  Foo foo;
+  Action<int(int, int, int, int, int, int)> a =  // NOLINT
+      Invoke(&foo, &Foo::SumOf6);
+  EXPECT_EQ(123456,
+            a.Perform(std::make_tuple(100000, 20000, 3000, 400, 50, 6)));
+}
+
+// Tests using Invoke() with a 7-argument method.
+TEST(InvokeMethodTest, MethodThatTakes7Arguments) {
+  Foo foo;
+  Action<std::string(const char*, const char*, const char*, const char*,
+                     const char*, const char*, const char*)>
+      a = Invoke(&foo, &Foo::Concat7);
+  EXPECT_EQ("1234567",
+            a.Perform(std::make_tuple(CharPtr("1"), CharPtr("2"), CharPtr("3"),
+                                      CharPtr("4"), CharPtr("5"), CharPtr("6"),
+                                      CharPtr("7"))));
+}
+
+// Tests using Invoke() with a 8-argument method.
+TEST(InvokeMethodTest, MethodThatTakes8Arguments) {
+  Foo foo;
+  Action<std::string(const char*, const char*, const char*, const char*,
+                     const char*, const char*, const char*, const char*)>
+      a = Invoke(&foo, &Foo::Concat8);
+  EXPECT_EQ("12345678",
+            a.Perform(std::make_tuple(CharPtr("1"), CharPtr("2"), CharPtr("3"),
+                                      CharPtr("4"), CharPtr("5"), CharPtr("6"),
+                                      CharPtr("7"), CharPtr("8"))));
+}
+
+// Tests using Invoke() with a 9-argument method.
+TEST(InvokeMethodTest, MethodThatTakes9Arguments) {
+  Foo foo;
+  Action<std::string(const char*, const char*, const char*, const char*,
+                     const char*, const char*, const char*, const char*,
+                     const char*)>
+      a = Invoke(&foo, &Foo::Concat9);
+  EXPECT_EQ("123456789", a.Perform(std::make_tuple(
+                             CharPtr("1"), CharPtr("2"), CharPtr("3"),
+                             CharPtr("4"), CharPtr("5"), CharPtr("6"),
+                             CharPtr("7"), CharPtr("8"), CharPtr("9"))));
+}
+
+// Tests using Invoke() with a 10-argument method.
+TEST(InvokeMethodTest, MethodThatTakes10Arguments) {
+  Foo foo;
+  Action<std::string(const char*, const char*, const char*, const char*,
+                     const char*, const char*, const char*, const char*,
+                     const char*, const char*)>
+      a = Invoke(&foo, &Foo::Concat10);
+  EXPECT_EQ("1234567890",
+            a.Perform(std::make_tuple(CharPtr("1"), CharPtr("2"), CharPtr("3"),
+                                      CharPtr("4"), CharPtr("5"), CharPtr("6"),
+                                      CharPtr("7"), CharPtr("8"), CharPtr("9"),
+                                      CharPtr("0"))));
+}
+
+// Tests using Invoke(f) as an action of a compatible type.
+TEST(InvokeMethodTest, MethodWithCompatibleType) {
+  Foo foo;
+  Action<long(int, short, char, bool)> a =  // NOLINT
+      Invoke(&foo, &Foo::SumOf4);
+  EXPECT_EQ(4444, a.Perform(std::make_tuple(4000, Short(300), Char(20), true)));
+}
+
+// Tests using WithoutArgs with an action that takes no argument.
+TEST(WithoutArgsTest, NoArg) {
+  Action<int(int n)> a = WithoutArgs(Invoke(Nullary));  // NOLINT
+  EXPECT_EQ(1, a.Perform(std::make_tuple(2)));
+}
+
+// Tests using WithArg with an action that takes 1 argument.
+TEST(WithArgTest, OneArg) {
+  Action<bool(double x, int n)> b = WithArg<1>(Invoke(Unary));  // NOLINT
+  EXPECT_TRUE(b.Perform(std::make_tuple(1.5, -1)));
+  EXPECT_FALSE(b.Perform(std::make_tuple(1.5, 1)));
+}
+
+TEST(ReturnArgActionTest, WorksForOneArgIntArg0) {
+  const Action<int(int)> a = ReturnArg<0>();
+  EXPECT_EQ(5, a.Perform(std::make_tuple(5)));
+}
+
+TEST(ReturnArgActionTest, WorksForMultiArgBoolArg0) {
+  const Action<bool(bool, bool, bool)> a = ReturnArg<0>();
+  EXPECT_TRUE(a.Perform(std::make_tuple(true, false, false)));
+}
+
+TEST(ReturnArgActionTest, WorksForMultiArgStringArg2) {
+  const Action<std::string(int, int, std::string, int)> a = ReturnArg<2>();
+  EXPECT_EQ("seven", a.Perform(std::make_tuple(5, 6, std::string("seven"), 8)));
+}
+
+TEST(ReturnArgActionTest, WorksForNonConstRefArg0) {
+  const Action<std::string&(std::string&)> a = ReturnArg<0>();
+  std::string s = "12345";
+  EXPECT_EQ(&s, &a.Perform(std::forward_as_tuple(s)));
+}
+
+TEST(SaveArgActionTest, WorksForSameType) {
+  int result = 0;
+  const Action<void(int n)> a1 = SaveArg<0>(&result);
+  a1.Perform(std::make_tuple(5));
+  EXPECT_EQ(5, result);
+}
+
+TEST(SaveArgActionTest, WorksForCompatibleType) {
+  int result = 0;
+  const Action<void(bool, char)> a1 = SaveArg<1>(&result);
+  a1.Perform(std::make_tuple(true, 'a'));
+  EXPECT_EQ('a', result);
+}
+
+TEST(SaveArgPointeeActionTest, WorksForSameType) {
+  int result = 0;
+  const int value = 5;
+  const Action<void(const int*)> a1 = SaveArgPointee<0>(&result);
+  a1.Perform(std::make_tuple(&value));
+  EXPECT_EQ(5, result);
+}
+
+TEST(SaveArgPointeeActionTest, WorksForCompatibleType) {
+  int result = 0;
+  char value = 'a';
+  const Action<void(bool, char*)> a1 = SaveArgPointee<1>(&result);
+  a1.Perform(std::make_tuple(true, &value));
+  EXPECT_EQ('a', result);
+}
+
+TEST(SetArgRefereeActionTest, WorksForSameType) {
+  int value = 0;
+  const Action<void(int&)> a1 = SetArgReferee<0>(1);
+  a1.Perform(std::tuple<int&>(value));
+  EXPECT_EQ(1, value);
+}
+
+TEST(SetArgRefereeActionTest, WorksForCompatibleType) {
+  int value = 0;
+  const Action<void(int, int&)> a1 = SetArgReferee<1>('a');
+  a1.Perform(std::tuple<int, int&>(0, value));
+  EXPECT_EQ('a', value);
+}
+
+TEST(SetArgRefereeActionTest, WorksWithExtraArguments) {
+  int value = 0;
+  const Action<void(bool, int, int&, const char*)> a1 = SetArgReferee<2>('a');
+  a1.Perform(std::tuple<bool, int, int&, const char*>(true, 0, value, "hi"));
+  EXPECT_EQ('a', value);
+}
+
+// A class that can be used to verify that its destructor is called: it will set
+// the bool provided to the constructor to true when destroyed.
+class DeletionTester {
+ public:
+  explicit DeletionTester(bool* is_deleted) : is_deleted_(is_deleted) {
+    // Make sure the bit is set to false.
+    *is_deleted_ = false;
+  }
+
+  ~DeletionTester() { *is_deleted_ = true; }
+
+ private:
+  bool* is_deleted_;
+};
+
+TEST(DeleteArgActionTest, OneArg) {
+  bool is_deleted = false;
+  DeletionTester* t = new DeletionTester(&is_deleted);
+  const Action<void(DeletionTester*)> a1 = DeleteArg<0>();  // NOLINT
+  EXPECT_FALSE(is_deleted);
+  a1.Perform(std::make_tuple(t));
+  EXPECT_TRUE(is_deleted);
+}
+
+TEST(DeleteArgActionTest, TenArgs) {
+  bool is_deleted = false;
+  DeletionTester* t = new DeletionTester(&is_deleted);
+  const Action<void(bool, int, int, const char*, bool, int, int, int, int,
+                    DeletionTester*)>
+      a1 = DeleteArg<9>();
+  EXPECT_FALSE(is_deleted);
+  a1.Perform(std::make_tuple(true, 5, 6, CharPtr("hi"), false, 7, 8, 9, 10, t));
+  EXPECT_TRUE(is_deleted);
+}
+
+#if GTEST_HAS_EXCEPTIONS
+
+TEST(ThrowActionTest, ThrowsGivenExceptionInVoidFunction) {
+  const Action<void(int n)> a = Throw('a');
+  EXPECT_THROW(a.Perform(std::make_tuple(0)), char);
+}
+
+class MyException {};
+
+TEST(ThrowActionTest, ThrowsGivenExceptionInNonVoidFunction) {
+  const Action<double(char ch)> a = Throw(MyException());
+  EXPECT_THROW(a.Perform(std::make_tuple('0')), MyException);
+}
+
+TEST(ThrowActionTest, ThrowsGivenExceptionInNullaryFunction) {
+  const Action<double()> a = Throw(MyException());
+  EXPECT_THROW(a.Perform(std::make_tuple()), MyException);
+}
+
+class Object {
+ public:
+  virtual ~Object() {}
+  virtual void Func() {}
+};
+
+class MockObject : public Object {
+ public:
+  ~MockObject() override {}
+  MOCK_METHOD(void, Func, (), (override));
+};
+
+TEST(ThrowActionTest, Times0) {
+  EXPECT_NONFATAL_FAILURE(
+      [] {
+        try {
+          MockObject m;
+          ON_CALL(m, Func()).WillByDefault([] { throw "something"; });
+          EXPECT_CALL(m, Func()).Times(0);
+          m.Func();
+        } catch (...) {
+          // Exception is caught but Times(0) still triggers a failure.
+        }
+      }(),
+      "");
+}
+
+#endif  // GTEST_HAS_EXCEPTIONS
+
+// Tests that SetArrayArgument<N>(first, last) sets the elements of the array
+// pointed to by the N-th (0-based) argument to values in range [first, last).
+TEST(SetArrayArgumentTest, SetsTheNthArray) {
+  using MyFunction = void(bool, int*, char*);
+  int numbers[] = {1, 2, 3};
+  Action<MyFunction> a = SetArrayArgument<1>(numbers, numbers + 3);
+
+  int n[4] = {};
+  int* pn = n;
+  char ch[4] = {};
+  char* pch = ch;
+  a.Perform(std::make_tuple(true, pn, pch));
+  EXPECT_EQ(1, n[0]);
+  EXPECT_EQ(2, n[1]);
+  EXPECT_EQ(3, n[2]);
+  EXPECT_EQ(0, n[3]);
+  EXPECT_EQ('\0', ch[0]);
+  EXPECT_EQ('\0', ch[1]);
+  EXPECT_EQ('\0', ch[2]);
+  EXPECT_EQ('\0', ch[3]);
+
+  // Tests first and last are iterators.
+  std::string letters = "abc";
+  a = SetArrayArgument<2>(letters.begin(), letters.end());
+  std::fill_n(n, 4, 0);
+  std::fill_n(ch, 4, '\0');
+  a.Perform(std::make_tuple(true, pn, pch));
+  EXPECT_EQ(0, n[0]);
+  EXPECT_EQ(0, n[1]);
+  EXPECT_EQ(0, n[2]);
+  EXPECT_EQ(0, n[3]);
+  EXPECT_EQ('a', ch[0]);
+  EXPECT_EQ('b', ch[1]);
+  EXPECT_EQ('c', ch[2]);
+  EXPECT_EQ('\0', ch[3]);
+}
+
+// Tests SetArrayArgument<N>(first, last) where first == last.
+TEST(SetArrayArgumentTest, SetsTheNthArrayWithEmptyRange) {
+  using MyFunction = void(bool, int*);
+  int numbers[] = {1, 2, 3};
+  Action<MyFunction> a = SetArrayArgument<1>(numbers, numbers);
+
+  int n[4] = {};
+  int* pn = n;
+  a.Perform(std::make_tuple(true, pn));
+  EXPECT_EQ(0, n[0]);
+  EXPECT_EQ(0, n[1]);
+  EXPECT_EQ(0, n[2]);
+  EXPECT_EQ(0, n[3]);
+}
+
+// Tests SetArrayArgument<N>(first, last) where *first is convertible
+// (but not equal) to the argument type.
+TEST(SetArrayArgumentTest, SetsTheNthArrayWithConvertibleType) {
+  using MyFunction = void(bool, int*);
+  char chars[] = {97, 98, 99};
+  Action<MyFunction> a = SetArrayArgument<1>(chars, chars + 3);
+
+  int codes[4] = {111, 222, 333, 444};
+  int* pcodes = codes;
+  a.Perform(std::make_tuple(true, pcodes));
+  EXPECT_EQ(97, codes[0]);
+  EXPECT_EQ(98, codes[1]);
+  EXPECT_EQ(99, codes[2]);
+  EXPECT_EQ(444, codes[3]);
+}
+
+// Test SetArrayArgument<N>(first, last) with iterator as argument.
+TEST(SetArrayArgumentTest, SetsTheNthArrayWithIteratorArgument) {
+  using MyFunction = void(bool, std::back_insert_iterator<std::string>);
+  std::string letters = "abc";
+  Action<MyFunction> a = SetArrayArgument<1>(letters.begin(), letters.end());
+
+  std::string s;
+  a.Perform(std::make_tuple(true, std::back_inserter(s)));
+  EXPECT_EQ(letters, s);
+}
+
+TEST(ReturnPointeeTest, Works) {
+  int n = 42;
+  const Action<int()> a = ReturnPointee(&n);
+  EXPECT_EQ(42, a.Perform(std::make_tuple()));
+
+  n = 43;
+  EXPECT_EQ(43, a.Perform(std::make_tuple()));
+}
+
+// Tests InvokeArgument<N>(...).
+
+// Tests using InvokeArgument with a nullary function.
+TEST(InvokeArgumentTest, Function0) {
+  Action<int(int, int (*)())> a = InvokeArgument<1>();  // NOLINT
+  EXPECT_EQ(1, a.Perform(std::make_tuple(2, &Nullary)));
+}
+
+// Tests using InvokeArgument with a unary function.
+TEST(InvokeArgumentTest, Functor1) {
+  Action<int(UnaryFunctor)> a = InvokeArgument<0>(true);  // NOLINT
+  EXPECT_EQ(1, a.Perform(std::make_tuple(UnaryFunctor())));
+}
+
+// Tests using InvokeArgument with a 5-ary function.
+TEST(InvokeArgumentTest, Function5) {
+  Action<int(int (*)(int, int, int, int, int))> a =  // NOLINT
+      InvokeArgument<0>(10000, 2000, 300, 40, 5);
+  EXPECT_EQ(12345, a.Perform(std::make_tuple(&SumOf5)));
+}
+
+// Tests using InvokeArgument with a 5-ary functor.
+TEST(InvokeArgumentTest, Functor5) {
+  Action<int(SumOf5Functor)> a =  // NOLINT
+      InvokeArgument<0>(10000, 2000, 300, 40, 5);
+  EXPECT_EQ(12345, a.Perform(std::make_tuple(SumOf5Functor())));
+}
+
+// Tests using InvokeArgument with a 6-ary function.
+TEST(InvokeArgumentTest, Function6) {
+  Action<int(int (*)(int, int, int, int, int, int))> a =  // NOLINT
+      InvokeArgument<0>(100000, 20000, 3000, 400, 50, 6);
+  EXPECT_EQ(123456, a.Perform(std::make_tuple(&SumOf6)));
+}
+
+// Tests using InvokeArgument with a 6-ary functor.
+TEST(InvokeArgumentTest, Functor6) {
+  Action<int(SumOf6Functor)> a =  // NOLINT
+      InvokeArgument<0>(100000, 20000, 3000, 400, 50, 6);
+  EXPECT_EQ(123456, a.Perform(std::make_tuple(SumOf6Functor())));
+}
+
+// Tests using InvokeArgument with a 7-ary function.
+TEST(InvokeArgumentTest, Function7) {
+  Action<std::string(std::string(*)(const char*, const char*, const char*,
+                                    const char*, const char*, const char*,
+                                    const char*))>
+      a = InvokeArgument<0>("1", "2", "3", "4", "5", "6", "7");
+  EXPECT_EQ("1234567", a.Perform(std::make_tuple(&Concat7)));
+}
+
+// Tests using InvokeArgument with a 8-ary function.
+TEST(InvokeArgumentTest, Function8) {
+  Action<std::string(std::string(*)(const char*, const char*, const char*,
+                                    const char*, const char*, const char*,
+                                    const char*, const char*))>
+      a = InvokeArgument<0>("1", "2", "3", "4", "5", "6", "7", "8");
+  EXPECT_EQ("12345678", a.Perform(std::make_tuple(&Concat8)));
+}
+
+// Tests using InvokeArgument with a 9-ary function.
+TEST(InvokeArgumentTest, Function9) {
+  Action<std::string(std::string(*)(const char*, const char*, const char*,
+                                    const char*, const char*, const char*,
+                                    const char*, const char*, const char*))>
+      a = InvokeArgument<0>("1", "2", "3", "4", "5", "6", "7", "8", "9");
+  EXPECT_EQ("123456789", a.Perform(std::make_tuple(&Concat9)));
+}
+
+// Tests using InvokeArgument with a 10-ary function.
+TEST(InvokeArgumentTest, Function10) {
+  Action<std::string(std::string(*)(
+      const char*, const char*, const char*, const char*, const char*,
+      const char*, const char*, const char*, const char*, const char*))>
+      a = InvokeArgument<0>("1", "2", "3", "4", "5", "6", "7", "8", "9", "0");
+  EXPECT_EQ("1234567890", a.Perform(std::make_tuple(&Concat10)));
+}
+
+// Tests using InvokeArgument with a function that takes a pointer argument.
+TEST(InvokeArgumentTest, ByPointerFunction) {
+  Action<const char*(const char* (*)(const char* input, short n))>  // NOLINT
+      a = InvokeArgument<0>(static_cast<const char*>("Hi"), Short(1));
+  EXPECT_STREQ("i", a.Perform(std::make_tuple(&Binary)));
+}
+
+// Tests using InvokeArgument with a function that takes a const char*
+// by passing it a C-string literal.
+TEST(InvokeArgumentTest, FunctionWithCStringLiteral) {
+  Action<const char*(const char* (*)(const char* input, short n))>  // NOLINT
+      a = InvokeArgument<0>("Hi", Short(1));
+  EXPECT_STREQ("i", a.Perform(std::make_tuple(&Binary)));
+}
+
+// Tests using InvokeArgument with a function that takes a const reference.
+TEST(InvokeArgumentTest, ByConstReferenceFunction) {
+  Action<bool(bool (*function)(const std::string& s))> a =  // NOLINT
+      InvokeArgument<0>(std::string("Hi"));
+  // When action 'a' is constructed, it makes a copy of the temporary
+  // string object passed to it, so it's OK to use 'a' later, when the
+  // temporary object has already died.
+  EXPECT_TRUE(a.Perform(std::make_tuple(&ByConstRef)));
+}
+
+// Tests using InvokeArgument with ByRef() and a function that takes a
+// const reference.
+TEST(InvokeArgumentTest, ByExplicitConstReferenceFunction) {
+  Action<bool(bool (*)(const double& x))> a =  // NOLINT
+      InvokeArgument<0>(ByRef(g_double));
+  // The above line calls ByRef() on a const value.
+  EXPECT_TRUE(a.Perform(std::make_tuple(&ReferencesGlobalDouble)));
+
+  double x = 0;
+  a = InvokeArgument<0>(ByRef(x));  // This calls ByRef() on a non-const.
+  EXPECT_FALSE(a.Perform(std::make_tuple(&ReferencesGlobalDouble)));
+}
+
+// Tests DoAll(a1, a2).
+TEST(DoAllTest, TwoActions) {
+  int n = 0;
+  Action<int(int*)> a = DoAll(SetArgPointee<0>(1),  // NOLINT
+                              Return(2));
+  EXPECT_EQ(2, a.Perform(std::make_tuple(&n)));
+  EXPECT_EQ(1, n);
+}
+
+// Tests DoAll(a1, a2, a3).
+TEST(DoAllTest, ThreeActions) {
+  int m = 0, n = 0;
+  Action<int(int*, int*)> a = DoAll(SetArgPointee<0>(1),  // NOLINT
+                                    SetArgPointee<1>(2), Return(3));
+  EXPECT_EQ(3, a.Perform(std::make_tuple(&m, &n)));
+  EXPECT_EQ(1, m);
+  EXPECT_EQ(2, n);
+}
+
+// Tests DoAll(a1, a2, a3, a4).
+TEST(DoAllTest, FourActions) {
+  int m = 0, n = 0;
+  char ch = '\0';
+  Action<int(int*, int*, char*)> a =  // NOLINT
+      DoAll(SetArgPointee<0>(1), SetArgPointee<1>(2), SetArgPointee<2>('a'),
+            Return(3));
+  EXPECT_EQ(3, a.Perform(std::make_tuple(&m, &n, &ch)));
+  EXPECT_EQ(1, m);
+  EXPECT_EQ(2, n);
+  EXPECT_EQ('a', ch);
+}
+
+// Tests DoAll(a1, a2, a3, a4, a5).
+TEST(DoAllTest, FiveActions) {
+  int m = 0, n = 0;
+  char a = '\0', b = '\0';
+  Action<int(int*, int*, char*, char*)> action =  // NOLINT
+      DoAll(SetArgPointee<0>(1), SetArgPointee<1>(2), SetArgPointee<2>('a'),
+            SetArgPointee<3>('b'), Return(3));
+  EXPECT_EQ(3, action.Perform(std::make_tuple(&m, &n, &a, &b)));
+  EXPECT_EQ(1, m);
+  EXPECT_EQ(2, n);
+  EXPECT_EQ('a', a);
+  EXPECT_EQ('b', b);
+}
+
+// Tests DoAll(a1, a2, ..., a6).
+TEST(DoAllTest, SixActions) {
+  int m = 0, n = 0;
+  char a = '\0', b = '\0', c = '\0';
+  Action<int(int*, int*, char*, char*, char*)> action =  // NOLINT
+      DoAll(SetArgPointee<0>(1), SetArgPointee<1>(2), SetArgPointee<2>('a'),
+            SetArgPointee<3>('b'), SetArgPointee<4>('c'), Return(3));
+  EXPECT_EQ(3, action.Perform(std::make_tuple(&m, &n, &a, &b, &c)));
+  EXPECT_EQ(1, m);
+  EXPECT_EQ(2, n);
+  EXPECT_EQ('a', a);
+  EXPECT_EQ('b', b);
+  EXPECT_EQ('c', c);
+}
+
+// Tests DoAll(a1, a2, ..., a7).
+TEST(DoAllTest, SevenActions) {
+  int m = 0, n = 0;
+  char a = '\0', b = '\0', c = '\0', d = '\0';
+  Action<int(int*, int*, char*, char*, char*, char*)> action =  // NOLINT
+      DoAll(SetArgPointee<0>(1), SetArgPointee<1>(2), SetArgPointee<2>('a'),
+            SetArgPointee<3>('b'), SetArgPointee<4>('c'), SetArgPointee<5>('d'),
+            Return(3));
+  EXPECT_EQ(3, action.Perform(std::make_tuple(&m, &n, &a, &b, &c, &d)));
+  EXPECT_EQ(1, m);
+  EXPECT_EQ(2, n);
+  EXPECT_EQ('a', a);
+  EXPECT_EQ('b', b);
+  EXPECT_EQ('c', c);
+  EXPECT_EQ('d', d);
+}
+
+// Tests DoAll(a1, a2, ..., a8).
+TEST(DoAllTest, EightActions) {
+  int m = 0, n = 0;
+  char a = '\0', b = '\0', c = '\0', d = '\0', e = '\0';
+  Action<int(int*, int*, char*, char*, char*, char*,  // NOLINT
+             char*)>
+      action =
+          DoAll(SetArgPointee<0>(1), SetArgPointee<1>(2), SetArgPointee<2>('a'),
+                SetArgPointee<3>('b'), SetArgPointee<4>('c'),
+                SetArgPointee<5>('d'), SetArgPointee<6>('e'), Return(3));
+  EXPECT_EQ(3, action.Perform(std::make_tuple(&m, &n, &a, &b, &c, &d, &e)));
+  EXPECT_EQ(1, m);
+  EXPECT_EQ(2, n);
+  EXPECT_EQ('a', a);
+  EXPECT_EQ('b', b);
+  EXPECT_EQ('c', c);
+  EXPECT_EQ('d', d);
+  EXPECT_EQ('e', e);
+}
+
+// Tests DoAll(a1, a2, ..., a9).
+TEST(DoAllTest, NineActions) {
+  int m = 0, n = 0;
+  char a = '\0', b = '\0', c = '\0', d = '\0', e = '\0', f = '\0';
+  Action<int(int*, int*, char*, char*, char*, char*,  // NOLINT
+             char*, char*)>
+      action = DoAll(SetArgPointee<0>(1), SetArgPointee<1>(2),
+                     SetArgPointee<2>('a'), SetArgPointee<3>('b'),
+                     SetArgPointee<4>('c'), SetArgPointee<5>('d'),
+                     SetArgPointee<6>('e'), SetArgPointee<7>('f'), Return(3));
+  EXPECT_EQ(3, action.Perform(std::make_tuple(&m, &n, &a, &b, &c, &d, &e, &f)));
+  EXPECT_EQ(1, m);
+  EXPECT_EQ(2, n);
+  EXPECT_EQ('a', a);
+  EXPECT_EQ('b', b);
+  EXPECT_EQ('c', c);
+  EXPECT_EQ('d', d);
+  EXPECT_EQ('e', e);
+  EXPECT_EQ('f', f);
+}
+
+// Tests DoAll(a1, a2, ..., a10).
+TEST(DoAllTest, TenActions) {
+  int m = 0, n = 0;
+  char a = '\0', b = '\0', c = '\0', d = '\0';
+  char e = '\0', f = '\0', g = '\0';
+  Action<int(int*, int*, char*, char*, char*, char*,  // NOLINT
+             char*, char*, char*)>
+      action =
+          DoAll(SetArgPointee<0>(1), SetArgPointee<1>(2), SetArgPointee<2>('a'),
+                SetArgPointee<3>('b'), SetArgPointee<4>('c'),
+                SetArgPointee<5>('d'), SetArgPointee<6>('e'),
+                SetArgPointee<7>('f'), SetArgPointee<8>('g'), Return(3));
+  EXPECT_EQ(
+      3, action.Perform(std::make_tuple(&m, &n, &a, &b, &c, &d, &e, &f, &g)));
+  EXPECT_EQ(1, m);
+  EXPECT_EQ(2, n);
+  EXPECT_EQ('a', a);
+  EXPECT_EQ('b', b);
+  EXPECT_EQ('c', c);
+  EXPECT_EQ('d', d);
+  EXPECT_EQ('e', e);
+  EXPECT_EQ('f', f);
+  EXPECT_EQ('g', g);
+}
+
+TEST(DoAllTest, NoArgs) {
+  bool ran_first = false;
+  Action<bool()> a =
+      DoAll([&] { ran_first = true; }, [&] { return ran_first; });
+  EXPECT_TRUE(a.Perform({}));
+}
+
+TEST(DoAllTest, MoveOnlyArgs) {
+  bool ran_first = false;
+  Action<int(std::unique_ptr<int>)> a =
+      DoAll(InvokeWithoutArgs([&] { ran_first = true; }),
+            [](std::unique_ptr<int> p) { return *p; });
+  EXPECT_EQ(7, a.Perform(std::make_tuple(std::unique_ptr<int>(new int(7)))));
+  EXPECT_TRUE(ran_first);
+}
+
+TEST(DoAllTest, ImplicitlyConvertsActionArguments) {
+  bool ran_first = false;
+  // Action<void(std::vector<int>)> isn't an
+  // Action<void(const std::vector<int>&) but can be converted.
+  Action<void(std::vector<int>)> first = [&] { ran_first = true; };
+  Action<int(std::vector<int>)> a =
+      DoAll(first, [](std::vector<int> arg) { return arg.front(); });
+  EXPECT_EQ(7, a.Perform(std::make_tuple(std::vector<int>{7})));
+  EXPECT_TRUE(ran_first);
+}
+
+// The ACTION*() macros trigger warning C4100 (unreferenced formal
+// parameter) in MSVC with -W4.  Unfortunately they cannot be fixed in
+// the macro definition, as the warnings are generated when the macro
+// is expanded and macro expansion cannot contain #pragma.  Therefore
+// we suppress them here.
+// Also suppress C4503 decorated name length exceeded, name was truncated
+GTEST_DISABLE_MSC_WARNINGS_PUSH_(4100 4503)
+// Tests the ACTION*() macro family.
+
+// Tests that ACTION() can define an action that doesn't reference the
+// mock function arguments.
+ACTION(Return5) { return 5; }
+
+TEST(ActionMacroTest, WorksWhenNotReferencingArguments) {
+  Action<double()> a1 = Return5();
+  EXPECT_DOUBLE_EQ(5, a1.Perform(std::make_tuple()));
+
+  Action<int(double, bool)> a2 = Return5();
+  EXPECT_EQ(5, a2.Perform(std::make_tuple(1, true)));
+}
+
+// Tests that ACTION() can define an action that returns void.
+ACTION(IncrementArg1) { (*arg1)++; }
+
+TEST(ActionMacroTest, WorksWhenReturningVoid) {
+  Action<void(int, int*)> a1 = IncrementArg1();
+  int n = 0;
+  a1.Perform(std::make_tuple(5, &n));
+  EXPECT_EQ(1, n);
+}
+
+// Tests that the body of ACTION() can reference the type of the
+// argument.
+ACTION(IncrementArg2) {
+  StaticAssertTypeEq<int*, arg2_type>();
+  arg2_type temp = arg2;
+  (*temp)++;
+}
+
+TEST(ActionMacroTest, CanReferenceArgumentType) {
+  Action<void(int, bool, int*)> a1 = IncrementArg2();
+  int n = 0;
+  a1.Perform(std::make_tuple(5, false, &n));
+  EXPECT_EQ(1, n);
+}
+
+// Tests that the body of ACTION() can reference the argument tuple
+// via args_type and args.
+ACTION(Sum2) {
+  StaticAssertTypeEq<std::tuple<int, char, int*>, args_type>();
+  args_type args_copy = args;
+  return std::get<0>(args_copy) + std::get<1>(args_copy);
+}
+
+TEST(ActionMacroTest, CanReferenceArgumentTuple) {
+  Action<int(int, char, int*)> a1 = Sum2();
+  int dummy = 0;
+  EXPECT_EQ(11, a1.Perform(std::make_tuple(5, Char(6), &dummy)));
+}
+
+namespace {
+
+// Tests that the body of ACTION() can reference the mock function
+// type.
+int Dummy(bool flag) { return flag ? 1 : 0; }
+
+}  // namespace
+
+ACTION(InvokeDummy) {
+  StaticAssertTypeEq<int(bool), function_type>();
+  function_type* fp = &Dummy;
+  return (*fp)(true);
+}
+
+TEST(ActionMacroTest, CanReferenceMockFunctionType) {
+  Action<int(bool)> a1 = InvokeDummy();
+  EXPECT_EQ(1, a1.Perform(std::make_tuple(true)));
+  EXPECT_EQ(1, a1.Perform(std::make_tuple(false)));
+}
+
+// Tests that the body of ACTION() can reference the mock function's
+// return type.
+ACTION(InvokeDummy2) {
+  StaticAssertTypeEq<int, return_type>();
+  return_type result = Dummy(true);
+  return result;
+}
+
+TEST(ActionMacroTest, CanReferenceMockFunctionReturnType) {
+  Action<int(bool)> a1 = InvokeDummy2();
+  EXPECT_EQ(1, a1.Perform(std::make_tuple(true)));
+  EXPECT_EQ(1, a1.Perform(std::make_tuple(false)));
+}
+
+// Tests that ACTION() works for arguments passed by const reference.
+ACTION(ReturnAddrOfConstBoolReferenceArg) {
+  StaticAssertTypeEq<const bool&, arg1_type>();
+  return &arg1;
+}
+
+TEST(ActionMacroTest, WorksForConstReferenceArg) {
+  Action<const bool*(int, const bool&)> a = ReturnAddrOfConstBoolReferenceArg();
+  const bool b = false;
+  EXPECT_EQ(&b, a.Perform(std::tuple<int, const bool&>(0, b)));
+}
+
+// Tests that ACTION() works for arguments passed by non-const reference.
+ACTION(ReturnAddrOfIntReferenceArg) {
+  StaticAssertTypeEq<int&, arg0_type>();
+  return &arg0;
+}
+
+TEST(ActionMacroTest, WorksForNonConstReferenceArg) {
+  Action<int*(int&, bool, int)> a = ReturnAddrOfIntReferenceArg();
+  int n = 0;
+  EXPECT_EQ(&n, a.Perform(std::tuple<int&, bool, int>(n, true, 1)));
+}
+
+// Tests that ACTION() can be used in a namespace.
+namespace action_test {
+ACTION(Sum) { return arg0 + arg1; }
+}  // namespace action_test
+
+TEST(ActionMacroTest, WorksInNamespace) {
+  Action<int(int, int)> a1 = action_test::Sum();
+  EXPECT_EQ(3, a1.Perform(std::make_tuple(1, 2)));
+}
+
+// Tests that the same ACTION definition works for mock functions with
+// different argument numbers.
+ACTION(PlusTwo) { return arg0 + 2; }
+
+TEST(ActionMacroTest, WorksForDifferentArgumentNumbers) {
+  Action<int(int)> a1 = PlusTwo();
+  EXPECT_EQ(4, a1.Perform(std::make_tuple(2)));
+
+  Action<double(float, void*)> a2 = PlusTwo();
+  int dummy;
+  EXPECT_DOUBLE_EQ(6, a2.Perform(std::make_tuple(4.0f, &dummy)));
+}
+
+// Tests that ACTION_P can define a parameterized action.
+ACTION_P(Plus, n) { return arg0 + n; }
+
+TEST(ActionPMacroTest, DefinesParameterizedAction) {
+  Action<int(int m, bool t)> a1 = Plus(9);
+  EXPECT_EQ(10, a1.Perform(std::make_tuple(1, true)));
+}
+
+// Tests that the body of ACTION_P can reference the argument types
+// and the parameter type.
+ACTION_P(TypedPlus, n) {
+  arg0_type t1 = arg0;
+  n_type t2 = n;
+  return t1 + t2;
+}
+
+TEST(ActionPMacroTest, CanReferenceArgumentAndParameterTypes) {
+  Action<int(char m, bool t)> a1 = TypedPlus(9);
+  EXPECT_EQ(10, a1.Perform(std::make_tuple(Char(1), true)));
+}
+
+// Tests that a parameterized action can be used in any mock function
+// whose type is compatible.
+TEST(ActionPMacroTest, WorksInCompatibleMockFunction) {
+  Action<std::string(const std::string& s)> a1 = Plus("tail");
+  const std::string re = "re";
+  std::tuple<const std::string> dummy = std::make_tuple(re);
+  EXPECT_EQ("retail", a1.Perform(dummy));
+}
+
+// Tests that we can use ACTION*() to define actions overloaded on the
+// number of parameters.
+
+ACTION(OverloadedAction) { return arg0 ? arg1 : "hello"; }
+
+ACTION_P(OverloadedAction, default_value) {
+  return arg0 ? arg1 : default_value;
+}
+
+ACTION_P2(OverloadedAction, true_value, false_value) {
+  return arg0 ? true_value : false_value;
+}
+
+TEST(ActionMacroTest, CanDefineOverloadedActions) {
+  using MyAction = Action<const char*(bool, const char*)>;
+
+  const MyAction a1 = OverloadedAction();
+  EXPECT_STREQ("hello", a1.Perform(std::make_tuple(false, CharPtr("world"))));
+  EXPECT_STREQ("world", a1.Perform(std::make_tuple(true, CharPtr("world"))));
+
+  const MyAction a2 = OverloadedAction("hi");
+  EXPECT_STREQ("hi", a2.Perform(std::make_tuple(false, CharPtr("world"))));
+  EXPECT_STREQ("world", a2.Perform(std::make_tuple(true, CharPtr("world"))));
+
+  const MyAction a3 = OverloadedAction("hi", "you");
+  EXPECT_STREQ("hi", a3.Perform(std::make_tuple(true, CharPtr("world"))));
+  EXPECT_STREQ("you", a3.Perform(std::make_tuple(false, CharPtr("world"))));
+}
+
+// Tests ACTION_Pn where n >= 3.
+
+ACTION_P3(Plus, m, n, k) { return arg0 + m + n + k; }
+
+TEST(ActionPnMacroTest, WorksFor3Parameters) {
+  Action<double(int m, bool t)> a1 = Plus(100, 20, 3.4);
+  EXPECT_DOUBLE_EQ(3123.4, a1.Perform(std::make_tuple(3000, true)));
+
+  Action<std::string(const std::string& s)> a2 = Plus("tail", "-", ">");
+  const std::string re = "re";
+  std::tuple<const std::string> dummy = std::make_tuple(re);
+  EXPECT_EQ("retail->", a2.Perform(dummy));
+}
+
+ACTION_P4(Plus, p0, p1, p2, p3) { return arg0 + p0 + p1 + p2 + p3; }
+
+TEST(ActionPnMacroTest, WorksFor4Parameters) {
+  Action<int(int)> a1 = Plus(1, 2, 3, 4);
+  EXPECT_EQ(10 + 1 + 2 + 3 + 4, a1.Perform(std::make_tuple(10)));
+}
+
+ACTION_P5(Plus, p0, p1, p2, p3, p4) { return arg0 + p0 + p1 + p2 + p3 + p4; }
+
+TEST(ActionPnMacroTest, WorksFor5Parameters) {
+  Action<int(int)> a1 = Plus(1, 2, 3, 4, 5);
+  EXPECT_EQ(10 + 1 + 2 + 3 + 4 + 5, a1.Perform(std::make_tuple(10)));
+}
+
+ACTION_P6(Plus, p0, p1, p2, p3, p4, p5) {
+  return arg0 + p0 + p1 + p2 + p3 + p4 + p5;
+}
+
+TEST(ActionPnMacroTest, WorksFor6Parameters) {
+  Action<int(int)> a1 = Plus(1, 2, 3, 4, 5, 6);
+  EXPECT_EQ(10 + 1 + 2 + 3 + 4 + 5 + 6, a1.Perform(std::make_tuple(10)));
+}
+
+ACTION_P7(Plus, p0, p1, p2, p3, p4, p5, p6) {
+  return arg0 + p0 + p1 + p2 + p3 + p4 + p5 + p6;
+}
+
+TEST(ActionPnMacroTest, WorksFor7Parameters) {
+  Action<int(int)> a1 = Plus(1, 2, 3, 4, 5, 6, 7);
+  EXPECT_EQ(10 + 1 + 2 + 3 + 4 + 5 + 6 + 7, a1.Perform(std::make_tuple(10)));
+}
+
+ACTION_P8(Plus, p0, p1, p2, p3, p4, p5, p6, p7) {
+  return arg0 + p0 + p1 + p2 + p3 + p4 + p5 + p6 + p7;
+}
+
+TEST(ActionPnMacroTest, WorksFor8Parameters) {
+  Action<int(int)> a1 = Plus(1, 2, 3, 4, 5, 6, 7, 8);
+  EXPECT_EQ(10 + 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8,
+            a1.Perform(std::make_tuple(10)));
+}
+
+ACTION_P9(Plus, p0, p1, p2, p3, p4, p5, p6, p7, p8) {
+  return arg0 + p0 + p1 + p2 + p3 + p4 + p5 + p6 + p7 + p8;
+}
+
+TEST(ActionPnMacroTest, WorksFor9Parameters) {
+  Action<int(int)> a1 = Plus(1, 2, 3, 4, 5, 6, 7, 8, 9);
+  EXPECT_EQ(10 + 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9,
+            a1.Perform(std::make_tuple(10)));
+}
+
+ACTION_P10(Plus, p0, p1, p2, p3, p4, p5, p6, p7, p8, last_param) {
+  arg0_type t0 = arg0;
+  last_param_type t9 = last_param;
+  return t0 + p0 + p1 + p2 + p3 + p4 + p5 + p6 + p7 + p8 + t9;
+}
+
+TEST(ActionPnMacroTest, WorksFor10Parameters) {
+  Action<int(int)> a1 = Plus(1, 2, 3, 4, 5, 6, 7, 8, 9, 10);
+  EXPECT_EQ(10 + 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10,
+            a1.Perform(std::make_tuple(10)));
+}
+
+// Tests that the action body can promote the parameter types.
+
+ACTION_P2(PadArgument, prefix, suffix) {
+  // The following lines promote the two parameters to desired types.
+  std::string prefix_str(prefix);
+  char suffix_char = static_cast<char>(suffix);
+  return prefix_str + arg0 + suffix_char;
+}
+
+TEST(ActionPnMacroTest, SimpleTypePromotion) {
+  Action<std::string(const char*)> no_promo =
+      PadArgument(std::string("foo"), 'r');
+  Action<std::string(const char*)> promo =
+      PadArgument("foo", static_cast<int>('r'));
+  EXPECT_EQ("foobar", no_promo.Perform(std::make_tuple(CharPtr("ba"))));
+  EXPECT_EQ("foobar", promo.Perform(std::make_tuple(CharPtr("ba"))));
+}
+
+// Tests that we can partially restrict parameter types using a
+// straight-forward pattern.
+
+// Defines a generic action that doesn't restrict the types of its
+// parameters.
+ACTION_P3(ConcatImpl, a, b, c) {
+  std::stringstream ss;
+  ss << a << b << c;
+  return ss.str();
+}
+
+// Next, we try to restrict that either the first parameter is a
+// string, or the second parameter is an int.
+
+// Defines a partially specialized wrapper that restricts the first
+// parameter to std::string.
+template <typename T1, typename T2>
+// ConcatImplActionP3 is the class template ACTION_P3 uses to
+// implement ConcatImpl.  We shouldn't change the name as this
+// pattern requires the user to use it directly.
+ConcatImplActionP3<std::string, T1, T2> Concat(const std::string& a, T1 b,
+                                               T2 c) {
+  GTEST_INTENTIONAL_CONST_COND_PUSH_()
+  if (true) {
+    GTEST_INTENTIONAL_CONST_COND_POP_()
+    // This branch verifies that ConcatImpl() can be invoked without
+    // explicit template arguments.
+    return ConcatImpl(a, b, c);
+  } else {
+    // This branch verifies that ConcatImpl() can also be invoked with
+    // explicit template arguments.  It doesn't really need to be
+    // executed as this is a compile-time verification.
+    return ConcatImpl<std::string, T1, T2>(a, b, c);
+  }
+}
+
+// Defines another partially specialized wrapper that restricts the
+// second parameter to int.
+template <typename T1, typename T2>
+ConcatImplActionP3<T1, int, T2> Concat(T1 a, int b, T2 c) {
+  return ConcatImpl(a, b, c);
+}
+
+TEST(ActionPnMacroTest, CanPartiallyRestrictParameterTypes) {
+  Action<const std::string()> a1 = Concat("Hello", "1", 2);
+  EXPECT_EQ("Hello12", a1.Perform(std::make_tuple()));
+
+  a1 = Concat(1, 2, 3);
+  EXPECT_EQ("123", a1.Perform(std::make_tuple()));
+}
+
+// Verifies the type of an ACTION*.
+
+ACTION(DoFoo) {}
+ACTION_P(DoFoo, p) {}
+ACTION_P2(DoFoo, p0, p1) {}
+
+TEST(ActionPnMacroTest, TypesAreCorrect) {
+  // DoFoo() must be assignable to a DoFooAction variable.
+  DoFooAction a0 = DoFoo();
+
+  // DoFoo(1) must be assignable to a DoFooActionP variable.
+  DoFooActionP<int> a1 = DoFoo(1);
+
+  // DoFoo(p1, ..., pk) must be assignable to a DoFooActionPk
+  // variable, and so on.
+  DoFooActionP2<int, char> a2 = DoFoo(1, '2');
+  PlusActionP3<int, int, char> a3 = Plus(1, 2, '3');
+  PlusActionP4<int, int, int, char> a4 = Plus(1, 2, 3, '4');
+  PlusActionP5<int, int, int, int, char> a5 = Plus(1, 2, 3, 4, '5');
+  PlusActionP6<int, int, int, int, int, char> a6 = Plus(1, 2, 3, 4, 5, '6');
+  PlusActionP7<int, int, int, int, int, int, char> a7 =
+      Plus(1, 2, 3, 4, 5, 6, '7');
+  PlusActionP8<int, int, int, int, int, int, int, char> a8 =
+      Plus(1, 2, 3, 4, 5, 6, 7, '8');
+  PlusActionP9<int, int, int, int, int, int, int, int, char> a9 =
+      Plus(1, 2, 3, 4, 5, 6, 7, 8, '9');
+  PlusActionP10<int, int, int, int, int, int, int, int, int, char> a10 =
+      Plus(1, 2, 3, 4, 5, 6, 7, 8, 9, '0');
+
+  // Avoid "unused variable" warnings.
+  (void)a0;
+  (void)a1;
+  (void)a2;
+  (void)a3;
+  (void)a4;
+  (void)a5;
+  (void)a6;
+  (void)a7;
+  (void)a8;
+  (void)a9;
+  (void)a10;
+}
+
+// Tests that an ACTION_P*() action can be explicitly instantiated
+// with reference-typed parameters.
+
+ACTION_P(Plus1, x) { return x; }
+ACTION_P2(Plus2, x, y) { return x + y; }
+ACTION_P3(Plus3, x, y, z) { return x + y + z; }
+ACTION_P10(Plus10, a0, a1, a2, a3, a4, a5, a6, a7, a8, a9) {
+  return a0 + a1 + a2 + a3 + a4 + a5 + a6 + a7 + a8 + a9;
+}
+
+TEST(ActionPnMacroTest, CanExplicitlyInstantiateWithReferenceTypes) {
+  int x = 1, y = 2, z = 3;
+  const std::tuple<> empty = std::make_tuple();
+
+  Action<int()> a = Plus1<int&>(x);
+  EXPECT_EQ(1, a.Perform(empty));
+
+  a = Plus2<const int&, int&>(x, y);
+  EXPECT_EQ(3, a.Perform(empty));
+
+  a = Plus3<int&, const int&, int&>(x, y, z);
+  EXPECT_EQ(6, a.Perform(empty));
+
+  int n[10] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
+  a = Plus10<const int&, int&, const int&, int&, const int&, int&, const int&,
+             int&, const int&, int&>(n[0], n[1], n[2], n[3], n[4], n[5], n[6],
+                                     n[7], n[8], n[9]);
+  EXPECT_EQ(55, a.Perform(empty));
+}
+
+class TenArgConstructorClass {
+ public:
+  TenArgConstructorClass(int a1, int a2, int a3, int a4, int a5, int a6, int a7,
+                         int a8, int a9, int a10)
+      : value_(a1 + a2 + a3 + a4 + a5 + a6 + a7 + a8 + a9 + a10) {}
+  int value_;
+};
+
+// Tests that ACTION_TEMPLATE works when there is no value parameter.
+ACTION_TEMPLATE(CreateNew, HAS_1_TEMPLATE_PARAMS(typename, T),
+                AND_0_VALUE_PARAMS()) {
+  return new T;
+}
+
+TEST(ActionTemplateTest, WorksWithoutValueParam) {
+  const Action<int*()> a = CreateNew<int>();
+  int* p = a.Perform(std::make_tuple());
+  delete p;
+}
+
+// Tests that ACTION_TEMPLATE works when there are value parameters.
+ACTION_TEMPLATE(CreateNew, HAS_1_TEMPLATE_PARAMS(typename, T),
+                AND_1_VALUE_PARAMS(a0)) {
+  return new T(a0);
+}
+
+TEST(ActionTemplateTest, WorksWithValueParams) {
+  const Action<int*()> a = CreateNew<int>(42);
+  int* p = a.Perform(std::make_tuple());
+  EXPECT_EQ(42, *p);
+  delete p;
+}
+
+// Tests that ACTION_TEMPLATE works for integral template parameters.
+ACTION_TEMPLATE(MyDeleteArg, HAS_1_TEMPLATE_PARAMS(int, k),
+                AND_0_VALUE_PARAMS()) {
+  delete std::get<k>(args);
+}
+
+// Resets a bool variable in the destructor.
+class BoolResetter {
+ public:
+  explicit BoolResetter(bool* value) : value_(value) {}
+  ~BoolResetter() { *value_ = false; }
+
+ private:
+  bool* value_;
+};
+
+TEST(ActionTemplateTest, WorksForIntegralTemplateParams) {
+  const Action<void(int*, BoolResetter*)> a = MyDeleteArg<1>();
+  int n = 0;
+  bool b = true;
+  auto* resetter = new BoolResetter(&b);
+  a.Perform(std::make_tuple(&n, resetter));
+  EXPECT_FALSE(b);  // Verifies that resetter is deleted.
+}
+
+// Tests that ACTION_TEMPLATES works for template template parameters.
+ACTION_TEMPLATE(ReturnSmartPointer,
+                HAS_1_TEMPLATE_PARAMS(template <typename Pointee> class,
+                                      Pointer),
+                AND_1_VALUE_PARAMS(pointee)) {
+  return Pointer<pointee_type>(new pointee_type(pointee));
+}
+
+TEST(ActionTemplateTest, WorksForTemplateTemplateParameters) {
+  const Action<std::shared_ptr<int>()> a =
+      ReturnSmartPointer<std::shared_ptr>(42);
+  std::shared_ptr<int> p = a.Perform(std::make_tuple());
+  EXPECT_EQ(42, *p);
+}
+
+// Tests that ACTION_TEMPLATE works for 10 template parameters.
+template <typename T1, typename T2, typename T3, int k4, bool k5,
+          unsigned int k6, typename T7, typename T8, typename T9>
+struct GiantTemplate {
+ public:
+  explicit GiantTemplate(int a_value) : value(a_value) {}
+  int value;
+};
+
+ACTION_TEMPLATE(ReturnGiant,
+                HAS_10_TEMPLATE_PARAMS(typename, T1, typename, T2, typename, T3,
+                                       int, k4, bool, k5, unsigned int, k6,
+                                       class, T7, class, T8, class, T9,
+                                       template <typename T> class, T10),
+                AND_1_VALUE_PARAMS(value)) {
+  return GiantTemplate<T10<T1>, T2, T3, k4, k5, k6, T7, T8, T9>(value);
+}
+
+TEST(ActionTemplateTest, WorksFor10TemplateParameters) {
+  using Giant = GiantTemplate<std::shared_ptr<int>, bool, double, 5, true, 6,
+                              char, unsigned, int>;
+  const Action<Giant()> a = ReturnGiant<int, bool, double, 5, true, 6, char,
+                                        unsigned, int, std::shared_ptr>(42);
+  Giant giant = a.Perform(std::make_tuple());
+  EXPECT_EQ(42, giant.value);
+}
+
+// Tests that ACTION_TEMPLATE works for 10 value parameters.
+ACTION_TEMPLATE(ReturnSum, HAS_1_TEMPLATE_PARAMS(typename, Number),
+                AND_10_VALUE_PARAMS(v1, v2, v3, v4, v5, v6, v7, v8, v9, v10)) {
+  return static_cast<Number>(v1) + v2 + v3 + v4 + v5 + v6 + v7 + v8 + v9 + v10;
+}
+
+TEST(ActionTemplateTest, WorksFor10ValueParameters) {
+  const Action<int()> a = ReturnSum<int>(1, 2, 3, 4, 5, 6, 7, 8, 9, 10);
+  EXPECT_EQ(55, a.Perform(std::make_tuple()));
+}
+
+// Tests that ACTION_TEMPLATE and ACTION/ACTION_P* can be overloaded
+// on the number of value parameters.
+
+ACTION(ReturnSum) { return 0; }
+
+ACTION_P(ReturnSum, x) { return x; }
+
+ACTION_TEMPLATE(ReturnSum, HAS_1_TEMPLATE_PARAMS(typename, Number),
+                AND_2_VALUE_PARAMS(v1, v2)) {
+  return static_cast<Number>(v1) + v2;
+}
+
+ACTION_TEMPLATE(ReturnSum, HAS_1_TEMPLATE_PARAMS(typename, Number),
+                AND_3_VALUE_PARAMS(v1, v2, v3)) {
+  return static_cast<Number>(v1) + v2 + v3;
+}
+
+ACTION_TEMPLATE(ReturnSum, HAS_2_TEMPLATE_PARAMS(typename, Number, int, k),
+                AND_4_VALUE_PARAMS(v1, v2, v3, v4)) {
+  return static_cast<Number>(v1) + v2 + v3 + v4 + k;
+}
+
+TEST(ActionTemplateTest, CanBeOverloadedOnNumberOfValueParameters) {
+  const Action<int()> a0 = ReturnSum();
+  const Action<int()> a1 = ReturnSum(1);
+  const Action<int()> a2 = ReturnSum<int>(1, 2);
+  const Action<int()> a3 = ReturnSum<int>(1, 2, 3);
+  const Action<int()> a4 = ReturnSum<int, 10000>(2000, 300, 40, 5);
+  EXPECT_EQ(0, a0.Perform(std::make_tuple()));
+  EXPECT_EQ(1, a1.Perform(std::make_tuple()));
+  EXPECT_EQ(3, a2.Perform(std::make_tuple()));
+  EXPECT_EQ(6, a3.Perform(std::make_tuple()));
+  EXPECT_EQ(12345, a4.Perform(std::make_tuple()));
+}
+
+}  // namespace gmock_more_actions_test
+}  // namespace testing
+
+GTEST_DISABLE_MSC_WARNINGS_POP_()  // 4100 4503
+GTEST_DISABLE_MSC_WARNINGS_POP_()  // 4577
diff --git a/third_party/googletest/googlemock/test/gmock-nice-strict_test.cc b/third_party/googletest/googlemock/test/gmock-nice-strict_test.cc
new file mode 100644
index 0000000..95f0969
--- /dev/null
+++ b/third_party/googletest/googlemock/test/gmock-nice-strict_test.cc
@@ -0,0 +1,541 @@
+// Copyright 2008, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include "gmock/gmock-nice-strict.h"
+
+#include <string>
+#include <utility>
+
+#include "gmock/gmock.h"
+#include "gtest/gtest-spi.h"
+#include "gtest/gtest.h"
+
+// This must not be defined inside the ::testing namespace, or it will
+// clash with ::testing::Mock.
+class Mock {
+ public:
+  Mock() = default;
+
+  MOCK_METHOD0(DoThis, void());
+
+ private:
+  Mock(const Mock&) = delete;
+  Mock& operator=(const Mock&) = delete;
+};
+
+namespace testing {
+namespace gmock_nice_strict_test {
+
+using testing::HasSubstr;
+using testing::NaggyMock;
+using testing::NiceMock;
+using testing::StrictMock;
+
+#if GTEST_HAS_STREAM_REDIRECTION
+using testing::internal::CaptureStdout;
+using testing::internal::GetCapturedStdout;
+#endif
+
+// Class without default constructor.
+class NotDefaultConstructible {
+ public:
+  explicit NotDefaultConstructible(int) {}
+};
+
+class CallsMockMethodInDestructor {
+ public:
+  ~CallsMockMethodInDestructor() { OnDestroy(); }
+  MOCK_METHOD(void, OnDestroy, ());
+};
+
+// Defines some mock classes needed by the tests.
+
+class Foo {
+ public:
+  virtual ~Foo() = default;
+
+  virtual void DoThis() = 0;
+  virtual int DoThat(bool flag) = 0;
+};
+
+class MockFoo : public Foo {
+ public:
+  MockFoo() = default;
+  void Delete() { delete this; }
+
+  MOCK_METHOD0(DoThis, void());
+  MOCK_METHOD1(DoThat, int(bool flag));
+  MOCK_METHOD0(ReturnNonDefaultConstructible, NotDefaultConstructible());
+
+ private:
+  MockFoo(const MockFoo&) = delete;
+  MockFoo& operator=(const MockFoo&) = delete;
+};
+
+class MockBar {
+ public:
+  explicit MockBar(const std::string& s) : str_(s) {}
+
+  MockBar(char a1, char a2, std::string a3, std::string a4, int a5, int a6,
+          const std::string& a7, const std::string& a8, bool a9, bool a10) {
+    str_ = std::string() + a1 + a2 + a3 + a4 + static_cast<char>(a5) +
+           static_cast<char>(a6) + a7 + a8 + (a9 ? 'T' : 'F') +
+           (a10 ? 'T' : 'F');
+  }
+
+  virtual ~MockBar() = default;
+
+  const std::string& str() const { return str_; }
+
+  MOCK_METHOD0(This, int());
+  MOCK_METHOD2(That, std::string(int, bool));
+
+ private:
+  std::string str_;
+
+  MockBar(const MockBar&) = delete;
+  MockBar& operator=(const MockBar&) = delete;
+};
+
+class MockBaz {
+ public:
+  class MoveOnly {
+   public:
+    MoveOnly() = default;
+
+    MoveOnly(const MoveOnly&) = delete;
+    MoveOnly& operator=(const MoveOnly&) = delete;
+
+    MoveOnly(MoveOnly&&) = default;
+    MoveOnly& operator=(MoveOnly&&) = default;
+  };
+
+  MockBaz(MoveOnly) {}
+};
+
+#if GTEST_HAS_STREAM_REDIRECTION
+
+// Tests that a raw mock generates warnings for uninteresting calls.
+TEST(RawMockTest, WarningForUninterestingCall) {
+  const std::string saved_flag = GMOCK_FLAG_GET(verbose);
+  GMOCK_FLAG_SET(verbose, "warning");
+
+  MockFoo raw_foo;
+
+  CaptureStdout();
+  raw_foo.DoThis();
+  raw_foo.DoThat(true);
+  EXPECT_THAT(GetCapturedStdout(),
+              HasSubstr("Uninteresting mock function call"));
+
+  GMOCK_FLAG_SET(verbose, saved_flag);
+}
+
+// Tests that a raw mock generates warnings for uninteresting calls
+// that delete the mock object.
+TEST(RawMockTest, WarningForUninterestingCallAfterDeath) {
+  const std::string saved_flag = GMOCK_FLAG_GET(verbose);
+  GMOCK_FLAG_SET(verbose, "warning");
+
+  MockFoo* const raw_foo = new MockFoo;
+
+  ON_CALL(*raw_foo, DoThis()).WillByDefault(Invoke(raw_foo, &MockFoo::Delete));
+
+  CaptureStdout();
+  raw_foo->DoThis();
+  EXPECT_THAT(GetCapturedStdout(),
+              HasSubstr("Uninteresting mock function call"));
+
+  GMOCK_FLAG_SET(verbose, saved_flag);
+}
+
+// Tests that a raw mock generates informational logs for
+// uninteresting calls.
+TEST(RawMockTest, InfoForUninterestingCall) {
+  MockFoo raw_foo;
+
+  const std::string saved_flag = GMOCK_FLAG_GET(verbose);
+  GMOCK_FLAG_SET(verbose, "info");
+  CaptureStdout();
+  raw_foo.DoThis();
+  EXPECT_THAT(GetCapturedStdout(),
+              HasSubstr("Uninteresting mock function call"));
+
+  GMOCK_FLAG_SET(verbose, saved_flag);
+}
+
+TEST(RawMockTest, IsNaggy_IsNice_IsStrict) {
+  MockFoo raw_foo;
+  EXPECT_TRUE(Mock::IsNaggy(&raw_foo));
+  EXPECT_FALSE(Mock::IsNice(&raw_foo));
+  EXPECT_FALSE(Mock::IsStrict(&raw_foo));
+}
+
+// Tests that a nice mock generates no warning for uninteresting calls.
+TEST(NiceMockTest, NoWarningForUninterestingCall) {
+  NiceMock<MockFoo> nice_foo;
+
+  CaptureStdout();
+  nice_foo.DoThis();
+  nice_foo.DoThat(true);
+  EXPECT_EQ("", GetCapturedStdout());
+}
+
+// Tests that a nice mock generates no warning for uninteresting calls
+// that delete the mock object.
+TEST(NiceMockTest, NoWarningForUninterestingCallAfterDeath) {
+  NiceMock<MockFoo>* const nice_foo = new NiceMock<MockFoo>;
+
+  ON_CALL(*nice_foo, DoThis())
+      .WillByDefault(Invoke(nice_foo, &MockFoo::Delete));
+
+  CaptureStdout();
+  nice_foo->DoThis();
+  EXPECT_EQ("", GetCapturedStdout());
+}
+
+// Tests that a nice mock generates informational logs for
+// uninteresting calls.
+TEST(NiceMockTest, InfoForUninterestingCall) {
+  NiceMock<MockFoo> nice_foo;
+
+  const std::string saved_flag = GMOCK_FLAG_GET(verbose);
+  GMOCK_FLAG_SET(verbose, "info");
+  CaptureStdout();
+  nice_foo.DoThis();
+  EXPECT_THAT(GetCapturedStdout(),
+              HasSubstr("Uninteresting mock function call"));
+
+  GMOCK_FLAG_SET(verbose, saved_flag);
+}
+
+#endif  // GTEST_HAS_STREAM_REDIRECTION
+
+// Tests that a nice mock allows expected calls.
+TEST(NiceMockTest, AllowsExpectedCall) {
+  NiceMock<MockFoo> nice_foo;
+
+  EXPECT_CALL(nice_foo, DoThis());
+  nice_foo.DoThis();
+}
+
+// Tests that an unexpected call on a nice mock which returns a
+// not-default-constructible type throws an exception and the exception contains
+// the method's name.
+TEST(NiceMockTest, ThrowsExceptionForUnknownReturnTypes) {
+  NiceMock<MockFoo> nice_foo;
+#if GTEST_HAS_EXCEPTIONS
+  try {
+    nice_foo.ReturnNonDefaultConstructible();
+    FAIL();
+  } catch (const std::runtime_error& ex) {
+    EXPECT_THAT(ex.what(), HasSubstr("ReturnNonDefaultConstructible"));
+  }
+#else
+  EXPECT_DEATH_IF_SUPPORTED({ nice_foo.ReturnNonDefaultConstructible(); }, "");
+#endif
+}
+
+// Tests that an unexpected call on a nice mock fails.
+TEST(NiceMockTest, UnexpectedCallFails) {
+  NiceMock<MockFoo> nice_foo;
+
+  EXPECT_CALL(nice_foo, DoThis()).Times(0);
+  EXPECT_NONFATAL_FAILURE(nice_foo.DoThis(), "called more times than expected");
+}
+
+// Tests that NiceMock works with a mock class that has a non-default
+// constructor.
+TEST(NiceMockTest, NonDefaultConstructor) {
+  NiceMock<MockBar> nice_bar("hi");
+  EXPECT_EQ("hi", nice_bar.str());
+
+  nice_bar.This();
+  nice_bar.That(5, true);
+}
+
+// Tests that NiceMock works with a mock class that has a 10-ary
+// non-default constructor.
+TEST(NiceMockTest, NonDefaultConstructor10) {
+  NiceMock<MockBar> nice_bar('a', 'b', "c", "d", 'e', 'f', "g", "h", true,
+                             false);
+  EXPECT_EQ("abcdefghTF", nice_bar.str());
+
+  nice_bar.This();
+  nice_bar.That(5, true);
+}
+
+TEST(NiceMockTest, AllowLeak) {
+  NiceMock<MockFoo>* leaked = new NiceMock<MockFoo>;
+  Mock::AllowLeak(leaked);
+  EXPECT_CALL(*leaked, DoThis());
+  leaked->DoThis();
+}
+
+TEST(NiceMockTest, MoveOnlyConstructor) {
+  NiceMock<MockBaz> nice_baz(MockBaz::MoveOnly{});
+}
+
+// Tests that NiceMock<Mock> compiles where Mock is a user-defined
+// class (as opposed to ::testing::Mock).
+TEST(NiceMockTest, AcceptsClassNamedMock) {
+  NiceMock< ::Mock> nice;
+  EXPECT_CALL(nice, DoThis());
+  nice.DoThis();
+}
+
+TEST(NiceMockTest, IsNiceInDestructor) {
+  {
+    NiceMock<CallsMockMethodInDestructor> nice_on_destroy;
+    // Don't add an expectation for the call before the mock goes out of scope.
+  }
+}
+
+TEST(NiceMockTest, IsNaggy_IsNice_IsStrict) {
+  NiceMock<MockFoo> nice_foo;
+  EXPECT_FALSE(Mock::IsNaggy(&nice_foo));
+  EXPECT_TRUE(Mock::IsNice(&nice_foo));
+  EXPECT_FALSE(Mock::IsStrict(&nice_foo));
+}
+
+#if GTEST_HAS_STREAM_REDIRECTION
+
+// Tests that a naggy mock generates warnings for uninteresting calls.
+TEST(NaggyMockTest, WarningForUninterestingCall) {
+  const std::string saved_flag = GMOCK_FLAG_GET(verbose);
+  GMOCK_FLAG_SET(verbose, "warning");
+
+  NaggyMock<MockFoo> naggy_foo;
+
+  CaptureStdout();
+  naggy_foo.DoThis();
+  naggy_foo.DoThat(true);
+  EXPECT_THAT(GetCapturedStdout(),
+              HasSubstr("Uninteresting mock function call"));
+
+  GMOCK_FLAG_SET(verbose, saved_flag);
+}
+
+// Tests that a naggy mock generates a warning for an uninteresting call
+// that deletes the mock object.
+TEST(NaggyMockTest, WarningForUninterestingCallAfterDeath) {
+  const std::string saved_flag = GMOCK_FLAG_GET(verbose);
+  GMOCK_FLAG_SET(verbose, "warning");
+
+  NaggyMock<MockFoo>* const naggy_foo = new NaggyMock<MockFoo>;
+
+  ON_CALL(*naggy_foo, DoThis())
+      .WillByDefault(Invoke(naggy_foo, &MockFoo::Delete));
+
+  CaptureStdout();
+  naggy_foo->DoThis();
+  EXPECT_THAT(GetCapturedStdout(),
+              HasSubstr("Uninteresting mock function call"));
+
+  GMOCK_FLAG_SET(verbose, saved_flag);
+}
+
+#endif  // GTEST_HAS_STREAM_REDIRECTION
+
+// Tests that a naggy mock allows expected calls.
+TEST(NaggyMockTest, AllowsExpectedCall) {
+  NaggyMock<MockFoo> naggy_foo;
+
+  EXPECT_CALL(naggy_foo, DoThis());
+  naggy_foo.DoThis();
+}
+
+// Tests that an unexpected call on a naggy mock fails.
+TEST(NaggyMockTest, UnexpectedCallFails) {
+  NaggyMock<MockFoo> naggy_foo;
+
+  EXPECT_CALL(naggy_foo, DoThis()).Times(0);
+  EXPECT_NONFATAL_FAILURE(naggy_foo.DoThis(),
+                          "called more times than expected");
+}
+
+// Tests that NaggyMock works with a mock class that has a non-default
+// constructor.
+TEST(NaggyMockTest, NonDefaultConstructor) {
+  NaggyMock<MockBar> naggy_bar("hi");
+  EXPECT_EQ("hi", naggy_bar.str());
+
+  naggy_bar.This();
+  naggy_bar.That(5, true);
+}
+
+// Tests that NaggyMock works with a mock class that has a 10-ary
+// non-default constructor.
+TEST(NaggyMockTest, NonDefaultConstructor10) {
+  NaggyMock<MockBar> naggy_bar('0', '1', "2", "3", '4', '5', "6", "7", true,
+                               false);
+  EXPECT_EQ("01234567TF", naggy_bar.str());
+
+  naggy_bar.This();
+  naggy_bar.That(5, true);
+}
+
+TEST(NaggyMockTest, AllowLeak) {
+  NaggyMock<MockFoo>* leaked = new NaggyMock<MockFoo>;
+  Mock::AllowLeak(leaked);
+  EXPECT_CALL(*leaked, DoThis());
+  leaked->DoThis();
+}
+
+TEST(NaggyMockTest, MoveOnlyConstructor) {
+  NaggyMock<MockBaz> naggy_baz(MockBaz::MoveOnly{});
+}
+
+// Tests that NaggyMock<Mock> compiles where Mock is a user-defined
+// class (as opposed to ::testing::Mock).
+TEST(NaggyMockTest, AcceptsClassNamedMock) {
+  NaggyMock< ::Mock> naggy;
+  EXPECT_CALL(naggy, DoThis());
+  naggy.DoThis();
+}
+
+TEST(NaggyMockTest, IsNaggyInDestructor) {
+  const std::string saved_flag = GMOCK_FLAG_GET(verbose);
+  GMOCK_FLAG_SET(verbose, "warning");
+  CaptureStdout();
+
+  {
+    NaggyMock<CallsMockMethodInDestructor> naggy_on_destroy;
+    // Don't add an expectation for the call before the mock goes out of scope.
+  }
+
+  EXPECT_THAT(GetCapturedStdout(),
+              HasSubstr("Uninteresting mock function call"));
+
+  GMOCK_FLAG_SET(verbose, saved_flag);
+}
+
+TEST(NaggyMockTest, IsNaggy_IsNice_IsStrict) {
+  NaggyMock<MockFoo> naggy_foo;
+  EXPECT_TRUE(Mock::IsNaggy(&naggy_foo));
+  EXPECT_FALSE(Mock::IsNice(&naggy_foo));
+  EXPECT_FALSE(Mock::IsStrict(&naggy_foo));
+}
+
+// Tests that a strict mock allows expected calls.
+TEST(StrictMockTest, AllowsExpectedCall) {
+  StrictMock<MockFoo> strict_foo;
+
+  EXPECT_CALL(strict_foo, DoThis());
+  strict_foo.DoThis();
+}
+
+// Tests that an unexpected call on a strict mock fails.
+TEST(StrictMockTest, UnexpectedCallFails) {
+  StrictMock<MockFoo> strict_foo;
+
+  EXPECT_CALL(strict_foo, DoThis()).Times(0);
+  EXPECT_NONFATAL_FAILURE(strict_foo.DoThis(),
+                          "called more times than expected");
+}
+
+// Tests that an uninteresting call on a strict mock fails.
+TEST(StrictMockTest, UninterestingCallFails) {
+  StrictMock<MockFoo> strict_foo;
+
+  EXPECT_NONFATAL_FAILURE(strict_foo.DoThis(),
+                          "Uninteresting mock function call");
+}
+
+// Tests that an uninteresting call on a strict mock fails, even if
+// the call deletes the mock object.
+TEST(StrictMockTest, UninterestingCallFailsAfterDeath) {
+  StrictMock<MockFoo>* const strict_foo = new StrictMock<MockFoo>;
+
+  ON_CALL(*strict_foo, DoThis())
+      .WillByDefault(Invoke(strict_foo, &MockFoo::Delete));
+
+  EXPECT_NONFATAL_FAILURE(strict_foo->DoThis(),
+                          "Uninteresting mock function call");
+}
+
+// Tests that StrictMock works with a mock class that has a
+// non-default constructor.
+TEST(StrictMockTest, NonDefaultConstructor) {
+  StrictMock<MockBar> strict_bar("hi");
+  EXPECT_EQ("hi", strict_bar.str());
+
+  EXPECT_NONFATAL_FAILURE(strict_bar.That(5, true),
+                          "Uninteresting mock function call");
+}
+
+// Tests that StrictMock works with a mock class that has a 10-ary
+// non-default constructor.
+TEST(StrictMockTest, NonDefaultConstructor10) {
+  StrictMock<MockBar> strict_bar('a', 'b', "c", "d", 'e', 'f', "g", "h", true,
+                                 false);
+  EXPECT_EQ("abcdefghTF", strict_bar.str());
+
+  EXPECT_NONFATAL_FAILURE(strict_bar.That(5, true),
+                          "Uninteresting mock function call");
+}
+
+TEST(StrictMockTest, AllowLeak) {
+  StrictMock<MockFoo>* leaked = new StrictMock<MockFoo>;
+  Mock::AllowLeak(leaked);
+  EXPECT_CALL(*leaked, DoThis());
+  leaked->DoThis();
+}
+
+TEST(StrictMockTest, MoveOnlyConstructor) {
+  StrictMock<MockBaz> strict_baz(MockBaz::MoveOnly{});
+}
+
+// Tests that StrictMock<Mock> compiles where Mock is a user-defined
+// class (as opposed to ::testing::Mock).
+TEST(StrictMockTest, AcceptsClassNamedMock) {
+  StrictMock< ::Mock> strict;
+  EXPECT_CALL(strict, DoThis());
+  strict.DoThis();
+}
+
+TEST(StrictMockTest, IsStrictInDestructor) {
+  EXPECT_NONFATAL_FAILURE(
+      {
+        StrictMock<CallsMockMethodInDestructor> strict_on_destroy;
+        // Don't add an expectation for the call before the mock goes out of
+        // scope.
+      },
+      "Uninteresting mock function call");
+}
+
+TEST(StrictMockTest, IsNaggy_IsNice_IsStrict) {
+  StrictMock<MockFoo> strict_foo;
+  EXPECT_FALSE(Mock::IsNaggy(&strict_foo));
+  EXPECT_FALSE(Mock::IsNice(&strict_foo));
+  EXPECT_TRUE(Mock::IsStrict(&strict_foo));
+}
+
+}  // namespace gmock_nice_strict_test
+}  // namespace testing
diff --git a/third_party/googletest/googlemock/test/gmock-port_test.cc b/third_party/googletest/googlemock/test/gmock-port_test.cc
new file mode 100644
index 0000000..c31af82
--- /dev/null
+++ b/third_party/googletest/googlemock/test/gmock-port_test.cc
@@ -0,0 +1,42 @@
+// Copyright 2008, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Google Mock - a framework for writing C++ mock classes.
+//
+// This file tests the internal cross-platform support utilities.
+
+#include "gmock/internal/gmock-port.h"
+
+#include "gtest/gtest.h"
+
+// NOTE: if this file is left without tests for some reason, put a dummy
+// test here to make references to symbols in the gtest library and avoid
+// 'undefined symbol' linker errors in gmock_main:
+
+TEST(DummyTest, Dummy) {}
diff --git a/third_party/googletest/googlemock/test/gmock-pp-string_test.cc b/third_party/googletest/googlemock/test/gmock-pp-string_test.cc
new file mode 100644
index 0000000..53c80f4
--- /dev/null
+++ b/third_party/googletest/googlemock/test/gmock-pp-string_test.cc
@@ -0,0 +1,205 @@
+// Copyright 2018, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Google Mock - a framework for writing C++ mock classes.
+//
+// This file tests the internal preprocessor macro library.
+#include <string>
+
+#include "gmock/gmock.h"
+#include "gmock/internal/gmock-pp.h"
+
+namespace testing {
+namespace {
+
+// Matcher to verify that to strings are identical up to whitespace
+// Not 100% correct, because it treats "AB" as equal to "A B".
+::testing::Matcher<const std::string&> SameExceptSpaces(const std::string& s) {
+  auto remove_spaces = [](std::string to_split) {
+    to_split.erase(std::remove(to_split.begin(), to_split.end(), ' '),
+                   to_split.end());
+    return to_split;
+  };
+  return ::testing::ResultOf(remove_spaces, remove_spaces(s));
+}
+
+// Verify that a macro expands to a given text. Ignores whitespace difference.
+// In MSVC, GMOCK_PP_STRINGIZE() returns nothing, rather than "". So concatenate
+// with an empty string.
+#define EXPECT_EXPANSION(Result, Macro) \
+  EXPECT_THAT("" GMOCK_PP_STRINGIZE(Macro), SameExceptSpaces(Result))
+
+TEST(Macros, Cat) {
+  EXPECT_EXPANSION("14", GMOCK_PP_CAT(1, 4));
+  EXPECT_EXPANSION("+=", GMOCK_PP_CAT(+, =));
+}
+
+TEST(Macros, Narg) {
+  EXPECT_EXPANSION("1", GMOCK_PP_NARG());
+  EXPECT_EXPANSION("1", GMOCK_PP_NARG(x));
+  EXPECT_EXPANSION("2", GMOCK_PP_NARG(x, y));
+  EXPECT_EXPANSION("3", GMOCK_PP_NARG(x, y, z));
+  EXPECT_EXPANSION("4", GMOCK_PP_NARG(x, y, z, w));
+
+  EXPECT_EXPANSION("0", GMOCK_PP_NARG0());
+  EXPECT_EXPANSION("1", GMOCK_PP_NARG0(x));
+  EXPECT_EXPANSION("2", GMOCK_PP_NARG0(x, y));
+}
+
+TEST(Macros, Comma) {
+  EXPECT_EXPANSION("0", GMOCK_PP_HAS_COMMA());
+  EXPECT_EXPANSION("1", GMOCK_PP_HAS_COMMA(, ));
+  EXPECT_EXPANSION("0", GMOCK_PP_HAS_COMMA((, )));
+}
+
+TEST(Macros, IsEmpty) {
+  EXPECT_EXPANSION("1", GMOCK_PP_IS_EMPTY());
+  EXPECT_EXPANSION("0", GMOCK_PP_IS_EMPTY(, ));
+  EXPECT_EXPANSION("0", GMOCK_PP_IS_EMPTY(a));
+  EXPECT_EXPANSION("0", GMOCK_PP_IS_EMPTY(()));
+
+#define GMOCK_PP_INTERNAL_IS_EMPTY_TEST_1
+  EXPECT_EXPANSION("1", GMOCK_PP_IS_EMPTY(GMOCK_PP_INTERNAL_IS_EMPTY_TEST_1));
+}
+
+TEST(Macros, If) {
+  EXPECT_EXPANSION("1", GMOCK_PP_IF(1, 1, 2));
+  EXPECT_EXPANSION("2", GMOCK_PP_IF(0, 1, 2));
+}
+
+TEST(Macros, HeadTail) {
+  EXPECT_EXPANSION("1", GMOCK_PP_HEAD(1));
+  EXPECT_EXPANSION("1", GMOCK_PP_HEAD(1, 2));
+  EXPECT_EXPANSION("1", GMOCK_PP_HEAD(1, 2, 3));
+
+  EXPECT_EXPANSION("", GMOCK_PP_TAIL(1));
+  EXPECT_EXPANSION("2", GMOCK_PP_TAIL(1, 2));
+  EXPECT_EXPANSION("2", GMOCK_PP_HEAD(GMOCK_PP_TAIL(1, 2, 3)));
+}
+
+TEST(Macros, Parentheses) {
+  EXPECT_EXPANSION("0", GMOCK_PP_IS_BEGIN_PARENS(sss));
+  EXPECT_EXPANSION("0", GMOCK_PP_IS_BEGIN_PARENS(sss()));
+  EXPECT_EXPANSION("0", GMOCK_PP_IS_BEGIN_PARENS(sss() sss));
+  EXPECT_EXPANSION("1", GMOCK_PP_IS_BEGIN_PARENS((sss)));
+  EXPECT_EXPANSION("1", GMOCK_PP_IS_BEGIN_PARENS((sss)ss));
+
+  EXPECT_EXPANSION("0", GMOCK_PP_IS_ENCLOSED_PARENS(sss));
+  EXPECT_EXPANSION("0", GMOCK_PP_IS_ENCLOSED_PARENS(sss()));
+  EXPECT_EXPANSION("0", GMOCK_PP_IS_ENCLOSED_PARENS(sss() sss));
+  EXPECT_EXPANSION("1", GMOCK_PP_IS_ENCLOSED_PARENS((sss)));
+  EXPECT_EXPANSION("0", GMOCK_PP_IS_ENCLOSED_PARENS((sss)ss));
+
+  EXPECT_EXPANSION("1 + 1", GMOCK_PP_REMOVE_PARENS((1 + 1)));
+}
+
+TEST(Macros, Increment) {
+  EXPECT_EXPANSION("1", GMOCK_PP_INC(0));
+  EXPECT_EXPANSION("2", GMOCK_PP_INC(1));
+  EXPECT_EXPANSION("3", GMOCK_PP_INC(2));
+  EXPECT_EXPANSION("4", GMOCK_PP_INC(3));
+  EXPECT_EXPANSION("5", GMOCK_PP_INC(4));
+
+  EXPECT_EXPANSION("16", GMOCK_PP_INC(15));
+}
+
+#define JOINER_CAT(a, b) a##b
+#define JOINER(_N, _Data, _Elem) JOINER_CAT(_Data, _N) = _Elem
+
+TEST(Macros, Repeat) {
+  EXPECT_EXPANSION("", GMOCK_PP_REPEAT(JOINER, X, 0));
+  EXPECT_EXPANSION("X0=", GMOCK_PP_REPEAT(JOINER, X, 1));
+  EXPECT_EXPANSION("X0= X1=", GMOCK_PP_REPEAT(JOINER, X, 2));
+  EXPECT_EXPANSION("X0= X1= X2=", GMOCK_PP_REPEAT(JOINER, X, 3));
+  EXPECT_EXPANSION("X0= X1= X2= X3=", GMOCK_PP_REPEAT(JOINER, X, 4));
+  EXPECT_EXPANSION("X0= X1= X2= X3= X4=", GMOCK_PP_REPEAT(JOINER, X, 5));
+  EXPECT_EXPANSION("X0= X1= X2= X3= X4= X5=", GMOCK_PP_REPEAT(JOINER, X, 6));
+  EXPECT_EXPANSION("X0= X1= X2= X3= X4= X5= X6=",
+                   GMOCK_PP_REPEAT(JOINER, X, 7));
+  EXPECT_EXPANSION("X0= X1= X2= X3= X4= X5= X6= X7=",
+                   GMOCK_PP_REPEAT(JOINER, X, 8));
+  EXPECT_EXPANSION("X0= X1= X2= X3= X4= X5= X6= X7= X8=",
+                   GMOCK_PP_REPEAT(JOINER, X, 9));
+  EXPECT_EXPANSION("X0= X1= X2= X3= X4= X5= X6= X7= X8= X9=",
+                   GMOCK_PP_REPEAT(JOINER, X, 10));
+  EXPECT_EXPANSION("X0= X1= X2= X3= X4= X5= X6= X7= X8= X9= X10=",
+                   GMOCK_PP_REPEAT(JOINER, X, 11));
+  EXPECT_EXPANSION("X0= X1= X2= X3= X4= X5= X6= X7= X8= X9= X10= X11=",
+                   GMOCK_PP_REPEAT(JOINER, X, 12));
+  EXPECT_EXPANSION("X0= X1= X2= X3= X4= X5= X6= X7= X8= X9= X10= X11= X12=",
+                   GMOCK_PP_REPEAT(JOINER, X, 13));
+  EXPECT_EXPANSION(
+      "X0= X1= X2= X3= X4= X5= X6= X7= X8= X9= X10= X11= X12= X13=",
+      GMOCK_PP_REPEAT(JOINER, X, 14));
+  EXPECT_EXPANSION(
+      "X0= X1= X2= X3= X4= X5= X6= X7= X8= X9= X10= X11= X12= X13= X14=",
+      GMOCK_PP_REPEAT(JOINER, X, 15));
+}
+TEST(Macros, ForEach) {
+  EXPECT_EXPANSION("", GMOCK_PP_FOR_EACH(JOINER, X, ()));
+  EXPECT_EXPANSION("X0=a", GMOCK_PP_FOR_EACH(JOINER, X, (a)));
+  EXPECT_EXPANSION("X0=a X1=b", GMOCK_PP_FOR_EACH(JOINER, X, (a, b)));
+  EXPECT_EXPANSION("X0=a X1=b X2=c", GMOCK_PP_FOR_EACH(JOINER, X, (a, b, c)));
+  EXPECT_EXPANSION("X0=a X1=b X2=c X3=d",
+                   GMOCK_PP_FOR_EACH(JOINER, X, (a, b, c, d)));
+  EXPECT_EXPANSION("X0=a X1=b X2=c X3=d X4=e",
+                   GMOCK_PP_FOR_EACH(JOINER, X, (a, b, c, d, e)));
+  EXPECT_EXPANSION("X0=a X1=b X2=c X3=d X4=e X5=f",
+                   GMOCK_PP_FOR_EACH(JOINER, X, (a, b, c, d, e, f)));
+  EXPECT_EXPANSION("X0=a X1=b X2=c X3=d X4=e X5=f X6=g",
+                   GMOCK_PP_FOR_EACH(JOINER, X, (a, b, c, d, e, f, g)));
+  EXPECT_EXPANSION("X0=a X1=b X2=c X3=d X4=e X5=f X6=g X7=h",
+                   GMOCK_PP_FOR_EACH(JOINER, X, (a, b, c, d, e, f, g, h)));
+  EXPECT_EXPANSION("X0=a X1=b X2=c X3=d X4=e X5=f X6=g X7=h X8=i",
+                   GMOCK_PP_FOR_EACH(JOINER, X, (a, b, c, d, e, f, g, h, i)));
+  EXPECT_EXPANSION(
+      "X0=a X1=b X2=c X3=d X4=e X5=f X6=g X7=h X8=i X9=j",
+      GMOCK_PP_FOR_EACH(JOINER, X, (a, b, c, d, e, f, g, h, i, j)));
+  EXPECT_EXPANSION(
+      "X0=a X1=b X2=c X3=d X4=e X5=f X6=g X7=h X8=i X9=j X10=k",
+      GMOCK_PP_FOR_EACH(JOINER, X, (a, b, c, d, e, f, g, h, i, j, k)));
+  EXPECT_EXPANSION(
+      "X0=a X1=b X2=c X3=d X4=e X5=f X6=g X7=h X8=i X9=j X10=k X11=l",
+      GMOCK_PP_FOR_EACH(JOINER, X, (a, b, c, d, e, f, g, h, i, j, k, l)));
+  EXPECT_EXPANSION(
+      "X0=a X1=b X2=c X3=d X4=e X5=f X6=g X7=h X8=i X9=j X10=k X11=l X12=m",
+      GMOCK_PP_FOR_EACH(JOINER, X, (a, b, c, d, e, f, g, h, i, j, k, l, m)));
+  EXPECT_EXPANSION(
+      "X0=a X1=b X2=c X3=d X4=e X5=f X6=g X7=h X8=i X9=j X10=k X11=l X12=m "
+      "X13=n",
+      GMOCK_PP_FOR_EACH(JOINER, X, (a, b, c, d, e, f, g, h, i, j, k, l, m, n)));
+  EXPECT_EXPANSION(
+      "X0=a X1=b X2=c X3=d X4=e X5=f X6=g X7=h X8=i X9=j X10=k X11=l X12=m "
+      "X13=n X14=o",
+      GMOCK_PP_FOR_EACH(JOINER, X,
+                        (a, b, c, d, e, f, g, h, i, j, k, l, m, n, o)));
+}
+
+}  // namespace
+}  // namespace testing
diff --git a/third_party/googletest/googlemock/test/gmock-pp_test.cc b/third_party/googletest/googlemock/test/gmock-pp_test.cc
new file mode 100644
index 0000000..5d1566e
--- /dev/null
+++ b/third_party/googletest/googlemock/test/gmock-pp_test.cc
@@ -0,0 +1,83 @@
+#include "gmock/internal/gmock-pp.h"
+
+// Used to test MSVC treating __VA_ARGS__ with a comma in it as one value
+#define GMOCK_TEST_REPLACE_comma_WITH_COMMA_I_comma ,
+#define GMOCK_TEST_REPLACE_comma_WITH_COMMA(x) \
+  GMOCK_PP_CAT(GMOCK_TEST_REPLACE_comma_WITH_COMMA_I_, x)
+
+// Static assertions.
+namespace testing {
+namespace internal {
+namespace gmockpp {
+
+static_assert(GMOCK_PP_CAT(1, 4) == 14, "");
+static_assert(GMOCK_PP_INTERNAL_INTERNAL_16TH(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11,
+                                              12, 13, 14, 15, 16, 17, 18) == 16,
+              "");
+static_assert(GMOCK_PP_NARG() == 1, "");
+static_assert(GMOCK_PP_NARG(x) == 1, "");
+static_assert(GMOCK_PP_NARG(x, y) == 2, "");
+static_assert(GMOCK_PP_NARG(x, y, z) == 3, "");
+static_assert(GMOCK_PP_NARG(x, y, z, w) == 4, "");
+static_assert(!GMOCK_PP_HAS_COMMA(), "");
+static_assert(GMOCK_PP_HAS_COMMA(b, ), "");
+static_assert(!GMOCK_PP_HAS_COMMA((, )), "");
+static_assert(GMOCK_PP_HAS_COMMA(GMOCK_TEST_REPLACE_comma_WITH_COMMA(comma)),
+              "");
+static_assert(
+    GMOCK_PP_HAS_COMMA(GMOCK_TEST_REPLACE_comma_WITH_COMMA(comma(unrelated))),
+    "");
+static_assert(!GMOCK_PP_IS_EMPTY(, ), "");
+static_assert(!GMOCK_PP_IS_EMPTY(a), "");
+static_assert(!GMOCK_PP_IS_EMPTY(()), "");
+static_assert(GMOCK_PP_IF(1, 1, 2) == 1, "");
+static_assert(GMOCK_PP_IF(0, 1, 2) == 2, "");
+static_assert(GMOCK_PP_NARG0(x) == 1, "");
+static_assert(GMOCK_PP_NARG0(x, y) == 2, "");
+static_assert(GMOCK_PP_HEAD(1) == 1, "");
+static_assert(GMOCK_PP_HEAD(1, 2) == 1, "");
+static_assert(GMOCK_PP_HEAD(1, 2, 3) == 1, "");
+static_assert(GMOCK_PP_TAIL(1, 2) == 2, "");
+static_assert(GMOCK_PP_HEAD(GMOCK_PP_TAIL(1, 2, 3)) == 2, "");
+static_assert(!GMOCK_PP_IS_BEGIN_PARENS(sss), "");
+static_assert(!GMOCK_PP_IS_BEGIN_PARENS(sss()), "");
+static_assert(!GMOCK_PP_IS_BEGIN_PARENS(sss() sss), "");
+static_assert(GMOCK_PP_IS_BEGIN_PARENS((sss)), "");
+static_assert(GMOCK_PP_IS_BEGIN_PARENS((sss)ss), "");
+static_assert(!GMOCK_PP_IS_ENCLOSED_PARENS(sss), "");
+static_assert(!GMOCK_PP_IS_ENCLOSED_PARENS(sss()), "");
+static_assert(!GMOCK_PP_IS_ENCLOSED_PARENS(sss() sss), "");
+static_assert(!GMOCK_PP_IS_ENCLOSED_PARENS((sss)ss), "");
+static_assert(GMOCK_PP_REMOVE_PARENS((1 + 1)) * 2 == 3, "");
+static_assert(GMOCK_PP_INC(4) == 5, "");
+
+template <class... Args>
+struct Test {
+  static constexpr int kArgs = sizeof...(Args);
+};
+#define GMOCK_PP_INTERNAL_TYPE_TEST(_i, _Data, _element) \
+  GMOCK_PP_COMMA_IF(_i) _element
+static_assert(Test<GMOCK_PP_FOR_EACH(GMOCK_PP_INTERNAL_TYPE_TEST, ~,
+                                     (int, float, double, char))>::kArgs == 4,
+              "");
+#define GMOCK_PP_INTERNAL_VAR_TEST_1(_x) 1
+#define GMOCK_PP_INTERNAL_VAR_TEST_2(_x, _y) 2
+#define GMOCK_PP_INTERNAL_VAR_TEST_3(_x, _y, _z) 3
+
+#define GMOCK_PP_INTERNAL_VAR_TEST(...) \
+  GMOCK_PP_VARIADIC_CALL(GMOCK_PP_INTERNAL_VAR_TEST_, __VA_ARGS__)
+static_assert(GMOCK_PP_INTERNAL_VAR_TEST(x, y) == 2, "");
+static_assert(GMOCK_PP_INTERNAL_VAR_TEST(silly) == 1, "");
+static_assert(GMOCK_PP_INTERNAL_VAR_TEST(x, y, z) == 3, "");
+
+// TODO(iserna): The following asserts fail in --config=lexan.
+#define GMOCK_PP_INTERNAL_IS_EMPTY_TEST_1
+static_assert(GMOCK_PP_IS_EMPTY(GMOCK_PP_INTERNAL_IS_EMPTY_TEST_1), "");
+static_assert(GMOCK_PP_IS_EMPTY(), "");
+static_assert(GMOCK_PP_IS_ENCLOSED_PARENS((sss)), "");
+static_assert(GMOCK_PP_IS_EMPTY(GMOCK_PP_TAIL(1)), "");
+static_assert(GMOCK_PP_NARG0() == 0, "");
+
+}  // namespace gmockpp
+}  // namespace internal
+}  // namespace testing
diff --git a/third_party/googletest/googlemock/test/gmock-spec-builders_test.cc b/third_party/googletest/googlemock/test/gmock-spec-builders_test.cc
new file mode 100644
index 0000000..aaf88d7
--- /dev/null
+++ b/third_party/googletest/googlemock/test/gmock-spec-builders_test.cc
@@ -0,0 +1,2600 @@
+// Copyright 2007, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Google Mock - a framework for writing C++ mock classes.
+//
+// This file tests the spec builder syntax.
+
+#include "gmock/gmock-spec-builders.h"
+
+#include <memory>
+#include <ostream>  // NOLINT
+#include <sstream>
+#include <string>
+#include <type_traits>
+
+#include "gmock/gmock.h"
+#include "gmock/internal/gmock-port.h"
+#include "gtest/gtest-spi.h"
+#include "gtest/gtest.h"
+#include "gtest/internal/gtest-port.h"
+
+namespace testing {
+namespace {
+
+using ::testing::internal::FormatFileLocation;
+using ::testing::internal::kAllow;
+using ::testing::internal::kErrorVerbosity;
+using ::testing::internal::kFail;
+using ::testing::internal::kInfoVerbosity;
+using ::testing::internal::kWarn;
+using ::testing::internal::kWarningVerbosity;
+
+#if GTEST_HAS_STREAM_REDIRECTION
+using ::testing::internal::CaptureStdout;
+using ::testing::internal::GetCapturedStdout;
+#endif
+
+class Incomplete;
+
+class MockIncomplete {
+ public:
+  // This line verifies that a mock method can take a by-reference
+  // argument of an incomplete type.
+  MOCK_METHOD1(ByRefFunc, void(const Incomplete& x));
+};
+
+// Tells Google Mock how to print a value of type Incomplete.
+void PrintTo(const Incomplete& x, ::std::ostream* os);
+
+TEST(MockMethodTest, CanInstantiateWithIncompleteArgType) {
+  // Even though this mock class contains a mock method that takes
+  // by-reference an argument whose type is incomplete, we can still
+  // use the mock, as long as Google Mock knows how to print the
+  // argument.
+  MockIncomplete incomplete;
+  EXPECT_CALL(incomplete, ByRefFunc(_)).Times(AnyNumber());
+}
+
+// The definition of the printer for the argument type doesn't have to
+// be visible where the mock is used.
+void PrintTo(const Incomplete& /* x */, ::std::ostream* os) {
+  *os << "incomplete";
+}
+
+class Result {};
+
+// A type that's not default constructible.
+class NonDefaultConstructible {
+ public:
+  explicit NonDefaultConstructible(int /* dummy */) {}
+};
+
+class MockA {
+ public:
+  MockA() = default;
+
+  MOCK_METHOD1(DoA, void(int n));
+  MOCK_METHOD1(ReturnResult, Result(int n));
+  MOCK_METHOD0(ReturnNonDefaultConstructible, NonDefaultConstructible());
+  MOCK_METHOD2(Binary, bool(int x, int y));
+  MOCK_METHOD2(ReturnInt, int(int x, int y));
+
+ private:
+  MockA(const MockA&) = delete;
+  MockA& operator=(const MockA&) = delete;
+};
+
+class MockB {
+ public:
+  MockB() = default;
+
+  MOCK_CONST_METHOD0(DoB, int());  // NOLINT
+  MOCK_METHOD1(DoB, int(int n));   // NOLINT
+
+ private:
+  MockB(const MockB&) = delete;
+  MockB& operator=(const MockB&) = delete;
+};
+
+class ReferenceHoldingMock {
+ public:
+  ReferenceHoldingMock() = default;
+
+  MOCK_METHOD1(AcceptReference, void(std::shared_ptr<MockA>*));
+
+ private:
+  ReferenceHoldingMock(const ReferenceHoldingMock&) = delete;
+  ReferenceHoldingMock& operator=(const ReferenceHoldingMock&) = delete;
+};
+
+// Tests that EXPECT_CALL and ON_CALL compile in a presence of macro
+// redefining a mock method name. This could happen, for example, when
+// the tested code #includes Win32 API headers which define many APIs
+// as macros, e.g. #define TextOut TextOutW.
+
+#define Method MethodW
+
+class CC {
+ public:
+  virtual ~CC() = default;
+  virtual int Method() = 0;
+};
+class MockCC : public CC {
+ public:
+  MockCC() = default;
+
+  MOCK_METHOD0(Method, int());
+
+ private:
+  MockCC(const MockCC&) = delete;
+  MockCC& operator=(const MockCC&) = delete;
+};
+
+// Tests that a method with expanded name compiles.
+TEST(OnCallSyntaxTest, CompilesWithMethodNameExpandedFromMacro) {
+  MockCC cc;
+  ON_CALL(cc, Method());
+}
+
+// Tests that the method with expanded name not only compiles but runs
+// and returns a correct value, too.
+TEST(OnCallSyntaxTest, WorksWithMethodNameExpandedFromMacro) {
+  MockCC cc;
+  ON_CALL(cc, Method()).WillByDefault(Return(42));
+  EXPECT_EQ(42, cc.Method());
+}
+
+// Tests that a method with expanded name compiles.
+TEST(ExpectCallSyntaxTest, CompilesWithMethodNameExpandedFromMacro) {
+  MockCC cc;
+  EXPECT_CALL(cc, Method());
+  cc.Method();
+}
+
+// Tests that it works, too.
+TEST(ExpectCallSyntaxTest, WorksWithMethodNameExpandedFromMacro) {
+  MockCC cc;
+  EXPECT_CALL(cc, Method()).WillOnce(Return(42));
+  EXPECT_EQ(42, cc.Method());
+}
+
+#undef Method  // Done with macro redefinition tests.
+
+// Tests that ON_CALL evaluates its arguments exactly once as promised
+// by Google Mock.
+TEST(OnCallSyntaxTest, EvaluatesFirstArgumentOnce) {
+  MockA a;
+  MockA* pa = &a;
+
+  ON_CALL(*pa++, DoA(_));
+  EXPECT_EQ(&a + 1, pa);
+}
+
+TEST(OnCallSyntaxTest, EvaluatesSecondArgumentOnce) {
+  MockA a;
+  int n = 0;
+
+  ON_CALL(a, DoA(n++));
+  EXPECT_EQ(1, n);
+}
+
+// Tests that the syntax of ON_CALL() is enforced at run time.
+
+TEST(OnCallSyntaxTest, WithIsOptional) {
+  MockA a;
+
+  ON_CALL(a, DoA(5)).WillByDefault(Return());
+  ON_CALL(a, DoA(_)).With(_).WillByDefault(Return());
+}
+
+TEST(OnCallSyntaxTest, WithCanAppearAtMostOnce) {
+  MockA a;
+
+  EXPECT_NONFATAL_FAILURE(
+      {  // NOLINT
+        ON_CALL(a, ReturnResult(_))
+            .With(_)
+            .With(_)
+            .WillByDefault(Return(Result()));
+      },
+      ".With() cannot appear more than once in an ON_CALL()");
+}
+
+TEST(OnCallSyntaxTest, WillByDefaultIsMandatory) {
+  MockA a;
+
+  EXPECT_DEATH_IF_SUPPORTED(
+      {
+        ON_CALL(a, DoA(5));
+        a.DoA(5);
+      },
+      "");
+}
+
+TEST(OnCallSyntaxTest, WillByDefaultCanAppearAtMostOnce) {
+  MockA a;
+
+  EXPECT_NONFATAL_FAILURE(
+      {  // NOLINT
+        ON_CALL(a, DoA(5)).WillByDefault(Return()).WillByDefault(Return());
+      },
+      ".WillByDefault() must appear exactly once in an ON_CALL()");
+}
+
+// Tests that EXPECT_CALL evaluates its arguments exactly once as
+// promised by Google Mock.
+TEST(ExpectCallSyntaxTest, EvaluatesFirstArgumentOnce) {
+  MockA a;
+  MockA* pa = &a;
+
+  EXPECT_CALL(*pa++, DoA(_));
+  a.DoA(0);
+  EXPECT_EQ(&a + 1, pa);
+}
+
+TEST(ExpectCallSyntaxTest, EvaluatesSecondArgumentOnce) {
+  MockA a;
+  int n = 0;
+
+  EXPECT_CALL(a, DoA(n++));
+  a.DoA(0);
+  EXPECT_EQ(1, n);
+}
+
+// Tests that the syntax of EXPECT_CALL() is enforced at run time.
+
+TEST(ExpectCallSyntaxTest, WithIsOptional) {
+  MockA a;
+
+  EXPECT_CALL(a, DoA(5)).Times(0);
+  EXPECT_CALL(a, DoA(6)).With(_).Times(0);
+}
+
+TEST(ExpectCallSyntaxTest, WithCanAppearAtMostOnce) {
+  MockA a;
+
+  EXPECT_NONFATAL_FAILURE(
+      {  // NOLINT
+        EXPECT_CALL(a, DoA(6)).With(_).With(_);
+      },
+      ".With() cannot appear more than once in an EXPECT_CALL()");
+
+  a.DoA(6);
+}
+
+TEST(ExpectCallSyntaxTest, WithMustBeFirstClause) {
+  MockA a;
+
+  EXPECT_NONFATAL_FAILURE(
+      {  // NOLINT
+        EXPECT_CALL(a, DoA(1)).Times(1).With(_);
+      },
+      ".With() must be the first clause in an EXPECT_CALL()");
+
+  a.DoA(1);
+
+  EXPECT_NONFATAL_FAILURE(
+      {  // NOLINT
+        EXPECT_CALL(a, DoA(2)).WillOnce(Return()).With(_);
+      },
+      ".With() must be the first clause in an EXPECT_CALL()");
+
+  a.DoA(2);
+}
+
+TEST(ExpectCallSyntaxTest, TimesCanBeInferred) {
+  MockA a;
+
+  EXPECT_CALL(a, DoA(1)).WillOnce(Return());
+
+  EXPECT_CALL(a, DoA(2)).WillOnce(Return()).WillRepeatedly(Return());
+
+  a.DoA(1);
+  a.DoA(2);
+  a.DoA(2);
+}
+
+TEST(ExpectCallSyntaxTest, TimesCanAppearAtMostOnce) {
+  MockA a;
+
+  EXPECT_NONFATAL_FAILURE(
+      {  // NOLINT
+        EXPECT_CALL(a, DoA(1)).Times(1).Times(2);
+      },
+      ".Times() cannot appear more than once in an EXPECT_CALL()");
+
+  a.DoA(1);
+  a.DoA(1);
+}
+
+TEST(ExpectCallSyntaxTest, TimesMustBeBeforeInSequence) {
+  MockA a;
+  Sequence s;
+
+  EXPECT_NONFATAL_FAILURE(
+      {  // NOLINT
+        EXPECT_CALL(a, DoA(1)).InSequence(s).Times(1);
+      },
+      ".Times() may only appear *before* ");
+
+  a.DoA(1);
+}
+
+TEST(ExpectCallSyntaxTest, InSequenceIsOptional) {
+  MockA a;
+  Sequence s;
+
+  EXPECT_CALL(a, DoA(1));
+  EXPECT_CALL(a, DoA(2)).InSequence(s);
+
+  a.DoA(1);
+  a.DoA(2);
+}
+
+TEST(ExpectCallSyntaxTest, InSequenceCanAppearMultipleTimes) {
+  MockA a;
+  Sequence s1, s2;
+
+  EXPECT_CALL(a, DoA(1)).InSequence(s1, s2).InSequence(s1);
+
+  a.DoA(1);
+}
+
+TEST(ExpectCallSyntaxTest, InSequenceMustBeBeforeAfter) {
+  MockA a;
+  Sequence s;
+
+  Expectation e = EXPECT_CALL(a, DoA(1)).Times(AnyNumber());
+  EXPECT_NONFATAL_FAILURE(
+      {  // NOLINT
+        EXPECT_CALL(a, DoA(2)).After(e).InSequence(s);
+      },
+      ".InSequence() cannot appear after ");
+
+  a.DoA(2);
+}
+
+TEST(ExpectCallSyntaxTest, InSequenceMustBeBeforeWillOnce) {
+  MockA a;
+  Sequence s;
+
+  EXPECT_NONFATAL_FAILURE(
+      {  // NOLINT
+        EXPECT_CALL(a, DoA(1)).WillOnce(Return()).InSequence(s);
+      },
+      ".InSequence() cannot appear after ");
+
+  a.DoA(1);
+}
+
+TEST(ExpectCallSyntaxTest, AfterMustBeBeforeWillOnce) {
+  MockA a;
+
+  Expectation e = EXPECT_CALL(a, DoA(1));
+  EXPECT_NONFATAL_FAILURE(
+      { EXPECT_CALL(a, DoA(2)).WillOnce(Return()).After(e); },
+      ".After() cannot appear after ");
+
+  a.DoA(1);
+  a.DoA(2);
+}
+
+TEST(ExpectCallSyntaxTest, WillIsOptional) {
+  MockA a;
+
+  EXPECT_CALL(a, DoA(1));
+  EXPECT_CALL(a, DoA(2)).WillOnce(Return());
+
+  a.DoA(1);
+  a.DoA(2);
+}
+
+TEST(ExpectCallSyntaxTest, WillCanAppearMultipleTimes) {
+  MockA a;
+
+  EXPECT_CALL(a, DoA(1))
+      .Times(AnyNumber())
+      .WillOnce(Return())
+      .WillOnce(Return())
+      .WillOnce(Return());
+}
+
+TEST(ExpectCallSyntaxTest, WillMustBeBeforeWillRepeatedly) {
+  MockA a;
+
+  EXPECT_NONFATAL_FAILURE(
+      {  // NOLINT
+        EXPECT_CALL(a, DoA(1)).WillRepeatedly(Return()).WillOnce(Return());
+      },
+      ".WillOnce() cannot appear after ");
+
+  a.DoA(1);
+}
+
+TEST(ExpectCallSyntaxTest, WillRepeatedlyIsOptional) {
+  MockA a;
+
+  EXPECT_CALL(a, DoA(1)).WillOnce(Return());
+  EXPECT_CALL(a, DoA(2)).WillOnce(Return()).WillRepeatedly(Return());
+
+  a.DoA(1);
+  a.DoA(2);
+  a.DoA(2);
+}
+
+TEST(ExpectCallSyntaxTest, WillRepeatedlyCannotAppearMultipleTimes) {
+  MockA a;
+
+  EXPECT_NONFATAL_FAILURE(
+      {  // NOLINT
+        EXPECT_CALL(a, DoA(1)).WillRepeatedly(Return()).WillRepeatedly(
+            Return());
+      },
+      ".WillRepeatedly() cannot appear more than once in an "
+      "EXPECT_CALL()");
+}
+
+TEST(ExpectCallSyntaxTest, WillRepeatedlyMustBeBeforeRetiresOnSaturation) {
+  MockA a;
+
+  EXPECT_NONFATAL_FAILURE(
+      {  // NOLINT
+        EXPECT_CALL(a, DoA(1)).RetiresOnSaturation().WillRepeatedly(Return());
+      },
+      ".WillRepeatedly() cannot appear after ");
+}
+
+TEST(ExpectCallSyntaxTest, RetiresOnSaturationIsOptional) {
+  MockA a;
+
+  EXPECT_CALL(a, DoA(1));
+  EXPECT_CALL(a, DoA(1)).RetiresOnSaturation();
+
+  a.DoA(1);
+  a.DoA(1);
+}
+
+TEST(ExpectCallSyntaxTest, RetiresOnSaturationCannotAppearMultipleTimes) {
+  MockA a;
+
+  EXPECT_NONFATAL_FAILURE(
+      {  // NOLINT
+        EXPECT_CALL(a, DoA(1)).RetiresOnSaturation().RetiresOnSaturation();
+      },
+      ".RetiresOnSaturation() cannot appear more than once");
+
+  a.DoA(1);
+}
+
+TEST(ExpectCallSyntaxTest, DefaultCardinalityIsOnce) {
+  {
+    MockA a;
+    EXPECT_CALL(a, DoA(1));
+    a.DoA(1);
+  }
+  EXPECT_NONFATAL_FAILURE(
+      {  // NOLINT
+        MockA a;
+        EXPECT_CALL(a, DoA(1));
+      },
+      "to be called once");
+  EXPECT_NONFATAL_FAILURE(
+      {  // NOLINT
+        MockA a;
+        EXPECT_CALL(a, DoA(1));
+        a.DoA(1);
+        a.DoA(1);
+      },
+      "to be called once");
+}
+
+#if GTEST_HAS_STREAM_REDIRECTION
+
+// Tests that Google Mock doesn't print a warning when the number of
+// WillOnce() is adequate.
+TEST(ExpectCallSyntaxTest, DoesNotWarnOnAdequateActionCount) {
+  CaptureStdout();
+  {
+    MockB b;
+
+    // It's always fine to omit WillOnce() entirely.
+    EXPECT_CALL(b, DoB()).Times(0);
+    EXPECT_CALL(b, DoB(1)).Times(AtMost(1));
+    EXPECT_CALL(b, DoB(2)).Times(1).WillRepeatedly(Return(1));
+
+    // It's fine for the number of WillOnce()s to equal the upper bound.
+    EXPECT_CALL(b, DoB(3))
+        .Times(Between(1, 2))
+        .WillOnce(Return(1))
+        .WillOnce(Return(2));
+
+    // It's fine for the number of WillOnce()s to be smaller than the
+    // upper bound when there is a WillRepeatedly().
+    EXPECT_CALL(b, DoB(4)).Times(AtMost(3)).WillOnce(Return(1)).WillRepeatedly(
+        Return(2));
+
+    // Satisfies the above expectations.
+    b.DoB(2);
+    b.DoB(3);
+  }
+  EXPECT_STREQ("", GetCapturedStdout().c_str());
+}
+
+// Tests that Google Mock warns on having too many actions in an
+// expectation compared to its cardinality.
+TEST(ExpectCallSyntaxTest, WarnsOnTooManyActions) {
+  CaptureStdout();
+  {
+    MockB b;
+
+    // Warns when the number of WillOnce()s is larger than the upper bound.
+    EXPECT_CALL(b, DoB()).Times(0).WillOnce(Return(1));  // #1
+    EXPECT_CALL(b, DoB()).Times(AtMost(1)).WillOnce(Return(1)).WillOnce(
+        Return(2));  // #2
+    EXPECT_CALL(b, DoB(1))
+        .Times(1)
+        .WillOnce(Return(1))
+        .WillOnce(Return(2))
+        .RetiresOnSaturation();  // #3
+
+    // Warns when the number of WillOnce()s equals the upper bound and
+    // there is a WillRepeatedly().
+    EXPECT_CALL(b, DoB()).Times(0).WillRepeatedly(Return(1));  // #4
+    EXPECT_CALL(b, DoB(2)).Times(1).WillOnce(Return(1)).WillRepeatedly(
+        Return(2));  // #5
+
+    // Satisfies the above expectations.
+    b.DoB(1);
+    b.DoB(2);
+  }
+  const std::string output = GetCapturedStdout();
+  EXPECT_PRED_FORMAT2(IsSubstring,
+                      "Too many actions specified in EXPECT_CALL(b, DoB())...\n"
+                      "Expected to be never called, but has 1 WillOnce().",
+                      output);  // #1
+  EXPECT_PRED_FORMAT2(IsSubstring,
+                      "Too many actions specified in EXPECT_CALL(b, DoB())...\n"
+                      "Expected to be called at most once, "
+                      "but has 2 WillOnce()s.",
+                      output);  // #2
+  EXPECT_PRED_FORMAT2(
+      IsSubstring,
+      "Too many actions specified in EXPECT_CALL(b, DoB(1))...\n"
+      "Expected to be called once, but has 2 WillOnce()s.",
+      output);  // #3
+  EXPECT_PRED_FORMAT2(IsSubstring,
+                      "Too many actions specified in EXPECT_CALL(b, DoB())...\n"
+                      "Expected to be never called, but has 0 WillOnce()s "
+                      "and a WillRepeatedly().",
+                      output);  // #4
+  EXPECT_PRED_FORMAT2(
+      IsSubstring,
+      "Too many actions specified in EXPECT_CALL(b, DoB(2))...\n"
+      "Expected to be called once, but has 1 WillOnce() "
+      "and a WillRepeatedly().",
+      output);  // #5
+}
+
+// Tests that Google Mock warns on having too few actions in an
+// expectation compared to its cardinality.
+TEST(ExpectCallSyntaxTest, WarnsOnTooFewActions) {
+  MockB b;
+
+  EXPECT_CALL(b, DoB()).Times(Between(2, 3)).WillOnce(Return(1));
+
+  CaptureStdout();
+  b.DoB();
+  const std::string output = GetCapturedStdout();
+  EXPECT_PRED_FORMAT2(IsSubstring,
+                      "Too few actions specified in EXPECT_CALL(b, DoB())...\n"
+                      "Expected to be called between 2 and 3 times, "
+                      "but has only 1 WillOnce().",
+                      output);
+  b.DoB();
+}
+
+TEST(ExpectCallSyntaxTest, WarningIsErrorWithFlag) {
+  int original_behavior = GMOCK_FLAG_GET(default_mock_behavior);
+
+  GMOCK_FLAG_SET(default_mock_behavior, kAllow);
+  CaptureStdout();
+  {
+    MockA a;
+    a.DoA(0);
+  }
+  std::string output = GetCapturedStdout();
+  EXPECT_TRUE(output.empty()) << output;
+
+  GMOCK_FLAG_SET(default_mock_behavior, kWarn);
+  CaptureStdout();
+  {
+    MockA a;
+    a.DoA(0);
+  }
+  std::string warning_output = GetCapturedStdout();
+  EXPECT_PRED_FORMAT2(IsSubstring, "GMOCK WARNING", warning_output);
+  EXPECT_PRED_FORMAT2(IsSubstring, "Uninteresting mock function call",
+                      warning_output);
+
+  GMOCK_FLAG_SET(default_mock_behavior, kFail);
+  EXPECT_NONFATAL_FAILURE(
+      {
+        MockA a;
+        a.DoA(0);
+      },
+      "Uninteresting mock function call");
+
+  // Out of bounds values are converted to kWarn
+  GMOCK_FLAG_SET(default_mock_behavior, -1);
+  CaptureStdout();
+  {
+    MockA a;
+    a.DoA(0);
+  }
+  warning_output = GetCapturedStdout();
+  EXPECT_PRED_FORMAT2(IsSubstring, "GMOCK WARNING", warning_output);
+  EXPECT_PRED_FORMAT2(IsSubstring, "Uninteresting mock function call",
+                      warning_output);
+  GMOCK_FLAG_SET(default_mock_behavior, 3);
+  CaptureStdout();
+  {
+    MockA a;
+    a.DoA(0);
+  }
+  warning_output = GetCapturedStdout();
+  EXPECT_PRED_FORMAT2(IsSubstring, "GMOCK WARNING", warning_output);
+  EXPECT_PRED_FORMAT2(IsSubstring, "Uninteresting mock function call",
+                      warning_output);
+
+  GMOCK_FLAG_SET(default_mock_behavior, original_behavior);
+}
+
+#endif  // GTEST_HAS_STREAM_REDIRECTION
+
+// Tests the semantics of ON_CALL().
+
+// Tests that the built-in default action is taken when no ON_CALL()
+// is specified.
+TEST(OnCallTest, TakesBuiltInDefaultActionWhenNoOnCall) {
+  MockB b;
+  EXPECT_CALL(b, DoB());
+
+  EXPECT_EQ(0, b.DoB());
+}
+
+// Tests that the built-in default action is taken when no ON_CALL()
+// matches the invocation.
+TEST(OnCallTest, TakesBuiltInDefaultActionWhenNoOnCallMatches) {
+  MockB b;
+  ON_CALL(b, DoB(1)).WillByDefault(Return(1));
+  EXPECT_CALL(b, DoB(_));
+
+  EXPECT_EQ(0, b.DoB(2));
+}
+
+// Tests that the last matching ON_CALL() action is taken.
+TEST(OnCallTest, PicksLastMatchingOnCall) {
+  MockB b;
+  ON_CALL(b, DoB(_)).WillByDefault(Return(3));
+  ON_CALL(b, DoB(2)).WillByDefault(Return(2));
+  ON_CALL(b, DoB(1)).WillByDefault(Return(1));
+  EXPECT_CALL(b, DoB(_));
+
+  EXPECT_EQ(2, b.DoB(2));
+}
+
+// Tests the semantics of EXPECT_CALL().
+
+// Tests that any call is allowed when no EXPECT_CALL() is specified.
+TEST(ExpectCallTest, AllowsAnyCallWhenNoSpec) {
+  MockB b;
+  EXPECT_CALL(b, DoB());
+  // There is no expectation on DoB(int).
+
+  b.DoB();
+
+  // DoB(int) can be called any number of times.
+  b.DoB(1);
+  b.DoB(2);
+}
+
+// Tests that the last matching EXPECT_CALL() fires.
+TEST(ExpectCallTest, PicksLastMatchingExpectCall) {
+  MockB b;
+  EXPECT_CALL(b, DoB(_)).WillRepeatedly(Return(2));
+  EXPECT_CALL(b, DoB(1)).WillRepeatedly(Return(1));
+
+  EXPECT_EQ(1, b.DoB(1));
+}
+
+// Tests lower-bound violation.
+TEST(ExpectCallTest, CatchesTooFewCalls) {
+  EXPECT_NONFATAL_FAILURE(
+      {  // NOLINT
+        MockB b;
+        EXPECT_CALL(b, DoB(5)).Description("DoB Method").Times(AtLeast(2));
+
+        b.DoB(5);
+      },
+      "Actual function \"DoB Method\" call count "
+      "doesn't match EXPECT_CALL(b, DoB(5))...\n"
+      "         Expected: to be called at least twice\n"
+      "           Actual: called once - unsatisfied and active");
+}
+
+// Tests that the cardinality can be inferred when no Times(...) is
+// specified.
+TEST(ExpectCallTest, InfersCardinalityWhenThereIsNoWillRepeatedly) {
+  {
+    MockB b;
+    EXPECT_CALL(b, DoB()).WillOnce(Return(1)).WillOnce(Return(2));
+
+    EXPECT_EQ(1, b.DoB());
+    EXPECT_EQ(2, b.DoB());
+  }
+
+  EXPECT_NONFATAL_FAILURE(
+      {  // NOLINT
+        MockB b;
+        EXPECT_CALL(b, DoB()).WillOnce(Return(1)).WillOnce(Return(2));
+
+        EXPECT_EQ(1, b.DoB());
+      },
+      "to be called twice");
+
+  {  // NOLINT
+    MockB b;
+    EXPECT_CALL(b, DoB()).WillOnce(Return(1)).WillOnce(Return(2));
+
+    EXPECT_EQ(1, b.DoB());
+    EXPECT_EQ(2, b.DoB());
+    EXPECT_NONFATAL_FAILURE(b.DoB(), "to be called twice");
+  }
+}
+
+TEST(ExpectCallTest, InfersCardinality1WhenThereIsWillRepeatedly) {
+  {
+    MockB b;
+    EXPECT_CALL(b, DoB()).WillOnce(Return(1)).WillRepeatedly(Return(2));
+
+    EXPECT_EQ(1, b.DoB());
+  }
+
+  {  // NOLINT
+    MockB b;
+    EXPECT_CALL(b, DoB()).WillOnce(Return(1)).WillRepeatedly(Return(2));
+
+    EXPECT_EQ(1, b.DoB());
+    EXPECT_EQ(2, b.DoB());
+    EXPECT_EQ(2, b.DoB());
+  }
+
+  EXPECT_NONFATAL_FAILURE(
+      {  // NOLINT
+        MockB b;
+        EXPECT_CALL(b, DoB()).WillOnce(Return(1)).WillRepeatedly(Return(2));
+      },
+      "to be called at least once");
+}
+
+#if defined(GTEST_INTERNAL_CPLUSPLUS_LANG) && \
+    GTEST_INTERNAL_CPLUSPLUS_LANG >= 201703L
+
+// It should be possible to return a non-moveable type from a mock action in
+// C++17 and above, where it's guaranteed that such a type can be initialized
+// from a prvalue returned from a function.
+TEST(ExpectCallTest, NonMoveableType) {
+  // Define a non-moveable result type.
+  struct NonMoveableStruct {
+    explicit NonMoveableStruct(int x_in) : x(x_in) {}
+    NonMoveableStruct(NonMoveableStruct&&) = delete;
+
+    int x;
+  };
+
+  static_assert(!std::is_move_constructible_v<NonMoveableStruct>);
+  static_assert(!std::is_copy_constructible_v<NonMoveableStruct>);
+
+  static_assert(!std::is_move_assignable_v<NonMoveableStruct>);
+  static_assert(!std::is_copy_assignable_v<NonMoveableStruct>);
+
+  // We should be able to use a callable that returns that result as both a
+  // OnceAction and an Action, whether the callable ignores arguments or not.
+  const auto return_17 = [] { return NonMoveableStruct(17); };
+
+  static_cast<void>(OnceAction<NonMoveableStruct()>{return_17});
+  static_cast<void>(Action<NonMoveableStruct()>{return_17});
+
+  static_cast<void>(OnceAction<NonMoveableStruct(int)>{return_17});
+  static_cast<void>(Action<NonMoveableStruct(int)>{return_17});
+
+  // It should be possible to return the result end to end through an
+  // EXPECT_CALL statement, with both WillOnce and WillRepeatedly.
+  MockFunction<NonMoveableStruct()> mock;
+  EXPECT_CALL(mock, Call)   //
+      .WillOnce(return_17)  //
+      .WillRepeatedly(return_17);
+
+  EXPECT_EQ(17, mock.AsStdFunction()().x);
+  EXPECT_EQ(17, mock.AsStdFunction()().x);
+  EXPECT_EQ(17, mock.AsStdFunction()().x);
+}
+
+#endif  // C++17 and above
+
+// Tests that the n-th action is taken for the n-th matching
+// invocation.
+TEST(ExpectCallTest, NthMatchTakesNthAction) {
+  MockB b;
+  EXPECT_CALL(b, DoB()).WillOnce(Return(1)).WillOnce(Return(2)).WillOnce(
+      Return(3));
+
+  EXPECT_EQ(1, b.DoB());
+  EXPECT_EQ(2, b.DoB());
+  EXPECT_EQ(3, b.DoB());
+}
+
+// Tests that the WillRepeatedly() action is taken when the WillOnce(...)
+// list is exhausted.
+TEST(ExpectCallTest, TakesRepeatedActionWhenWillListIsExhausted) {
+  MockB b;
+  EXPECT_CALL(b, DoB()).WillOnce(Return(1)).WillRepeatedly(Return(2));
+
+  EXPECT_EQ(1, b.DoB());
+  EXPECT_EQ(2, b.DoB());
+  EXPECT_EQ(2, b.DoB());
+}
+
+#if GTEST_HAS_STREAM_REDIRECTION
+
+// Tests that the default action is taken when the WillOnce(...) list is
+// exhausted and there is no WillRepeatedly().
+TEST(ExpectCallTest, TakesDefaultActionWhenWillListIsExhausted) {
+  MockB b;
+  EXPECT_CALL(b, DoB(_)).Times(1);
+  EXPECT_CALL(b, DoB())
+      .Times(AnyNumber())
+      .WillOnce(Return(1))
+      .WillOnce(Return(2));
+
+  CaptureStdout();
+  EXPECT_EQ(0, b.DoB(1));  // Shouldn't generate a warning as the
+                           // expectation has no action clause at all.
+  EXPECT_EQ(1, b.DoB());
+  EXPECT_EQ(2, b.DoB());
+  const std::string output1 = GetCapturedStdout();
+  EXPECT_STREQ("", output1.c_str());
+
+  CaptureStdout();
+  EXPECT_EQ(0, b.DoB());
+  EXPECT_EQ(0, b.DoB());
+  const std::string output2 = GetCapturedStdout();
+  EXPECT_THAT(output2.c_str(),
+              HasSubstr("Actions ran out in EXPECT_CALL(b, DoB())...\n"
+                        "Called 3 times, but only 2 WillOnce()s are specified"
+                        " - returning default value."));
+  EXPECT_THAT(output2.c_str(),
+              HasSubstr("Actions ran out in EXPECT_CALL(b, DoB())...\n"
+                        "Called 4 times, but only 2 WillOnce()s are specified"
+                        " - returning default value."));
+}
+
+TEST(FunctionMockerMessageTest, ReportsExpectCallLocationForExhaustedActions) {
+  MockB b;
+  std::string expect_call_location = FormatFileLocation(__FILE__, __LINE__ + 1);
+  EXPECT_CALL(b, DoB()).Times(AnyNumber()).WillOnce(Return(1));
+
+  EXPECT_EQ(1, b.DoB());
+
+  CaptureStdout();
+  EXPECT_EQ(0, b.DoB());
+  const std::string output = GetCapturedStdout();
+  // The warning message should contain the call location.
+  EXPECT_PRED_FORMAT2(IsSubstring, expect_call_location, output);
+}
+
+TEST(FunctionMockerMessageTest,
+     ReportsDefaultActionLocationOfUninterestingCallsForNaggyMock) {
+  std::string on_call_location;
+  CaptureStdout();
+  {
+    NaggyMock<MockB> b;
+    on_call_location = FormatFileLocation(__FILE__, __LINE__ + 1);
+    ON_CALL(b, DoB(_)).WillByDefault(Return(0));
+    b.DoB(0);
+  }
+  EXPECT_PRED_FORMAT2(IsSubstring, on_call_location, GetCapturedStdout());
+}
+
+#endif  // GTEST_HAS_STREAM_REDIRECTION
+
+// Tests that an uninteresting call performs the default action.
+TEST(UninterestingCallTest, DoesDefaultAction) {
+  // When there is an ON_CALL() statement, the action specified by it
+  // should be taken.
+  MockA a;
+  ON_CALL(a, Binary(_, _)).WillByDefault(Return(true));
+  EXPECT_TRUE(a.Binary(1, 2));
+
+  // When there is no ON_CALL(), the default value for the return type
+  // should be returned.
+  MockB b;
+  EXPECT_EQ(0, b.DoB());
+}
+
+// Tests that an unexpected call performs the default action.
+TEST(UnexpectedCallTest, DoesDefaultAction) {
+  // When there is an ON_CALL() statement, the action specified by it
+  // should be taken.
+  MockA a;
+  ON_CALL(a, Binary(_, _)).WillByDefault(Return(true));
+  EXPECT_CALL(a, Binary(0, 0));
+  a.Binary(0, 0);
+  bool result = false;
+  EXPECT_NONFATAL_FAILURE(result = a.Binary(1, 2),
+                          "Unexpected mock function call");
+  EXPECT_TRUE(result);
+
+  // When there is no ON_CALL(), the default value for the return type
+  // should be returned.
+  MockB b;
+  EXPECT_CALL(b, DoB(0)).Times(0);
+  int n = -1;
+  EXPECT_NONFATAL_FAILURE(n = b.DoB(1), "Unexpected mock function call");
+  EXPECT_EQ(0, n);
+}
+
+// Tests that when an unexpected void function generates the right
+// failure message.
+TEST(UnexpectedCallTest, GeneratesFailureForVoidFunction) {
+  // First, tests the message when there is only one EXPECT_CALL().
+  MockA a1;
+  EXPECT_CALL(a1, DoA(1));
+  a1.DoA(1);
+  // Ideally we should match the failure message against a regex, but
+  // EXPECT_NONFATAL_FAILURE doesn't support that, so we test for
+  // multiple sub-strings instead.
+  EXPECT_NONFATAL_FAILURE(
+      a1.DoA(9),
+      "Unexpected mock function call - returning directly.\n"
+      "    Function call: DoA(9)\n"
+      "Google Mock tried the following 1 expectation, but it didn't match:");
+  EXPECT_NONFATAL_FAILURE(
+      a1.DoA(9),
+      "  Expected arg #0: is equal to 1\n"
+      "           Actual: 9\n"
+      "         Expected: to be called once\n"
+      "           Actual: called once - saturated and active");
+
+  // Next, tests the message when there are more than one EXPECT_CALL().
+  MockA a2;
+  EXPECT_CALL(a2, DoA(1));
+  EXPECT_CALL(a2, DoA(3));
+  a2.DoA(1);
+  EXPECT_NONFATAL_FAILURE(
+      a2.DoA(2),
+      "Unexpected mock function call - returning directly.\n"
+      "    Function call: DoA(2)\n"
+      "Google Mock tried the following 2 expectations, but none matched:");
+  EXPECT_NONFATAL_FAILURE(
+      a2.DoA(2),
+      "tried expectation #0: EXPECT_CALL(a2, DoA(1))...\n"
+      "  Expected arg #0: is equal to 1\n"
+      "           Actual: 2\n"
+      "         Expected: to be called once\n"
+      "           Actual: called once - saturated and active");
+  EXPECT_NONFATAL_FAILURE(
+      a2.DoA(2),
+      "tried expectation #1: EXPECT_CALL(a2, DoA(3))...\n"
+      "  Expected arg #0: is equal to 3\n"
+      "           Actual: 2\n"
+      "         Expected: to be called once\n"
+      "           Actual: never called - unsatisfied and active");
+  a2.DoA(3);
+}
+
+// Tests that an unexpected non-void function generates the right
+// failure message.
+TEST(UnexpectedCallTest, GeneartesFailureForNonVoidFunction) {
+  MockB b1;
+  EXPECT_CALL(b1, DoB(1));
+  b1.DoB(1);
+  EXPECT_NONFATAL_FAILURE(
+      b1.DoB(2),
+      "Unexpected mock function call - returning default value.\n"
+      "    Function call: DoB(2)\n"
+      "          Returns: 0\n"
+      "Google Mock tried the following 1 expectation, but it didn't match:");
+  EXPECT_NONFATAL_FAILURE(
+      b1.DoB(2),
+      "  Expected arg #0: is equal to 1\n"
+      "           Actual: 2\n"
+      "         Expected: to be called once\n"
+      "           Actual: called once - saturated and active");
+}
+
+// Tests that Google Mock explains that an retired expectation doesn't
+// match the call.
+TEST(UnexpectedCallTest, RetiredExpectation) {
+  MockB b;
+  EXPECT_CALL(b, DoB(1)).RetiresOnSaturation();
+
+  b.DoB(1);
+  EXPECT_NONFATAL_FAILURE(b.DoB(1),
+                          "         Expected: the expectation is active\n"
+                          "           Actual: it is retired");
+}
+
+// Tests that Google Mock explains that an expectation that doesn't
+// match the arguments doesn't match the call.
+TEST(UnexpectedCallTest, UnmatchedArguments) {
+  MockB b;
+  EXPECT_CALL(b, DoB(1));
+
+  EXPECT_NONFATAL_FAILURE(b.DoB(2),
+                          "  Expected arg #0: is equal to 1\n"
+                          "           Actual: 2\n");
+  b.DoB(1);
+}
+
+// Tests that Google Mock explains that an expectation with
+// unsatisfied pre-requisites doesn't match the call.
+TEST(UnexpectedCallTest, UnsatisfiedPrerequisites) {
+  Sequence s1, s2;
+  MockB b;
+  EXPECT_CALL(b, DoB(1)).InSequence(s1);
+  EXPECT_CALL(b, DoB(2)).Times(AnyNumber()).InSequence(s1);
+  EXPECT_CALL(b, DoB(3)).InSequence(s2);
+  EXPECT_CALL(b, DoB(4)).InSequence(s1, s2);
+
+  ::testing::TestPartResultArray failures;
+  {
+    ::testing::ScopedFakeTestPartResultReporter reporter(&failures);
+    b.DoB(4);
+    // Now 'failures' contains the Google Test failures generated by
+    // the above statement.
+  }
+
+  // There should be one non-fatal failure.
+  ASSERT_EQ(1, failures.size());
+  const ::testing::TestPartResult& r = failures.GetTestPartResult(0);
+  EXPECT_EQ(::testing::TestPartResult::kNonFatalFailure, r.type());
+
+  // Verifies that the failure message contains the two unsatisfied
+  // pre-requisites but not the satisfied one.
+#ifdef GTEST_USES_POSIX_RE
+  EXPECT_THAT(r.message(),
+              ContainsRegex(
+                  // POSIX RE doesn't understand the (?s) prefix, but has no
+                  // trouble with (.|\n).
+                  "the following immediate pre-requisites are not satisfied:\n"
+                  "(.|\n)*: pre-requisite #0\n"
+                  "(.|\n)*: pre-requisite #1"));
+#else
+  // We can only use Google Test's own simple regex.
+  EXPECT_THAT(r.message(),
+              ContainsRegex(
+                  "the following immediate pre-requisites are not satisfied:"));
+  EXPECT_THAT(r.message(), ContainsRegex(": pre-requisite #0"));
+  EXPECT_THAT(r.message(), ContainsRegex(": pre-requisite #1"));
+#endif  // GTEST_USES_POSIX_RE
+
+  b.DoB(1);
+  b.DoB(3);
+  b.DoB(4);
+}
+
+TEST(UndefinedReturnValueTest,
+     ReturnValueIsMandatoryWhenNotDefaultConstructible) {
+  MockA a;
+  // FIXME: We should really verify the output message,
+  // but we cannot yet due to that EXPECT_DEATH only captures stderr
+  // while Google Mock logs to stdout.
+#if GTEST_HAS_EXCEPTIONS
+  EXPECT_ANY_THROW(a.ReturnNonDefaultConstructible());
+#else
+  EXPECT_DEATH_IF_SUPPORTED(a.ReturnNonDefaultConstructible(), "");
+#endif
+}
+
+// Tests that an excessive call (one whose arguments match the
+// matchers but is called too many times) performs the default action.
+TEST(ExcessiveCallTest, DoesDefaultAction) {
+  // When there is an ON_CALL() statement, the action specified by it
+  // should be taken.
+  MockA a;
+  ON_CALL(a, Binary(_, _)).WillByDefault(Return(true));
+  EXPECT_CALL(a, Binary(0, 0));
+  a.Binary(0, 0);
+  bool result = false;
+  EXPECT_NONFATAL_FAILURE(result = a.Binary(0, 0),
+                          "Mock function called more times than expected");
+  EXPECT_TRUE(result);
+
+  // When there is no ON_CALL(), the default value for the return type
+  // should be returned.
+  MockB b;
+  EXPECT_CALL(b, DoB(0)).Description("DoB Method").Times(0);
+  int n = -1;
+  EXPECT_NONFATAL_FAILURE(
+      n = b.DoB(0),
+      "Mock function \"DoB Method\" called more times than expected");
+  EXPECT_EQ(0, n);
+}
+
+// Tests that when a void function is called too many times,
+// the failure message contains the argument values.
+TEST(ExcessiveCallTest, GeneratesFailureForVoidFunction) {
+  MockA a;
+  EXPECT_CALL(a, DoA(_)).Description("DoA Method").Times(0);
+  EXPECT_NONFATAL_FAILURE(
+      a.DoA(9),
+      "Mock function \"DoA Method\" called more times than expected - "
+      "returning directly.\n"
+      "    Function call: DoA(9)\n"
+      "         Expected: to be never called\n"
+      "           Actual: called once - over-saturated and active");
+}
+
+// Tests that when a non-void function is called too many times, the
+// failure message contains the argument values and the return value.
+TEST(ExcessiveCallTest, GeneratesFailureForNonVoidFunction) {
+  MockB b;
+  EXPECT_CALL(b, DoB(_));
+  b.DoB(1);
+  EXPECT_NONFATAL_FAILURE(
+      b.DoB(2),
+      "Mock function called more times than expected - "
+      "returning default value.\n"
+      "    Function call: DoB(2)\n"
+      "          Returns: 0\n"
+      "         Expected: to be called once\n"
+      "           Actual: called twice - over-saturated and active");
+}
+
+// Tests using sequences.
+
+TEST(InSequenceTest, AllExpectationInScopeAreInSequence) {
+  MockA a;
+  {
+    InSequence dummy;
+
+    EXPECT_CALL(a, DoA(1));
+    EXPECT_CALL(a, DoA(2));
+  }
+
+  EXPECT_NONFATAL_FAILURE(
+      {  // NOLINT
+        a.DoA(2);
+      },
+      "Unexpected mock function call");
+
+  a.DoA(1);
+  a.DoA(2);
+}
+
+TEST(InSequenceTest, NestedInSequence) {
+  MockA a;
+  {
+    InSequence dummy;
+
+    EXPECT_CALL(a, DoA(1));
+    {
+      InSequence dummy2;
+
+      EXPECT_CALL(a, DoA(2));
+      EXPECT_CALL(a, DoA(3));
+    }
+  }
+
+  EXPECT_NONFATAL_FAILURE(
+      {  // NOLINT
+        a.DoA(1);
+        a.DoA(3);
+      },
+      "Unexpected mock function call");
+
+  a.DoA(2);
+  a.DoA(3);
+}
+
+TEST(InSequenceTest, ExpectationsOutOfScopeAreNotAffected) {
+  MockA a;
+  {
+    InSequence dummy;
+
+    EXPECT_CALL(a, DoA(1));
+    EXPECT_CALL(a, DoA(2));
+  }
+  EXPECT_CALL(a, DoA(3));
+
+  EXPECT_NONFATAL_FAILURE(
+      {  // NOLINT
+        a.DoA(2);
+      },
+      "Unexpected mock function call");
+
+  a.DoA(3);
+  a.DoA(1);
+  a.DoA(2);
+}
+
+// Tests that any order is allowed when no sequence is used.
+TEST(SequenceTest, AnyOrderIsOkByDefault) {
+  {
+    MockA a;
+    MockB b;
+
+    EXPECT_CALL(a, DoA(1));
+    EXPECT_CALL(b, DoB()).Times(AnyNumber());
+
+    a.DoA(1);
+    b.DoB();
+  }
+
+  {  // NOLINT
+    MockA a;
+    MockB b;
+
+    EXPECT_CALL(a, DoA(1));
+    EXPECT_CALL(b, DoB()).Times(AnyNumber());
+
+    b.DoB();
+    a.DoA(1);
+  }
+}
+
+// Tests that the calls must be in strict order when a complete order
+// is specified.
+TEST(SequenceTest, CallsMustBeInStrictOrderWhenSaidSo1) {
+  MockA a;
+  ON_CALL(a, ReturnResult(_)).WillByDefault(Return(Result()));
+
+  Sequence s;
+  EXPECT_CALL(a, ReturnResult(1)).InSequence(s);
+  EXPECT_CALL(a, ReturnResult(2)).InSequence(s);
+  EXPECT_CALL(a, ReturnResult(3)).InSequence(s);
+
+  a.ReturnResult(1);
+
+  // May only be called after a.ReturnResult(2).
+  EXPECT_NONFATAL_FAILURE(a.ReturnResult(3), "Unexpected mock function call");
+
+  a.ReturnResult(2);
+  a.ReturnResult(3);
+}
+
+// Tests that the calls must be in strict order when a complete order
+// is specified.
+TEST(SequenceTest, CallsMustBeInStrictOrderWhenSaidSo2) {
+  MockA a;
+  ON_CALL(a, ReturnResult(_)).WillByDefault(Return(Result()));
+
+  Sequence s;
+  EXPECT_CALL(a, ReturnResult(1)).InSequence(s);
+  EXPECT_CALL(a, ReturnResult(2)).InSequence(s);
+
+  // May only be called after a.ReturnResult(1).
+  EXPECT_NONFATAL_FAILURE(a.ReturnResult(2), "Unexpected mock function call");
+
+  a.ReturnResult(1);
+  a.ReturnResult(2);
+}
+
+// Tests specifying a DAG using multiple sequences.
+class PartialOrderTest : public testing::Test {
+ protected:
+  PartialOrderTest() {
+    ON_CALL(a_, ReturnResult(_)).WillByDefault(Return(Result()));
+
+    // Specifies this partial ordering:
+    //
+    // a.ReturnResult(1) ==>
+    //                       a.ReturnResult(2) * n  ==>  a.ReturnResult(3)
+    // b.DoB() * 2       ==>
+    Sequence x, y;
+    EXPECT_CALL(a_, ReturnResult(1)).InSequence(x);
+    EXPECT_CALL(b_, DoB()).Times(2).InSequence(y);
+    EXPECT_CALL(a_, ReturnResult(2)).Times(AnyNumber()).InSequence(x, y);
+    EXPECT_CALL(a_, ReturnResult(3)).InSequence(x);
+  }
+
+  MockA a_;
+  MockB b_;
+};
+
+TEST_F(PartialOrderTest, CallsMustConformToSpecifiedDag1) {
+  a_.ReturnResult(1);
+  b_.DoB();
+
+  // May only be called after the second DoB().
+  EXPECT_NONFATAL_FAILURE(a_.ReturnResult(2), "Unexpected mock function call");
+
+  b_.DoB();
+  a_.ReturnResult(3);
+}
+
+TEST_F(PartialOrderTest, CallsMustConformToSpecifiedDag2) {
+  // May only be called after ReturnResult(1).
+  EXPECT_NONFATAL_FAILURE(a_.ReturnResult(2), "Unexpected mock function call");
+
+  a_.ReturnResult(1);
+  b_.DoB();
+  b_.DoB();
+  a_.ReturnResult(3);
+}
+
+TEST_F(PartialOrderTest, CallsMustConformToSpecifiedDag3) {
+  // May only be called last.
+  EXPECT_NONFATAL_FAILURE(a_.ReturnResult(3), "Unexpected mock function call");
+
+  a_.ReturnResult(1);
+  b_.DoB();
+  b_.DoB();
+  a_.ReturnResult(3);
+}
+
+TEST_F(PartialOrderTest, CallsMustConformToSpecifiedDag4) {
+  a_.ReturnResult(1);
+  b_.DoB();
+  b_.DoB();
+  a_.ReturnResult(3);
+
+  // May only be called before ReturnResult(3).
+  EXPECT_NONFATAL_FAILURE(a_.ReturnResult(2), "Unexpected mock function call");
+}
+
+TEST(SequenceTest, Retirement) {
+  MockA a;
+  Sequence s;
+
+  EXPECT_CALL(a, DoA(1)).InSequence(s);
+  EXPECT_CALL(a, DoA(_)).InSequence(s).RetiresOnSaturation();
+  EXPECT_CALL(a, DoA(1)).InSequence(s);
+
+  a.DoA(1);
+  a.DoA(2);
+  a.DoA(1);
+}
+
+// Tests Expectation.
+
+TEST(ExpectationTest, ConstrutorsWork) {
+  MockA a;
+  Expectation e1;  // Default ctor.
+
+  // Ctor from various forms of EXPECT_CALL.
+  Expectation e2 = EXPECT_CALL(a, DoA(2));
+  Expectation e3 = EXPECT_CALL(a, DoA(3)).With(_);
+  {
+    Sequence s;
+    Expectation e4 = EXPECT_CALL(a, DoA(4)).Times(1);
+    Expectation e5 = EXPECT_CALL(a, DoA(5)).InSequence(s);
+  }
+  Expectation e6 = EXPECT_CALL(a, DoA(6)).After(e2);
+  Expectation e7 = EXPECT_CALL(a, DoA(7)).WillOnce(Return());
+  Expectation e8 = EXPECT_CALL(a, DoA(8)).WillRepeatedly(Return());
+  Expectation e9 = EXPECT_CALL(a, DoA(9)).RetiresOnSaturation();
+
+  Expectation e10 = e2;  // Copy ctor.
+
+  EXPECT_THAT(e1, Ne(e2));
+  EXPECT_THAT(e2, Eq(e10));
+
+  a.DoA(2);
+  a.DoA(3);
+  a.DoA(4);
+  a.DoA(5);
+  a.DoA(6);
+  a.DoA(7);
+  a.DoA(8);
+  a.DoA(9);
+}
+
+TEST(ExpectationTest, AssignmentWorks) {
+  MockA a;
+  Expectation e1;
+  Expectation e2 = EXPECT_CALL(a, DoA(1));
+
+  EXPECT_THAT(e1, Ne(e2));
+
+  e1 = e2;
+  EXPECT_THAT(e1, Eq(e2));
+
+  a.DoA(1);
+}
+
+// Tests ExpectationSet.
+
+TEST(ExpectationSetTest, MemberTypesAreCorrect) {
+  ::testing::StaticAssertTypeEq<Expectation, ExpectationSet::value_type>();
+}
+
+TEST(ExpectationSetTest, ConstructorsWork) {
+  MockA a;
+
+  Expectation e1;
+  const Expectation e2;
+  ExpectationSet es1;                           // Default ctor.
+  ExpectationSet es2 = EXPECT_CALL(a, DoA(1));  // Ctor from EXPECT_CALL.
+  ExpectationSet es3 = e1;                      // Ctor from Expectation.
+  ExpectationSet es4(e1);    // Ctor from Expectation; alternative syntax.
+  ExpectationSet es5 = e2;   // Ctor from const Expectation.
+  ExpectationSet es6(e2);    // Ctor from const Expectation; alternative syntax.
+  ExpectationSet es7 = es2;  // Copy ctor.
+
+  EXPECT_EQ(0, es1.size());
+  EXPECT_EQ(1, es2.size());
+  EXPECT_EQ(1, es3.size());
+  EXPECT_EQ(1, es4.size());
+  EXPECT_EQ(1, es5.size());
+  EXPECT_EQ(1, es6.size());
+  EXPECT_EQ(1, es7.size());
+
+  EXPECT_THAT(es3, Ne(es2));
+  EXPECT_THAT(es4, Eq(es3));
+  EXPECT_THAT(es5, Eq(es4));
+  EXPECT_THAT(es6, Eq(es5));
+  EXPECT_THAT(es7, Eq(es2));
+  a.DoA(1);
+}
+
+TEST(ExpectationSetTest, AssignmentWorks) {
+  ExpectationSet es1;
+  ExpectationSet es2 = Expectation();
+
+  es1 = es2;
+  EXPECT_EQ(1, es1.size());
+  EXPECT_THAT(*(es1.begin()), Eq(Expectation()));
+  EXPECT_THAT(es1, Eq(es2));
+}
+
+TEST(ExpectationSetTest, InsertionWorks) {
+  ExpectationSet es1;
+  Expectation e1;
+  es1 += e1;
+  EXPECT_EQ(1, es1.size());
+  EXPECT_THAT(*(es1.begin()), Eq(e1));
+
+  MockA a;
+  Expectation e2 = EXPECT_CALL(a, DoA(1));
+  es1 += e2;
+  EXPECT_EQ(2, es1.size());
+
+  ExpectationSet::const_iterator it1 = es1.begin();
+  ExpectationSet::const_iterator it2 = it1;
+  ++it2;
+  EXPECT_TRUE(*it1 == e1 || *it2 == e1);  // e1 must be in the set.
+  EXPECT_TRUE(*it1 == e2 || *it2 == e2);  // e2 must be in the set too.
+  a.DoA(1);
+}
+
+TEST(ExpectationSetTest, SizeWorks) {
+  ExpectationSet es;
+  EXPECT_EQ(0, es.size());
+
+  es += Expectation();
+  EXPECT_EQ(1, es.size());
+
+  MockA a;
+  es += EXPECT_CALL(a, DoA(1));
+  EXPECT_EQ(2, es.size());
+
+  a.DoA(1);
+}
+
+TEST(ExpectationSetTest, IsEnumerable) {
+  ExpectationSet es;
+  EXPECT_TRUE(es.begin() == es.end());
+
+  es += Expectation();
+  ExpectationSet::const_iterator it = es.begin();
+  EXPECT_TRUE(it != es.end());
+  EXPECT_THAT(*it, Eq(Expectation()));
+  ++it;
+  EXPECT_TRUE(it == es.end());
+}
+
+// Tests the .After() clause.
+
+TEST(AfterTest, SucceedsWhenPartialOrderIsSatisfied) {
+  MockA a;
+  ExpectationSet es;
+  es += EXPECT_CALL(a, DoA(1));
+  es += EXPECT_CALL(a, DoA(2));
+  EXPECT_CALL(a, DoA(3)).After(es);
+
+  a.DoA(1);
+  a.DoA(2);
+  a.DoA(3);
+}
+
+TEST(AfterTest, SucceedsWhenTotalOrderIsSatisfied) {
+  MockA a;
+  MockB b;
+  // The following also verifies that const Expectation objects work
+  // too.  Do not remove the const modifiers.
+  const Expectation e1 = EXPECT_CALL(a, DoA(1));
+  const Expectation e2 = EXPECT_CALL(b, DoB()).Times(2).After(e1);
+  EXPECT_CALL(a, DoA(2)).After(e2);
+
+  a.DoA(1);
+  b.DoB();
+  b.DoB();
+  a.DoA(2);
+}
+
+// Calls must be in strict order when specified so using .After().
+TEST(AfterTest, CallsMustBeInStrictOrderWhenSpecifiedSo1) {
+  MockA a;
+  MockB b;
+
+  // Define ordering:
+  //   a.DoA(1) ==> b.DoB() ==> a.DoA(2)
+  Expectation e1 = EXPECT_CALL(a, DoA(1));
+  Expectation e2 = EXPECT_CALL(b, DoB()).After(e1);
+  EXPECT_CALL(a, DoA(2)).After(e2);
+
+  a.DoA(1);
+
+  // May only be called after DoB().
+  EXPECT_NONFATAL_FAILURE(a.DoA(2), "Unexpected mock function call");
+
+  b.DoB();
+  a.DoA(2);
+}
+
+// Calls must be in strict order when specified so using .After().
+TEST(AfterTest, CallsMustBeInStrictOrderWhenSpecifiedSo2) {
+  MockA a;
+  MockB b;
+
+  // Define ordering:
+  //   a.DoA(1) ==> b.DoB() * 2 ==> a.DoA(2)
+  Expectation e1 = EXPECT_CALL(a, DoA(1));
+  Expectation e2 = EXPECT_CALL(b, DoB()).Times(2).After(e1);
+  EXPECT_CALL(a, DoA(2)).After(e2);
+
+  a.DoA(1);
+  b.DoB();
+
+  // May only be called after the second DoB().
+  EXPECT_NONFATAL_FAILURE(a.DoA(2), "Unexpected mock function call");
+
+  b.DoB();
+  a.DoA(2);
+}
+
+// Calls must satisfy the partial order when specified so.
+TEST(AfterTest, CallsMustSatisfyPartialOrderWhenSpecifiedSo) {
+  MockA a;
+  ON_CALL(a, ReturnResult(_)).WillByDefault(Return(Result()));
+
+  // Define ordering:
+  //   a.DoA(1) ==>
+  //   a.DoA(2) ==> a.ReturnResult(3)
+  Expectation e = EXPECT_CALL(a, DoA(1));
+  const ExpectationSet es = EXPECT_CALL(a, DoA(2));
+  EXPECT_CALL(a, ReturnResult(3)).After(e, es);
+
+  // May only be called last.
+  EXPECT_NONFATAL_FAILURE(a.ReturnResult(3), "Unexpected mock function call");
+
+  a.DoA(2);
+  a.DoA(1);
+  a.ReturnResult(3);
+}
+
+// Calls must satisfy the partial order when specified so.
+TEST(AfterTest, CallsMustSatisfyPartialOrderWhenSpecifiedSo2) {
+  MockA a;
+
+  // Define ordering:
+  //   a.DoA(1) ==>
+  //   a.DoA(2) ==> a.DoA(3)
+  Expectation e = EXPECT_CALL(a, DoA(1));
+  const ExpectationSet es = EXPECT_CALL(a, DoA(2));
+  EXPECT_CALL(a, DoA(3)).After(e, es);
+
+  a.DoA(2);
+
+  // May only be called last.
+  EXPECT_NONFATAL_FAILURE(a.DoA(3), "Unexpected mock function call");
+
+  a.DoA(1);
+  a.DoA(3);
+}
+
+// .After() can be combined with .InSequence().
+TEST(AfterTest, CanBeUsedWithInSequence) {
+  MockA a;
+  Sequence s;
+  Expectation e = EXPECT_CALL(a, DoA(1));
+  EXPECT_CALL(a, DoA(2)).InSequence(s);
+  EXPECT_CALL(a, DoA(3)).InSequence(s).After(e);
+
+  a.DoA(1);
+
+  // May only be after DoA(2).
+  EXPECT_NONFATAL_FAILURE(a.DoA(3), "Unexpected mock function call");
+
+  a.DoA(2);
+  a.DoA(3);
+}
+
+// .After() can be called multiple times.
+TEST(AfterTest, CanBeCalledManyTimes) {
+  MockA a;
+  Expectation e1 = EXPECT_CALL(a, DoA(1));
+  Expectation e2 = EXPECT_CALL(a, DoA(2));
+  Expectation e3 = EXPECT_CALL(a, DoA(3));
+  EXPECT_CALL(a, DoA(4)).After(e1).After(e2).After(e3);
+
+  a.DoA(3);
+  a.DoA(1);
+  a.DoA(2);
+  a.DoA(4);
+}
+
+// .After() accepts up to 5 arguments.
+TEST(AfterTest, AcceptsUpToFiveArguments) {
+  MockA a;
+  Expectation e1 = EXPECT_CALL(a, DoA(1));
+  Expectation e2 = EXPECT_CALL(a, DoA(2));
+  Expectation e3 = EXPECT_CALL(a, DoA(3));
+  ExpectationSet es1 = EXPECT_CALL(a, DoA(4));
+  ExpectationSet es2 = EXPECT_CALL(a, DoA(5));
+  EXPECT_CALL(a, DoA(6)).After(e1, e2, e3, es1, es2);
+
+  a.DoA(5);
+  a.DoA(2);
+  a.DoA(4);
+  a.DoA(1);
+  a.DoA(3);
+  a.DoA(6);
+}
+
+// .After() allows input to contain duplicated Expectations.
+TEST(AfterTest, AcceptsDuplicatedInput) {
+  MockA a;
+  ON_CALL(a, ReturnResult(_)).WillByDefault(Return(Result()));
+
+  // Define ordering:
+  //   DoA(1) ==>
+  //   DoA(2) ==> ReturnResult(3)
+  Expectation e1 = EXPECT_CALL(a, DoA(1));
+  Expectation e2 = EXPECT_CALL(a, DoA(2));
+  ExpectationSet es;
+  es += e1;
+  es += e2;
+  EXPECT_CALL(a, ReturnResult(3)).After(e1, e2, es, e1);
+
+  a.DoA(1);
+
+  // May only be after DoA(2).
+  EXPECT_NONFATAL_FAILURE(a.ReturnResult(3), "Unexpected mock function call");
+
+  a.DoA(2);
+  a.ReturnResult(3);
+}
+
+// An Expectation added to an ExpectationSet after it has been used in
+// an .After() has no effect.
+TEST(AfterTest, ChangesToExpectationSetHaveNoEffectAfterwards) {
+  MockA a;
+  ExpectationSet es1 = EXPECT_CALL(a, DoA(1));
+  Expectation e2 = EXPECT_CALL(a, DoA(2));
+  EXPECT_CALL(a, DoA(3)).After(es1);
+  es1 += e2;
+
+  a.DoA(1);
+  a.DoA(3);
+  a.DoA(2);
+}
+
+// Tests that Google Mock correctly handles calls to mock functions
+// after a mock object owning one of their pre-requisites has died.
+
+// Tests that calls that satisfy the original spec are successful.
+TEST(DeletingMockEarlyTest, Success1) {
+  MockB* const b1 = new MockB;
+  MockA* const a = new MockA;
+  MockB* const b2 = new MockB;
+
+  {
+    InSequence dummy;
+    EXPECT_CALL(*b1, DoB(_)).WillOnce(Return(1));
+    EXPECT_CALL(*a, Binary(_, _))
+        .Times(AnyNumber())
+        .WillRepeatedly(Return(true));
+    EXPECT_CALL(*b2, DoB(_)).Times(AnyNumber()).WillRepeatedly(Return(2));
+  }
+
+  EXPECT_EQ(1, b1->DoB(1));
+  delete b1;
+  // a's pre-requisite has died.
+  EXPECT_TRUE(a->Binary(0, 1));
+  delete b2;
+  // a's successor has died.
+  EXPECT_TRUE(a->Binary(1, 2));
+  delete a;
+}
+
+// Tests that calls that satisfy the original spec are successful.
+TEST(DeletingMockEarlyTest, Success2) {
+  MockB* const b1 = new MockB;
+  MockA* const a = new MockA;
+  MockB* const b2 = new MockB;
+
+  {
+    InSequence dummy;
+    EXPECT_CALL(*b1, DoB(_)).WillOnce(Return(1));
+    EXPECT_CALL(*a, Binary(_, _)).Times(AnyNumber());
+    EXPECT_CALL(*b2, DoB(_)).Times(AnyNumber()).WillRepeatedly(Return(2));
+  }
+
+  delete a;  // a is trivially satisfied.
+  EXPECT_EQ(1, b1->DoB(1));
+  EXPECT_EQ(2, b2->DoB(2));
+  delete b1;
+  delete b2;
+}
+
+// Tests that it's OK to delete a mock object itself in its action.
+
+// Suppresses warning on unreferenced formal parameter in MSVC with
+// -W4.
+GTEST_DISABLE_MSC_WARNINGS_PUSH_(4100)
+
+ACTION_P(Delete, ptr) { delete ptr; }
+
+GTEST_DISABLE_MSC_WARNINGS_POP_()  // 4100
+
+TEST(DeletingMockEarlyTest, CanDeleteSelfInActionReturningVoid) {
+  MockA* const a = new MockA;
+  EXPECT_CALL(*a, DoA(_)).WillOnce(Delete(a));
+  a->DoA(42);  // This will cause a to be deleted.
+}
+
+TEST(DeletingMockEarlyTest, CanDeleteSelfInActionReturningValue) {
+  MockA* const a = new MockA;
+  EXPECT_CALL(*a, ReturnResult(_)).WillOnce(DoAll(Delete(a), Return(Result())));
+  a->ReturnResult(42);  // This will cause a to be deleted.
+}
+
+// Tests that calls that violate the original spec yield failures.
+TEST(DeletingMockEarlyTest, Failure1) {
+  MockB* const b1 = new MockB;
+  MockA* const a = new MockA;
+  MockB* const b2 = new MockB;
+
+  {
+    InSequence dummy;
+    EXPECT_CALL(*b1, DoB(_)).WillOnce(Return(1));
+    EXPECT_CALL(*a, Binary(_, _)).Times(AnyNumber());
+    EXPECT_CALL(*b2, DoB(_)).Times(AnyNumber()).WillRepeatedly(Return(2));
+  }
+
+  delete a;  // a is trivially satisfied.
+  EXPECT_NONFATAL_FAILURE({ b2->DoB(2); }, "Unexpected mock function call");
+  EXPECT_EQ(1, b1->DoB(1));
+  delete b1;
+  delete b2;
+}
+
+// Tests that calls that violate the original spec yield failures.
+TEST(DeletingMockEarlyTest, Failure2) {
+  MockB* const b1 = new MockB;
+  MockA* const a = new MockA;
+  MockB* const b2 = new MockB;
+
+  {
+    InSequence dummy;
+    EXPECT_CALL(*b1, DoB(_));
+    EXPECT_CALL(*a, Binary(_, _)).Times(AnyNumber());
+    EXPECT_CALL(*b2, DoB(_)).Times(AnyNumber());
+  }
+
+  EXPECT_NONFATAL_FAILURE(delete b1, "Actual: never called");
+  EXPECT_NONFATAL_FAILURE(a->Binary(0, 1), "Unexpected mock function call");
+  EXPECT_NONFATAL_FAILURE(b2->DoB(1), "Unexpected mock function call");
+  delete a;
+  delete b2;
+}
+
+class EvenNumberCardinality : public CardinalityInterface {
+ public:
+  // Returns true if and only if call_count calls will satisfy this
+  // cardinality.
+  bool IsSatisfiedByCallCount(int call_count) const override {
+    return call_count % 2 == 0;
+  }
+
+  // Returns true if and only if call_count calls will saturate this
+  // cardinality.
+  bool IsSaturatedByCallCount(int /* call_count */) const override {
+    return false;
+  }
+
+  // Describes self to an ostream.
+  void DescribeTo(::std::ostream* os) const override {
+    *os << "called even number of times";
+  }
+};
+
+Cardinality EvenNumber() { return Cardinality(new EvenNumberCardinality); }
+
+TEST(ExpectationBaseTest,
+     AllPrerequisitesAreSatisfiedWorksForNonMonotonicCardinality) {
+  MockA* a = new MockA;
+  Sequence s;
+
+  EXPECT_CALL(*a, DoA(1)).Times(EvenNumber()).InSequence(s);
+  EXPECT_CALL(*a, DoA(2)).Times(AnyNumber()).InSequence(s);
+  EXPECT_CALL(*a, DoA(3)).Times(AnyNumber());
+
+  a->DoA(3);
+  a->DoA(1);
+  EXPECT_NONFATAL_FAILURE(a->DoA(2), "Unexpected mock function call");
+  EXPECT_NONFATAL_FAILURE(delete a, "to be called even number of times");
+}
+
+// The following tests verify the message generated when a mock
+// function is called.
+
+struct Printable {};
+
+inline void operator<<(::std::ostream& os, const Printable&) {
+  os << "Printable";
+}
+
+struct Unprintable {
+  Unprintable() : value(0) {}
+  int value;
+};
+
+class MockC {
+ public:
+  MockC() = default;
+
+  MOCK_METHOD6(VoidMethod, void(bool cond, int n, std::string s, void* p,
+                                const Printable& x, Unprintable y));
+  MOCK_METHOD0(NonVoidMethod, int());  // NOLINT
+
+ private:
+  MockC(const MockC&) = delete;
+  MockC& operator=(const MockC&) = delete;
+};
+
+class VerboseFlagPreservingFixture : public testing::Test {
+ protected:
+  VerboseFlagPreservingFixture()
+      : saved_verbose_flag_(GMOCK_FLAG_GET(verbose)) {}
+
+  ~VerboseFlagPreservingFixture() override {
+    GMOCK_FLAG_SET(verbose, saved_verbose_flag_);
+  }
+
+ private:
+  const std::string saved_verbose_flag_;
+
+  VerboseFlagPreservingFixture(const VerboseFlagPreservingFixture&) = delete;
+  VerboseFlagPreservingFixture& operator=(const VerboseFlagPreservingFixture&) =
+      delete;
+};
+
+#if GTEST_HAS_STREAM_REDIRECTION
+
+// Tests that an uninteresting mock function call on a naggy mock
+// generates a warning without the stack trace when
+// --gmock_verbose=warning is specified.
+TEST(FunctionCallMessageTest,
+     UninterestingCallOnNaggyMockGeneratesNoStackTraceWhenVerboseWarning) {
+  GMOCK_FLAG_SET(verbose, kWarningVerbosity);
+  NaggyMock<MockC> c;
+  CaptureStdout();
+  c.VoidMethod(false, 5, "Hi", nullptr, Printable(), Unprintable());
+  const std::string output = GetCapturedStdout();
+  EXPECT_PRED_FORMAT2(IsSubstring, "GMOCK WARNING", output);
+  EXPECT_PRED_FORMAT2(IsNotSubstring, "Stack trace:", output);
+}
+
+// Tests that an uninteresting mock function call on a naggy mock
+// generates a warning containing the stack trace when
+// --gmock_verbose=info is specified.
+TEST(FunctionCallMessageTest,
+     UninterestingCallOnNaggyMockGeneratesFyiWithStackTraceWhenVerboseInfo) {
+  GMOCK_FLAG_SET(verbose, kInfoVerbosity);
+  NaggyMock<MockC> c;
+  CaptureStdout();
+  c.VoidMethod(false, 5, "Hi", nullptr, Printable(), Unprintable());
+  const std::string output = GetCapturedStdout();
+  EXPECT_PRED_FORMAT2(IsSubstring, "GMOCK WARNING", output);
+  EXPECT_PRED_FORMAT2(IsSubstring, "Stack trace:", output);
+
+#ifndef NDEBUG
+
+  // We check the stack trace content in dbg-mode only, as opt-mode
+  // may inline the call we are interested in seeing.
+
+  // Verifies that a void mock function's name appears in the stack
+  // trace.
+  EXPECT_PRED_FORMAT2(IsSubstring, "VoidMethod(", output);
+
+  // Verifies that a non-void mock function's name appears in the
+  // stack trace.
+  CaptureStdout();
+  c.NonVoidMethod();
+  const std::string output2 = GetCapturedStdout();
+  EXPECT_PRED_FORMAT2(IsSubstring, "NonVoidMethod(", output2);
+
+#endif  // NDEBUG
+}
+
+// Tests that an uninteresting mock function call on a naggy mock
+// causes the function arguments and return value to be printed.
+TEST(FunctionCallMessageTest,
+     UninterestingCallOnNaggyMockPrintsArgumentsAndReturnValue) {
+  // A non-void mock function.
+  NaggyMock<MockB> b;
+  CaptureStdout();
+  b.DoB();
+  const std::string output1 = GetCapturedStdout();
+  EXPECT_PRED_FORMAT2(
+      IsSubstring,
+      "Uninteresting mock function call - returning default value.\n"
+      "    Function call: DoB()\n"
+      "          Returns: 0\n",
+      output1.c_str());
+  // Makes sure the return value is printed.
+
+  // A void mock function.
+  NaggyMock<MockC> c;
+  CaptureStdout();
+  c.VoidMethod(false, 5, "Hi", nullptr, Printable(), Unprintable());
+  const std::string output2 = GetCapturedStdout();
+  EXPECT_THAT(
+      output2.c_str(),
+      ContainsRegex("Uninteresting mock function call - returning directly\\.\n"
+                    "    Function call: VoidMethod"
+                    "\\(false, 5, \"Hi\", NULL, @.+ "
+                    "Printable, 4-byte object <00-00 00-00>\\)"));
+  // A void function has no return value to print.
+}
+
+// Tests how the --gmock_verbose flag affects Google Mock's output.
+
+class GMockVerboseFlagTest : public VerboseFlagPreservingFixture {
+ public:
+  // Verifies that the given Google Mock output is correct.  (When
+  // should_print is true, the output should match the given regex and
+  // contain the given function name in the stack trace.  When it's
+  // false, the output should be empty.)
+  void VerifyOutput(const std::string& output, bool should_print,
+                    const std::string& expected_substring,
+                    const std::string& function_name) {
+    if (should_print) {
+      EXPECT_THAT(output.c_str(), HasSubstr(expected_substring));
+#ifndef NDEBUG
+      // We check the stack trace content in dbg-mode only, as opt-mode
+      // may inline the call we are interested in seeing.
+      EXPECT_THAT(output.c_str(), HasSubstr(function_name));
+#else
+      // Suppresses 'unused function parameter' warnings.
+      static_cast<void>(function_name);
+#endif  // NDEBUG
+    } else {
+      EXPECT_STREQ("", output.c_str());
+    }
+  }
+
+  // Tests how the flag affects expected calls.
+  void TestExpectedCall(bool should_print) {
+    MockA a;
+    EXPECT_CALL(a, DoA(5));
+    EXPECT_CALL(a, Binary(_, 1)).WillOnce(Return(true));
+
+    // A void-returning function.
+    CaptureStdout();
+    a.DoA(5);
+    VerifyOutput(GetCapturedStdout(), should_print,
+                 "Mock function call matches EXPECT_CALL(a, DoA(5))...\n"
+                 "    Function call: DoA(5)\n"
+                 "Stack trace:\n",
+                 "DoA");
+
+    // A non-void-returning function.
+    CaptureStdout();
+    a.Binary(2, 1);
+    VerifyOutput(GetCapturedStdout(), should_print,
+                 "Mock function call matches EXPECT_CALL(a, Binary(_, 1))...\n"
+                 "    Function call: Binary(2, 1)\n"
+                 "          Returns: true\n"
+                 "Stack trace:\n",
+                 "Binary");
+  }
+
+  // Tests how the flag affects uninteresting calls on a naggy mock.
+  void TestUninterestingCallOnNaggyMock(bool should_print) {
+    NaggyMock<MockA> a;
+    const std::string note =
+        "NOTE: You can safely ignore the above warning unless this "
+        "call should not happen.  Do not suppress it by blindly adding "
+        "an EXPECT_CALL() if you don't mean to enforce the call.  "
+        "See "
+        "https://github.com/google/googletest/blob/main/docs/"
+        "gmock_cook_book.md#"
+        "knowing-when-to-expect-useoncall for details.";
+
+    // A void-returning function.
+    CaptureStdout();
+    a.DoA(5);
+    VerifyOutput(GetCapturedStdout(), should_print,
+                 "\nGMOCK WARNING:\n"
+                 "Uninteresting mock function call - returning directly.\n"
+                 "    Function call: DoA(5)\n" +
+                     note,
+                 "DoA");
+
+    // A non-void-returning function.
+    CaptureStdout();
+    a.Binary(2, 1);
+    VerifyOutput(GetCapturedStdout(), should_print,
+                 "\nGMOCK WARNING:\n"
+                 "Uninteresting mock function call - returning default value.\n"
+                 "    Function call: Binary(2, 1)\n"
+                 "          Returns: false\n" +
+                     note,
+                 "Binary");
+  }
+};
+
+// Tests that --gmock_verbose=info causes both expected and
+// uninteresting calls to be reported.
+TEST_F(GMockVerboseFlagTest, Info) {
+  GMOCK_FLAG_SET(verbose, kInfoVerbosity);
+  TestExpectedCall(true);
+  TestUninterestingCallOnNaggyMock(true);
+}
+
+// Tests that --gmock_verbose=warning causes uninteresting calls to be
+// reported.
+TEST_F(GMockVerboseFlagTest, Warning) {
+  GMOCK_FLAG_SET(verbose, kWarningVerbosity);
+  TestExpectedCall(false);
+  TestUninterestingCallOnNaggyMock(true);
+}
+
+// Tests that --gmock_verbose=warning causes neither expected nor
+// uninteresting calls to be reported.
+TEST_F(GMockVerboseFlagTest, Error) {
+  GMOCK_FLAG_SET(verbose, kErrorVerbosity);
+  TestExpectedCall(false);
+  TestUninterestingCallOnNaggyMock(false);
+}
+
+// Tests that --gmock_verbose=SOME_INVALID_VALUE has the same effect
+// as --gmock_verbose=warning.
+TEST_F(GMockVerboseFlagTest, InvalidFlagIsTreatedAsWarning) {
+  GMOCK_FLAG_SET(verbose, "invalid");  // Treated as "warning".
+  TestExpectedCall(false);
+  TestUninterestingCallOnNaggyMock(true);
+}
+
+#endif  // GTEST_HAS_STREAM_REDIRECTION
+
+// A helper class that generates a failure when printed.  We use it to
+// ensure that Google Mock doesn't print a value (even to an internal
+// buffer) when it is not supposed to do so.
+class PrintMeNot {};
+
+void PrintTo(PrintMeNot /* dummy */, ::std::ostream* /* os */) {
+  ADD_FAILURE() << "Google Mock is printing a value that shouldn't be "
+                << "printed even to an internal buffer.";
+}
+
+class LogTestHelper {
+ public:
+  LogTestHelper() = default;
+
+  MOCK_METHOD1(Foo, PrintMeNot(PrintMeNot));
+
+ private:
+  LogTestHelper(const LogTestHelper&) = delete;
+  LogTestHelper& operator=(const LogTestHelper&) = delete;
+};
+
+class GMockLogTest : public VerboseFlagPreservingFixture {
+ protected:
+  LogTestHelper helper_;
+};
+
+TEST_F(GMockLogTest, DoesNotPrintGoodCallInternallyIfVerbosityIsWarning) {
+  GMOCK_FLAG_SET(verbose, kWarningVerbosity);
+  EXPECT_CALL(helper_, Foo(_)).WillOnce(Return(PrintMeNot()));
+  helper_.Foo(PrintMeNot());  // This is an expected call.
+}
+
+TEST_F(GMockLogTest, DoesNotPrintGoodCallInternallyIfVerbosityIsError) {
+  GMOCK_FLAG_SET(verbose, kErrorVerbosity);
+  EXPECT_CALL(helper_, Foo(_)).WillOnce(Return(PrintMeNot()));
+  helper_.Foo(PrintMeNot());  // This is an expected call.
+}
+
+TEST_F(GMockLogTest, DoesNotPrintWarningInternallyIfVerbosityIsError) {
+  GMOCK_FLAG_SET(verbose, kErrorVerbosity);
+  ON_CALL(helper_, Foo(_)).WillByDefault(Return(PrintMeNot()));
+  helper_.Foo(PrintMeNot());  // This should generate a warning.
+}
+
+// Tests Mock::AllowLeak().
+
+TEST(AllowLeakTest, AllowsLeakingUnusedMockObject) {
+  MockA* a = new MockA;
+  Mock::AllowLeak(a);
+}
+
+TEST(AllowLeakTest, CanBeCalledBeforeOnCall) {
+  MockA* a = new MockA;
+  Mock::AllowLeak(a);
+  ON_CALL(*a, DoA(_)).WillByDefault(Return());
+  a->DoA(0);
+}
+
+TEST(AllowLeakTest, CanBeCalledAfterOnCall) {
+  MockA* a = new MockA;
+  ON_CALL(*a, DoA(_)).WillByDefault(Return());
+  Mock::AllowLeak(a);
+}
+
+TEST(AllowLeakTest, CanBeCalledBeforeExpectCall) {
+  MockA* a = new MockA;
+  Mock::AllowLeak(a);
+  EXPECT_CALL(*a, DoA(_));
+  a->DoA(0);
+}
+
+TEST(AllowLeakTest, CanBeCalledAfterExpectCall) {
+  MockA* a = new MockA;
+  EXPECT_CALL(*a, DoA(_)).Times(AnyNumber());
+  Mock::AllowLeak(a);
+}
+
+TEST(AllowLeakTest, WorksWhenBothOnCallAndExpectCallArePresent) {
+  MockA* a = new MockA;
+  ON_CALL(*a, DoA(_)).WillByDefault(Return());
+  EXPECT_CALL(*a, DoA(_)).Times(AnyNumber());
+  Mock::AllowLeak(a);
+}
+
+// Tests that we can verify and clear a mock object's expectations
+// when none of its methods has expectations.
+TEST(VerifyAndClearExpectationsTest, NoMethodHasExpectations) {
+  MockB b;
+  ASSERT_TRUE(Mock::VerifyAndClearExpectations(&b));
+
+  // There should be no expectations on the methods now, so we can
+  // freely call them.
+  EXPECT_EQ(0, b.DoB());
+  EXPECT_EQ(0, b.DoB(1));
+}
+
+// Tests that we can verify and clear a mock object's expectations
+// when some, but not all, of its methods have expectations *and* the
+// verification succeeds.
+TEST(VerifyAndClearExpectationsTest, SomeMethodsHaveExpectationsAndSucceed) {
+  MockB b;
+  EXPECT_CALL(b, DoB()).WillOnce(Return(1));
+  b.DoB();
+  ASSERT_TRUE(Mock::VerifyAndClearExpectations(&b));
+
+  // There should be no expectations on the methods now, so we can
+  // freely call them.
+  EXPECT_EQ(0, b.DoB());
+  EXPECT_EQ(0, b.DoB(1));
+}
+
+// Tests that we can verify and clear a mock object's expectations
+// when some, but not all, of its methods have expectations *and* the
+// verification fails.
+TEST(VerifyAndClearExpectationsTest, SomeMethodsHaveExpectationsAndFail) {
+  MockB b;
+  EXPECT_CALL(b, DoB()).WillOnce(Return(1));
+  bool result = true;
+  EXPECT_NONFATAL_FAILURE(result = Mock::VerifyAndClearExpectations(&b),
+                          "Actual: never called");
+  ASSERT_FALSE(result);
+
+  // There should be no expectations on the methods now, so we can
+  // freely call them.
+  EXPECT_EQ(0, b.DoB());
+  EXPECT_EQ(0, b.DoB(1));
+}
+
+// Tests that we can verify and clear a mock object's expectations
+// when all of its methods have expectations.
+TEST(VerifyAndClearExpectationsTest, AllMethodsHaveExpectations) {
+  MockB b;
+  EXPECT_CALL(b, DoB()).WillOnce(Return(1));
+  EXPECT_CALL(b, DoB(_)).WillOnce(Return(2));
+  b.DoB();
+  b.DoB(1);
+  ASSERT_TRUE(Mock::VerifyAndClearExpectations(&b));
+
+  // There should be no expectations on the methods now, so we can
+  // freely call them.
+  EXPECT_EQ(0, b.DoB());
+  EXPECT_EQ(0, b.DoB(1));
+}
+
+// Tests that we can verify and clear a mock object's expectations
+// when a method has more than one expectation.
+TEST(VerifyAndClearExpectationsTest, AMethodHasManyExpectations) {
+  MockB b;
+  EXPECT_CALL(b, DoB(0)).WillOnce(Return(1));
+  EXPECT_CALL(b, DoB(_)).WillOnce(Return(2));
+  b.DoB(1);
+  bool result = true;
+  EXPECT_NONFATAL_FAILURE(result = Mock::VerifyAndClearExpectations(&b),
+                          "Actual: never called");
+  ASSERT_FALSE(result);
+
+  // There should be no expectations on the methods now, so we can
+  // freely call them.
+  EXPECT_EQ(0, b.DoB());
+  EXPECT_EQ(0, b.DoB(1));
+}
+
+// Tests that we can call VerifyAndClearExpectations() on the same
+// mock object multiple times.
+TEST(VerifyAndClearExpectationsTest, CanCallManyTimes) {
+  MockB b;
+  EXPECT_CALL(b, DoB());
+  b.DoB();
+  Mock::VerifyAndClearExpectations(&b);
+
+  EXPECT_CALL(b, DoB(_)).WillOnce(Return(1));
+  b.DoB(1);
+  Mock::VerifyAndClearExpectations(&b);
+  Mock::VerifyAndClearExpectations(&b);
+
+  // There should be no expectations on the methods now, so we can
+  // freely call them.
+  EXPECT_EQ(0, b.DoB());
+  EXPECT_EQ(0, b.DoB(1));
+}
+
+// Tests that we can clear a mock object's default actions when none
+// of its methods has default actions.
+TEST(VerifyAndClearTest, NoMethodHasDefaultActions) {
+  MockB b;
+  // If this crashes or generates a failure, the test will catch it.
+  Mock::VerifyAndClear(&b);
+  EXPECT_EQ(0, b.DoB());
+}
+
+// Tests that we can clear a mock object's default actions when some,
+// but not all of its methods have default actions.
+TEST(VerifyAndClearTest, SomeMethodsHaveDefaultActions) {
+  MockB b;
+  ON_CALL(b, DoB()).WillByDefault(Return(1));
+
+  Mock::VerifyAndClear(&b);
+
+  // Verifies that the default action of int DoB() was removed.
+  EXPECT_EQ(0, b.DoB());
+}
+
+// Tests that we can clear a mock object's default actions when all of
+// its methods have default actions.
+TEST(VerifyAndClearTest, AllMethodsHaveDefaultActions) {
+  MockB b;
+  ON_CALL(b, DoB()).WillByDefault(Return(1));
+  ON_CALL(b, DoB(_)).WillByDefault(Return(2));
+
+  Mock::VerifyAndClear(&b);
+
+  // Verifies that the default action of int DoB() was removed.
+  EXPECT_EQ(0, b.DoB());
+
+  // Verifies that the default action of int DoB(int) was removed.
+  EXPECT_EQ(0, b.DoB(0));
+}
+
+// Tests that we can clear a mock object's default actions when a
+// method has more than one ON_CALL() set on it.
+TEST(VerifyAndClearTest, AMethodHasManyDefaultActions) {
+  MockB b;
+  ON_CALL(b, DoB(0)).WillByDefault(Return(1));
+  ON_CALL(b, DoB(_)).WillByDefault(Return(2));
+
+  Mock::VerifyAndClear(&b);
+
+  // Verifies that the default actions (there are two) of int DoB(int)
+  // were removed.
+  EXPECT_EQ(0, b.DoB(0));
+  EXPECT_EQ(0, b.DoB(1));
+}
+
+// Tests that we can call VerifyAndClear() on a mock object multiple
+// times.
+TEST(VerifyAndClearTest, CanCallManyTimes) {
+  MockB b;
+  ON_CALL(b, DoB()).WillByDefault(Return(1));
+  Mock::VerifyAndClear(&b);
+  Mock::VerifyAndClear(&b);
+
+  ON_CALL(b, DoB(_)).WillByDefault(Return(1));
+  Mock::VerifyAndClear(&b);
+
+  EXPECT_EQ(0, b.DoB());
+  EXPECT_EQ(0, b.DoB(1));
+}
+
+// Tests that VerifyAndClear() works when the verification succeeds.
+TEST(VerifyAndClearTest, Success) {
+  MockB b;
+  ON_CALL(b, DoB()).WillByDefault(Return(1));
+  EXPECT_CALL(b, DoB(1)).WillOnce(Return(2));
+
+  b.DoB();
+  b.DoB(1);
+  ASSERT_TRUE(Mock::VerifyAndClear(&b));
+
+  // There should be no expectations on the methods now, so we can
+  // freely call them.
+  EXPECT_EQ(0, b.DoB());
+  EXPECT_EQ(0, b.DoB(1));
+}
+
+// Tests that VerifyAndClear() works when the verification fails.
+TEST(VerifyAndClearTest, Failure) {
+  MockB b;
+  ON_CALL(b, DoB(_)).WillByDefault(Return(1));
+  EXPECT_CALL(b, DoB()).WillOnce(Return(2));
+
+  b.DoB(1);
+  bool result = true;
+  EXPECT_NONFATAL_FAILURE(result = Mock::VerifyAndClear(&b),
+                          "Actual: never called");
+  ASSERT_FALSE(result);
+
+  // There should be no expectations on the methods now, so we can
+  // freely call them.
+  EXPECT_EQ(0, b.DoB());
+  EXPECT_EQ(0, b.DoB(1));
+}
+
+// Tests that VerifyAndClear() works when the default actions and
+// expectations are set on a const mock object.
+TEST(VerifyAndClearTest, Const) {
+  MockB b;
+  ON_CALL(Const(b), DoB()).WillByDefault(Return(1));
+
+  EXPECT_CALL(Const(b), DoB()).WillOnce(DoDefault()).WillOnce(Return(2));
+
+  b.DoB();
+  b.DoB();
+  ASSERT_TRUE(Mock::VerifyAndClear(&b));
+
+  // There should be no expectations on the methods now, so we can
+  // freely call them.
+  EXPECT_EQ(0, b.DoB());
+  EXPECT_EQ(0, b.DoB(1));
+}
+
+// Tests that we can set default actions and expectations on a mock
+// object after VerifyAndClear() has been called on it.
+TEST(VerifyAndClearTest, CanSetDefaultActionsAndExpectationsAfterwards) {
+  MockB b;
+  ON_CALL(b, DoB()).WillByDefault(Return(1));
+  EXPECT_CALL(b, DoB(_)).WillOnce(Return(2));
+  b.DoB(1);
+
+  Mock::VerifyAndClear(&b);
+
+  EXPECT_CALL(b, DoB()).WillOnce(Return(3));
+  ON_CALL(b, DoB(_)).WillByDefault(Return(4));
+
+  EXPECT_EQ(3, b.DoB());
+  EXPECT_EQ(4, b.DoB(1));
+}
+
+// Tests that calling VerifyAndClear() on one mock object does not
+// affect other mock objects (either of the same type or not).
+TEST(VerifyAndClearTest, DoesNotAffectOtherMockObjects) {
+  MockA a;
+  MockB b1;
+  MockB b2;
+
+  ON_CALL(a, Binary(_, _)).WillByDefault(Return(true));
+  EXPECT_CALL(a, Binary(_, _)).WillOnce(DoDefault()).WillOnce(Return(false));
+
+  ON_CALL(b1, DoB()).WillByDefault(Return(1));
+  EXPECT_CALL(b1, DoB(_)).WillOnce(Return(2));
+
+  ON_CALL(b2, DoB()).WillByDefault(Return(3));
+  EXPECT_CALL(b2, DoB(_));
+
+  b2.DoB(0);
+  Mock::VerifyAndClear(&b2);
+
+  // Verifies that the default actions and expectations of a and b1
+  // are still in effect.
+  EXPECT_TRUE(a.Binary(0, 0));
+  EXPECT_FALSE(a.Binary(0, 0));
+
+  EXPECT_EQ(1, b1.DoB());
+  EXPECT_EQ(2, b1.DoB(0));
+}
+
+TEST(VerifyAndClearTest,
+     DestroyingChainedMocksDoesNotDeadlockThroughExpectations) {
+  std::shared_ptr<MockA> a(new MockA);
+  ReferenceHoldingMock test_mock;
+
+  // EXPECT_CALL stores a reference to a inside test_mock.
+  EXPECT_CALL(test_mock, AcceptReference(_))
+      .WillRepeatedly(SetArgPointee<0>(a));
+
+  // Throw away the reference to the mock that we have in a. After this, the
+  // only reference to it is stored by test_mock.
+  a.reset();
+
+  // When test_mock goes out of scope, it destroys the last remaining reference
+  // to the mock object originally pointed to by a. This will cause the MockA
+  // destructor to be called from inside the ReferenceHoldingMock destructor.
+  // The state of all mocks is protected by a single global lock, but there
+  // should be no deadlock.
+}
+
+TEST(VerifyAndClearTest,
+     DestroyingChainedMocksDoesNotDeadlockThroughDefaultAction) {
+  std::shared_ptr<MockA> a(new MockA);
+  ReferenceHoldingMock test_mock;
+
+  // ON_CALL stores a reference to a inside test_mock.
+  ON_CALL(test_mock, AcceptReference(_)).WillByDefault(SetArgPointee<0>(a));
+
+  // Throw away the reference to the mock that we have in a. After this, the
+  // only reference to it is stored by test_mock.
+  a.reset();
+
+  // When test_mock goes out of scope, it destroys the last remaining reference
+  // to the mock object originally pointed to by a. This will cause the MockA
+  // destructor to be called from inside the ReferenceHoldingMock destructor.
+  // The state of all mocks is protected by a single global lock, but there
+  // should be no deadlock.
+}
+
+// Tests that a mock function's action can call a mock function
+// (either the same function or a different one) either as an explicit
+// action or as a default action without causing a dead lock.  It
+// verifies that the action is not performed inside the critical
+// section.
+TEST(SynchronizationTest, CanCallMockMethodInAction) {
+  MockA a;
+  MockC c;
+  ON_CALL(a, DoA(_)).WillByDefault(
+      IgnoreResult(InvokeWithoutArgs(&c, &MockC::NonVoidMethod)));
+  EXPECT_CALL(a, DoA(1));
+  EXPECT_CALL(a, DoA(1))
+      .WillOnce(Invoke(&a, &MockA::DoA))
+      .RetiresOnSaturation();
+  EXPECT_CALL(c, NonVoidMethod());
+
+  a.DoA(1);
+  // This will match the second EXPECT_CALL() and trigger another a.DoA(1),
+  // which will in turn match the first EXPECT_CALL() and trigger a call to
+  // c.NonVoidMethod() that was specified by the ON_CALL() since the first
+  // EXPECT_CALL() did not specify an action.
+}
+
+TEST(ParameterlessExpectationsTest, CanSetExpectationsWithoutMatchers) {
+  MockA a;
+  int do_a_arg0 = 0;
+  ON_CALL(a, DoA).WillByDefault(SaveArg<0>(&do_a_arg0));
+  int do_a_47_arg0 = 0;
+  ON_CALL(a, DoA(47)).WillByDefault(SaveArg<0>(&do_a_47_arg0));
+
+  a.DoA(17);
+  EXPECT_THAT(do_a_arg0, 17);
+  EXPECT_THAT(do_a_47_arg0, 0);
+  a.DoA(47);
+  EXPECT_THAT(do_a_arg0, 17);
+  EXPECT_THAT(do_a_47_arg0, 47);
+
+  ON_CALL(a, Binary).WillByDefault(Return(true));
+  ON_CALL(a, Binary(_, 14)).WillByDefault(Return(false));
+  EXPECT_THAT(a.Binary(14, 17), true);
+  EXPECT_THAT(a.Binary(17, 14), false);
+}
+
+TEST(ParameterlessExpectationsTest, CanSetExpectationsForOverloadedMethods) {
+  MockB b;
+  ON_CALL(b, DoB()).WillByDefault(Return(9));
+  ON_CALL(b, DoB(5)).WillByDefault(Return(11));
+
+  EXPECT_THAT(b.DoB(), 9);
+  EXPECT_THAT(b.DoB(1), 0);  // default value
+  EXPECT_THAT(b.DoB(5), 11);
+}
+
+struct MockWithConstMethods {
+ public:
+  MOCK_CONST_METHOD1(Foo, int(int));
+  MOCK_CONST_METHOD2(Bar, int(int, const char*));
+};
+
+TEST(ParameterlessExpectationsTest, CanSetExpectationsForConstMethods) {
+  MockWithConstMethods mock;
+  ON_CALL(mock, Foo).WillByDefault(Return(7));
+  ON_CALL(mock, Bar).WillByDefault(Return(33));
+
+  EXPECT_THAT(mock.Foo(17), 7);
+  EXPECT_THAT(mock.Bar(27, "purple"), 33);
+}
+
+class MockConstOverload {
+ public:
+  MOCK_METHOD1(Overloaded, int(int));
+  MOCK_CONST_METHOD1(Overloaded, int(int));
+};
+
+TEST(ParameterlessExpectationsTest,
+     CanSetExpectationsForConstOverloadedMethods) {
+  MockConstOverload mock;
+  ON_CALL(mock, Overloaded(_)).WillByDefault(Return(7));
+  ON_CALL(mock, Overloaded(5)).WillByDefault(Return(9));
+  ON_CALL(Const(mock), Overloaded(5)).WillByDefault(Return(11));
+  ON_CALL(Const(mock), Overloaded(7)).WillByDefault(Return(13));
+
+  EXPECT_THAT(mock.Overloaded(1), 7);
+  EXPECT_THAT(mock.Overloaded(5), 9);
+  EXPECT_THAT(mock.Overloaded(7), 7);
+
+  const MockConstOverload& const_mock = mock;
+  EXPECT_THAT(const_mock.Overloaded(1), 0);
+  EXPECT_THAT(const_mock.Overloaded(5), 11);
+  EXPECT_THAT(const_mock.Overloaded(7), 13);
+}
+
+}  // namespace
+}  // namespace testing
+
+int main(int argc, char** argv) {
+  testing::InitGoogleMock(&argc, argv);
+  // Ensures that the tests pass no matter what value of
+  // --gmock_catch_leaked_mocks and --gmock_verbose the user specifies.
+  GMOCK_FLAG_SET(catch_leaked_mocks, true);
+  GMOCK_FLAG_SET(verbose, testing::internal::kWarningVerbosity);
+
+  return RUN_ALL_TESTS();
+}
diff --git a/third_party/googletest/googlemock/test/gmock_all_test.cc b/third_party/googletest/googlemock/test/gmock_all_test.cc
new file mode 100644
index 0000000..6db0086
--- /dev/null
+++ b/third_party/googletest/googlemock/test/gmock_all_test.cc
@@ -0,0 +1,49 @@
+// Copyright 2009, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+//
+// Tests for Google C++ Mocking Framework (Google Mock)
+//
+// Some users use a build system that Google Mock doesn't support directly,
+// yet they still want to build and run Google Mock's own tests.  This file
+// includes most such tests, making it easier for these users to maintain
+// their build scripts (they just need to build this file, even though the
+// below list of actual *_test.cc files might change).
+#include "test/gmock-actions_test.cc"
+#include "test/gmock-cardinalities_test.cc"
+#include "test/gmock-internal-utils_test.cc"
+#include "test/gmock-matchers-arithmetic_test.cc"
+#include "test/gmock-matchers-comparisons_test.cc"
+#include "test/gmock-matchers-containers_test.cc"
+#include "test/gmock-matchers-misc_test.cc"
+#include "test/gmock-more-actions_test.cc"
+#include "test/gmock-nice-strict_test.cc"
+#include "test/gmock-port_test.cc"
+#include "test/gmock-spec-builders_test.cc"
+#include "test/gmock_test.cc"
diff --git a/third_party/googletest/googlemock/test/gmock_ex_test.cc b/third_party/googletest/googlemock/test/gmock_ex_test.cc
new file mode 100644
index 0000000..e174122
--- /dev/null
+++ b/third_party/googletest/googlemock/test/gmock_ex_test.cc
@@ -0,0 +1,80 @@
+// Copyright 2013, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Tests Google Mock's functionality that depends on exceptions.
+
+#include <exception>
+
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+
+#if GTEST_HAS_EXCEPTIONS
+namespace {
+
+using testing::HasSubstr;
+
+using testing::internal::GoogleTestFailureException;
+
+// A type that cannot be default constructed.
+class NonDefaultConstructible {
+ public:
+  explicit NonDefaultConstructible(int /* dummy */) {}
+};
+
+class MockFoo {
+ public:
+  // A mock method that returns a user-defined type.  Google Mock
+  // doesn't know what the default value for this type is.
+  MOCK_METHOD0(GetNonDefaultConstructible, NonDefaultConstructible());
+};
+
+TEST(DefaultValueTest, ThrowsRuntimeErrorWhenNoDefaultValue) {
+  MockFoo mock;
+  try {
+    // No expectation is set on this method, so Google Mock must
+    // return the default value.  However, since Google Mock knows
+    // nothing about the return type, it doesn't know what to return,
+    // and has to throw (when exceptions are enabled) or abort
+    // (otherwise).
+    mock.GetNonDefaultConstructible();
+    FAIL() << "GetNonDefaultConstructible()'s return type has no default "
+           << "value, so Google Mock should have thrown.";
+  } catch (const GoogleTestFailureException& /* unused */) {
+    FAIL() << "Google Test does not try to catch an exception of type "
+           << "GoogleTestFailureException, which is used for reporting "
+           << "a failure to other testing frameworks.  Google Mock should "
+           << "not throw a GoogleTestFailureException as it will kill the "
+           << "entire test program instead of just the current TEST.";
+  } catch (const std::exception& ex) {
+    EXPECT_THAT(ex.what(), HasSubstr("has no default value"));
+  }
+}
+
+}  // unnamed namespace
+#endif
diff --git a/third_party/googletest/googlemock/test/gmock_leak_test.py b/third_party/googletest/googlemock/test/gmock_leak_test.py
new file mode 100755
index 0000000..8b02bc4
--- /dev/null
+++ b/third_party/googletest/googlemock/test/gmock_leak_test.py
@@ -0,0 +1,113 @@
+#!/usr/bin/env python
+#
+# Copyright 2009, Google Inc.
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"""Tests that leaked mock objects can be caught be Google Mock."""
+
+from googlemock.test import gmock_test_utils
+
+PROGRAM_PATH = gmock_test_utils.GetTestExecutablePath('gmock_leak_test_')
+TEST_WITH_EXPECT_CALL = [PROGRAM_PATH, '--gtest_filter=*ExpectCall*']
+TEST_WITH_ON_CALL = [PROGRAM_PATH, '--gtest_filter=*OnCall*']
+TEST_MULTIPLE_LEAKS = [PROGRAM_PATH, '--gtest_filter=*MultipleLeaked*']
+
+environ = gmock_test_utils.environ
+SetEnvVar = gmock_test_utils.SetEnvVar
+
+# Tests in this file run a Google-Test-based test program and expect it
+# to terminate prematurely.  Therefore they are incompatible with
+# the premature-exit-file protocol by design.  Unset the
+# premature-exit filepath to prevent Google Test from creating
+# the file.
+SetEnvVar(gmock_test_utils.PREMATURE_EXIT_FILE_ENV_VAR, None)
+
+
+class GMockLeakTest(gmock_test_utils.TestCase):
+
+  def testCatchesLeakedMockByDefault(self):
+    self.assertNotEqual(
+        0,
+        gmock_test_utils.Subprocess(
+            TEST_WITH_EXPECT_CALL, env=environ
+        ).exit_code,
+    )
+    self.assertNotEqual(
+        0, gmock_test_utils.Subprocess(TEST_WITH_ON_CALL, env=environ).exit_code
+    )
+
+  def testDoesNotCatchLeakedMockWhenDisabled(self):
+    self.assertEqual(
+        0,
+        gmock_test_utils.Subprocess(
+            TEST_WITH_EXPECT_CALL + ['--gmock_catch_leaked_mocks=0'],
+            env=environ,
+        ).exit_code,
+    )
+    self.assertEqual(
+        0,
+        gmock_test_utils.Subprocess(
+            TEST_WITH_ON_CALL + ['--gmock_catch_leaked_mocks=0'], env=environ
+        ).exit_code,
+    )
+
+  def testCatchesLeakedMockWhenEnabled(self):
+    self.assertNotEqual(
+        0,
+        gmock_test_utils.Subprocess(
+            TEST_WITH_EXPECT_CALL + ['--gmock_catch_leaked_mocks'], env=environ
+        ).exit_code,
+    )
+    self.assertNotEqual(
+        0,
+        gmock_test_utils.Subprocess(
+            TEST_WITH_ON_CALL + ['--gmock_catch_leaked_mocks'], env=environ
+        ).exit_code,
+    )
+
+  def testCatchesLeakedMockWhenEnabledWithExplictFlagValue(self):
+    self.assertNotEqual(
+        0,
+        gmock_test_utils.Subprocess(
+            TEST_WITH_EXPECT_CALL + ['--gmock_catch_leaked_mocks=1'],
+            env=environ,
+        ).exit_code,
+    )
+
+  def testCatchesMultipleLeakedMocks(self):
+    self.assertNotEqual(
+        0,
+        gmock_test_utils.Subprocess(
+            TEST_MULTIPLE_LEAKS + ['--gmock_catch_leaked_mocks'], env=environ
+        ).exit_code,
+    )
+
+
+if __name__ == '__main__':
+  gmock_test_utils.Main()
diff --git a/third_party/googletest/googlemock/test/gmock_leak_test_.cc b/third_party/googletest/googlemock/test/gmock_leak_test_.cc
new file mode 100644
index 0000000..a6bb339
--- /dev/null
+++ b/third_party/googletest/googlemock/test/gmock_leak_test_.cc
@@ -0,0 +1,99 @@
+// Copyright 2009, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Google Mock - a framework for writing C++ mock classes.
+//
+// This program is for verifying that a leaked mock object can be
+// caught by Google Mock's leak detector.
+
+#include "gmock/gmock.h"
+
+namespace {
+
+using ::testing::Return;
+
+class FooInterface {
+ public:
+  virtual ~FooInterface() = default;
+  virtual void DoThis() = 0;
+};
+
+class MockFoo : public FooInterface {
+ public:
+  MockFoo() = default;
+
+  MOCK_METHOD0(DoThis, void());
+
+ private:
+  MockFoo(const MockFoo&) = delete;
+  MockFoo& operator=(const MockFoo&) = delete;
+};
+
+TEST(LeakTest, LeakedMockWithExpectCallCausesFailureWhenLeakCheckingIsEnabled) {
+  MockFoo* foo = new MockFoo;
+
+  EXPECT_CALL(*foo, DoThis());
+  foo->DoThis();
+
+  // In order to test the leak detector, we deliberately leak foo.
+
+  // Makes sure Google Mock's leak detector can change the exit code
+  // to 1 even when the code is already exiting with 0.
+  exit(0);
+}
+
+TEST(LeakTest, LeakedMockWithOnCallCausesFailureWhenLeakCheckingIsEnabled) {
+  MockFoo* foo = new MockFoo;
+
+  ON_CALL(*foo, DoThis()).WillByDefault(Return());
+
+  // In order to test the leak detector, we deliberately leak foo.
+
+  // Makes sure Google Mock's leak detector can change the exit code
+  // to 1 even when the code is already exiting with 0.
+  exit(0);
+}
+
+TEST(LeakTest, CatchesMultipleLeakedMockObjects) {
+  MockFoo* foo1 = new MockFoo;
+  MockFoo* foo2 = new MockFoo;
+
+  ON_CALL(*foo1, DoThis()).WillByDefault(Return());
+  EXPECT_CALL(*foo2, DoThis());
+  foo2->DoThis();
+
+  // In order to test the leak detector, we deliberately leak foo1 and
+  // foo2.
+
+  // Makes sure Google Mock's leak detector can change the exit code
+  // to 1 even when the code is already exiting with 0.
+  exit(0);
+}
+
+}  // namespace
diff --git a/third_party/googletest/googlemock/test/gmock_link2_test.cc b/third_party/googletest/googlemock/test/gmock_link2_test.cc
new file mode 100644
index 0000000..cd3d690
--- /dev/null
+++ b/third_party/googletest/googlemock/test/gmock_link2_test.cc
@@ -0,0 +1,38 @@
+// Copyright 2008, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Google Mock - a framework for writing C++ mock classes.
+//
+// This file is for verifying that various Google Mock constructs do not
+// produce linker errors when instantiated in different translation units.
+// Please see gmock_link_test.h for details.
+
+#define LinkTest LinkTest2
+
+#include "test/gmock_link_test.h"
diff --git a/third_party/googletest/googlemock/test/gmock_link_test.cc b/third_party/googletest/googlemock/test/gmock_link_test.cc
new file mode 100644
index 0000000..f51e398
--- /dev/null
+++ b/third_party/googletest/googlemock/test/gmock_link_test.cc
@@ -0,0 +1,38 @@
+// Copyright 2008, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Google Mock - a framework for writing C++ mock classes.
+//
+// This file is for verifying that various Google Mock constructs do not
+// produce linker errors when instantiated in different translation units.
+// Please see gmock_link_test.h for details.
+
+#define LinkTest LinkTest1
+
+#include "test/gmock_link_test.h"
diff --git a/third_party/googletest/googlemock/test/gmock_link_test.h b/third_party/googletest/googlemock/test/gmock_link_test.h
new file mode 100644
index 0000000..db11c2d
--- /dev/null
+++ b/third_party/googletest/googlemock/test/gmock_link_test.h
@@ -0,0 +1,684 @@
+// Copyright 2009, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Google Mock - a framework for writing C++ mock classes.
+//
+// This file tests that:
+// a. A header file defining a mock class can be included in multiple
+//    translation units without causing a link error.
+// b. Actions and matchers can be instantiated with identical template
+//    arguments in different translation units without causing link
+//    errors.
+//    The following constructs are currently tested:
+//    Actions:
+//      Return()
+//      Return(value)
+//      ReturnNull
+//      ReturnRef
+//      Assign
+//      SetArgPointee
+//      SetArrayArgument
+//      SetErrnoAndReturn
+//      Invoke(function)
+//      Invoke(object, method)
+//      InvokeWithoutArgs(function)
+//      InvokeWithoutArgs(object, method)
+//      InvokeArgument
+//      WithArg
+//      WithArgs
+//      WithoutArgs
+//      DoAll
+//      DoDefault
+//      IgnoreResult
+//      Throw
+//      ACTION()-generated
+//      ACTION_P()-generated
+//      ACTION_P2()-generated
+//    Matchers:
+//      _
+//      A
+//      An
+//      Eq
+//      Gt, Lt, Ge, Le, Ne
+//      NotNull
+//      Ref
+//      TypedEq
+//      DoubleEq
+//      FloatEq
+//      NanSensitiveDoubleEq
+//      NanSensitiveFloatEq
+//      ContainsRegex
+//      MatchesRegex
+//      EndsWith
+//      HasSubstr
+//      StartsWith
+//      StrCaseEq
+//      StrCaseNe
+//      StrEq
+//      StrNe
+//      ElementsAre
+//      ElementsAreArray
+//      ContainerEq
+//      Field
+//      Property
+//      ResultOf(function)
+//      ResultOf(callback)
+//      Pointee
+//      Truly(predicate)
+//      AddressSatisfies
+//      AllOf
+//      AnyOf
+//      Not
+//      MatcherCast<T>
+//
+//  Please note: this test does not verify the functioning of these
+//  constructs, only that the programs using them will link successfully.
+//
+// Implementation note:
+// This test requires identical definitions of Interface and Mock to be
+// included in different translation units.  We achieve this by writing
+// them in this header and #including it in gmock_link_test.cc and
+// gmock_link2_test.cc.  Because the symbols generated by the compiler for
+// those constructs must be identical in both translation units,
+// definitions of Interface and Mock tests MUST be kept in the SAME
+// NON-ANONYMOUS namespace in this file.  The test fixture class LinkTest
+// is defined as LinkTest1 in gmock_link_test.cc and as LinkTest2 in
+// gmock_link2_test.cc to avoid producing linker errors.
+
+#ifndef GOOGLEMOCK_TEST_GMOCK_LINK_TEST_H_
+#define GOOGLEMOCK_TEST_GMOCK_LINK_TEST_H_
+
+#include "gmock/gmock.h"
+
+#ifndef GTEST_OS_WINDOWS_MOBILE
+#include <errno.h>
+#endif
+
+#include <iostream>
+#include <vector>
+
+#include "gtest/gtest.h"
+#include "gtest/internal/gtest-port.h"
+
+using testing::_;
+using testing::A;
+using testing::Action;
+using testing::AllOf;
+using testing::AnyOf;
+using testing::Assign;
+using testing::ContainerEq;
+using testing::DoAll;
+using testing::DoDefault;
+using testing::DoubleEq;
+using testing::ElementsAre;
+using testing::ElementsAreArray;
+using testing::EndsWith;
+using testing::Eq;
+using testing::Field;
+using testing::FloatEq;
+using testing::Ge;
+using testing::Gt;
+using testing::HasSubstr;
+using testing::IgnoreResult;
+using testing::Invoke;
+using testing::InvokeArgument;
+using testing::InvokeWithoutArgs;
+using testing::IsNull;
+using testing::IsSubsetOf;
+using testing::IsSupersetOf;
+using testing::Le;
+using testing::Lt;
+using testing::Matcher;
+using testing::MatcherCast;
+using testing::NanSensitiveDoubleEq;
+using testing::NanSensitiveFloatEq;
+using testing::Ne;
+using testing::Not;
+using testing::NotNull;
+using testing::Pointee;
+using testing::Property;
+using testing::Ref;
+using testing::ResultOf;
+using testing::Return;
+using testing::ReturnNull;
+using testing::ReturnRef;
+using testing::SetArgPointee;
+using testing::SetArrayArgument;
+using testing::StartsWith;
+using testing::StrCaseEq;
+using testing::StrCaseNe;
+using testing::StrEq;
+using testing::StrNe;
+using testing::Truly;
+using testing::TypedEq;
+using testing::WithArg;
+using testing::WithArgs;
+using testing::WithoutArgs;
+
+#ifndef GTEST_OS_WINDOWS_MOBILE
+using testing::SetErrnoAndReturn;
+#endif
+
+#if GTEST_HAS_EXCEPTIONS
+using testing::Throw;
+#endif
+
+using testing::ContainsRegex;
+using testing::MatchesRegex;
+
+class Interface {
+ public:
+  virtual ~Interface() = default;
+  virtual void VoidFromString(char* str) = 0;
+  virtual char* StringFromString(char* str) = 0;
+  virtual int IntFromString(char* str) = 0;
+  virtual int& IntRefFromString(char* str) = 0;
+  virtual void VoidFromFunc(void (*func)(char* str)) = 0;
+  virtual void VoidFromIntRef(int& n) = 0;  // NOLINT
+  virtual void VoidFromFloat(float n) = 0;
+  virtual void VoidFromDouble(double n) = 0;
+  virtual void VoidFromVector(const std::vector<int>& v) = 0;
+};
+
+class Mock : public Interface {
+ public:
+  Mock() = default;
+
+  MOCK_METHOD1(VoidFromString, void(char* str));
+  MOCK_METHOD1(StringFromString, char*(char* str));
+  MOCK_METHOD1(IntFromString, int(char* str));
+  MOCK_METHOD1(IntRefFromString, int&(char* str));
+  MOCK_METHOD1(VoidFromFunc, void(void (*func)(char* str)));
+  MOCK_METHOD1(VoidFromIntRef, void(int& n));  // NOLINT
+  MOCK_METHOD1(VoidFromFloat, void(float n));
+  MOCK_METHOD1(VoidFromDouble, void(double n));
+  MOCK_METHOD1(VoidFromVector, void(const std::vector<int>& v));
+
+ private:
+  Mock(const Mock&) = delete;
+  Mock& operator=(const Mock&) = delete;
+};
+
+class InvokeHelper {
+ public:
+  static void StaticVoidFromVoid() {}
+  void VoidFromVoid() {}
+  static void StaticVoidFromString(char* /* str */) {}
+  void VoidFromString(char* /* str */) {}
+  static int StaticIntFromString(char* /* str */) { return 1; }
+  static bool StaticBoolFromString(const char* /* str */) { return true; }
+};
+
+class FieldHelper {
+ public:
+  explicit FieldHelper(int a_field) : field_(a_field) {}
+  int field() const { return field_; }
+  int field_;  // NOLINT -- need external access to field_ to test
+               //           the Field matcher.
+};
+
+// Tests the linkage of the ReturnVoid action.
+TEST(LinkTest, TestReturnVoid) {
+  Mock mock;
+
+  EXPECT_CALL(mock, VoidFromString(_)).WillOnce(Return());
+  mock.VoidFromString(nullptr);
+}
+
+// Tests the linkage of the Return action.
+TEST(LinkTest, TestReturn) {
+  Mock mock;
+  char ch = 'x';
+
+  EXPECT_CALL(mock, StringFromString(_)).WillOnce(Return(&ch));
+  mock.StringFromString(nullptr);
+}
+
+// Tests the linkage of the ReturnNull action.
+TEST(LinkTest, TestReturnNull) {
+  Mock mock;
+
+  EXPECT_CALL(mock, VoidFromString(_)).WillOnce(Return());
+  mock.VoidFromString(nullptr);
+}
+
+// Tests the linkage of the ReturnRef action.
+TEST(LinkTest, TestReturnRef) {
+  Mock mock;
+  int n = 42;
+
+  EXPECT_CALL(mock, IntRefFromString(_)).WillOnce(ReturnRef(n));
+  mock.IntRefFromString(nullptr);
+}
+
+// Tests the linkage of the Assign action.
+TEST(LinkTest, TestAssign) {
+  Mock mock;
+  char ch = 'x';
+
+  EXPECT_CALL(mock, VoidFromString(_)).WillOnce(Assign(&ch, 'y'));
+  mock.VoidFromString(nullptr);
+}
+
+// Tests the linkage of the SetArgPointee action.
+TEST(LinkTest, TestSetArgPointee) {
+  Mock mock;
+  char ch = 'x';
+
+  EXPECT_CALL(mock, VoidFromString(_)).WillOnce(SetArgPointee<0>('y'));
+  mock.VoidFromString(&ch);
+}
+
+// Tests the linkage of the SetArrayArgument action.
+TEST(LinkTest, TestSetArrayArgument) {
+  Mock mock;
+  char ch = 'x';
+  char ch2 = 'y';
+
+  EXPECT_CALL(mock, VoidFromString(_))
+      .WillOnce(SetArrayArgument<0>(&ch2, &ch2 + 1));
+  mock.VoidFromString(&ch);
+}
+
+#ifndef GTEST_OS_WINDOWS_MOBILE
+
+// Tests the linkage of the SetErrnoAndReturn action.
+TEST(LinkTest, TestSetErrnoAndReturn) {
+  Mock mock;
+
+  int saved_errno = errno;
+  EXPECT_CALL(mock, IntFromString(_)).WillOnce(SetErrnoAndReturn(1, -1));
+  mock.IntFromString(nullptr);
+  errno = saved_errno;
+}
+
+#endif  // !GTEST_OS_WINDOWS_MOBILE
+
+// Tests the linkage of the Invoke(function) and Invoke(object, method) actions.
+TEST(LinkTest, TestInvoke) {
+  Mock mock;
+  InvokeHelper test_invoke_helper;
+
+  EXPECT_CALL(mock, VoidFromString(_))
+      .WillOnce(Invoke(&InvokeHelper::StaticVoidFromString))
+      .WillOnce(Invoke(&test_invoke_helper, &InvokeHelper::VoidFromString));
+  mock.VoidFromString(nullptr);
+  mock.VoidFromString(nullptr);
+}
+
+// Tests the linkage of the InvokeWithoutArgs action.
+TEST(LinkTest, TestInvokeWithoutArgs) {
+  Mock mock;
+  InvokeHelper test_invoke_helper;
+
+  EXPECT_CALL(mock, VoidFromString(_))
+      .WillOnce(InvokeWithoutArgs(&InvokeHelper::StaticVoidFromVoid))
+      .WillOnce(
+          InvokeWithoutArgs(&test_invoke_helper, &InvokeHelper::VoidFromVoid));
+  mock.VoidFromString(nullptr);
+  mock.VoidFromString(nullptr);
+}
+
+// Tests the linkage of the InvokeArgument action.
+TEST(LinkTest, TestInvokeArgument) {
+  Mock mock;
+  char ch = 'x';
+
+  EXPECT_CALL(mock, VoidFromFunc(_)).WillOnce(InvokeArgument<0>(&ch));
+  mock.VoidFromFunc(InvokeHelper::StaticVoidFromString);
+}
+
+// Tests the linkage of the WithArg action.
+TEST(LinkTest, TestWithArg) {
+  Mock mock;
+
+  EXPECT_CALL(mock, VoidFromString(_))
+      .WillOnce(WithArg<0>(Invoke(&InvokeHelper::StaticVoidFromString)));
+  mock.VoidFromString(nullptr);
+}
+
+// Tests the linkage of the WithArgs action.
+TEST(LinkTest, TestWithArgs) {
+  Mock mock;
+
+  EXPECT_CALL(mock, VoidFromString(_))
+      .WillOnce(WithArgs<0>(Invoke(&InvokeHelper::StaticVoidFromString)));
+  mock.VoidFromString(nullptr);
+}
+
+// Tests the linkage of the WithoutArgs action.
+TEST(LinkTest, TestWithoutArgs) {
+  Mock mock;
+
+  EXPECT_CALL(mock, VoidFromString(_)).WillOnce(WithoutArgs(Return()));
+  mock.VoidFromString(nullptr);
+}
+
+// Tests the linkage of the DoAll action.
+TEST(LinkTest, TestDoAll) {
+  Mock mock;
+  char ch = 'x';
+
+  EXPECT_CALL(mock, VoidFromString(_))
+      .WillOnce(DoAll(SetArgPointee<0>('y'), Return()));
+  mock.VoidFromString(&ch);
+}
+
+// Tests the linkage of the DoDefault action.
+TEST(LinkTest, TestDoDefault) {
+  Mock mock;
+  char ch = 'x';
+
+  ON_CALL(mock, VoidFromString(_)).WillByDefault(Return());
+  EXPECT_CALL(mock, VoidFromString(_)).WillOnce(DoDefault());
+  mock.VoidFromString(&ch);
+}
+
+// Tests the linkage of the IgnoreResult action.
+TEST(LinkTest, TestIgnoreResult) {
+  Mock mock;
+
+  EXPECT_CALL(mock, VoidFromString(_)).WillOnce(IgnoreResult(Return(42)));
+  mock.VoidFromString(nullptr);
+}
+
+#if GTEST_HAS_EXCEPTIONS
+// Tests the linkage of the Throw action.
+TEST(LinkTest, TestThrow) {
+  Mock mock;
+
+  EXPECT_CALL(mock, VoidFromString(_)).WillOnce(Throw(42));
+  EXPECT_THROW(mock.VoidFromString(nullptr), int);
+}
+#endif  // GTEST_HAS_EXCEPTIONS
+
+// The ACTION*() macros trigger warning C4100 (unreferenced formal
+// parameter) in MSVC with -W4.  Unfortunately they cannot be fixed in
+// the macro definition, as the warnings are generated when the macro
+// is expanded and macro expansion cannot contain #pragma.  Therefore
+// we suppress them here.
+GTEST_DISABLE_MSC_WARNINGS_PUSH_(4100)
+
+// Tests the linkage of actions created using ACTION macro.
+namespace {
+ACTION(Return1) { return 1; }
+}  // namespace
+
+TEST(LinkTest, TestActionMacro) {
+  Mock mock;
+
+  EXPECT_CALL(mock, IntFromString(_)).WillOnce(Return1());
+  mock.IntFromString(nullptr);
+}
+
+// Tests the linkage of actions created using ACTION_P macro.
+namespace {
+ACTION_P(ReturnArgument, ret_value) { return ret_value; }
+}  // namespace
+
+TEST(LinkTest, TestActionPMacro) {
+  Mock mock;
+
+  EXPECT_CALL(mock, IntFromString(_)).WillOnce(ReturnArgument(42));
+  mock.IntFromString(nullptr);
+}
+
+// Tests the linkage of actions created using ACTION_P2 macro.
+namespace {
+ACTION_P2(ReturnEqualsEitherOf, first, second) {
+  return arg0 == first || arg0 == second;
+}
+}  // namespace
+
+GTEST_DISABLE_MSC_WARNINGS_POP_()  // 4100
+
+TEST(LinkTest, TestActionP2Macro) {
+  Mock mock;
+  char ch = 'x';
+
+  EXPECT_CALL(mock, IntFromString(_))
+      .WillOnce(ReturnEqualsEitherOf("one", "two"));
+  mock.IntFromString(&ch);
+}
+
+// Tests the linkage of the "_" matcher.
+TEST(LinkTest, TestMatcherAnything) {
+  Mock mock;
+
+  ON_CALL(mock, VoidFromString(_)).WillByDefault(Return());
+}
+
+// Tests the linkage of the A matcher.
+TEST(LinkTest, TestMatcherA) {
+  Mock mock;
+
+  ON_CALL(mock, VoidFromString(A<char*>())).WillByDefault(Return());
+}
+
+// Tests the linkage of the Eq and the "bare value" matcher.
+TEST(LinkTest, TestMatchersEq) {
+  Mock mock;
+  const char* p = "x";
+
+  ON_CALL(mock, VoidFromString(Eq(p))).WillByDefault(Return());
+  ON_CALL(mock, VoidFromString(const_cast<char*>("y"))).WillByDefault(Return());
+}
+
+// Tests the linkage of the Lt, Gt, Le, Ge, and Ne matchers.
+TEST(LinkTest, TestMatchersRelations) {
+  Mock mock;
+
+  ON_CALL(mock, VoidFromFloat(Lt(1.0f))).WillByDefault(Return());
+  ON_CALL(mock, VoidFromFloat(Gt(1.0f))).WillByDefault(Return());
+  ON_CALL(mock, VoidFromFloat(Le(1.0f))).WillByDefault(Return());
+  ON_CALL(mock, VoidFromFloat(Ge(1.0f))).WillByDefault(Return());
+  ON_CALL(mock, VoidFromFloat(Ne(1.0f))).WillByDefault(Return());
+}
+
+// Tests the linkage of the NotNull matcher.
+TEST(LinkTest, TestMatcherNotNull) {
+  Mock mock;
+
+  ON_CALL(mock, VoidFromString(NotNull())).WillByDefault(Return());
+}
+
+// Tests the linkage of the IsNull matcher.
+TEST(LinkTest, TestMatcherIsNull) {
+  Mock mock;
+
+  ON_CALL(mock, VoidFromString(IsNull())).WillByDefault(Return());
+}
+
+// Tests the linkage of the Ref matcher.
+TEST(LinkTest, TestMatcherRef) {
+  Mock mock;
+  int a = 0;
+
+  ON_CALL(mock, VoidFromIntRef(Ref(a))).WillByDefault(Return());
+}
+
+// Tests the linkage of the TypedEq matcher.
+TEST(LinkTest, TestMatcherTypedEq) {
+  Mock mock;
+  long a = 0;
+
+  ON_CALL(mock, VoidFromIntRef(TypedEq<int&>(a))).WillByDefault(Return());
+}
+
+// Tests the linkage of the FloatEq, DoubleEq, NanSensitiveFloatEq and
+// NanSensitiveDoubleEq matchers.
+TEST(LinkTest, TestMatchersFloatingPoint) {
+  Mock mock;
+  float a = 0;
+
+  ON_CALL(mock, VoidFromFloat(FloatEq(a))).WillByDefault(Return());
+  ON_CALL(mock, VoidFromDouble(DoubleEq(a))).WillByDefault(Return());
+  ON_CALL(mock, VoidFromFloat(NanSensitiveFloatEq(a))).WillByDefault(Return());
+  ON_CALL(mock, VoidFromDouble(NanSensitiveDoubleEq(a)))
+      .WillByDefault(Return());
+}
+
+// Tests the linkage of the ContainsRegex matcher.
+TEST(LinkTest, TestMatcherContainsRegex) {
+  Mock mock;
+
+  ON_CALL(mock, VoidFromString(ContainsRegex(".*"))).WillByDefault(Return());
+}
+
+// Tests the linkage of the MatchesRegex matcher.
+TEST(LinkTest, TestMatcherMatchesRegex) {
+  Mock mock;
+
+  ON_CALL(mock, VoidFromString(MatchesRegex(".*"))).WillByDefault(Return());
+}
+
+// Tests the linkage of the StartsWith, EndsWith, and HasSubstr matchers.
+TEST(LinkTest, TestMatchersSubstrings) {
+  Mock mock;
+
+  ON_CALL(mock, VoidFromString(StartsWith("a"))).WillByDefault(Return());
+  ON_CALL(mock, VoidFromString(EndsWith("c"))).WillByDefault(Return());
+  ON_CALL(mock, VoidFromString(HasSubstr("b"))).WillByDefault(Return());
+}
+
+// Tests the linkage of the StrEq, StrNe, StrCaseEq, and StrCaseNe matchers.
+TEST(LinkTest, TestMatchersStringEquality) {
+  Mock mock;
+  ON_CALL(mock, VoidFromString(StrEq("a"))).WillByDefault(Return());
+  ON_CALL(mock, VoidFromString(StrNe("a"))).WillByDefault(Return());
+  ON_CALL(mock, VoidFromString(StrCaseEq("a"))).WillByDefault(Return());
+  ON_CALL(mock, VoidFromString(StrCaseNe("a"))).WillByDefault(Return());
+}
+
+// Tests the linkage of the ElementsAre matcher.
+TEST(LinkTest, TestMatcherElementsAre) {
+  Mock mock;
+
+  ON_CALL(mock, VoidFromVector(ElementsAre('a', _))).WillByDefault(Return());
+}
+
+// Tests the linkage of the ElementsAreArray matcher.
+TEST(LinkTest, TestMatcherElementsAreArray) {
+  Mock mock;
+  char arr[] = {'a', 'b'};
+
+  ON_CALL(mock, VoidFromVector(ElementsAreArray(arr))).WillByDefault(Return());
+}
+
+// Tests the linkage of the IsSubsetOf matcher.
+TEST(LinkTest, TestMatcherIsSubsetOf) {
+  Mock mock;
+  char arr[] = {'a', 'b'};
+
+  ON_CALL(mock, VoidFromVector(IsSubsetOf(arr))).WillByDefault(Return());
+}
+
+// Tests the linkage of the IsSupersetOf matcher.
+TEST(LinkTest, TestMatcherIsSupersetOf) {
+  Mock mock;
+  char arr[] = {'a', 'b'};
+
+  ON_CALL(mock, VoidFromVector(IsSupersetOf(arr))).WillByDefault(Return());
+}
+
+// Tests the linkage of the ContainerEq matcher.
+TEST(LinkTest, TestMatcherContainerEq) {
+  Mock mock;
+  std::vector<int> v;
+
+  ON_CALL(mock, VoidFromVector(ContainerEq(v))).WillByDefault(Return());
+}
+
+// Tests the linkage of the Field matcher.
+TEST(LinkTest, TestMatcherField) {
+  FieldHelper helper(0);
+
+  Matcher<const FieldHelper&> m = Field(&FieldHelper::field_, Eq(0));
+  EXPECT_TRUE(m.Matches(helper));
+
+  Matcher<const FieldHelper*> m2 = Field(&FieldHelper::field_, Eq(0));
+  EXPECT_TRUE(m2.Matches(&helper));
+}
+
+// Tests the linkage of the Property matcher.
+TEST(LinkTest, TestMatcherProperty) {
+  FieldHelper helper(0);
+
+  Matcher<const FieldHelper&> m = Property(&FieldHelper::field, Eq(0));
+  EXPECT_TRUE(m.Matches(helper));
+
+  Matcher<const FieldHelper*> m2 = Property(&FieldHelper::field, Eq(0));
+  EXPECT_TRUE(m2.Matches(&helper));
+}
+
+// Tests the linkage of the ResultOf matcher.
+TEST(LinkTest, TestMatcherResultOf) {
+  Matcher<char*> m = ResultOf(&InvokeHelper::StaticIntFromString, Eq(1));
+  EXPECT_TRUE(m.Matches(nullptr));
+}
+
+// Tests the linkage of the ResultOf matcher.
+TEST(LinkTest, TestMatcherPointee) {
+  int n = 1;
+
+  Matcher<int*> m = Pointee(Eq(1));
+  EXPECT_TRUE(m.Matches(&n));
+}
+
+// Tests the linkage of the Truly matcher.
+TEST(LinkTest, TestMatcherTruly) {
+  Matcher<const char*> m = Truly(&InvokeHelper::StaticBoolFromString);
+  EXPECT_TRUE(m.Matches(nullptr));
+}
+
+// Tests the linkage of the AllOf matcher.
+TEST(LinkTest, TestMatcherAllOf) {
+  Matcher<int> m = AllOf(_, Eq(1));
+  EXPECT_TRUE(m.Matches(1));
+}
+
+// Tests the linkage of the AnyOf matcher.
+TEST(LinkTest, TestMatcherAnyOf) {
+  Matcher<int> m = AnyOf(_, Eq(1));
+  EXPECT_TRUE(m.Matches(1));
+}
+
+// Tests the linkage of the Not matcher.
+TEST(LinkTest, TestMatcherNot) {
+  Matcher<int> m = Not(_);
+  EXPECT_FALSE(m.Matches(1));
+}
+
+// Tests the linkage of the MatcherCast<T>() function.
+TEST(LinkTest, TestMatcherCast) {
+  Matcher<const char*> m = MatcherCast<const char*>(_);
+  EXPECT_TRUE(m.Matches(nullptr));
+}
+
+#endif  // GOOGLEMOCK_TEST_GMOCK_LINK_TEST_H_
diff --git a/third_party/googletest/googlemock/test/gmock_output_test.py b/third_party/googletest/googlemock/test/gmock_output_test.py
new file mode 100755
index 0000000..7c24d68
--- /dev/null
+++ b/third_party/googletest/googlemock/test/gmock_output_test.py
@@ -0,0 +1,190 @@
+#!/usr/bin/env python
+#
+# Copyright 2008, Google Inc.
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+r"""Tests the text output of Google C++ Mocking Framework.
+
+To update the golden file:
+gmock_output_test.py --build_dir=BUILD/DIR --gengolden
+where BUILD/DIR contains the built gmock_output_test_ file.
+gmock_output_test.py --gengolden
+gmock_output_test.py
+
+"""
+
+from io import open  # pylint: disable=redefined-builtin, g-importing-member
+import os
+import re
+import sys
+from googlemock.test import gmock_test_utils
+
+
+# The flag for generating the golden file
+GENGOLDEN_FLAG = '--gengolden'
+
+PROGRAM_PATH = gmock_test_utils.GetTestExecutablePath('gmock_output_test_')
+COMMAND = [PROGRAM_PATH, '--gtest_stack_trace_depth=0', '--gtest_print_time=0']
+GOLDEN_NAME = 'gmock_output_test_golden.txt'
+GOLDEN_PATH = os.path.join(gmock_test_utils.GetSourceDir(), GOLDEN_NAME)
+
+
+def ToUnixLineEnding(s):
+  """Changes all Windows/Mac line endings in s to UNIX line endings."""
+
+  return s.replace('\r\n', '\n').replace('\r', '\n')
+
+
+def RemoveReportHeaderAndFooter(output):
+  """Removes Google Test result report's header and footer from the output."""
+
+  output = re.sub(r'.*gtest_main.*\n', '', output)
+  output = re.sub(r'\[.*\d+ tests.*\n', '', output)
+  output = re.sub(r'\[.* test environment .*\n', '', output)
+  output = re.sub(r'\[=+\] \d+ tests .* ran.*', '', output)
+  output = re.sub(r'.* FAILED TESTS\n', '', output)
+  return output
+
+
+def RemoveLocations(output):
+  """Removes all file location info from a Google Test program's output.
+
+  Args:
+       output:  the output of a Google Test program.
+
+  Returns:
+       output with all file location info (in the form of
+       'DIRECTORY/FILE_NAME:LINE_NUMBER: 'or
+       'DIRECTORY\\FILE_NAME(LINE_NUMBER): ') replaced by
+       'FILE:#: '.
+  """
+
+  return re.sub(r'.*[/\\](.+)(\:\d+|\(\d+\))\:', 'FILE:#:', output)
+
+
+def NormalizeErrorMarker(output):
+  """Normalizes the error marker, which is different on Windows vs on Linux."""
+
+  return re.sub(r' error: ', ' Failure\n', output)
+
+
+def RemoveMemoryAddresses(output):
+  """Removes memory addresses from the test output."""
+
+  return re.sub(r'@\w+', '@0x#', output)
+
+
+def RemoveTestNamesOfLeakedMocks(output):
+  """Removes the test names of leaked mock objects from the test output."""
+
+  return re.sub(r'\(used in test .+\) ', '', output)
+
+
+def GetLeakyTests(output):
+  """Returns a list of test names that leak mock objects."""
+
+  # findall() returns a list of all matches of the regex in output.
+  # For example, if '(used in test FooTest.Bar)' is in output, the
+  # list will contain 'FooTest.Bar'.
+  return re.findall(r'\(used in test (.+)\)', output)
+
+
+def GetNormalizedOutputAndLeakyTests(output):
+  """Normalizes the output of gmock_output_test_.
+
+  Args:
+    output: The test output.
+
+  Returns:
+    A tuple (the normalized test output, the list of test names that have
+    leaked mocks).
+  """
+
+  output = ToUnixLineEnding(output)
+  output = RemoveReportHeaderAndFooter(output)
+  output = NormalizeErrorMarker(output)
+  output = RemoveLocations(output)
+  output = RemoveMemoryAddresses(output)
+  return (RemoveTestNamesOfLeakedMocks(output), GetLeakyTests(output))
+
+
+def GetShellCommandOutput(cmd):
+  """Runs a command in a sub-process, and returns its STDOUT in a string."""
+
+  return gmock_test_utils.Subprocess(cmd, capture_stderr=False).output
+
+
+def GetNormalizedCommandOutputAndLeakyTests(cmd):
+  """Runs a command and returns its normalized output and a list of leaky tests.
+
+  Args:
+    cmd:  the shell command.
+  """
+
+  # Disables exception pop-ups on Windows.
+  os.environ['GTEST_CATCH_EXCEPTIONS'] = '1'
+  return GetNormalizedOutputAndLeakyTests(GetShellCommandOutput(cmd))
+
+
+class GMockOutputTest(gmock_test_utils.TestCase):
+
+  def testOutput(self):
+    (output, leaky_tests) = GetNormalizedCommandOutputAndLeakyTests(COMMAND)
+    golden_file = open(GOLDEN_PATH, 'rb')
+    golden = golden_file.read().decode('utf-8')
+    golden_file.close()
+    # On Windows the repository might have been checked out with \r\n line
+    # endings, so normalize it here.
+    golden = ToUnixLineEnding(golden)
+
+    # The normalized output should match the golden file.
+    self.assertEqual(golden, output)
+
+    # The raw output should contain 2 leaked mock object errors for
+    # test GMockOutputTest.CatchesLeakedMocks.
+    self.assertEqual(
+        [
+            'GMockOutputTest.CatchesLeakedMocks',
+            'GMockOutputTest.CatchesLeakedMocks',
+        ],
+        leaky_tests,
+    )
+
+
+if __name__ == '__main__':
+  if sys.argv[1:] == [GENGOLDEN_FLAG]:
+    (output, _) = GetNormalizedCommandOutputAndLeakyTests(COMMAND)
+    golden_file = open(GOLDEN_PATH, 'wb')
+    golden_file.write(output)
+    golden_file.close()
+    # Suppress the error "googletest was imported but a call to its main()
+    # was never detected."
+    os._exit(0)
+  else:
+    gmock_test_utils.Main()
diff --git a/third_party/googletest/googlemock/test/gmock_output_test_.cc b/third_party/googletest/googlemock/test/gmock_output_test_.cc
new file mode 100644
index 0000000..03d8421
--- /dev/null
+++ b/third_party/googletest/googlemock/test/gmock_output_test_.cc
@@ -0,0 +1,286 @@
+// Copyright 2008, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Tests Google Mock's output in various scenarios.  This ensures that
+// Google Mock's messages are readable and useful.
+
+#include <stdio.h>
+
+#include <string>
+
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+
+// Silence C4100 (unreferenced formal parameter)
+GTEST_DISABLE_MSC_WARNINGS_PUSH_(4100)
+
+using testing::_;
+using testing::AnyNumber;
+using testing::Ge;
+using testing::InSequence;
+using testing::NaggyMock;
+using testing::Ref;
+using testing::Return;
+using testing::Sequence;
+using testing::Value;
+
+class MockFoo {
+ public:
+  MockFoo() = default;
+
+  MOCK_METHOD3(Bar, char(const std::string& s, int i, double x));
+  MOCK_METHOD2(Bar2, bool(int x, int y));
+  MOCK_METHOD2(Bar3, void(int x, int y));
+
+ private:
+  MockFoo(const MockFoo&) = delete;
+  MockFoo& operator=(const MockFoo&) = delete;
+};
+
+class GMockOutputTest : public testing::Test {
+ protected:
+  NaggyMock<MockFoo> foo_;
+};
+
+TEST_F(GMockOutputTest, ExpectedCall) {
+  GMOCK_FLAG_SET(verbose, "info");
+
+  EXPECT_CALL(foo_, Bar2(0, _));
+  foo_.Bar2(0, 0);  // Expected call
+
+  GMOCK_FLAG_SET(verbose, "warning");
+}
+
+TEST_F(GMockOutputTest, ExpectedCallToVoidFunction) {
+  GMOCK_FLAG_SET(verbose, "info");
+
+  EXPECT_CALL(foo_, Bar3(0, _));
+  foo_.Bar3(0, 0);  // Expected call
+
+  GMOCK_FLAG_SET(verbose, "warning");
+}
+
+TEST_F(GMockOutputTest, ExplicitActionsRunOut) {
+  EXPECT_CALL(foo_, Bar2(_, _)).Times(2).WillOnce(Return(false));
+  foo_.Bar2(2, 2);
+  foo_.Bar2(1, 1);  // Explicit actions in EXPECT_CALL run out.
+}
+
+TEST_F(GMockOutputTest, UnexpectedCall) {
+  EXPECT_CALL(foo_, Bar2(0, _));
+
+  foo_.Bar2(1, 0);  // Unexpected call
+  foo_.Bar2(0, 0);  // Expected call
+}
+
+TEST_F(GMockOutputTest, UnexpectedCallToVoidFunction) {
+  EXPECT_CALL(foo_, Bar3(0, _));
+
+  foo_.Bar3(1, 0);  // Unexpected call
+  foo_.Bar3(0, 0);  // Expected call
+}
+
+TEST_F(GMockOutputTest, ExcessiveCall) {
+  EXPECT_CALL(foo_, Bar2(0, _));
+
+  foo_.Bar2(0, 0);  // Expected call
+  foo_.Bar2(0, 1);  // Excessive call
+}
+
+TEST_F(GMockOutputTest, ExcessiveCallToVoidFunction) {
+  EXPECT_CALL(foo_, Bar3(0, _));
+
+  foo_.Bar3(0, 0);  // Expected call
+  foo_.Bar3(0, 1);  // Excessive call
+}
+
+TEST_F(GMockOutputTest, UninterestingCall) {
+  foo_.Bar2(0, 1);  // Uninteresting call
+}
+
+TEST_F(GMockOutputTest, UninterestingCallToVoidFunction) {
+  foo_.Bar3(0, 1);  // Uninteresting call
+}
+
+TEST_F(GMockOutputTest, RetiredExpectation) {
+  EXPECT_CALL(foo_, Bar2(_, _)).RetiresOnSaturation();
+  EXPECT_CALL(foo_, Bar2(0, 0));
+
+  foo_.Bar2(1, 1);
+  foo_.Bar2(1, 1);  // Matches a retired expectation
+  foo_.Bar2(0, 0);
+}
+
+TEST_F(GMockOutputTest, UnsatisfiedPrerequisite) {
+  {
+    InSequence s;
+    EXPECT_CALL(foo_, Bar(_, 0, _));
+    EXPECT_CALL(foo_, Bar2(0, 0));
+    EXPECT_CALL(foo_, Bar2(1, _));
+  }
+
+  foo_.Bar2(1, 0);  // Has one immediate unsatisfied pre-requisite
+  foo_.Bar("Hi", 0, 0);
+  foo_.Bar2(0, 0);
+  foo_.Bar2(1, 0);
+}
+
+TEST_F(GMockOutputTest, UnsatisfiedPrerequisites) {
+  Sequence s1, s2;
+
+  EXPECT_CALL(foo_, Bar(_, 0, _)).InSequence(s1);
+  EXPECT_CALL(foo_, Bar2(0, 0)).InSequence(s2);
+  EXPECT_CALL(foo_, Bar2(1, _)).InSequence(s1, s2);
+
+  foo_.Bar2(1, 0);  // Has two immediate unsatisfied pre-requisites
+  foo_.Bar("Hi", 0, 0);
+  foo_.Bar2(0, 0);
+  foo_.Bar2(1, 0);
+}
+
+TEST_F(GMockOutputTest, UnsatisfiedWith) {
+  EXPECT_CALL(foo_, Bar2(_, _)).With(Ge());
+}
+
+TEST_F(GMockOutputTest, UnsatisfiedExpectation) {
+  EXPECT_CALL(foo_, Bar(_, _, _));
+  EXPECT_CALL(foo_, Bar2(0, _)).Times(2);
+
+  foo_.Bar2(0, 1);
+}
+
+TEST_F(GMockOutputTest, MismatchArguments) {
+  const std::string s = "Hi";
+  EXPECT_CALL(foo_, Bar(Ref(s), _, Ge(0)));
+
+  foo_.Bar("Ho", 0, -0.1);  // Mismatch arguments
+  foo_.Bar(s, 0, 0);
+}
+
+TEST_F(GMockOutputTest, MismatchWith) {
+  EXPECT_CALL(foo_, Bar2(Ge(2), Ge(1))).With(Ge());
+
+  foo_.Bar2(2, 3);  // Mismatch With()
+  foo_.Bar2(2, 1);
+}
+
+TEST_F(GMockOutputTest, MismatchArgumentsAndWith) {
+  EXPECT_CALL(foo_, Bar2(Ge(2), Ge(1))).With(Ge());
+
+  foo_.Bar2(1, 3);  // Mismatch arguments and mismatch With()
+  foo_.Bar2(2, 1);
+}
+
+TEST_F(GMockOutputTest, UnexpectedCallWithDefaultAction) {
+  ON_CALL(foo_, Bar2(_, _)).WillByDefault(Return(true));   // Default action #1
+  ON_CALL(foo_, Bar2(1, _)).WillByDefault(Return(false));  // Default action #2
+
+  EXPECT_CALL(foo_, Bar2(2, 2));
+  foo_.Bar2(1, 0);  // Unexpected call, takes default action #2.
+  foo_.Bar2(0, 0);  // Unexpected call, takes default action #1.
+  foo_.Bar2(2, 2);  // Expected call.
+}
+
+TEST_F(GMockOutputTest, ExcessiveCallWithDefaultAction) {
+  ON_CALL(foo_, Bar2(_, _)).WillByDefault(Return(true));   // Default action #1
+  ON_CALL(foo_, Bar2(1, _)).WillByDefault(Return(false));  // Default action #2
+
+  EXPECT_CALL(foo_, Bar2(2, 2));
+  EXPECT_CALL(foo_, Bar2(1, 1));
+
+  foo_.Bar2(2, 2);  // Expected call.
+  foo_.Bar2(2, 2);  // Excessive call, takes default action #1.
+  foo_.Bar2(1, 1);  // Expected call.
+  foo_.Bar2(1, 1);  // Excessive call, takes default action #2.
+}
+
+TEST_F(GMockOutputTest, UninterestingCallWithDefaultAction) {
+  ON_CALL(foo_, Bar2(_, _)).WillByDefault(Return(true));   // Default action #1
+  ON_CALL(foo_, Bar2(1, _)).WillByDefault(Return(false));  // Default action #2
+
+  foo_.Bar2(2, 2);  // Uninteresting call, takes default action #1.
+  foo_.Bar2(1, 1);  // Uninteresting call, takes default action #2.
+}
+
+TEST_F(GMockOutputTest, ExplicitActionsRunOutWithDefaultAction) {
+  ON_CALL(foo_, Bar2(_, _)).WillByDefault(Return(true));  // Default action #1
+
+  EXPECT_CALL(foo_, Bar2(_, _)).Times(2).WillOnce(Return(false));
+  foo_.Bar2(2, 2);
+  foo_.Bar2(1, 1);  // Explicit actions in EXPECT_CALL run out.
+}
+
+TEST_F(GMockOutputTest, CatchesLeakedMocks) {
+  MockFoo* foo1 = new MockFoo;
+  MockFoo* foo2 = new MockFoo;
+
+  // Invokes ON_CALL on foo1.
+  ON_CALL(*foo1, Bar(_, _, _)).WillByDefault(Return('a'));
+
+  // Invokes EXPECT_CALL on foo2.
+  EXPECT_CALL(*foo2, Bar2(_, _));
+  EXPECT_CALL(*foo2, Bar2(1, _));
+  EXPECT_CALL(*foo2, Bar3(_, _)).Times(AnyNumber());
+  foo2->Bar2(2, 1);
+  foo2->Bar2(1, 1);
+
+  // Both foo1 and foo2 are deliberately leaked.
+}
+
+MATCHER_P2(IsPair, first, second, "") {
+  return Value(arg.first, first) && Value(arg.second, second);
+}
+
+TEST_F(GMockOutputTest, PrintsMatcher) {
+  const testing::Matcher<int> m1 = Ge(48);
+  EXPECT_THAT((std::pair<int, bool>(42, true)), IsPair(m1, true));
+}
+
+void TestCatchesLeakedMocksInAdHocTests() {
+  MockFoo* foo = new MockFoo;
+
+  // Invokes EXPECT_CALL on foo.
+  EXPECT_CALL(*foo, Bar2(_, _));
+  foo->Bar2(2, 1);
+
+  // foo is deliberately leaked.
+}
+
+int main(int argc, char** argv) {
+  testing::InitGoogleMock(&argc, argv);
+  // Ensures that the tests pass no matter what value of
+  // --gmock_catch_leaked_mocks and --gmock_verbose the user specifies.
+  GMOCK_FLAG_SET(catch_leaked_mocks, true);
+  GMOCK_FLAG_SET(verbose, "warning");
+
+  TestCatchesLeakedMocksInAdHocTests();
+  return RUN_ALL_TESTS();
+}
+
+GTEST_DISABLE_MSC_WARNINGS_POP_()  // 4100
diff --git a/third_party/googletest/googlemock/test/gmock_output_test_golden.txt b/third_party/googletest/googlemock/test/gmock_output_test_golden.txt
new file mode 100644
index 0000000..ca88af0
--- /dev/null
+++ b/third_party/googletest/googlemock/test/gmock_output_test_golden.txt
@@ -0,0 +1,335 @@
+[ RUN      ] GMockOutputTest.ExpectedCall
+
+FILE:#: EXPECT_CALL(foo_, Bar2(0, _)) invoked
+Stack trace:
+
+FILE:#: Mock function call matches EXPECT_CALL(foo_, Bar2(0, _))...
+    Function call: Bar2(0, 0)
+          Returns: false
+Stack trace:
+[       OK ] GMockOutputTest.ExpectedCall
+[ RUN      ] GMockOutputTest.ExpectedCallToVoidFunction
+
+FILE:#: EXPECT_CALL(foo_, Bar3(0, _)) invoked
+Stack trace:
+
+FILE:#: Mock function call matches EXPECT_CALL(foo_, Bar3(0, _))...
+    Function call: Bar3(0, 0)
+Stack trace:
+[       OK ] GMockOutputTest.ExpectedCallToVoidFunction
+[ RUN      ] GMockOutputTest.ExplicitActionsRunOut
+
+GMOCK WARNING:
+FILE:#: Too few actions specified in EXPECT_CALL(foo_, Bar2(_, _))...
+Expected to be called twice, but has only 1 WillOnce().
+GMOCK WARNING:
+FILE:#: Actions ran out in EXPECT_CALL(foo_, Bar2(_, _))...
+Called 2 times, but only 1 WillOnce() is specified - returning default value.
+Stack trace:
+[       OK ] GMockOutputTest.ExplicitActionsRunOut
+[ RUN      ] GMockOutputTest.UnexpectedCall
+unknown file: Failure
+
+Unexpected mock function call - returning default value.
+    Function call: Bar2(1, 0)
+          Returns: false
+Google Mock tried the following 1 expectation, but it didn't match:
+
+FILE:#: EXPECT_CALL(foo_, Bar2(0, _))...
+  Expected arg #0: is equal to 0
+           Actual: 1
+         Expected: to be called once
+           Actual: never called - unsatisfied and active
+
+[  FAILED  ] GMockOutputTest.UnexpectedCall
+[ RUN      ] GMockOutputTest.UnexpectedCallToVoidFunction
+unknown file: Failure
+
+Unexpected mock function call - returning directly.
+    Function call: Bar3(1, 0)
+Google Mock tried the following 1 expectation, but it didn't match:
+
+FILE:#: EXPECT_CALL(foo_, Bar3(0, _))...
+  Expected arg #0: is equal to 0
+           Actual: 1
+         Expected: to be called once
+           Actual: never called - unsatisfied and active
+
+[  FAILED  ] GMockOutputTest.UnexpectedCallToVoidFunction
+[ RUN      ] GMockOutputTest.ExcessiveCall
+FILE:#: Failure
+Mock function called more times than expected - returning default value.
+    Function call: Bar2(0, 1)
+          Returns: false
+         Expected: to be called once
+           Actual: called twice - over-saturated and active
+
+[  FAILED  ] GMockOutputTest.ExcessiveCall
+[ RUN      ] GMockOutputTest.ExcessiveCallToVoidFunction
+FILE:#: Failure
+Mock function called more times than expected - returning directly.
+    Function call: Bar3(0, 1)
+         Expected: to be called once
+           Actual: called twice - over-saturated and active
+
+[  FAILED  ] GMockOutputTest.ExcessiveCallToVoidFunction
+[ RUN      ] GMockOutputTest.UninterestingCall
+
+GMOCK WARNING:
+Uninteresting mock function call - returning default value.
+    Function call: Bar2(0, 1)
+          Returns: false
+NOTE: You can safely ignore the above warning unless this call should not happen.  Do not suppress it by blindly adding an EXPECT_CALL() if you don't mean to enforce the call.  See https://github.com/google/googletest/blob/main/docs/gmock_cook_book.md#knowing-when-to-expect-useoncall for details.
+[       OK ] GMockOutputTest.UninterestingCall
+[ RUN      ] GMockOutputTest.UninterestingCallToVoidFunction
+
+GMOCK WARNING:
+Uninteresting mock function call - returning directly.
+    Function call: Bar3(0, 1)
+NOTE: You can safely ignore the above warning unless this call should not happen.  Do not suppress it by blindly adding an EXPECT_CALL() if you don't mean to enforce the call.  See https://github.com/google/googletest/blob/main/docs/gmock_cook_book.md#knowing-when-to-expect-useoncall for details.
+[       OK ] GMockOutputTest.UninterestingCallToVoidFunction
+[ RUN      ] GMockOutputTest.RetiredExpectation
+unknown file: Failure
+
+Unexpected mock function call - returning default value.
+    Function call: Bar2(1, 1)
+          Returns: false
+Google Mock tried the following 2 expectations, but none matched:
+
+FILE:#: tried expectation #0: EXPECT_CALL(foo_, Bar2(_, _))...
+         Expected: the expectation is active
+           Actual: it is retired
+         Expected: to be called once
+           Actual: called once - saturated and retired
+FILE:#: tried expectation #1: EXPECT_CALL(foo_, Bar2(0, 0))...
+  Expected arg #0: is equal to 0
+           Actual: 1
+  Expected arg #1: is equal to 0
+           Actual: 1
+         Expected: to be called once
+           Actual: never called - unsatisfied and active
+
+[  FAILED  ] GMockOutputTest.RetiredExpectation
+[ RUN      ] GMockOutputTest.UnsatisfiedPrerequisite
+unknown file: Failure
+
+Unexpected mock function call - returning default value.
+    Function call: Bar2(1, 0)
+          Returns: false
+Google Mock tried the following 2 expectations, but none matched:
+
+FILE:#: tried expectation #0: EXPECT_CALL(foo_, Bar2(0, 0))...
+  Expected arg #0: is equal to 0
+           Actual: 1
+         Expected: to be called once
+           Actual: never called - unsatisfied and active
+FILE:#: tried expectation #1: EXPECT_CALL(foo_, Bar2(1, _))...
+         Expected: all pre-requisites are satisfied
+           Actual: the following immediate pre-requisites are not satisfied:
+FILE:#: pre-requisite #0
+                   (end of pre-requisites)
+         Expected: to be called once
+           Actual: never called - unsatisfied and active
+
+[  FAILED  ] GMockOutputTest.UnsatisfiedPrerequisite
+[ RUN      ] GMockOutputTest.UnsatisfiedPrerequisites
+unknown file: Failure
+
+Unexpected mock function call - returning default value.
+    Function call: Bar2(1, 0)
+          Returns: false
+Google Mock tried the following 2 expectations, but none matched:
+
+FILE:#: tried expectation #0: EXPECT_CALL(foo_, Bar2(0, 0))...
+  Expected arg #0: is equal to 0
+           Actual: 1
+         Expected: to be called once
+           Actual: never called - unsatisfied and active
+FILE:#: tried expectation #1: EXPECT_CALL(foo_, Bar2(1, _))...
+         Expected: all pre-requisites are satisfied
+           Actual: the following immediate pre-requisites are not satisfied:
+FILE:#: pre-requisite #0
+FILE:#: pre-requisite #1
+                   (end of pre-requisites)
+         Expected: to be called once
+           Actual: never called - unsatisfied and active
+
+[  FAILED  ] GMockOutputTest.UnsatisfiedPrerequisites
+[ RUN      ] GMockOutputTest.UnsatisfiedWith
+FILE:#: Failure
+Actual function call count doesn't match EXPECT_CALL(foo_, Bar2(_, _))...
+    Expected args: are a pair where the first >= the second
+         Expected: to be called once
+           Actual: never called - unsatisfied and active
+
+[  FAILED  ] GMockOutputTest.UnsatisfiedWith
+[ RUN      ] GMockOutputTest.UnsatisfiedExpectation
+FILE:#: Failure
+Actual function call count doesn't match EXPECT_CALL(foo_, Bar2(0, _))...
+         Expected: to be called twice
+           Actual: called once - unsatisfied and active
+
+FILE:#: Failure
+Actual function call count doesn't match EXPECT_CALL(foo_, Bar(_, _, _))...
+         Expected: to be called once
+           Actual: never called - unsatisfied and active
+
+[  FAILED  ] GMockOutputTest.UnsatisfiedExpectation
+[ RUN      ] GMockOutputTest.MismatchArguments
+unknown file: Failure
+
+Unexpected mock function call - returning default value.
+    Function call: Bar(@0x# "Ho", 0, -0.1)
+          Returns: '\0'
+Google Mock tried the following 1 expectation, but it didn't match:
+
+FILE:#: EXPECT_CALL(foo_, Bar(Ref(s), _, Ge(0)))...
+  Expected arg #0: references the variable @0x# "Hi"
+           Actual: "Ho", which is located @0x#
+  Expected arg #2: is >= 0
+           Actual: -0.1
+         Expected: to be called once
+           Actual: never called - unsatisfied and active
+
+[  FAILED  ] GMockOutputTest.MismatchArguments
+[ RUN      ] GMockOutputTest.MismatchWith
+unknown file: Failure
+
+Unexpected mock function call - returning default value.
+    Function call: Bar2(2, 3)
+          Returns: false
+Google Mock tried the following 1 expectation, but it didn't match:
+
+FILE:#: EXPECT_CALL(foo_, Bar2(Ge(2), Ge(1)))...
+    Expected args: are a pair where the first >= the second
+           Actual: don't match
+         Expected: to be called once
+           Actual: never called - unsatisfied and active
+
+[  FAILED  ] GMockOutputTest.MismatchWith
+[ RUN      ] GMockOutputTest.MismatchArgumentsAndWith
+unknown file: Failure
+
+Unexpected mock function call - returning default value.
+    Function call: Bar2(1, 3)
+          Returns: false
+Google Mock tried the following 1 expectation, but it didn't match:
+
+FILE:#: EXPECT_CALL(foo_, Bar2(Ge(2), Ge(1)))...
+  Expected arg #0: is >= 2
+           Actual: 1
+    Expected args: are a pair where the first >= the second
+           Actual: don't match
+         Expected: to be called once
+           Actual: never called - unsatisfied and active
+
+[  FAILED  ] GMockOutputTest.MismatchArgumentsAndWith
+[ RUN      ] GMockOutputTest.UnexpectedCallWithDefaultAction
+unknown file: Failure
+
+Unexpected mock function call - taking default action specified at:
+FILE:#:
+    Function call: Bar2(1, 0)
+          Returns: false
+Google Mock tried the following 1 expectation, but it didn't match:
+
+FILE:#: EXPECT_CALL(foo_, Bar2(2, 2))...
+  Expected arg #0: is equal to 2
+           Actual: 1
+  Expected arg #1: is equal to 2
+           Actual: 0
+         Expected: to be called once
+           Actual: never called - unsatisfied and active
+
+unknown file: Failure
+
+Unexpected mock function call - taking default action specified at:
+FILE:#:
+    Function call: Bar2(0, 0)
+          Returns: true
+Google Mock tried the following 1 expectation, but it didn't match:
+
+FILE:#: EXPECT_CALL(foo_, Bar2(2, 2))...
+  Expected arg #0: is equal to 2
+           Actual: 0
+  Expected arg #1: is equal to 2
+           Actual: 0
+         Expected: to be called once
+           Actual: never called - unsatisfied and active
+
+[  FAILED  ] GMockOutputTest.UnexpectedCallWithDefaultAction
+[ RUN      ] GMockOutputTest.ExcessiveCallWithDefaultAction
+FILE:#: Failure
+Mock function called more times than expected - taking default action specified at:
+FILE:#:
+    Function call: Bar2(2, 2)
+          Returns: true
+         Expected: to be called once
+           Actual: called twice - over-saturated and active
+
+FILE:#: Failure
+Mock function called more times than expected - taking default action specified at:
+FILE:#:
+    Function call: Bar2(1, 1)
+          Returns: false
+         Expected: to be called once
+           Actual: called twice - over-saturated and active
+
+[  FAILED  ] GMockOutputTest.ExcessiveCallWithDefaultAction
+[ RUN      ] GMockOutputTest.UninterestingCallWithDefaultAction
+
+GMOCK WARNING:
+Uninteresting mock function call - taking default action specified at:
+FILE:#:
+    Function call: Bar2(2, 2)
+          Returns: true
+NOTE: You can safely ignore the above warning unless this call should not happen.  Do not suppress it by blindly adding an EXPECT_CALL() if you don't mean to enforce the call.  See https://github.com/google/googletest/blob/main/docs/gmock_cook_book.md#knowing-when-to-expect-useoncall for details.
+
+GMOCK WARNING:
+Uninteresting mock function call - taking default action specified at:
+FILE:#:
+    Function call: Bar2(1, 1)
+          Returns: false
+NOTE: You can safely ignore the above warning unless this call should not happen.  Do not suppress it by blindly adding an EXPECT_CALL() if you don't mean to enforce the call.  See https://github.com/google/googletest/blob/main/docs/gmock_cook_book.md#knowing-when-to-expect-useoncall for details.
+[       OK ] GMockOutputTest.UninterestingCallWithDefaultAction
+[ RUN      ] GMockOutputTest.ExplicitActionsRunOutWithDefaultAction
+
+GMOCK WARNING:
+FILE:#: Too few actions specified in EXPECT_CALL(foo_, Bar2(_, _))...
+Expected to be called twice, but has only 1 WillOnce().
+GMOCK WARNING:
+FILE:#: Actions ran out in EXPECT_CALL(foo_, Bar2(_, _))...
+Called 2 times, but only 1 WillOnce() is specified - taking default action specified at:
+FILE:#:
+Stack trace:
+[       OK ] GMockOutputTest.ExplicitActionsRunOutWithDefaultAction
+[ RUN      ] GMockOutputTest.CatchesLeakedMocks
+[       OK ] GMockOutputTest.CatchesLeakedMocks
+[ RUN      ] GMockOutputTest.PrintsMatcher
+FILE:#: Failure
+Value of: (std::pair<int, bool>(42, true))
+Expected: is pair (first: is >= 48, second: true)
+  Actual: (42, true) (of type std::pair<int,bool>)
+
+[  FAILED  ] GMockOutputTest.PrintsMatcher
+[  FAILED  ] GMockOutputTest.UnexpectedCall
+[  FAILED  ] GMockOutputTest.UnexpectedCallToVoidFunction
+[  FAILED  ] GMockOutputTest.ExcessiveCall
+[  FAILED  ] GMockOutputTest.ExcessiveCallToVoidFunction
+[  FAILED  ] GMockOutputTest.RetiredExpectation
+[  FAILED  ] GMockOutputTest.UnsatisfiedPrerequisite
+[  FAILED  ] GMockOutputTest.UnsatisfiedPrerequisites
+[  FAILED  ] GMockOutputTest.UnsatisfiedWith
+[  FAILED  ] GMockOutputTest.UnsatisfiedExpectation
+[  FAILED  ] GMockOutputTest.MismatchArguments
+[  FAILED  ] GMockOutputTest.MismatchWith
+[  FAILED  ] GMockOutputTest.MismatchArgumentsAndWith
+[  FAILED  ] GMockOutputTest.UnexpectedCallWithDefaultAction
+[  FAILED  ] GMockOutputTest.ExcessiveCallWithDefaultAction
+[  FAILED  ] GMockOutputTest.PrintsMatcher
+
+
+FILE:#: ERROR: this mock object should be deleted but never is. Its address is @0x#.
+FILE:#: ERROR: this mock object should be deleted but never is. Its address is @0x#.
+FILE:#: ERROR: this mock object should be deleted but never is. Its address is @0x#.
+ERROR: 3 leaked mock objects found at program exit. Expectations on a mock object are verified when the object is destructed. Leaking a mock means that its expectations aren't verified, which is usually a test bug. If you really intend to leak a mock, you can suppress this error using testing::Mock::AllowLeak(mock_object), or you may use a fake or stub instead of a mock.
diff --git a/third_party/googletest/googlemock/test/gmock_stress_test.cc b/third_party/googletest/googlemock/test/gmock_stress_test.cc
new file mode 100644
index 0000000..9e42cd9
--- /dev/null
+++ b/third_party/googletest/googlemock/test/gmock_stress_test.cc
@@ -0,0 +1,227 @@
+// Copyright 2007, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Tests that Google Mock constructs can be used in a large number of
+// threads concurrently.
+
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+
+namespace testing {
+namespace {
+
+// From gtest-port.h.
+using ::testing::internal::ThreadWithParam;
+
+// The maximum number of test threads (not including helper threads)
+// to create.
+const int kMaxTestThreads = 50;
+
+// How many times to repeat a task in a test thread.
+const int kRepeat = 50;
+
+class MockFoo {
+ public:
+  MOCK_METHOD1(Bar, int(int n));                                   // NOLINT
+  MOCK_METHOD2(Baz, char(const char* s1, const std::string& s2));  // NOLINT
+};
+
+// Helper for waiting for the given thread to finish and then deleting it.
+template <typename T>
+void JoinAndDelete(ThreadWithParam<T>* t) {
+  t->Join();
+  delete t;
+}
+
+struct Dummy {};
+
+// Tests that different mock objects can be used in their respective
+// threads.  This should generate no Google Test failure.
+void TestConcurrentMockObjects(Dummy /* dummy */) {
+  // Creates a mock and does some typical operations on it.
+  MockFoo foo;
+  ON_CALL(foo, Bar(_)).WillByDefault(Return(1));
+  ON_CALL(foo, Baz(_, _)).WillByDefault(Return('b'));
+  ON_CALL(foo, Baz(_, "you")).WillByDefault(Return('a'));
+
+  EXPECT_CALL(foo, Bar(0)).Times(AtMost(3));
+  EXPECT_CALL(foo, Baz(_, _));
+  EXPECT_CALL(foo, Baz("hi", "you"))
+      .WillOnce(Return('z'))
+      .WillRepeatedly(DoDefault());
+
+  EXPECT_EQ(1, foo.Bar(0));
+  EXPECT_EQ(1, foo.Bar(0));
+  EXPECT_EQ('z', foo.Baz("hi", "you"));
+  EXPECT_EQ('a', foo.Baz("hi", "you"));
+  EXPECT_EQ('b', foo.Baz("hi", "me"));
+}
+
+// Tests invoking methods of the same mock object in multiple threads.
+
+struct Helper1Param {
+  MockFoo* mock_foo;
+  int* count;
+};
+
+void Helper1(Helper1Param param) {
+  for (int i = 0; i < kRepeat; i++) {
+    const char ch = param.mock_foo->Baz("a", "b");
+    if (ch == 'a') {
+      // It was an expected call.
+      (*param.count)++;
+    } else {
+      // It was an excessive call.
+      EXPECT_EQ('\0', ch);
+    }
+
+    // An unexpected call.
+    EXPECT_EQ('\0', param.mock_foo->Baz("x", "y")) << "Expected failure.";
+
+    // An uninteresting call.
+    EXPECT_EQ(1, param.mock_foo->Bar(5));
+  }
+}
+
+// This should generate 3*kRepeat + 1 failures in total.
+void TestConcurrentCallsOnSameObject(Dummy /* dummy */) {
+  MockFoo foo;
+
+  ON_CALL(foo, Bar(_)).WillByDefault(Return(1));
+  EXPECT_CALL(foo, Baz(_, "b")).Times(kRepeat).WillRepeatedly(Return('a'));
+  EXPECT_CALL(foo, Baz(_, "c"));  // Expected to be unsatisfied.
+
+  // This chunk of code should generate kRepeat failures about
+  // excessive calls, and 2*kRepeat failures about unexpected calls.
+  int count1 = 0;
+  const Helper1Param param = {&foo, &count1};
+  ThreadWithParam<Helper1Param>* const t =
+      new ThreadWithParam<Helper1Param>(Helper1, param, nullptr);
+
+  int count2 = 0;
+  const Helper1Param param2 = {&foo, &count2};
+  Helper1(param2);
+  JoinAndDelete(t);
+
+  EXPECT_EQ(kRepeat, count1 + count2);
+
+  // foo's destructor should generate one failure about unsatisfied
+  // expectation.
+}
+
+// Tests using the same mock object in multiple threads when the
+// expectations are partially ordered.
+
+void Helper2(MockFoo* foo) {
+  for (int i = 0; i < kRepeat; i++) {
+    foo->Bar(2);
+    foo->Bar(3);
+  }
+}
+
+// This should generate no Google Test failures.
+void TestPartiallyOrderedExpectationsWithThreads(Dummy /* dummy */) {
+  MockFoo foo;
+  Sequence s1, s2;
+
+  {
+    InSequence dummy;
+    EXPECT_CALL(foo, Bar(0));
+    EXPECT_CALL(foo, Bar(1)).InSequence(s1, s2);
+  }
+
+  EXPECT_CALL(foo, Bar(2))
+      .Times(2 * kRepeat)
+      .InSequence(s1)
+      .RetiresOnSaturation();
+  EXPECT_CALL(foo, Bar(3)).Times(2 * kRepeat).InSequence(s2);
+
+  {
+    InSequence dummy;
+    EXPECT_CALL(foo, Bar(2)).InSequence(s1, s2);
+    EXPECT_CALL(foo, Bar(4));
+  }
+
+  foo.Bar(0);
+  foo.Bar(1);
+
+  ThreadWithParam<MockFoo*>* const t =
+      new ThreadWithParam<MockFoo*>(Helper2, &foo, nullptr);
+  Helper2(&foo);
+  JoinAndDelete(t);
+
+  foo.Bar(2);
+  foo.Bar(4);
+}
+
+// Tests using Google Mock constructs in many threads concurrently.
+TEST(StressTest, CanUseGMockWithThreads) {
+  void (*test_routines[])(Dummy dummy) = {
+      &TestConcurrentMockObjects,
+      &TestConcurrentCallsOnSameObject,
+      &TestPartiallyOrderedExpectationsWithThreads,
+  };
+
+  const int kRoutines = sizeof(test_routines) / sizeof(test_routines[0]);
+  const int kCopiesOfEachRoutine = kMaxTestThreads / kRoutines;
+  const int kTestThreads = kCopiesOfEachRoutine * kRoutines;
+  ThreadWithParam<Dummy>* threads[kTestThreads] = {};
+  for (int i = 0; i < kTestThreads; i++) {
+    // Creates a thread to run the test function.
+    threads[i] = new ThreadWithParam<Dummy>(test_routines[i % kRoutines],
+                                            Dummy(), nullptr);
+    GTEST_LOG_(INFO) << "Thread #" << i << " running . . .";
+  }
+
+  // At this point, we have many threads running.
+  for (int i = 0; i < kTestThreads; i++) {
+    JoinAndDelete(threads[i]);
+  }
+
+  // Ensures that the correct number of failures have been reported.
+  const TestInfo* const info = UnitTest::GetInstance()->current_test_info();
+  const TestResult& result = *info->result();
+  const int kExpectedFailures = (3 * kRepeat + 1) * kCopiesOfEachRoutine;
+  GTEST_CHECK_(kExpectedFailures == result.total_part_count())
+      << "Expected " << kExpectedFailures << " failures, but got "
+      << result.total_part_count();
+}
+
+}  // namespace
+}  // namespace testing
+
+int main(int argc, char** argv) {
+  testing::InitGoogleMock(&argc, argv);
+
+  const int exit_code = RUN_ALL_TESTS();  // Expected to fail.
+  GTEST_CHECK_(exit_code != 0) << "RUN_ALL_TESTS() did not fail as expected";
+
+  printf("\nPASS\n");
+  return 0;
+}
diff --git a/third_party/googletest/googlemock/test/gmock_test.cc b/third_party/googletest/googlemock/test/gmock_test.cc
new file mode 100644
index 0000000..8cfff30
--- /dev/null
+++ b/third_party/googletest/googlemock/test/gmock_test.cc
@@ -0,0 +1,179 @@
+// Copyright 2008, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Google Mock - a framework for writing C++ mock classes.
+//
+// This file tests code in gmock.cc.
+
+#include "gmock/gmock.h"
+
+#include <string>
+
+#include "gtest/gtest.h"
+#include "gtest/internal/custom/gtest.h"
+
+#if !defined(GTEST_CUSTOM_INIT_GOOGLE_TEST_FUNCTION_)
+
+using testing::InitGoogleMock;
+
+// Verifies that calling InitGoogleMock() on argv results in new_argv,
+// and the gmock_verbose flag's value is set to expected_gmock_verbose.
+template <typename Char, int M, int N>
+void TestInitGoogleMock(const Char* (&argv)[M], const Char* (&new_argv)[N],
+                        const ::std::string& expected_gmock_verbose) {
+  const ::std::string old_verbose = GMOCK_FLAG_GET(verbose);
+
+  int argc = M - 1;
+  InitGoogleMock(&argc, const_cast<Char**>(argv));
+  ASSERT_EQ(N - 1, argc) << "The new argv has wrong number of elements.";
+
+  for (int i = 0; i < N; i++) {
+    EXPECT_STREQ(new_argv[i], argv[i]);
+  }
+
+  EXPECT_EQ(expected_gmock_verbose, GMOCK_FLAG_GET(verbose));
+  GMOCK_FLAG_SET(verbose, old_verbose);  // Restores the gmock_verbose flag.
+}
+
+TEST(InitGoogleMockTest, ParsesInvalidCommandLine) {
+  const char* argv[] = {nullptr};
+
+  const char* new_argv[] = {nullptr};
+
+  TestInitGoogleMock(argv, new_argv, GMOCK_FLAG_GET(verbose));
+}
+
+TEST(InitGoogleMockTest, ParsesEmptyCommandLine) {
+  const char* argv[] = {"foo.exe", nullptr};
+
+  const char* new_argv[] = {"foo.exe", nullptr};
+
+  TestInitGoogleMock(argv, new_argv, GMOCK_FLAG_GET(verbose));
+}
+
+TEST(InitGoogleMockTest, ParsesSingleFlag) {
+  const char* argv[] = {"foo.exe", "--gmock_verbose=info", nullptr};
+
+  const char* new_argv[] = {"foo.exe", nullptr};
+
+  TestInitGoogleMock(argv, new_argv, "info");
+}
+
+TEST(InitGoogleMockTest, ParsesMultipleFlags) {
+  int old_default_behavior = GMOCK_FLAG_GET(default_mock_behavior);
+  const wchar_t* argv[] = {L"foo.exe", L"--gmock_verbose=info",
+                           L"--gmock_default_mock_behavior=2", nullptr};
+
+  const wchar_t* new_argv[] = {L"foo.exe", nullptr};
+
+  TestInitGoogleMock(argv, new_argv, "info");
+  EXPECT_EQ(2, GMOCK_FLAG_GET(default_mock_behavior));
+  EXPECT_NE(2, old_default_behavior);
+  GMOCK_FLAG_SET(default_mock_behavior, old_default_behavior);
+}
+
+TEST(InitGoogleMockTest, ParsesUnrecognizedFlag) {
+  const char* argv[] = {"foo.exe", "--non_gmock_flag=blah", nullptr};
+
+  const char* new_argv[] = {"foo.exe", "--non_gmock_flag=blah", nullptr};
+
+  TestInitGoogleMock(argv, new_argv, GMOCK_FLAG_GET(verbose));
+}
+
+TEST(InitGoogleMockTest, ParsesGoogleMockFlagAndUnrecognizedFlag) {
+  const char* argv[] = {"foo.exe", "--non_gmock_flag=blah",
+                        "--gmock_verbose=error", nullptr};
+
+  const char* new_argv[] = {"foo.exe", "--non_gmock_flag=blah", nullptr};
+
+  TestInitGoogleMock(argv, new_argv, "error");
+}
+
+TEST(WideInitGoogleMockTest, ParsesInvalidCommandLine) {
+  const wchar_t* argv[] = {nullptr};
+
+  const wchar_t* new_argv[] = {nullptr};
+
+  TestInitGoogleMock(argv, new_argv, GMOCK_FLAG_GET(verbose));
+}
+
+TEST(WideInitGoogleMockTest, ParsesEmptyCommandLine) {
+  const wchar_t* argv[] = {L"foo.exe", nullptr};
+
+  const wchar_t* new_argv[] = {L"foo.exe", nullptr};
+
+  TestInitGoogleMock(argv, new_argv, GMOCK_FLAG_GET(verbose));
+}
+
+TEST(WideInitGoogleMockTest, ParsesSingleFlag) {
+  const wchar_t* argv[] = {L"foo.exe", L"--gmock_verbose=info", nullptr};
+
+  const wchar_t* new_argv[] = {L"foo.exe", nullptr};
+
+  TestInitGoogleMock(argv, new_argv, "info");
+}
+
+TEST(WideInitGoogleMockTest, ParsesMultipleFlags) {
+  int old_default_behavior = GMOCK_FLAG_GET(default_mock_behavior);
+  const wchar_t* argv[] = {L"foo.exe", L"--gmock_verbose=info",
+                           L"--gmock_default_mock_behavior=2", nullptr};
+
+  const wchar_t* new_argv[] = {L"foo.exe", nullptr};
+
+  TestInitGoogleMock(argv, new_argv, "info");
+  EXPECT_EQ(2, GMOCK_FLAG_GET(default_mock_behavior));
+  EXPECT_NE(2, old_default_behavior);
+  GMOCK_FLAG_SET(default_mock_behavior, old_default_behavior);
+}
+
+TEST(WideInitGoogleMockTest, ParsesUnrecognizedFlag) {
+  const wchar_t* argv[] = {L"foo.exe", L"--non_gmock_flag=blah", nullptr};
+
+  const wchar_t* new_argv[] = {L"foo.exe", L"--non_gmock_flag=blah", nullptr};
+
+  TestInitGoogleMock(argv, new_argv, GMOCK_FLAG_GET(verbose));
+}
+
+TEST(WideInitGoogleMockTest, ParsesGoogleMockFlagAndUnrecognizedFlag) {
+  const wchar_t* argv[] = {L"foo.exe", L"--non_gmock_flag=blah",
+                           L"--gmock_verbose=error", nullptr};
+
+  const wchar_t* new_argv[] = {L"foo.exe", L"--non_gmock_flag=blah", nullptr};
+
+  TestInitGoogleMock(argv, new_argv, "error");
+}
+
+#endif  // !defined(GTEST_CUSTOM_INIT_GOOGLE_TEST_FUNCTION_)
+
+// Makes sure Google Mock flags can be accessed in code.
+TEST(FlagTest, IsAccessibleInCode) {
+  bool dummy =
+      GMOCK_FLAG_GET(catch_leaked_mocks) && GMOCK_FLAG_GET(verbose).empty();
+  (void)dummy;  // Avoids the "unused local variable" warning.
+}
diff --git a/third_party/googletest/googlemock/test/gmock_test_utils.py b/third_party/googletest/googlemock/test/gmock_test_utils.py
new file mode 100755
index 0000000..edad1f7
--- /dev/null
+++ b/third_party/googletest/googlemock/test/gmock_test_utils.py
@@ -0,0 +1,91 @@
+# Copyright 2006, Google Inc.
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"""Unit test utilities for Google C++ Mocking Framework."""
+
+import os
+
+# pylint: disable=C6204
+from googletest.test import gtest_test_utils
+
+
+def GetSourceDir():
+  """Returns the absolute path of the directory where the .py files are."""
+
+  return gtest_test_utils.GetSourceDir()
+
+
+def GetTestExecutablePath(executable_name):
+  """Returns the absolute path of the test binary given its name.
+
+  The function will print a message and abort the program if the resulting file
+  doesn't exist.
+
+  Args:
+    executable_name: name of the test binary that the test script runs.
+
+  Returns:
+    The absolute path of the test binary.
+  """
+
+  return gtest_test_utils.GetTestExecutablePath(executable_name)
+
+
+def GetExitStatus(exit_code):
+  """Returns the argument to exit(), or -1 if exit() wasn't called.
+
+  Args:
+    exit_code: the result value of os.system(command).
+  """
+
+  if os.name == 'nt':
+    # On Windows, os.WEXITSTATUS() doesn't work and os.system() returns
+    # the argument to exit() directly.
+    return exit_code
+  else:
+    # On Unix, os.WEXITSTATUS() must be used to extract the exit status
+    # from the result of os.system().
+    if os.WIFEXITED(exit_code):
+      return os.WEXITSTATUS(exit_code)
+    else:
+      return -1
+
+
+# Exposes utilities from gtest_test_utils.
+Subprocess = gtest_test_utils.Subprocess
+TestCase = gtest_test_utils.TestCase
+environ = gtest_test_utils.environ
+SetEnvVar = gtest_test_utils.SetEnvVar
+PREMATURE_EXIT_FILE_ENV_VAR = gtest_test_utils.PREMATURE_EXIT_FILE_ENV_VAR
+
+
+def Main():
+  """Runs the unit test."""
+
+  gtest_test_utils.Main()
diff --git a/third_party/googletest/googletest/CMakeLists.txt b/third_party/googletest/googletest/CMakeLists.txt
new file mode 100644
index 0000000..caafa8c
--- /dev/null
+++ b/third_party/googletest/googletest/CMakeLists.txt
@@ -0,0 +1,330 @@
+########################################################################
+# Note: CMake support is community-based. The maintainers do not use CMake
+# internally.
+#
+# CMake build script for Google Test.
+#
+# To run the tests for Google Test itself on Linux, use 'make test' or
+# ctest.  You can select which tests to run using 'ctest -R regex'.
+# For more options, run 'ctest --help'.
+
+# When other libraries are using a shared version of runtime libraries,
+# Google Test also has to use one.
+option(
+  gtest_force_shared_crt
+  "Use shared (DLL) run-time lib even when Google Test is built as static lib."
+  OFF)
+
+option(gtest_build_tests "Build all of gtest's own tests." OFF)
+
+option(gtest_build_samples "Build gtest's sample programs." OFF)
+
+option(gtest_disable_pthreads "Disable uses of pthreads in gtest." OFF)
+
+option(
+  gtest_hide_internal_symbols
+  "Build gtest with internal symbols hidden in shared libraries."
+  OFF)
+
+# Defines pre_project_set_up_hermetic_build() and set_up_hermetic_build().
+include(cmake/hermetic_build.cmake OPTIONAL)
+
+if (COMMAND pre_project_set_up_hermetic_build)
+  pre_project_set_up_hermetic_build()
+endif()
+
+########################################################################
+#
+# Project-wide settings
+
+# Name of the project.
+#
+# CMake files in this project can refer to the root source directory
+# as ${gtest_SOURCE_DIR} and to the root binary directory as
+# ${gtest_BINARY_DIR}.
+# Language "C" is required for find_package(Threads).
+
+# Project version:
+
+cmake_minimum_required(VERSION 3.13)
+project(gtest VERSION ${GOOGLETEST_VERSION} LANGUAGES CXX C)
+
+if (COMMAND set_up_hermetic_build)
+  set_up_hermetic_build()
+endif()
+
+# These commands only run if this is the main project
+if(CMAKE_PROJECT_NAME STREQUAL "gtest" OR CMAKE_PROJECT_NAME STREQUAL "googletest-distribution")
+
+  # BUILD_SHARED_LIBS is a standard CMake variable, but we declare it here to
+  # make it prominent in the GUI.
+  option(BUILD_SHARED_LIBS "Build shared libraries (DLLs)." OFF)
+
+else()
+
+  mark_as_advanced(
+    gtest_force_shared_crt
+    gtest_build_tests
+    gtest_build_samples
+    gtest_disable_pthreads
+    gtest_hide_internal_symbols)
+
+endif()
+
+
+if (gtest_hide_internal_symbols)
+  set(CMAKE_CXX_VISIBILITY_PRESET hidden)
+  set(CMAKE_VISIBILITY_INLINES_HIDDEN 1)
+endif()
+
+# Define helper functions and macros used by Google Test.
+include(cmake/internal_utils.cmake)
+
+config_compiler_and_linker()  # Defined in internal_utils.cmake.
+
+# Needed to set the namespace for both the export targets and the
+# alias libraries
+set(cmake_package_name GTest CACHE INTERNAL "")
+
+# Create the CMake package file descriptors.
+if (INSTALL_GTEST)
+  include(CMakePackageConfigHelpers)
+  set(targets_export_name ${cmake_package_name}Targets CACHE INTERNAL "")
+  set(generated_dir "${CMAKE_CURRENT_BINARY_DIR}/generated" CACHE INTERNAL "")
+  set(cmake_files_install_dir "${CMAKE_INSTALL_LIBDIR}/cmake/${cmake_package_name}")
+  set(version_file "${generated_dir}/${cmake_package_name}ConfigVersion.cmake")
+  write_basic_package_version_file(${version_file} VERSION ${GOOGLETEST_VERSION} COMPATIBILITY AnyNewerVersion)
+  install(EXPORT ${targets_export_name}
+    COMPONENT "${PROJECT_NAME}"
+    NAMESPACE ${cmake_package_name}::
+    DESTINATION ${cmake_files_install_dir})
+  set(config_file "${generated_dir}/${cmake_package_name}Config.cmake")
+  configure_package_config_file("${gtest_SOURCE_DIR}/cmake/Config.cmake.in"
+    "${config_file}" INSTALL_DESTINATION ${cmake_files_install_dir})
+  install(FILES ${version_file} ${config_file}
+    COMPONENT "${PROJECT_NAME}"
+    DESTINATION ${cmake_files_install_dir})
+endif()
+
+# Where Google Test's .h files can be found.
+set(gtest_build_include_dirs
+  "${gtest_SOURCE_DIR}/include"
+  "${gtest_SOURCE_DIR}")
+include_directories(${gtest_build_include_dirs})
+
+########################################################################
+#
+# Defines the gtest & gtest_main libraries.  User tests should link
+# with one of them.
+
+# Google Test libraries.  We build them using more strict warnings than what
+# are used for other targets, to ensure that gtest can be compiled by a user
+# aggressive about warnings.
+cxx_library(gtest "${cxx_strict}" src/gtest-all.cc)
+set_target_properties(gtest PROPERTIES VERSION ${GOOGLETEST_VERSION})
+if(GTEST_HAS_ABSL)
+  target_compile_definitions(gtest PUBLIC GTEST_HAS_ABSL=1)
+  target_link_libraries(gtest PUBLIC
+    absl::failure_signal_handler
+    absl::stacktrace
+    absl::symbolize
+    absl::flags_parse
+    absl::flags_reflection
+    absl::flags_usage
+    absl::strings
+    absl::any
+    absl::optional
+    absl::variant
+    re2::re2
+  )
+endif()
+cxx_library(gtest_main "${cxx_strict}" src/gtest_main.cc)
+set_target_properties(gtest_main PROPERTIES VERSION ${GOOGLETEST_VERSION})
+string(REPLACE ";" "$<SEMICOLON>" dirs "${gtest_build_include_dirs}")
+target_include_directories(gtest SYSTEM INTERFACE
+  "$<BUILD_INTERFACE:${dirs}>"
+  "$<INSTALL_INTERFACE:$<INSTALL_PREFIX>/${CMAKE_INSTALL_INCLUDEDIR}>")
+target_include_directories(gtest_main SYSTEM INTERFACE
+  "$<BUILD_INTERFACE:${dirs}>"
+  "$<INSTALL_INTERFACE:$<INSTALL_PREFIX>/${CMAKE_INSTALL_INCLUDEDIR}>")
+if(CMAKE_SYSTEM_NAME MATCHES "QNX")
+  target_link_libraries(gtest PUBLIC regex)
+endif()
+target_link_libraries(gtest_main PUBLIC gtest)
+
+########################################################################
+#
+# Install rules
+install_project(gtest gtest_main)
+
+########################################################################
+#
+# Samples on how to link user tests with gtest or gtest_main.
+#
+# They are not built by default.  To build them, set the
+# gtest_build_samples option to ON.  You can do it by running ccmake
+# or specifying the -Dgtest_build_samples=ON flag when running cmake.
+
+if (gtest_build_samples)
+  cxx_executable(sample1_unittest samples gtest_main samples/sample1.cc)
+  cxx_executable(sample2_unittest samples gtest_main samples/sample2.cc)
+  cxx_executable(sample3_unittest samples gtest_main)
+  cxx_executable(sample4_unittest samples gtest_main samples/sample4.cc)
+  cxx_executable(sample5_unittest samples gtest_main samples/sample1.cc)
+  cxx_executable(sample6_unittest samples gtest_main)
+  cxx_executable(sample7_unittest samples gtest_main)
+  cxx_executable(sample8_unittest samples gtest_main)
+  cxx_executable(sample9_unittest samples gtest)
+  cxx_executable(sample10_unittest samples gtest)
+endif()
+
+########################################################################
+#
+# Google Test's own tests.
+#
+# You can skip this section if you aren't interested in testing
+# Google Test itself.
+#
+# The tests are not built by default.  To build them, set the
+# gtest_build_tests option to ON.  You can do it by running ccmake
+# or specifying the -Dgtest_build_tests=ON flag when running cmake.
+
+if (gtest_build_tests)
+  # This must be set in the root directory for the tests to be run by
+  # 'make test' or ctest.
+  enable_testing()
+
+  ############################################################
+  # C++ tests built with standard compiler flags.
+
+  cxx_test(googletest-death-test-test gtest_main)
+  cxx_test(gtest_environment_test gtest)
+  cxx_test(googletest-filepath-test gtest_main)
+  cxx_test(googletest-listener-test gtest_main)
+  cxx_test(gtest_main_unittest gtest_main)
+  cxx_test(googletest-message-test gtest_main)
+  cxx_test(gtest_no_test_unittest gtest)
+  cxx_test(googletest-options-test gtest_main)
+  cxx_test(googletest-param-test-test gtest
+    test/googletest-param-test2-test.cc)
+  cxx_test(googletest-port-test gtest_main)
+  cxx_test(gtest_pred_impl_unittest gtest_main)
+  cxx_test(gtest_premature_exit_test gtest
+    test/gtest_premature_exit_test.cc)
+  cxx_test(googletest-printers-test gtest_main)
+  cxx_test(gtest_prod_test gtest_main
+    test/production.cc)
+  cxx_test(gtest_repeat_test gtest)
+  cxx_test(gtest_sole_header_test gtest_main)
+  cxx_test(gtest_stress_test gtest)
+  cxx_test(googletest-test-part-test gtest_main)
+  cxx_test(gtest_throw_on_failure_ex_test gtest)
+  cxx_test(gtest-typed-test_test gtest_main
+    test/gtest-typed-test2_test.cc)
+  cxx_test(gtest_unittest gtest_main)
+  cxx_test(gtest-unittest-api_test gtest)
+  cxx_test(gtest_skip_in_environment_setup_test gtest_main)
+  cxx_test(gtest_skip_test gtest_main)
+
+  ############################################################
+  # C++ tests built with non-standard compiler flags.
+
+  # MSVC 7.1 does not support STL with exceptions disabled.
+  if (NOT MSVC OR MSVC_VERSION GREATER 1310)
+    cxx_library(gtest_no_exception "${cxx_no_exception}"
+      src/gtest-all.cc)
+    cxx_library(gtest_main_no_exception "${cxx_no_exception}"
+      src/gtest-all.cc src/gtest_main.cc)
+  endif()
+  cxx_library(gtest_main_no_rtti "${cxx_no_rtti}"
+    src/gtest-all.cc src/gtest_main.cc)
+
+  cxx_test_with_flags(gtest-death-test_ex_nocatch_test
+    "${cxx_exception} -DGTEST_ENABLE_CATCH_EXCEPTIONS_=0"
+    gtest test/googletest-death-test_ex_test.cc)
+  cxx_test_with_flags(gtest-death-test_ex_catch_test
+    "${cxx_exception} -DGTEST_ENABLE_CATCH_EXCEPTIONS_=1"
+    gtest test/googletest-death-test_ex_test.cc)
+
+  cxx_test_with_flags(gtest_no_rtti_unittest "${cxx_no_rtti}"
+    gtest_main_no_rtti test/gtest_unittest.cc)
+
+  cxx_shared_library(gtest_dll "${cxx_default}"
+    src/gtest-all.cc src/gtest_main.cc)
+
+  cxx_executable_with_flags(gtest_dll_test_ "${cxx_default}"
+    gtest_dll test/gtest_all_test.cc)
+  set_target_properties(gtest_dll_test_
+                        PROPERTIES
+                        COMPILE_DEFINITIONS "GTEST_LINKED_AS_SHARED_LIBRARY=1")
+
+  ############################################################
+  # Python tests.
+
+  cxx_executable(googletest-break-on-failure-unittest_ test gtest)
+  py_test(googletest-break-on-failure-unittest)
+
+  py_test(gtest_skip_check_output_test)
+  py_test(gtest_skip_environment_check_output_test)
+
+  # Visual Studio .NET 2003 does not support STL with exceptions disabled.
+  if (NOT MSVC OR MSVC_VERSION GREATER 1310)  # 1310 is Visual Studio .NET 2003
+    cxx_executable_with_flags(
+      googletest-catch-exceptions-no-ex-test_
+      "${cxx_no_exception}"
+      gtest_main_no_exception
+      test/googletest-catch-exceptions-test_.cc)
+  endif()
+
+  cxx_executable_with_flags(
+    googletest-catch-exceptions-ex-test_
+    "${cxx_exception}"
+    gtest_main
+    test/googletest-catch-exceptions-test_.cc)
+  py_test(googletest-catch-exceptions-test)
+
+  cxx_executable(googletest-color-test_ test gtest)
+  py_test(googletest-color-test)
+
+  cxx_executable(googletest-env-var-test_ test gtest)
+  py_test(googletest-env-var-test)
+
+  cxx_executable(googletest-filter-unittest_ test gtest)
+  py_test(googletest-filter-unittest)
+
+  cxx_executable(gtest_help_test_ test gtest_main)
+  py_test(gtest_help_test)
+
+  cxx_executable(googletest-list-tests-unittest_ test gtest)
+  py_test(googletest-list-tests-unittest)
+
+  cxx_executable(googletest-output-test_ test gtest)
+  py_test(googletest-output-test --no_stacktrace_support)
+
+  cxx_executable(googletest-shuffle-test_ test gtest)
+  py_test(googletest-shuffle-test)
+
+  # MSVC 7.1 does not support STL with exceptions disabled.
+  if (NOT MSVC OR MSVC_VERSION GREATER 1310)
+    cxx_executable(googletest-throw-on-failure-test_ test gtest_no_exception)
+    set_target_properties(googletest-throw-on-failure-test_
+      PROPERTIES
+      COMPILE_FLAGS "${cxx_no_exception}")
+    py_test(googletest-throw-on-failure-test)
+  endif()
+
+  cxx_executable(googletest-uninitialized-test_ test gtest)
+  py_test(googletest-uninitialized-test)
+
+  cxx_executable(gtest_list_output_unittest_ test gtest)
+  py_test(gtest_list_output_unittest)
+
+  cxx_executable(gtest_xml_outfile1_test_ test gtest_main)
+  cxx_executable(gtest_xml_outfile2_test_ test gtest_main)
+  py_test(gtest_xml_outfiles_test)
+  py_test(googletest-json-outfiles-test)
+
+  cxx_executable(gtest_xml_output_unittest_ test gtest)
+  py_test(gtest_xml_output_unittest --no_stacktrace_support)
+  py_test(googletest-json-output-unittest --no_stacktrace_support)
+endif()
diff --git a/third_party/googletest/googletest/README.md b/third_party/googletest/googletest/README.md
new file mode 100644
index 0000000..44fd69b
--- /dev/null
+++ b/third_party/googletest/googletest/README.md
@@ -0,0 +1,231 @@
+### Generic Build Instructions
+
+#### Setup
+
+To build GoogleTest and your tests that use it, you need to tell your build
+system where to find its headers and source files. The exact way to do it
+depends on which build system you use, and is usually straightforward.
+
+### Build with CMake
+
+GoogleTest comes with a CMake build script
+([CMakeLists.txt](https://github.com/google/googletest/blob/main/CMakeLists.txt))
+that can be used on a wide range of platforms ("C" stands for cross-platform.).
+If you don't have CMake installed already, you can download it for free from
+<https://cmake.org/>.
+
+CMake works by generating native makefiles or build projects that can be used in
+the compiler environment of your choice. You can either build GoogleTest as a
+standalone project or it can be incorporated into an existing CMake build for
+another project.
+
+#### Standalone CMake Project
+
+When building GoogleTest as a standalone project, the typical workflow starts
+with
+
+```
+git clone https://github.com/google/googletest.git -b v1.14.0
+cd googletest        # Main directory of the cloned repository.
+mkdir build          # Create a directory to hold the build output.
+cd build
+cmake ..             # Generate native build scripts for GoogleTest.
+```
+
+The above command also includes GoogleMock by default. And so, if you want to
+build only GoogleTest, you should replace the last command with
+
+```
+cmake .. -DBUILD_GMOCK=OFF
+```
+
+If you are on a \*nix system, you should now see a Makefile in the current
+directory. Just type `make` to build GoogleTest. And then you can simply install
+GoogleTest if you are a system administrator.
+
+```
+make
+sudo make install    # Install in /usr/local/ by default
+```
+
+If you use Windows and have Visual Studio installed, a `gtest.sln` file and
+several `.vcproj` files will be created. You can then build them using Visual
+Studio.
+
+On Mac OS X with Xcode installed, a `.xcodeproj` file will be generated.
+
+#### Incorporating Into An Existing CMake Project
+
+If you want to use GoogleTest in a project which already uses CMake, the easiest
+way is to get installed libraries and headers.
+
+*   Import GoogleTest by using `find_package` (or `pkg_check_modules`). For
+    example, if `find_package(GTest CONFIG REQUIRED)` succeeds, you can use the
+    libraries as `GTest::gtest`, `GTest::gmock`.
+
+And a more robust and flexible approach is to build GoogleTest as part of that
+project directly. This is done by making the GoogleTest source code available to
+the main build and adding it using CMake's `add_subdirectory()` command. This
+has the significant advantage that the same compiler and linker settings are
+used between GoogleTest and the rest of your project, so issues associated with
+using incompatible libraries (eg debug/release), etc. are avoided. This is
+particularly useful on Windows. Making GoogleTest's source code available to the
+main build can be done a few different ways:
+
+*   Download the GoogleTest source code manually and place it at a known
+    location. This is the least flexible approach and can make it more difficult
+    to use with continuous integration systems, etc.
+*   Embed the GoogleTest source code as a direct copy in the main project's
+    source tree. This is often the simplest approach, but is also the hardest to
+    keep up to date. Some organizations may not permit this method.
+*   Add GoogleTest as a git submodule or equivalent. This may not always be
+    possible or appropriate. Git submodules, for example, have their own set of
+    advantages and drawbacks.
+*   Use CMake to download GoogleTest as part of the build's configure step. This
+    approach doesn't have the limitations of the other methods.
+
+The last of the above methods is implemented with a small piece of CMake code
+that downloads and pulls the GoogleTest code into the main build.
+
+Just add to your `CMakeLists.txt`:
+
+```cmake
+include(FetchContent)
+FetchContent_Declare(
+  googletest
+  # Specify the commit you depend on and update it regularly.
+  URL https://github.com/google/googletest/archive/5376968f6948923e2411081fd9372e71a59d8e77.zip
+)
+# For Windows: Prevent overriding the parent project's compiler/linker settings
+set(gtest_force_shared_crt ON CACHE BOOL "" FORCE)
+FetchContent_MakeAvailable(googletest)
+
+# Now simply link against gtest or gtest_main as needed. Eg
+add_executable(example example.cpp)
+target_link_libraries(example gtest_main)
+add_test(NAME example_test COMMAND example)
+```
+
+Note that this approach requires CMake 3.14 or later due to its use of the
+`FetchContent_MakeAvailable()` command.
+
+##### Visual Studio Dynamic vs Static Runtimes
+
+By default, new Visual Studio projects link the C runtimes dynamically but
+GoogleTest links them statically. This will generate an error that looks
+something like the following: gtest.lib(gtest-all.obj) : error LNK2038: mismatch
+detected for 'RuntimeLibrary': value 'MTd_StaticDebug' doesn't match value
+'MDd_DynamicDebug' in main.obj
+
+GoogleTest already has a CMake option for this: `gtest_force_shared_crt`
+
+Enabling this option will make gtest link the runtimes dynamically too, and
+match the project in which it is included.
+
+#### C++ Standard Version
+
+An environment that supports C++14 is required in order to successfully build
+GoogleTest. One way to ensure this is to specify the standard in the top-level
+project, for example by using the `set(CMAKE_CXX_STANDARD 14)` command along
+with `set(CMAKE_CXX_STANDARD_REQUIRED ON)`. If this is not feasible, for example
+in a C project using GoogleTest for validation, then it can be specified by
+adding it to the options for cmake via the`-DCMAKE_CXX_FLAGS` option.
+
+### Tweaking GoogleTest
+
+GoogleTest can be used in diverse environments. The default configuration may
+not work (or may not work well) out of the box in some environments. However,
+you can easily tweak GoogleTest by defining control macros on the compiler
+command line. Generally, these macros are named like `GTEST_XYZ` and you define
+them to either 1 or 0 to enable or disable a certain feature.
+
+We list the most frequently used macros below. For a complete list, see file
+[include/gtest/internal/gtest-port.h](https://github.com/google/googletest/blob/main/googletest/include/gtest/internal/gtest-port.h).
+
+### Multi-threaded Tests
+
+GoogleTest is thread-safe where the pthread library is available. After
+`#include <gtest/gtest.h>`, you can check the
+`GTEST_IS_THREADSAFE` macro to see whether this is the case (yes if the macro is
+`#defined` to 1, no if it's undefined.).
+
+If GoogleTest doesn't correctly detect whether pthread is available in your
+environment, you can force it with
+
+```
+-DGTEST_HAS_PTHREAD=1
+```
+
+or
+
+```
+-DGTEST_HAS_PTHREAD=0
+```
+
+When GoogleTest uses pthread, you may need to add flags to your compiler and/or
+linker to select the pthread library, or you'll get link errors. If you use the
+CMake script, this is taken care of for you. If you use your own build script,
+you'll need to read your compiler and linker's manual to figure out what flags
+to add.
+
+### As a Shared Library (DLL)
+
+GoogleTest is compact, so most users can build and link it as a static library
+for the simplicity. You can choose to use GoogleTest as a shared library (known
+as a DLL on Windows) if you prefer.
+
+To compile *gtest* as a shared library, add
+
+```
+-DGTEST_CREATE_SHARED_LIBRARY=1
+```
+
+to the compiler flags. You'll also need to tell the linker to produce a shared
+library instead - consult your linker's manual for how to do it.
+
+To compile your *tests* that use the gtest shared library, add
+
+```
+-DGTEST_LINKED_AS_SHARED_LIBRARY=1
+```
+
+to the compiler flags.
+
+Note: while the above steps aren't technically necessary today when using some
+compilers (e.g. GCC), they may become necessary in the future, if we decide to
+improve the speed of loading the library (see
+<https://gcc.gnu.org/wiki/Visibility> for details). Therefore you are
+recommended to always add the above flags when using GoogleTest as a shared
+library. Otherwise a future release of GoogleTest may break your build script.
+
+### Avoiding Macro Name Clashes
+
+In C++, macros don't obey namespaces. Therefore two libraries that both define a
+macro of the same name will clash if you `#include` both definitions. In case a
+GoogleTest macro clashes with another library, you can force GoogleTest to
+rename its macro to avoid the conflict.
+
+Specifically, if both GoogleTest and some other code define macro FOO, you can
+add
+
+```
+-DGTEST_DONT_DEFINE_FOO=1
+```
+
+to the compiler flags to tell GoogleTest to change the macro's name from `FOO`
+to `GTEST_FOO`. Currently `FOO` can be `ASSERT_EQ`, `ASSERT_FALSE`, `ASSERT_GE`,
+`ASSERT_GT`, `ASSERT_LE`, `ASSERT_LT`, `ASSERT_NE`, `ASSERT_TRUE`,
+`EXPECT_FALSE`, `EXPECT_TRUE`, `FAIL`, `SUCCEED`, `TEST`, or `TEST_F`. For
+example, with `-DGTEST_DONT_DEFINE_TEST=1`, you'll need to write
+
+```
+GTEST_TEST(SomeTest, DoesThis) { ... }
+```
+
+instead of
+
+```
+TEST(SomeTest, DoesThis) { ... }
+```
+
+in order to define a test.
diff --git a/third_party/googletest/cmake/Config.cmake.in b/third_party/googletest/googletest/cmake/Config.cmake.in
index 12be449..12be449 100644
--- a/third_party/googletest/cmake/Config.cmake.in
+++ b/third_party/googletest/googletest/cmake/Config.cmake.in
diff --git a/third_party/googletest/cmake/gtest.pc.in b/third_party/googletest/googletest/cmake/gtest.pc.in
index b4148fa..b4148fa 100644
--- a/third_party/googletest/cmake/gtest.pc.in
+++ b/third_party/googletest/googletest/cmake/gtest.pc.in
diff --git a/third_party/googletest/cmake/gtest_main.pc.in b/third_party/googletest/googletest/cmake/gtest_main.pc.in
index 38c88c5..38c88c5 100644
--- a/third_party/googletest/cmake/gtest_main.pc.in
+++ b/third_party/googletest/googletest/cmake/gtest_main.pc.in
diff --git a/third_party/googletest/cmake/internal_utils.cmake b/third_party/googletest/googletest/cmake/internal_utils.cmake
index fa7da4e..d4f67f4 100644
--- a/third_party/googletest/cmake/internal_utils.cmake
+++ b/third_party/googletest/googletest/cmake/internal_utils.cmake
@@ -12,14 +12,6 @@
 #   Test and Google Mock's option() definitions, and thus must be
 #   called *after* the options have been defined.
 
-if (POLICY CMP0054)
-  cmake_policy(SET CMP0054 NEW)
-endif (POLICY CMP0054)
-
-if (POLICY CMP0069)
-  cmake_policy(SET CMP0069 NEW)
-endif (POLICY CMP0069)
-
 # Tweaks CMake's default compiler/linker settings to suit Google Test's needs.
 #
 # This must be a macro(), as inside a function string() can only
@@ -88,18 +80,28 @@ macro(config_compiler_and_linker)
     set(cxx_no_exception_flags "-EHs-c- -D_HAS_EXCEPTIONS=0")
     set(cxx_no_rtti_flags "-GR-")
     # Suppress "unreachable code" warning
-    # http://stackoverflow.com/questions/3232669 explains the issue.
+    # https://stackoverflow.com/questions/3232669 explains the issue.
     set(cxx_base_flags "${cxx_base_flags} -wd4702")
     # Ensure MSVC treats source files as UTF-8 encoded.
     if(CMAKE_CXX_COMPILER_ID STREQUAL "MSVC")
       set(cxx_base_flags "${cxx_base_flags} -utf-8")
     endif()
-  elseif (CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
+    if (CMAKE_CXX_COMPILER_ID STREQUAL "IntelLLVM")
+      set(cxx_base_flags "${cxx_base_flags} /fp:precise -Wno-inconsistent-missing-override -Wno-microsoft-exception-spec -Wno-unused-function -Wno-unused-but-set-variable")
+    endif()
+  elseif (CMAKE_CXX_COMPILER_ID STREQUAL "Clang" OR
+      CMAKE_CXX_COMPILER_ID STREQUAL "IntelLLVM")
     set(cxx_base_flags "-Wall -Wshadow -Wconversion -Wundef")
     set(cxx_exception_flags "-fexceptions")
     set(cxx_no_exception_flags "-fno-exceptions")
-    set(cxx_strict_flags "-W -Wpointer-arith -Wreturn-type -Wcast-qual -Wwrite-strings -Wswitch -Wunused-parameter -Wcast-align -Wchar-subscripts -Winline -Wredundant-decls")
+    set(cxx_strict_flags "-W -Wpointer-arith -Wreturn-type -Wcast-qual -Wwrite-strings -Wswitch -Wunused-parameter -Wcast-align -Winline -Wredundant-decls")
     set(cxx_no_rtti_flags "-fno-rtti")
+    if (CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
+      set(cxx_strict_flags "${cxx_strict_flags} -Wchar-subscripts")
+    endif()
+    if (CMAKE_CXX_COMPILER_ID STREQUAL "IntelLLVM")
+      set(cxx_base_flags "${cxx_base_flags} -Wno-implicit-float-size-conversion -ffp-model=precise")
+    endif()
   elseif (CMAKE_COMPILER_IS_GNUCXX)
     set(cxx_base_flags "-Wall -Wshadow -Wundef")
     if(NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 7.0.0)
@@ -186,23 +188,14 @@ function(cxx_library_with_type name type cxx_flags)
     set_target_properties(${name}
       PROPERTIES
       COMPILE_DEFINITIONS "GTEST_CREATE_SHARED_LIBRARY=1")
-    if (NOT "${CMAKE_VERSION}" VERSION_LESS "2.8.11")
-      target_compile_definitions(${name} INTERFACE
-        $<INSTALL_INTERFACE:GTEST_LINKED_AS_SHARED_LIBRARY=1>)
-    endif()
+    target_compile_definitions(${name} INTERFACE
+      $<INSTALL_INTERFACE:GTEST_LINKED_AS_SHARED_LIBRARY=1>)
   endif()
   if (DEFINED GTEST_HAS_PTHREAD)
-    if ("${CMAKE_VERSION}" VERSION_LESS "3.1.0")
-      set(threads_spec ${CMAKE_THREAD_LIBS_INIT})
-    else()
-      set(threads_spec Threads::Threads)
-    endif()
-    target_link_libraries(${name} PUBLIC ${threads_spec})
+    target_link_libraries(${name} PUBLIC Threads::Threads)
   endif()
 
-  if (NOT "${CMAKE_VERSION}" VERSION_LESS "3.8")
-    target_compile_features(${name} PUBLIC cxx_std_14)
-  endif()
+  target_compile_features(${name} PUBLIC cxx_std_14)
 endfunction()
 
 ########################################################################
@@ -254,22 +247,7 @@ function(cxx_executable name dir libs)
     ${name} "${cxx_default}" "${libs}" "${dir}/${name}.cc" ${ARGN})
 endfunction()
 
-# CMP0094 policy enables finding a Python executable in the LOCATION order, as
-# specified by the PATH environment variable.
-if (POLICY CMP0094)
-  cmake_policy(SET CMP0094 NEW)
-endif()
-
-# Sets PYTHONINTERP_FOUND and PYTHON_EXECUTABLE.
-if ("${CMAKE_VERSION}" VERSION_LESS "3.12.0")
-  find_package(PythonInterp)
-  set(PYTHONINTERP_FOUND ${PYTHONINTERP_FOUND} CACHE INTERNAL "")
-  set(PYTHON_EXECUTABLE ${PYTHON_EXECUTABLE} CACHE INTERNAL "")
-else()
-  find_package(Python COMPONENTS Interpreter)
-  set(PYTHONINTERP_FOUND ${Python_Interpreter_FOUND} CACHE INTERNAL "")
-  set(PYTHON_EXECUTABLE ${Python_EXECUTABLE} CACHE INTERNAL "")
-endif()
+find_package(Python3)
 
 # cxx_test_with_flags(name cxx_flags libs srcs...)
 #
@@ -295,34 +273,22 @@ endfunction()
 # creates a Python test with the given name whose main module is in
 # test/name.py.  It does nothing if Python is not installed.
 function(py_test name)
-  if (PYTHONINTERP_FOUND)
-    if ("${CMAKE_MAJOR_VERSION}.${CMAKE_MINOR_VERSION}" VERSION_GREATER 3.1)
-      if (CMAKE_CONFIGURATION_TYPES)
-        # Multi-configuration build generators as for Visual Studio save
-        # output in a subdirectory of CMAKE_CURRENT_BINARY_DIR (Debug,
-        # Release etc.), so we have to provide it here.
-        add_test(NAME ${name}
-          COMMAND ${PYTHON_EXECUTABLE} ${CMAKE_CURRENT_SOURCE_DIR}/test/${name}.py
-              --build_dir=${CMAKE_CURRENT_BINARY_DIR}/$<CONFIG> ${ARGN})
-      else (CMAKE_CONFIGURATION_TYPES)
-        # Single-configuration build generators like Makefile generators
-        # don't have subdirs below CMAKE_CURRENT_BINARY_DIR.
-        add_test(NAME ${name}
-          COMMAND ${PYTHON_EXECUTABLE} ${CMAKE_CURRENT_SOURCE_DIR}/test/${name}.py
-            --build_dir=${CMAKE_CURRENT_BINARY_DIR} ${ARGN})
-      endif (CMAKE_CONFIGURATION_TYPES)
-    else()
-      # ${CMAKE_CURRENT_BINARY_DIR} is known at configuration time, so we can
-      # directly bind it from cmake. ${CTEST_CONFIGURATION_TYPE} is known
-      # only at ctest runtime (by calling ctest -c <Configuration>), so
-      # we have to escape $ to delay variable substitution here.
-      add_test(NAME ${name}
-        COMMAND ${PYTHON_EXECUTABLE} ${CMAKE_CURRENT_SOURCE_DIR}/test/${name}.py
-          --build_dir=${CMAKE_CURRENT_BINARY_DIR}/\${CTEST_CONFIGURATION_TYPE} ${ARGN})
-    endif()
-    # Make the Python import path consistent between Bazel and CMake.
-    set_tests_properties(${name} PROPERTIES ENVIRONMENT PYTHONPATH=${CMAKE_SOURCE_DIR})
-  endif(PYTHONINTERP_FOUND)
+  if (NOT Python3_Interpreter_FOUND)
+    return()
+  endif()
+
+  get_cmake_property(is_multi "GENERATOR_IS_MULTI_CONFIG")
+  set(build_dir "${CMAKE_CURRENT_BINARY_DIR}")
+  if (is_multi)
+    set(build_dir "${CMAKE_CURRENT_BINARY_DIR}/$<CONFIG>")
+  endif()
+
+  add_test(NAME ${name}
+      COMMAND Python3::Interpreter ${CMAKE_CURRENT_SOURCE_DIR}/test/${name}.py
+          --build_dir=${build_dir} ${ARGN})
+
+  # Make the Python import path consistent between Bazel and CMake.
+  set_tests_properties(${name} PROPERTIES ENVIRONMENT PYTHONPATH=${CMAKE_SOURCE_DIR})
 endfunction()
 
 # install_project(targets...)
@@ -331,10 +297,12 @@ endfunction()
 function(install_project)
   if(INSTALL_GTEST)
     install(DIRECTORY "${PROJECT_SOURCE_DIR}/include/"
+      COMPONENT "${PROJECT_NAME}"
       DESTINATION "${CMAKE_INSTALL_INCLUDEDIR}")
     # Install the project targets.
     install(TARGETS ${ARGN}
       EXPORT ${targets_export_name}
+      COMPONENT "${PROJECT_NAME}"
       RUNTIME DESTINATION "${CMAKE_INSTALL_BINDIR}"
       ARCHIVE DESTINATION "${CMAKE_INSTALL_LIBDIR}"
       LIBRARY DESTINATION "${CMAKE_INSTALL_LIBDIR}")
@@ -346,6 +314,7 @@ function(install_project)
         get_target_property(t_pdb_output_directory ${t} PDB_OUTPUT_DIRECTORY)
         install(FILES
           "${t_pdb_output_directory}/\${CMAKE_INSTALL_CONFIG_NAME}/$<$<CONFIG:Debug>:${t_pdb_name_debug}>$<$<NOT:$<CONFIG:Debug>>:${t_pdb_name}>.pdb"
+          COMPONENT "${PROJECT_NAME}"
           DESTINATION ${CMAKE_INSTALL_LIBDIR}
           OPTIONAL)
       endforeach()
@@ -356,6 +325,7 @@ function(install_project)
       configure_file("${PROJECT_SOURCE_DIR}/cmake/${t}.pc.in"
         "${configured_pc}" @ONLY)
       install(FILES "${configured_pc}"
+        COMPONENT "${PROJECT_NAME}"
         DESTINATION "${CMAKE_INSTALL_LIBDIR}/pkgconfig")
     endforeach()
   endif()
diff --git a/third_party/googletest/cmake/libgtest.la.in b/third_party/googletest/googletest/cmake/libgtest.la.in
index 840c838..840c838 100644
--- a/third_party/googletest/cmake/libgtest.la.in
+++ b/third_party/googletest/googletest/cmake/libgtest.la.in
diff --git a/third_party/googletest/googletest/docs/README.md b/third_party/googletest/googletest/docs/README.md
new file mode 100644
index 0000000..1bc57b7
--- /dev/null
+++ b/third_party/googletest/googletest/docs/README.md
@@ -0,0 +1,4 @@
+# Content Moved
+
+We are working on updates to the GoogleTest documentation, which has moved to
+the top-level [docs](../../docs) directory.
diff --git a/third_party/googletest/include/gtest/gtest-assertion-result.h b/third_party/googletest/googletest/include/gtest/gtest-assertion-result.h
index 56fe128..56fe128 100644
--- a/third_party/googletest/include/gtest/gtest-assertion-result.h
+++ b/third_party/googletest/googletest/include/gtest/gtest-assertion-result.h
diff --git a/third_party/googletest/include/gtest/gtest-death-test.h b/third_party/googletest/googletest/include/gtest/gtest-death-test.h
index 08fef8c..08fef8c 100644
--- a/third_party/googletest/include/gtest/gtest-death-test.h
+++ b/third_party/googletest/googletest/include/gtest/gtest-death-test.h
diff --git a/third_party/googletest/include/gtest/gtest-matchers.h b/third_party/googletest/googletest/include/gtest/gtest-matchers.h
index eae210e..eae210e 100644
--- a/third_party/googletest/include/gtest/gtest-matchers.h
+++ b/third_party/googletest/googletest/include/gtest/gtest-matchers.h
diff --git a/third_party/googletest/include/gtest/gtest-message.h b/third_party/googletest/googletest/include/gtest/gtest-message.h
index 4d4b152..59b805e 100644
--- a/third_party/googletest/include/gtest/gtest-message.h
+++ b/third_party/googletest/googletest/include/gtest/gtest-message.h
@@ -56,6 +56,13 @@
 
 #include "gtest/internal/gtest-port.h"
 
+#ifdef GTEST_HAS_ABSL
+#include <type_traits>
+
+#include "absl/strings/internal/has_absl_stringify.h"
+#include "absl/strings/str_cat.h"
+#endif  // GTEST_HAS_ABSL
+
 GTEST_DISABLE_MSC_WARNINGS_PUSH_(4251 \
 /* class A needs to have dll-interface to be used by clients of class B */)
 
@@ -111,8 +118,17 @@ class GTEST_API_ Message {
     *ss_ << str;
   }
 
-  // Streams a non-pointer value to this object.
-  template <typename T>
+  // Streams a non-pointer value to this object. If building a version of
+  // GoogleTest with ABSL, this overload is only enabled if the value does not
+  // have an AbslStringify definition.
+  template <typename T
+#ifdef GTEST_HAS_ABSL
+            ,
+            typename std::enable_if<
+                !absl::strings_internal::HasAbslStringify<T>::value,  // NOLINT
+                int>::type = 0
+#endif  // GTEST_HAS_ABSL
+            >
   inline Message& operator<<(const T& val) {
         // Some libraries overload << for STL containers.  These
     // overloads are defined in the global namespace instead of ::std.
@@ -133,6 +149,22 @@ class GTEST_API_ Message {
     return *this;
   }
 
+#ifdef GTEST_HAS_ABSL
+  // Streams a non-pointer value with an AbslStringify definition to this
+  // object.
+  template <typename T,
+            typename std::enable_if<
+                absl::strings_internal::HasAbslStringify<T>::value,  // NOLINT
+                int>::type = 0>
+  inline Message& operator<<(const T& val) {
+    // ::operator<< is needed here for a similar reason as with the non-Abseil
+    // version above
+    using ::operator<<;
+    *ss_ << absl::StrCat(val);
+    return *this;
+  }
+#endif  // GTEST_HAS_ABSL
+
   // Streams a pointer value to this object.
   //
   // This function is an overload of the previous one.  When you
diff --git a/third_party/googletest/include/gtest/gtest-param-test.h b/third_party/googletest/googletest/include/gtest/gtest-param-test.h
index 49a47ea..49a47ea 100644
--- a/third_party/googletest/include/gtest/gtest-param-test.h
+++ b/third_party/googletest/googletest/include/gtest/gtest-param-test.h
diff --git a/third_party/googletest/include/gtest/gtest-printers.h b/third_party/googletest/googletest/include/gtest/gtest-printers.h
index 539d99c..9ccbff7 100644
--- a/third_party/googletest/include/gtest/gtest-printers.h
+++ b/third_party/googletest/googletest/include/gtest/gtest-printers.h
@@ -43,6 +43,9 @@
 //   1. foo::PrintTo(const T&, ostream*)
 //   2. operator<<(ostream&, const T&) defined in either foo or the
 //      global namespace.
+// * Prefer AbslStringify(..) to operator<<(..), per https://abseil.io/tips/215.
+// * Define foo::PrintTo(..) if the type already has AbslStringify(..), but an
+//   alternative presentation in test results is of interest.
 //
 // However if T is an STL-style container then it is printed element-wise
 // unless foo::PrintTo(const T&, ostream*) is defined. Note that
@@ -112,9 +115,17 @@
 #include <utility>
 #include <vector>
 
+#ifdef GTEST_HAS_ABSL
+#include "absl/strings/internal/has_absl_stringify.h"
+#include "absl/strings/str_cat.h"
+#endif  // GTEST_HAS_ABSL
 #include "gtest/internal/gtest-internal.h"
 #include "gtest/internal/gtest-port.h"
 
+#if GTEST_INTERNAL_HAS_STD_SPAN
+#include <span>  // NOLINT
+#endif  // GTEST_INTERNAL_HAS_STD_SPAN
+
 namespace testing {
 
 // Definitions in the internal* namespaces are subject to change without notice.
@@ -124,13 +135,32 @@ namespace internal {
 template <typename T>
 void UniversalPrint(const T& value, ::std::ostream* os);
 
+template <typename T>
+struct IsStdSpan {
+  static constexpr bool value = false;
+};
+
+#if GTEST_INTERNAL_HAS_STD_SPAN
+template <typename E>
+struct IsStdSpan<std::span<E>> {
+  static constexpr bool value = true;
+};
+#endif  // GTEST_INTERNAL_HAS_STD_SPAN
+
 // Used to print an STL-style container when the user doesn't define
 // a PrintTo() for it.
+//
+// NOTE: Since std::span does not have const_iterator until C++23, it would
+// fail IsContainerTest before C++23. However, IsContainerTest only uses
+// the presence of const_iterator to avoid treating iterators as containers
+// because of iterator::iterator. Which means std::span satisfies the *intended*
+// condition of IsContainerTest.
 struct ContainerPrinter {
   template <typename T,
             typename = typename std::enable_if<
-                (sizeof(IsContainerTest<T>(0)) == sizeof(IsContainer)) &&
-                !IsRecursiveContainer<T>::value>::type>
+                ((sizeof(IsContainerTest<T>(0)) == sizeof(IsContainer)) &&
+                 !IsRecursiveContainer<T>::value) ||
+                IsStdSpan<T>::value>::type>
   static void PrintValue(const T& container, std::ostream* os) {
     const size_t kMaxCount = 32;  // The maximum number of elements to print.
     *os << '{';
@@ -260,6 +290,18 @@ struct ConvertibleToStringViewPrinter {
 #endif
 };
 
+#ifdef GTEST_HAS_ABSL
+struct ConvertibleToAbslStringifyPrinter {
+  template <
+      typename T,
+      typename = typename std::enable_if<
+          absl::strings_internal::HasAbslStringify<T>::value>::type>  // NOLINT
+  static void PrintValue(const T& value, ::std::ostream* os) {
+    *os << absl::StrCat(value);
+  }
+};
+#endif  // GTEST_HAS_ABSL
+
 // Prints the given number of bytes in the given object to the given
 // ostream.
 GTEST_API_ void PrintBytesInObjectTo(const unsigned char* obj_bytes,
@@ -298,8 +340,8 @@ struct FindFirstPrinter<
 //  - Print containers (they have begin/end/etc).
 //  - Print function pointers.
 //  - Print object pointers.
-//  - Use the stream operator, if available.
 //  - Print protocol buffers.
+//  - Use the stream operator, if available.
 //  - Print types convertible to BiggestInt.
 //  - Print types convertible to StringView, if available.
 //  - Fallback to printing the raw bytes of the object.
@@ -308,6 +350,9 @@ void PrintWithFallback(const T& value, ::std::ostream* os) {
   using Printer = typename FindFirstPrinter<
       T, void, ContainerPrinter, FunctionPointerPrinter, PointerPrinter,
       ProtobufPrinter,
+#ifdef GTEST_HAS_ABSL
+      ConvertibleToAbslStringifyPrinter,
+#endif  // GTEST_HAS_ABSL
       internal_stream_operator_without_lexical_name_lookup::StreamPrinter,
       ConvertibleToIntegerPrinter, ConvertibleToStringViewPrinter,
       RawBytesPrinter, FallbackPrinter>::type;
@@ -475,7 +520,7 @@ GTEST_API_ void PrintTo(char32_t c, ::std::ostream* os);
 inline void PrintTo(char16_t c, ::std::ostream* os) {
   PrintTo(ImplicitCast_<char32_t>(c), os);
 }
-#ifdef __cpp_char8_t
+#ifdef __cpp_lib_char8_t
 inline void PrintTo(char8_t c, ::std::ostream* os) {
   PrintTo(ImplicitCast_<char32_t>(c), os);
 }
@@ -531,7 +576,7 @@ int AppropriateResolution(FloatType val) {
     } else if (val >= 0.0001) {
       mulfor6 = 1e9;
     }
-    if (static_cast<float>(static_cast<int32_t>(val * mulfor6 + 0.5)) /
+    if (static_cast<FloatType>(static_cast<int32_t>(val * mulfor6 + 0.5)) /
             mulfor6 ==
         val)
       return 6;
@@ -546,7 +591,7 @@ int AppropriateResolution(FloatType val) {
     } else if (val >= 1e6) {  // 1,000,000 to 9,999,999
       divfor6 = 10;
     }
-    if (static_cast<float>(static_cast<int32_t>(val / divfor6 + 0.5)) *
+    if (static_cast<FloatType>(static_cast<int32_t>(val / divfor6 + 0.5)) *
             divfor6 ==
         val)
       return 6;
@@ -588,7 +633,7 @@ inline void PrintTo(const unsigned char* s, ::std::ostream* os) {
 inline void PrintTo(unsigned char* s, ::std::ostream* os) {
   PrintTo(ImplicitCast_<const void*>(s), os);
 }
-#ifdef __cpp_char8_t
+#ifdef __cpp_lib_char8_t
 // Overloads for u8 strings.
 GTEST_API_ void PrintTo(const char8_t* s, ::std::ostream* os);
 inline void PrintTo(char8_t* s, ::std::ostream* os) {
@@ -908,7 +953,7 @@ void UniversalPrintArray(const T* begin, size_t len, ::std::ostream* os) {
 GTEST_API_ void UniversalPrintArray(const char* begin, size_t len,
                                     ::std::ostream* os);
 
-#ifdef __cpp_char8_t
+#ifdef __cpp_lib_char8_t
 // This overload prints a (const) char8_t array compactly.
 GTEST_API_ void UniversalPrintArray(const char8_t* begin, size_t len,
                                     ::std::ostream* os);
diff --git a/third_party/googletest/include/gtest/gtest-spi.h b/third_party/googletest/googletest/include/gtest/gtest-spi.h
index c0613b6..c0613b6 100644
--- a/third_party/googletest/include/gtest/gtest-spi.h
+++ b/third_party/googletest/googletest/include/gtest/gtest-spi.h
diff --git a/third_party/googletest/include/gtest/gtest-test-part.h b/third_party/googletest/googletest/include/gtest/gtest-test-part.h
index 41c8a9a..41c8a9a 100644
--- a/third_party/googletest/include/gtest/gtest-test-part.h
+++ b/third_party/googletest/googletest/include/gtest/gtest-test-part.h
diff --git a/third_party/googletest/include/gtest/gtest-typed-test.h b/third_party/googletest/googletest/include/gtest/gtest-typed-test.h
index 72de536..72de536 100644
--- a/third_party/googletest/include/gtest/gtest-typed-test.h
+++ b/third_party/googletest/googletest/include/gtest/gtest-typed-test.h
diff --git a/third_party/googletest/include/gtest/gtest.h b/third_party/googletest/googletest/include/gtest/gtest.h
index 8412503..a932e68 100644
--- a/third_party/googletest/include/gtest/gtest.h
+++ b/third_party/googletest/googletest/include/gtest/gtest.h
@@ -51,7 +51,6 @@
 
 #include <cstddef>
 #include <cstdint>
-#include <iomanip>
 #include <limits>
 #include <memory>
 #include <ostream>
@@ -1055,6 +1054,10 @@ class GTEST_API_ TestEventListeners {
     return default_xml_generator_;
   }
 
+  // Controls whether events will be forwarded by the repeater to the
+  // listeners in the list.
+  void SuppressEventForwarding(bool);
+
  private:
   friend class TestSuite;
   friend class TestInfo;
@@ -1084,7 +1087,6 @@ class GTEST_API_ TestEventListeners {
   // Controls whether events will be forwarded by the repeater to the
   // listeners in the list.
   bool EventForwardingEnabled() const;
-  void SuppressEventForwarding();
 
   // The actual list of listeners.
   internal::TestEventRepeater* repeater_;
@@ -1571,12 +1573,12 @@ AssertionResult CmpHelperFloatingPointEQ(const char* lhs_expression,
   }
 
   ::std::stringstream lhs_ss;
-  lhs_ss << std::setprecision(std::numeric_limits<RawType>::digits10 + 2)
-         << lhs_value;
+  lhs_ss.precision(std::numeric_limits<RawType>::digits10 + 2);
+  lhs_ss << lhs_value;
 
   ::std::stringstream rhs_ss;
-  rhs_ss << std::setprecision(std::numeric_limits<RawType>::digits10 + 2)
-         << rhs_value;
+  rhs_ss.precision(std::numeric_limits<RawType>::digits10 + 2);
+  rhs_ss << rhs_value;
 
   return EqFailure(lhs_expression, rhs_expression,
                    StringStreamToString(&lhs_ss), StringStreamToString(&rhs_ss),
@@ -2098,8 +2100,8 @@ class GTEST_API_ ScopedTrace {
 // Assuming that each thread maintains its own stack of traces.
 // Therefore, a SCOPED_TRACE() would (correctly) only affect the
 // assertions in its own thread.
-#define SCOPED_TRACE(message)                                         \
-  ::testing::ScopedTrace GTEST_CONCAT_TOKEN_(gtest_trace_, __LINE__)( \
+#define SCOPED_TRACE(message)                                               \
+  const ::testing::ScopedTrace GTEST_CONCAT_TOKEN_(gtest_trace_, __LINE__)( \
       __FILE__, __LINE__, (message))
 
 // Compile-time assertion for type equality.
diff --git a/third_party/googletest/include/gtest/gtest_pred_impl.h b/third_party/googletest/googletest/include/gtest/gtest_pred_impl.h
index 47a24aa..47a24aa 100644
--- a/third_party/googletest/include/gtest/gtest_pred_impl.h
+++ b/third_party/googletest/googletest/include/gtest/gtest_pred_impl.h
diff --git a/third_party/googletest/include/gtest/gtest_prod.h b/third_party/googletest/googletest/include/gtest/gtest_prod.h
index 1f37dc3..1f37dc3 100644
--- a/third_party/googletest/include/gtest/gtest_prod.h
+++ b/third_party/googletest/googletest/include/gtest/gtest_prod.h
diff --git a/third_party/googletest/include/gtest/internal/custom/README.md b/third_party/googletest/googletest/include/gtest/internal/custom/README.md
index cb49e2c..cb49e2c 100644
--- a/third_party/googletest/include/gtest/internal/custom/README.md
+++ b/third_party/googletest/googletest/include/gtest/internal/custom/README.md
diff --git a/third_party/googletest/include/gtest/internal/custom/gtest-port.h b/third_party/googletest/googletest/include/gtest/internal/custom/gtest-port.h
index db02881..db02881 100644
--- a/third_party/googletest/include/gtest/internal/custom/gtest-port.h
+++ b/third_party/googletest/googletest/include/gtest/internal/custom/gtest-port.h
diff --git a/third_party/googletest/include/gtest/internal/custom/gtest-printers.h b/third_party/googletest/googletest/include/gtest/internal/custom/gtest-printers.h
index b9495d8..b9495d8 100644
--- a/third_party/googletest/include/gtest/internal/custom/gtest-printers.h
+++ b/third_party/googletest/googletest/include/gtest/internal/custom/gtest-printers.h
diff --git a/third_party/googletest/include/gtest/internal/custom/gtest.h b/third_party/googletest/googletest/include/gtest/internal/custom/gtest.h
index afaaf17..afaaf17 100644
--- a/third_party/googletest/include/gtest/internal/custom/gtest.h
+++ b/third_party/googletest/googletest/include/gtest/internal/custom/gtest.h
diff --git a/third_party/googletest/include/gtest/internal/gtest-death-test-internal.h b/third_party/googletest/googletest/include/gtest/internal/gtest-death-test-internal.h
index 8e9c988..8e9c988 100644
--- a/third_party/googletest/include/gtest/internal/gtest-death-test-internal.h
+++ b/third_party/googletest/googletest/include/gtest/internal/gtest-death-test-internal.h
diff --git a/third_party/googletest/include/gtest/internal/gtest-filepath.h b/third_party/googletest/googletest/include/gtest/internal/gtest-filepath.h
index 5189c81..5189c81 100644
--- a/third_party/googletest/include/gtest/internal/gtest-filepath.h
+++ b/third_party/googletest/googletest/include/gtest/internal/gtest-filepath.h
diff --git a/third_party/googletest/include/gtest/internal/gtest-internal.h b/third_party/googletest/googletest/include/gtest/internal/gtest-internal.h
index 317894e..4f077fc 100644
--- a/third_party/googletest/include/gtest/internal/gtest-internal.h
+++ b/third_party/googletest/googletest/include/gtest/internal/gtest-internal.h
@@ -58,7 +58,6 @@
 
 #include <cstdint>
 #include <functional>
-#include <iomanip>
 #include <limits>
 #include <map>
 #include <set>
@@ -79,7 +78,7 @@
 //
 // will result in the token foo__LINE__, instead of foo followed by
 // the current line number.  For more details, see
-// http://www.parashift.com/c++-faq-lite/misc-technical-issues.html#faq-39.6
+// https://www.parashift.com/c++-faq-lite/misc-technical-issues.html#faq-39.6
 #define GTEST_CONCAT_TOKEN_(foo, bar) GTEST_CONCAT_TOKEN_IMPL_(foo, bar)
 #define GTEST_CONCAT_TOKEN_IMPL_(foo, bar) foo##bar
 
@@ -170,7 +169,7 @@ namespace edit_distance {
 // All edits cost the same, with replace having lower priority than
 // add/remove.
 // Simple implementation of the Wagner-Fischer algorithm.
-// See http://en.wikipedia.org/wiki/Wagner-Fischer_algorithm
+// See https://en.wikipedia.org/wiki/Wagner-Fischer_algorithm
 enum EditType { kMatch, kAdd, kRemove, kReplace };
 GTEST_API_ std::vector<EditType> CalculateOptimalEdits(
     const std::vector<size_t>& left, const std::vector<size_t>& right);
@@ -237,7 +236,7 @@ GTEST_API_ std::string GetBoolAssertionFailureMessage(
 //   For double, there are 11 exponent bits and 52 fraction bits.
 //
 //   More details can be found at
-//   http://en.wikipedia.org/wiki/IEEE_floating-point_standard.
+//   https://en.wikipedia.org/wiki/IEEE_floating-point_standard.
 //
 // Template parameter:
 //
@@ -282,7 +281,7 @@ class FloatingPoint {
   // bits.  Therefore, 4 should be enough for ordinary use.
   //
   // See the following article for more details on ULP:
-  // http://randomascii.wordpress.com/2012/02/25/comparing-floating-point-numbers-2012-edition/
+  // https://randomascii.wordpress.com/2012/02/25/comparing-floating-point-numbers-2012-edition/
   static const uint32_t kMaxUlps = 4;
 
   // Constructs a FloatingPoint from a raw floating-point number.
@@ -363,7 +362,7 @@ class FloatingPoint {
   //   N - 1  (the biggest number representable using
   //          sign-and-magnitude) is represented by 2N - 1.
   //
-  // Read http://en.wikipedia.org/wiki/Signed_number_representations
+  // Read https://en.wikipedia.org/wiki/Signed_number_representations
   // for more details on signed number representations.
   static Bits SignAndMagnitudeToBiased(const Bits& sam) {
     if (kSignBitMask & sam) {
@@ -1497,19 +1496,20 @@ class NeverThrown {
              gtest_ar_, text, #actual, #expected)                     \
              .c_str())
 
-#define GTEST_TEST_NO_FATAL_FAILURE_(statement, fail)                          \
-  GTEST_AMBIGUOUS_ELSE_BLOCKER_                                                \
-  if (::testing::internal::AlwaysTrue()) {                                     \
-    ::testing::internal::HasNewFatalFailureHelper gtest_fatal_failure_checker; \
-    GTEST_SUPPRESS_UNREACHABLE_CODE_WARNING_BELOW_(statement);                 \
-    if (gtest_fatal_failure_checker.has_new_fatal_failure()) {                 \
-      goto GTEST_CONCAT_TOKEN_(gtest_label_testnofatal_, __LINE__);            \
-    }                                                                          \
-  } else                                                                       \
-    GTEST_CONCAT_TOKEN_(gtest_label_testnofatal_, __LINE__)                    \
-        : fail("Expected: " #statement                                         \
-               " doesn't generate new fatal "                                  \
-               "failures in the current thread.\n"                             \
+#define GTEST_TEST_NO_FATAL_FAILURE_(statement, fail)               \
+  GTEST_AMBIGUOUS_ELSE_BLOCKER_                                     \
+  if (::testing::internal::AlwaysTrue()) {                          \
+    const ::testing::internal::HasNewFatalFailureHelper             \
+        gtest_fatal_failure_checker;                                \
+    GTEST_SUPPRESS_UNREACHABLE_CODE_WARNING_BELOW_(statement);      \
+    if (gtest_fatal_failure_checker.has_new_fatal_failure()) {      \
+      goto GTEST_CONCAT_TOKEN_(gtest_label_testnofatal_, __LINE__); \
+    }                                                               \
+  } else /* NOLINT */                                               \
+    GTEST_CONCAT_TOKEN_(gtest_label_testnofatal_, __LINE__)         \
+        : fail("Expected: " #statement                              \
+               " doesn't generate new fatal "                       \
+               "failures in the current thread.\n"                  \
                "  Actual: it does.")
 
 // Expands to the name of the class that implements the given test.
diff --git a/third_party/googletest/include/gtest/internal/gtest-param-util.h b/third_party/googletest/googletest/include/gtest/internal/gtest-param-util.h
index 6a81c37..dd39e98 100644
--- a/third_party/googletest/include/gtest/internal/gtest-param-util.h
+++ b/third_party/googletest/googletest/include/gtest/internal/gtest-param-util.h
@@ -584,7 +584,9 @@ class ParameterizedTestSuiteInfo : public ParameterizedTestSuiteInfoBase {
 
           GTEST_CHECK_(IsValidParamName(param_name))
               << "Parameterized test name '" << param_name
-              << "' is invalid, in " << file << " line " << line << std::endl;
+              << "' is invalid (contains spaces, dashes, underscores, or "
+                 "non-alphanumeric characters), in "
+              << file << " line " << line << "" << std::endl;
 
           GTEST_CHECK_(test_param_names.count(param_name) == 0)
               << "Duplicate parameterized test name '" << param_name << "', in "
diff --git a/third_party/googletest/include/gtest/internal/gtest-port-arch.h b/third_party/googletest/googletest/include/gtest/internal/gtest-port-arch.h
index 0406460..3162f2b 100644
--- a/third_party/googletest/include/gtest/internal/gtest-port-arch.h
+++ b/third_party/googletest/googletest/include/gtest/internal/gtest-port-arch.h
@@ -113,6 +113,10 @@
 #define GTEST_OS_XTENSA 1
 #elif defined(__hexagon__)
 #define GTEST_OS_QURT 1
+#elif defined(CPU_QN9090) || defined(CPU_QN9090HN)
+#define GTEST_OS_NXP_QN9090 1
+#elif defined(NRF52)
+#define GTEST_OS_NRF52 1
 #endif  // __CYGWIN__
 
 #endif  // GOOGLETEST_INCLUDE_GTEST_INTERNAL_GTEST_PORT_ARCH_H_
diff --git a/third_party/googletest/include/gtest/internal/gtest-port.h b/third_party/googletest/googletest/include/gtest/internal/gtest-port.h
index d71110c..35544a0 100644
--- a/third_party/googletest/include/gtest/internal/gtest-port.h
+++ b/third_party/googletest/googletest/include/gtest/internal/gtest-port.h
@@ -208,6 +208,8 @@
 //   or
 //                                 UniversalPrinter<absl::optional>
 //                                 specializations. Always defined to 0 or 1.
+//   GTEST_INTERNAL_HAS_STD_SPAN - for enabling UniversalPrinter<std::span>
+//                                 specializations. Always defined to 0 or 1
 //   GTEST_INTERNAL_HAS_STRING_VIEW - for enabling Matcher<std::string_view> or
 //                                    Matcher<absl::string_view>
 //                                    specializations. Always defined to 0 or 1.
@@ -220,7 +222,6 @@
 //   GTEST_HAS_ALT_PATH_SEP_ - Always defined to 0 or 1.
 //   GTEST_WIDE_STRING_USES_UTF16_ - Always defined to 0 or 1.
 //   GTEST_HAS_MUTEX_AND_THREAD_LOCAL_ - Always defined to 0 or 1.
-//   GTEST_HAS_DOWNCAST_ - Always defined to 0 or 1.
 //   GTEST_HAS_NOTIFICATION_- Always defined to 0 or 1.
 //
 // Synchronization:
@@ -313,10 +314,6 @@
 #include "gtest/internal/custom/gtest-port.h"
 #include "gtest/internal/gtest-port-arch.h"
 
-#ifndef GTEST_HAS_DOWNCAST_
-#define GTEST_HAS_DOWNCAST_ 0
-#endif
-
 #ifndef GTEST_HAS_MUTEX_AND_THREAD_LOCAL_
 #define GTEST_HAS_MUTEX_AND_THREAD_LOCAL_ 0
 #endif
@@ -505,7 +502,8 @@ typedef struct _RTL_CRITICAL_SECTION GTEST_CRITICAL_SECTION;
 #if (!(defined(GTEST_OS_LINUX_ANDROID) || defined(GTEST_OS_CYGWIN) || \
        defined(GTEST_OS_SOLARIS) || defined(GTEST_OS_HAIKU) ||        \
        defined(GTEST_OS_ESP32) || defined(GTEST_OS_ESP8266) ||        \
-       defined(GTEST_OS_XTENSA) || defined(GTEST_OS_QURT)))
+       defined(GTEST_OS_XTENSA) || defined(GTEST_OS_QURT) ||          \
+       defined(GTEST_OS_NXP_QN9090) || defined(GTEST_OS_NRF52)))
 #define GTEST_HAS_STD_WSTRING 1
 #else
 #define GTEST_HAS_STD_WSTRING 0
@@ -613,7 +611,7 @@ typedef struct _RTL_CRITICAL_SECTION GTEST_CRITICAL_SECTION;
 // Determines whether clone(2) is supported.
 // Usually it will only be available on Linux, excluding
 // Linux on the Itanium architecture.
-// Also see http://linux.die.net/man/2/clone.
+// Also see https://linux.die.net/man/2/clone.
 #ifndef GTEST_HAS_CLONE
 // The user didn't tell us, so we need to figure it out.
 
@@ -924,9 +922,11 @@ using std::tuple_size;
 namespace internal {
 
 // A secret type that Google Test users don't know about.  It has no
-// definition on purpose.  Therefore it's impossible to create a
+// accessible constructors on purpose.  Therefore it's impossible to create a
 // Secret object, which is what we want.
-class Secret;
+class Secret {
+  Secret(const Secret&) = delete;
+};
 
 // A helper for suppressing warnings on constant condition.  It just
 // returns 'condition'.
@@ -1143,47 +1143,6 @@ inline To ImplicitCast_(To x) {
   return x;
 }
 
-// When you upcast (that is, cast a pointer from type Foo to type
-// SuperclassOfFoo), it's fine to use ImplicitCast_<>, since upcasts
-// always succeed.  When you downcast (that is, cast a pointer from
-// type Foo to type SubclassOfFoo), static_cast<> isn't safe, because
-// how do you know the pointer is really of type SubclassOfFoo?  It
-// could be a bare Foo, or of type DifferentSubclassOfFoo.  Thus,
-// when you downcast, you should use this macro.  In debug mode, we
-// use dynamic_cast<> to double-check the downcast is legal (we die
-// if it's not).  In normal mode, we do the efficient static_cast<>
-// instead.  Thus, it's important to test in debug mode to make sure
-// the cast is legal!
-//    This is the only place in the code we should use dynamic_cast<>.
-// In particular, you SHOULDN'T be using dynamic_cast<> in order to
-// do RTTI (eg code like this:
-//    if (dynamic_cast<Subclass1>(foo)) HandleASubclass1Object(foo);
-//    if (dynamic_cast<Subclass2>(foo)) HandleASubclass2Object(foo);
-// You should design the code some other way not to need this.
-//
-// This relatively ugly name is intentional. It prevents clashes with
-// similar functions users may have (e.g., down_cast). The internal
-// namespace alone is not enough because the function can be found by ADL.
-template <typename To, typename From>  // use like this: DownCast_<T*>(foo);
-inline To DownCast_(From* f) {         // so we only accept pointers
-  // Ensures that To is a sub-type of From *.  This test is here only
-  // for compile-time type checking, and has no overhead in an
-  // optimized build at run-time, as it will be optimized away
-  // completely.
-  GTEST_INTENTIONAL_CONST_COND_PUSH_()
-  if (false) {
-    GTEST_INTENTIONAL_CONST_COND_POP_()
-    const To to = nullptr;
-    ::testing::internal::ImplicitCast_<From*>(to);
-  }
-
-#if GTEST_HAS_RTTI
-  // RTTI: debug mode only!
-  GTEST_CHECK_(f == nullptr || dynamic_cast<To>(f) != nullptr);
-#endif
-  return static_cast<To>(f);
-}
-
 // Downcasts the pointer of type Base to Derived.
 // Derived must be a subclass of Base. The parameter MUST
 // point to a class of type Derived, not any subclass of it.
@@ -1191,17 +1150,12 @@ inline To DownCast_(From* f) {         // so we only accept pointers
 // check to enforce this.
 template <class Derived, class Base>
 Derived* CheckedDowncastToActualType(Base* base) {
+  static_assert(std::is_base_of<Base, Derived>::value,
+                "target type not derived from source type");
 #if GTEST_HAS_RTTI
-  GTEST_CHECK_(typeid(*base) == typeid(Derived));
-#endif
-
-#if GTEST_HAS_DOWNCAST_
-  return ::down_cast<Derived*>(base);
-#elif GTEST_HAS_RTTI
-  return dynamic_cast<Derived*>(base);  // NOLINT
-#else
-  return static_cast<Derived*>(base);  // Poor man's downcast.
+  GTEST_CHECK_(base == nullptr || dynamic_cast<Derived*>(base) != nullptr);
 #endif
+  return static_cast<Derived*>(base);
 }
 
 #if GTEST_HAS_STREAM_REDIRECTION
@@ -1995,7 +1949,7 @@ inline bool IsUpper(char ch) {
 inline bool IsXDigit(char ch) {
   return isxdigit(static_cast<unsigned char>(ch)) != 0;
 }
-#ifdef __cpp_char8_t
+#ifdef __cpp_lib_char8_t
 inline bool IsXDigit(char8_t ch) {
   return isxdigit(static_cast<unsigned char>(ch)) != 0;
 }
@@ -2455,6 +2409,16 @@ inline ::std::nullopt_t Nullopt() { return ::std::nullopt; }
 #define GTEST_INTERNAL_HAS_OPTIONAL 0
 #endif
 
+#ifdef __has_include
+#if __has_include(<span>) && GTEST_INTERNAL_CPLUSPLUS_LANG >= 202002L
+#define GTEST_INTERNAL_HAS_STD_SPAN 1
+#endif  // __has_include(<span>) && GTEST_INTERNAL_CPLUSPLUS_LANG >= 202002L
+#endif  // __has_include
+
+#ifndef GTEST_INTERNAL_HAS_STD_SPAN
+#define GTEST_INTERNAL_HAS_STD_SPAN 0
+#endif
+
 #ifdef GTEST_HAS_ABSL
 // Always use absl::string_view for Matcher<> specializations if googletest
 // is built with absl support.
diff --git a/third_party/googletest/include/gtest/internal/gtest-string.h b/third_party/googletest/googletest/include/gtest/internal/gtest-string.h
index 7c05b58..7c05b58 100644
--- a/third_party/googletest/include/gtest/internal/gtest-string.h
+++ b/third_party/googletest/googletest/include/gtest/internal/gtest-string.h
diff --git a/third_party/googletest/include/gtest/internal/gtest-type-util.h b/third_party/googletest/googletest/include/gtest/internal/gtest-type-util.h
index f94cf61..f94cf61 100644
--- a/third_party/googletest/include/gtest/internal/gtest-type-util.h
+++ b/third_party/googletest/googletest/include/gtest/internal/gtest-type-util.h
diff --git a/third_party/googletest/samples/prime_tables.h b/third_party/googletest/googletest/samples/prime_tables.h
index 14c016a..14c016a 100644
--- a/third_party/googletest/samples/prime_tables.h
+++ b/third_party/googletest/googletest/samples/prime_tables.h
diff --git a/third_party/googletest/samples/sample1.cc b/third_party/googletest/googletest/samples/sample1.cc
index 80b69f4..80b69f4 100644
--- a/third_party/googletest/samples/sample1.cc
+++ b/third_party/googletest/googletest/samples/sample1.cc
diff --git a/third_party/googletest/samples/sample1.h b/third_party/googletest/googletest/samples/sample1.h
index ba392cf..ba392cf 100644
--- a/third_party/googletest/samples/sample1.h
+++ b/third_party/googletest/googletest/samples/sample1.h
diff --git a/third_party/googletest/samples/sample10_unittest.cc b/third_party/googletest/googletest/samples/sample10_unittest.cc
index 2107954..2107954 100644
--- a/third_party/googletest/samples/sample10_unittest.cc
+++ b/third_party/googletest/googletest/samples/sample10_unittest.cc
diff --git a/third_party/googletest/samples/sample1_unittest.cc b/third_party/googletest/googletest/samples/sample1_unittest.cc
index 60f2770..60f2770 100644
--- a/third_party/googletest/samples/sample1_unittest.cc
+++ b/third_party/googletest/googletest/samples/sample1_unittest.cc
diff --git a/third_party/googletest/samples/sample2.cc b/third_party/googletest/googletest/samples/sample2.cc
index be7c4c9..be7c4c9 100644
--- a/third_party/googletest/samples/sample2.cc
+++ b/third_party/googletest/googletest/samples/sample2.cc
diff --git a/third_party/googletest/samples/sample2.h b/third_party/googletest/googletest/samples/sample2.h
index 15a1ce7..15a1ce7 100644
--- a/third_party/googletest/samples/sample2.h
+++ b/third_party/googletest/googletest/samples/sample2.h
diff --git a/third_party/googletest/samples/sample2_unittest.cc b/third_party/googletest/googletest/samples/sample2_unittest.cc
index cd734f9..cd734f9 100644
--- a/third_party/googletest/samples/sample2_unittest.cc
+++ b/third_party/googletest/googletest/samples/sample2_unittest.cc
diff --git a/third_party/googletest/samples/sample3-inl.h b/third_party/googletest/googletest/samples/sample3-inl.h
index bc3ffb9..bc3ffb9 100644
--- a/third_party/googletest/samples/sample3-inl.h
+++ b/third_party/googletest/googletest/samples/sample3-inl.h
diff --git a/third_party/googletest/samples/sample3_unittest.cc b/third_party/googletest/googletest/samples/sample3_unittest.cc
index 71609c6..71609c6 100644
--- a/third_party/googletest/samples/sample3_unittest.cc
+++ b/third_party/googletest/googletest/samples/sample3_unittest.cc
diff --git a/third_party/googletest/samples/sample4.cc b/third_party/googletest/googletest/samples/sample4.cc
index 489c89b..489c89b 100644
--- a/third_party/googletest/samples/sample4.cc
+++ b/third_party/googletest/googletest/samples/sample4.cc
diff --git a/third_party/googletest/samples/sample4.h b/third_party/googletest/googletest/samples/sample4.h
index 0c4ed92..0c4ed92 100644
--- a/third_party/googletest/samples/sample4.h
+++ b/third_party/googletest/googletest/samples/sample4.h
diff --git a/third_party/googletest/samples/sample4_unittest.cc b/third_party/googletest/googletest/samples/sample4_unittest.cc
index fb9973f..fb9973f 100644
--- a/third_party/googletest/samples/sample4_unittest.cc
+++ b/third_party/googletest/googletest/samples/sample4_unittest.cc
diff --git a/third_party/googletest/samples/sample5_unittest.cc b/third_party/googletest/googletest/samples/sample5_unittest.cc
index cc8c0f0..cc8c0f0 100644
--- a/third_party/googletest/samples/sample5_unittest.cc
+++ b/third_party/googletest/googletest/samples/sample5_unittest.cc
diff --git a/third_party/googletest/samples/sample6_unittest.cc b/third_party/googletest/googletest/samples/sample6_unittest.cc
index cf576f0..cf576f0 100644
--- a/third_party/googletest/samples/sample6_unittest.cc
+++ b/third_party/googletest/googletest/samples/sample6_unittest.cc
diff --git a/third_party/googletest/samples/sample7_unittest.cc b/third_party/googletest/googletest/samples/sample7_unittest.cc
index 3ad22ca..3ad22ca 100644
--- a/third_party/googletest/samples/sample7_unittest.cc
+++ b/third_party/googletest/googletest/samples/sample7_unittest.cc
diff --git a/third_party/googletest/samples/sample8_unittest.cc b/third_party/googletest/googletest/samples/sample8_unittest.cc
index 4df81df..4df81df 100644
--- a/third_party/googletest/samples/sample8_unittest.cc
+++ b/third_party/googletest/googletest/samples/sample8_unittest.cc
diff --git a/third_party/googletest/samples/sample9_unittest.cc b/third_party/googletest/googletest/samples/sample9_unittest.cc
index 0a2f097..0a2f097 100644
--- a/third_party/googletest/samples/sample9_unittest.cc
+++ b/third_party/googletest/googletest/samples/sample9_unittest.cc
diff --git a/third_party/googletest/src/gtest-all.cc b/third_party/googletest/googletest/src/gtest-all.cc
index 2a70ed8..2a70ed8 100644
--- a/third_party/googletest/src/gtest-all.cc
+++ b/third_party/googletest/googletest/src/gtest-all.cc
diff --git a/third_party/googletest/src/gtest-assertion-result.cc b/third_party/googletest/googletest/src/gtest-assertion-result.cc
index 3998921..3998921 100644
--- a/third_party/googletest/src/gtest-assertion-result.cc
+++ b/third_party/googletest/googletest/src/gtest-assertion-result.cc
diff --git a/third_party/googletest/src/gtest-death-test.cc b/third_party/googletest/googletest/src/gtest-death-test.cc
index 4cf78e7..8417a30 100644
--- a/third_party/googletest/src/gtest-death-test.cc
+++ b/third_party/googletest/googletest/src/gtest-death-test.cc
@@ -783,7 +783,7 @@ DeathTest::TestRole WindowsDeathTest::AssumeRole() {
       StreamableToString(static_cast<unsigned int>(::GetCurrentProcessId())) +
       // size_t has the same width as pointers on both 32-bit and 64-bit
       // Windows platforms.
-      // See http://msdn.microsoft.com/en-us/library/tcxf1dw6.aspx.
+      // See https://msdn.microsoft.com/en-us/library/tcxf1dw6.aspx.
       "|" + StreamableToString(reinterpret_cast<size_t>(write_handle)) + "|" +
       StreamableToString(reinterpret_cast<size_t>(event_handle_.Get()));
 
@@ -1128,7 +1128,7 @@ DeathTest::TestRole NoExecDeathTest::AssumeRole() {
     LogToStderr();
     // Event forwarding to the listeners of event listener API mush be shut
     // down in death test subprocesses.
-    GetUnitTestImpl()->listeners()->SuppressEventForwarding();
+    GetUnitTestImpl()->listeners()->SuppressEventForwarding(true);
     g_in_fast_death_test_child = true;
     return EXECUTE_TEST;
   } else {
diff --git a/third_party/googletest/src/gtest-filepath.cc b/third_party/googletest/googletest/src/gtest-filepath.cc
index 75f52bc..513e947 100644
--- a/third_party/googletest/src/gtest-filepath.cc
+++ b/third_party/googletest/googletest/src/gtest-filepath.cc
@@ -102,7 +102,8 @@ FilePath FilePath::GetCurrentDir() {
 #if defined(GTEST_OS_WINDOWS_MOBILE) || defined(GTEST_OS_WINDOWS_PHONE) || \
     defined(GTEST_OS_WINDOWS_RT) || defined(GTEST_OS_ESP8266) ||           \
     defined(GTEST_OS_ESP32) || defined(GTEST_OS_XTENSA) ||                 \
-    defined(GTEST_OS_QURT)
+    defined(GTEST_OS_QURT) || defined(GTEST_OS_NXP_QN9090) ||              \
+    defined(GTEST_OS_NRF52)
   // These platforms do not have a current directory, so we just return
   // something reasonable.
   return FilePath(kCurrentDirectoryString);
@@ -356,7 +357,8 @@ bool FilePath::CreateFolder() const {
 #elif defined(GTEST_OS_WINDOWS)
   int result = _mkdir(pathname_.c_str());
 #elif defined(GTEST_OS_ESP8266) || defined(GTEST_OS_XTENSA) || \
-    defined(GTEST_OS_QURT)
+    defined(GTEST_OS_QURT) || defined(GTEST_OS_NXP_QN9090) ||  \
+    defined(GTEST_OS_NRF52)
   // do nothing
   int result = 0;
 #else
diff --git a/third_party/googletest/src/gtest-internal-inl.h b/third_party/googletest/googletest/src/gtest-internal-inl.h
index 5ba557f..4799a1e 100644
--- a/third_party/googletest/src/gtest-internal-inl.h
+++ b/third_party/googletest/googletest/src/gtest-internal-inl.h
@@ -312,7 +312,7 @@ void ShuffleRange(internal::Random* random, int begin, int end,
       << begin << ", " << size << "].";
 
   // Fisher-Yates shuffle, from
-  // http://en.wikipedia.org/wiki/Fisher-Yates_shuffle
+  // https://en.wikipedia.org/wiki/Fisher-Yates_shuffle
   for (int range_width = end - begin; range_width >= 2; range_width--) {
     const int last_in_range = begin + range_width - 1;
     const int selected =
@@ -387,10 +387,10 @@ class GTEST_API_ UnitTestOptions {
 #ifdef GTEST_OS_WINDOWS
   // Function for supporting the gtest_catch_exception flag.
 
-  // Returns EXCEPTION_EXECUTE_HANDLER if Google Test should handle the
-  // given SEH exception, or EXCEPTION_CONTINUE_SEARCH otherwise.
+  // Returns EXCEPTION_EXECUTE_HANDLER if given SEH exception was handled, or
+  // EXCEPTION_CONTINUE_SEARCH otherwise.
   // This function is useful as an __except condition.
-  static int GTestShouldProcessSEH(DWORD exception_code);
+  static int GTestProcessSEH(DWORD seh_code, const char* location);
 #endif  // GTEST_OS_WINDOWS
 
   // Returns true if "name" matches the ':' separated list of glob-style
@@ -672,7 +672,7 @@ class GTEST_API_ UnitTestImpl {
   void AddTestInfo(internal::SetUpTestSuiteFunc set_up_tc,
                    internal::TearDownTestSuiteFunc tear_down_tc,
                    TestInfo* test_info) {
-#ifdef GTEST_HAS_DEATH_TEST
+#if GTEST_HAS_FILE_SYSTEM
     // In order to support thread-safe death tests, we need to
     // remember the original working directory when the test program
     // was first invoked.  We cannot do this in RUN_ALL_TESTS(), as
@@ -685,7 +685,7 @@ class GTEST_API_ UnitTestImpl {
       GTEST_CHECK_(!original_working_dir_.IsEmpty())
           << "Failed to get the current working directory.";
     }
-#endif  // GTEST_HAS_DEATH_TEST
+#endif  // GTEST_HAS_FILE_SYSTEM
 
     GetTestSuite(test_info->test_suite_name(), test_info->type_param(),
                  set_up_tc, tear_down_tc)
diff --git a/third_party/googletest/src/gtest-matchers.cc b/third_party/googletest/googletest/src/gtest-matchers.cc
index 7e3bcc0..7e3bcc0 100644
--- a/third_party/googletest/src/gtest-matchers.cc
+++ b/third_party/googletest/googletest/src/gtest-matchers.cc
diff --git a/third_party/googletest/src/gtest-port.cc b/third_party/googletest/googletest/src/gtest-port.cc
index 2aaf2bc..2aaf2bc 100644
--- a/third_party/googletest/src/gtest-port.cc
+++ b/third_party/googletest/googletest/src/gtest-port.cc
diff --git a/third_party/googletest/src/gtest-printers.cc b/third_party/googletest/googletest/src/gtest-printers.cc
index 2b47067..e3acecb 100644
--- a/third_party/googletest/src/gtest-printers.cc
+++ b/third_party/googletest/googletest/src/gtest-printers.cc
@@ -216,7 +216,7 @@ static const char* GetCharWidthPrefix(signed char) { return ""; }
 
 static const char* GetCharWidthPrefix(unsigned char) { return ""; }
 
-#ifdef __cpp_char8_t
+#ifdef __cpp_lib_char8_t
 static const char* GetCharWidthPrefix(char8_t) { return "u8"; }
 #endif
 
@@ -232,7 +232,7 @@ static CharFormat PrintAsStringLiteralTo(char c, ostream* os) {
   return PrintAsStringLiteralTo(ToChar32(c), os);
 }
 
-#ifdef __cpp_char8_t
+#ifdef __cpp_lib_char8_t
 static CharFormat PrintAsStringLiteralTo(char8_t c, ostream* os) {
   return PrintAsStringLiteralTo(ToChar32(c), os);
 }
@@ -395,7 +395,7 @@ void UniversalPrintArray(const char* begin, size_t len, ostream* os) {
   UniversalPrintCharArray(begin, len, os);
 }
 
-#ifdef __cpp_char8_t
+#ifdef __cpp_lib_char8_t
 // Prints a (const) char8_t array of 'len' elements, starting at address
 // 'begin'.
 void UniversalPrintArray(const char8_t* begin, size_t len, ostream* os) {
@@ -438,7 +438,7 @@ void PrintCStringTo(const Char* s, ostream* os) {
 
 void PrintTo(const char* s, ostream* os) { PrintCStringTo(s, os); }
 
-#ifdef __cpp_char8_t
+#ifdef __cpp_lib_char8_t
 void PrintTo(const char8_t* s, ostream* os) { PrintCStringTo(s, os); }
 #endif
 
diff --git a/third_party/googletest/src/gtest-test-part.cc b/third_party/googletest/googletest/src/gtest-test-part.cc
index 6f8ddd7..6f8ddd7 100644
--- a/third_party/googletest/src/gtest-test-part.cc
+++ b/third_party/googletest/googletest/src/gtest-test-part.cc
diff --git a/third_party/googletest/src/gtest-typed-test.cc b/third_party/googletest/googletest/src/gtest-typed-test.cc
index b251c09..b251c09 100644
--- a/third_party/googletest/src/gtest-typed-test.cc
+++ b/third_party/googletest/googletest/src/gtest-typed-test.cc
diff --git a/third_party/googletest/src/gtest.cc b/third_party/googletest/googletest/src/gtest.cc
index fb7512c..62dfef6 100644
--- a/third_party/googletest/src/gtest.cc
+++ b/third_party/googletest/googletest/src/gtest.cc
@@ -863,30 +863,39 @@ bool UnitTestOptions::FilterMatchesTest(const std::string& test_suite_name,
 }
 
 #if GTEST_HAS_SEH
-// Returns EXCEPTION_EXECUTE_HANDLER if Google Test should handle the
-// given SEH exception, or EXCEPTION_CONTINUE_SEARCH otherwise.
-// This function is useful as an __except condition.
-int UnitTestOptions::GTestShouldProcessSEH(DWORD exception_code) {
+static std::string FormatSehExceptionMessage(DWORD exception_code,
+                                             const char* location) {
+  Message message;
+  message << "SEH exception with code 0x" << std::setbase(16) << exception_code
+          << std::setbase(10) << " thrown in " << location << ".";
+  return message.GetString();
+}
+
+int UnitTestOptions::GTestProcessSEH(DWORD seh_code, const char* location) {
   // Google Test should handle a SEH exception if:
   //   1. the user wants it to, AND
-  //   2. this is not a breakpoint exception, AND
+  //   2. this is not a breakpoint exception or stack overflow, AND
   //   3. this is not a C++ exception (VC++ implements them via SEH,
   //      apparently).
   //
   // SEH exception code for C++ exceptions.
-  // (see http://support.microsoft.com/kb/185294 for more information).
+  // (see https://support.microsoft.com/kb/185294 for more information).
   const DWORD kCxxExceptionCode = 0xe06d7363;
 
-  bool should_handle = true;
+  if (!GTEST_FLAG_GET(catch_exceptions) || seh_code == kCxxExceptionCode ||
+      seh_code == EXCEPTION_BREAKPOINT ||
+      seh_code == EXCEPTION_STACK_OVERFLOW) {
+    return EXCEPTION_CONTINUE_SEARCH;  // Don't handle these exceptions
+  }
 
-  if (!GTEST_FLAG_GET(catch_exceptions))
-    should_handle = false;
-  else if (exception_code == EXCEPTION_BREAKPOINT)
-    should_handle = false;
-  else if (exception_code == kCxxExceptionCode)
-    should_handle = false;
+  internal::ReportFailureInUnknownLocation(
+      TestPartResult::kFatalFailure,
+      FormatSehExceptionMessage(seh_code, location) +
+          "\n"
+          "Stack trace:\n" +
+          ::testing::internal::GetCurrentOsStackTraceExceptTop(1));
 
-  return should_handle ? EXCEPTION_EXECUTE_HANDLER : EXCEPTION_CONTINUE_SEARCH;
+  return EXCEPTION_EXECUTE_HANDLER;
 }
 #endif  // GTEST_HAS_SEH
 
@@ -2553,23 +2562,6 @@ bool Test::HasSameFixtureClass() {
   return true;
 }
 
-#if GTEST_HAS_SEH
-
-// Adds an "exception thrown" fatal failure to the current test.  This
-// function returns its result via an output parameter pointer because VC++
-// prohibits creation of objects with destructors on stack in functions
-// using __try (see error C2712).
-static std::string* FormatSehExceptionMessage(DWORD exception_code,
-                                              const char* location) {
-  Message message;
-  message << "SEH exception with code 0x" << std::setbase(16) << exception_code
-          << std::setbase(10) << " thrown in " << location << ".";
-
-  return new std::string(message.GetString());
-}
-
-#endif  // GTEST_HAS_SEH
-
 namespace internal {
 
 #if GTEST_HAS_EXCEPTIONS
@@ -2611,16 +2603,8 @@ Result HandleSehExceptionsInMethodIfSupported(T* object, Result (T::*method)(),
 #if GTEST_HAS_SEH
   __try {
     return (object->*method)();
-  } __except (internal::UnitTestOptions::GTestShouldProcessSEH(  // NOLINT
-      GetExceptionCode())) {
-    // We create the exception message on the heap because VC++ prohibits
-    // creation of objects with destructors on stack in functions using __try
-    // (see error C2712).
-    std::string* exception_message =
-        FormatSehExceptionMessage(GetExceptionCode(), location);
-    internal::ReportFailureInUnknownLocation(TestPartResult::kFatalFailure,
-                                             *exception_message);
-    delete exception_message;
+  } __except (internal::UnitTestOptions::GTestProcessSEH(  // NOLINT
+      GetExceptionCode(), location)) {
     return static_cast<Result>(0);
   }
 #else
@@ -3019,7 +3003,8 @@ void TestSuite::Run() {
   internal::HandleExceptionsInMethodIfSupported(
       this, &TestSuite::RunSetUpTestSuite, "SetUpTestSuite()");
 
-  const bool skip_all = ad_hoc_test_result().Failed();
+  const bool skip_all =
+      ad_hoc_test_result().Failed() || ad_hoc_test_result().Skipped();
 
   start_timestamp_ = internal::GetTimeInMillis();
   internal::Timer timer;
@@ -3243,7 +3228,8 @@ static const char* GetAnsiColorCode(GTestColor color) {
     case GTestColor::kYellow:
       return "3";
     default:
-      return nullptr;
+      assert(false);
+      return "9";
   }
 }
 
@@ -5155,8 +5141,8 @@ bool TestEventListeners::EventForwardingEnabled() const {
   return repeater_->forwarding_enabled();
 }
 
-void TestEventListeners::SuppressEventForwarding() {
-  repeater_->set_forwarding_enabled(false);
+void TestEventListeners::SuppressEventForwarding(bool suppress) {
+  repeater_->set_forwarding_enabled(!suppress);
 }
 
 // class UnitTest
@@ -5634,7 +5620,7 @@ void UnitTestImpl::RecordProperty(const TestProperty& test_property) {
 // subprocess. Must not be called before InitGoogleTest.
 void UnitTestImpl::SuppressTestEventsIfInSubprocess() {
   if (internal_run_death_test_flag_ != nullptr)
-    listeners()->SuppressEventForwarding();
+    listeners()->SuppressEventForwarding(true);
 }
 #endif  // GTEST_HAS_DEATH_TEST
 
@@ -5654,8 +5640,10 @@ void UnitTestImpl::ConfigureXmlOutput() {
                         << output_format << "\" ignored.";
   }
 #else
-  GTEST_LOG_(ERROR) << "ERROR: alternative output formats require "
-                    << "GTEST_HAS_FILE_SYSTEM to be enabled";
+  if (!output_format.empty()) {
+    GTEST_LOG_(ERROR) << "ERROR: alternative output formats require "
+                      << "GTEST_HAS_FILE_SYSTEM to be enabled";
+  }
 #endif  // GTEST_HAS_FILE_SYSTEM
 }
 
diff --git a/third_party/googletest/src/gtest_main.cc b/third_party/googletest/googletest/src/gtest_main.cc
index c2e3b3c..8141caf 100644
--- a/third_party/googletest/src/gtest_main.cc
+++ b/third_party/googletest/googletest/src/gtest_main.cc
@@ -31,7 +31,8 @@
 
 #include "gtest/gtest.h"
 
-#if defined(GTEST_OS_ESP8266) || defined(GTEST_OS_ESP32)
+#if defined(GTEST_OS_ESP8266) || defined(GTEST_OS_ESP32) || \
+    (defined(GTEST_OS_NRF52) && defined(ARDUINO))
 // Arduino-like platforms: program entry points are setup/loop instead of main.
 
 #ifdef GTEST_OS_ESP8266
diff --git a/third_party/googletest/test/BUILD.bazel b/third_party/googletest/googletest/test/BUILD.bazel
index 7754c13..1890b6f 100644
--- a/third_party/googletest/test/BUILD.bazel
+++ b/third_party/googletest/googletest/test/BUILD.bazel
@@ -64,6 +64,7 @@ cc_test(
             "googletest-global-environment-unittest_.cc",
             "googletest-break-on-failure-unittest_.cc",
             "googletest-listener-test.cc",
+            "googletest-message-test.cc",
             "googletest-output-test_.cc",
             "googletest-list-tests-unittest_.cc",
             "googletest-shuffle-test_.cc",
diff --git a/third_party/googletest/test/googletest-break-on-failure-unittest.py b/third_party/googletest/googletest/test/googletest-break-on-failure-unittest.py
index e314b5c..e314b5c 100755
--- a/third_party/googletest/test/googletest-break-on-failure-unittest.py
+++ b/third_party/googletest/googletest/test/googletest-break-on-failure-unittest.py
diff --git a/third_party/googletest/test/googletest-break-on-failure-unittest_.cc b/third_party/googletest/googletest/test/googletest-break-on-failure-unittest_.cc
index 337e34c..337e34c 100644
--- a/third_party/googletest/test/googletest-break-on-failure-unittest_.cc
+++ b/third_party/googletest/googletest/test/googletest-break-on-failure-unittest_.cc
diff --git a/third_party/googletest/test/googletest-catch-exceptions-test.py b/third_party/googletest/googletest/test/googletest-catch-exceptions-test.py
index ee4dc9a..180e18d 100755
--- a/third_party/googletest/test/googletest-catch-exceptions-test.py
+++ b/third_party/googletest/googletest/test/googletest-catch-exceptions-test.py
@@ -297,10 +297,10 @@ class CatchCxxExceptionsTest(gtest_test_utils.TestCase):
   def testUnhandledCxxExceptionsAbortTheProgram(self):
     # Filters out SEH exception tests on Windows. Unhandled SEH exceptions
     # cause tests to show pop-up windows there.
-    FITLER_OUT_SEH_TESTS_FLAG = FILTER_FLAG + '=-*Seh*'
+    filter_out_seh_tests_flag = FILTER_FLAG + '=-*Seh*'
     # By default, Google Test doesn't catch the exceptions.
     uncaught_exceptions_ex_binary_output = gtest_test_utils.Subprocess(
-        [EX_EXE_PATH, NO_CATCH_EXCEPTIONS_FLAG, FITLER_OUT_SEH_TESTS_FLAG],
+        [EX_EXE_PATH, NO_CATCH_EXCEPTIONS_FLAG, filter_out_seh_tests_flag],
         env=environ,
     ).output
 
diff --git a/third_party/googletest/test/googletest-catch-exceptions-test_.cc b/third_party/googletest/googletest/test/googletest-catch-exceptions-test_.cc
index 3c8f4f4..3c8f4f4 100644
--- a/third_party/googletest/test/googletest-catch-exceptions-test_.cc
+++ b/third_party/googletest/googletest/test/googletest-catch-exceptions-test_.cc
diff --git a/third_party/googletest/test/googletest-color-test.py b/third_party/googletest/googletest/test/googletest-color-test.py
index 8926a48..8926a48 100755
--- a/third_party/googletest/test/googletest-color-test.py
+++ b/third_party/googletest/googletest/test/googletest-color-test.py
diff --git a/third_party/googletest/test/googletest-color-test_.cc b/third_party/googletest/googletest/test/googletest-color-test_.cc
index 55657b7..55657b7 100644
--- a/third_party/googletest/test/googletest-color-test_.cc
+++ b/third_party/googletest/googletest/test/googletest-color-test_.cc
diff --git a/third_party/googletest/test/googletest-death-test-test.cc b/third_party/googletest/googletest/test/googletest-death-test-test.cc
index 4cc81b7..4cc81b7 100644
--- a/third_party/googletest/test/googletest-death-test-test.cc
+++ b/third_party/googletest/googletest/test/googletest-death-test-test.cc
diff --git a/third_party/googletest/test/googletest-death-test_ex_test.cc b/third_party/googletest/googletest/test/googletest-death-test_ex_test.cc
index 34d5501..34d5501 100644
--- a/third_party/googletest/test/googletest-death-test_ex_test.cc
+++ b/third_party/googletest/googletest/test/googletest-death-test_ex_test.cc
diff --git a/third_party/googletest/test/googletest-env-var-test.py b/third_party/googletest/googletest/test/googletest-env-var-test.py
index 24d8edb..24d8edb 100755
--- a/third_party/googletest/test/googletest-env-var-test.py
+++ b/third_party/googletest/googletest/test/googletest-env-var-test.py
diff --git a/third_party/googletest/test/googletest-env-var-test_.cc b/third_party/googletest/googletest/test/googletest-env-var-test_.cc
index 3653375..3653375 100644
--- a/third_party/googletest/test/googletest-env-var-test_.cc
+++ b/third_party/googletest/googletest/test/googletest-env-var-test_.cc
diff --git a/third_party/googletest/test/googletest-failfast-unittest.py b/third_party/googletest/googletest/test/googletest-failfast-unittest.py
index cdbce0c..cdbce0c 100755
--- a/third_party/googletest/test/googletest-failfast-unittest.py
+++ b/third_party/googletest/googletest/test/googletest-failfast-unittest.py
diff --git a/third_party/googletest/test/googletest-failfast-unittest_.cc b/third_party/googletest/googletest/test/googletest-failfast-unittest_.cc
index 3bd05a8..3bd05a8 100644
--- a/third_party/googletest/test/googletest-failfast-unittest_.cc
+++ b/third_party/googletest/googletest/test/googletest-failfast-unittest_.cc
diff --git a/third_party/googletest/test/googletest-filepath-test.cc b/third_party/googletest/googletest/test/googletest-filepath-test.cc
index 3e9c79f..3e9c79f 100644
--- a/third_party/googletest/test/googletest-filepath-test.cc
+++ b/third_party/googletest/googletest/test/googletest-filepath-test.cc
diff --git a/third_party/googletest/test/googletest-filter-unittest.py b/third_party/googletest/googletest/test/googletest-filter-unittest.py
index f1f3c7a..f1f3c7a 100755
--- a/third_party/googletest/test/googletest-filter-unittest.py
+++ b/third_party/googletest/googletest/test/googletest-filter-unittest.py
diff --git a/third_party/googletest/test/googletest-filter-unittest_.cc b/third_party/googletest/googletest/test/googletest-filter-unittest_.cc
index bc7aa59..bc7aa59 100644
--- a/third_party/googletest/test/googletest-filter-unittest_.cc
+++ b/third_party/googletest/googletest/test/googletest-filter-unittest_.cc
diff --git a/third_party/googletest/test/googletest-global-environment-unittest.py b/third_party/googletest/googletest/test/googletest-global-environment-unittest.py
index bd73a2e..bd73a2e 100644
--- a/third_party/googletest/test/googletest-global-environment-unittest.py
+++ b/third_party/googletest/googletest/test/googletest-global-environment-unittest.py
diff --git a/third_party/googletest/test/googletest-global-environment-unittest_.cc b/third_party/googletest/googletest/test/googletest-global-environment-unittest_.cc
index f401b2f..f401b2f 100644
--- a/third_party/googletest/test/googletest-global-environment-unittest_.cc
+++ b/third_party/googletest/googletest/test/googletest-global-environment-unittest_.cc
diff --git a/third_party/googletest/test/googletest-json-outfiles-test.py b/third_party/googletest/googletest/test/googletest-json-outfiles-test.py
index 5626004..5626004 100644
--- a/third_party/googletest/test/googletest-json-outfiles-test.py
+++ b/third_party/googletest/googletest/test/googletest-json-outfiles-test.py
diff --git a/third_party/googletest/test/googletest-json-output-unittest.py b/third_party/googletest/googletest/test/googletest-json-output-unittest.py
index cb97694..cb97694 100644
--- a/third_party/googletest/test/googletest-json-output-unittest.py
+++ b/third_party/googletest/googletest/test/googletest-json-output-unittest.py
diff --git a/third_party/googletest/test/googletest-list-tests-unittest.py b/third_party/googletest/googletest/test/googletest-list-tests-unittest.py
index 977e57f..977e57f 100755
--- a/third_party/googletest/test/googletest-list-tests-unittest.py
+++ b/third_party/googletest/googletest/test/googletest-list-tests-unittest.py
diff --git a/third_party/googletest/test/googletest-list-tests-unittest_.cc b/third_party/googletest/googletest/test/googletest-list-tests-unittest_.cc
index a1ea6cf..a1ea6cf 100644
--- a/third_party/googletest/test/googletest-list-tests-unittest_.cc
+++ b/third_party/googletest/googletest/test/googletest-list-tests-unittest_.cc
diff --git a/third_party/googletest/test/googletest-listener-test.cc b/third_party/googletest/googletest/test/googletest-listener-test.cc
index d7c47c2..d7c47c2 100644
--- a/third_party/googletest/test/googletest-listener-test.cc
+++ b/third_party/googletest/googletest/test/googletest-listener-test.cc
diff --git a/third_party/googletest/test/googletest-message-test.cc b/third_party/googletest/googletest/test/googletest-message-test.cc
index 54e9d43..bf1f094 100644
--- a/third_party/googletest/test/googletest-message-test.cc
+++ b/third_party/googletest/googletest/test/googletest-message-test.cc
@@ -36,10 +36,26 @@
 #include "gtest/gtest-message.h"
 #include "gtest/gtest.h"
 
+#ifdef GTEST_HAS_ABSL
+#include "absl/strings/str_format.h"
+#endif  // GTEST_HAS_ABSL
+
 namespace {
 
 using ::testing::Message;
 
+#ifdef GTEST_HAS_ABSL
+struct AbslStringifiablePoint {
+  template <typename Sink>
+  friend void AbslStringify(Sink& sink, const AbslStringifiablePoint& p) {
+    absl::Format(&sink, "(%d, %d)", p.x, p.y);
+  }
+
+  int x;
+  int y;
+};
+#endif  // GTEST_HAS_ABSL
+
 // Tests the testing::Message class
 
 // Tests the default constructor.
@@ -128,6 +144,13 @@ TEST(MessageTest, StreamsInt) {
   EXPECT_EQ("123", (Message() << 123).GetString());
 }
 
+#ifdef GTEST_HAS_ABSL
+// Tests streaming a type with an AbslStringify definition.
+TEST(MessageTest, StreamsAbslStringify) {
+  EXPECT_EQ("(1, 2)", (Message() << AbslStringifiablePoint{1, 2}).GetString());
+}
+#endif  // GTEST_HAS_ABSL
+
 // Tests that basic IO manipulators (endl, ends, and flush) can be
 // streamed to Message.
 TEST(MessageTest, StreamsBasicIoManip) {
diff --git a/third_party/googletest/test/googletest-options-test.cc b/third_party/googletest/googletest/test/googletest-options-test.cc
index b712c06..b712c06 100644
--- a/third_party/googletest/test/googletest-options-test.cc
+++ b/third_party/googletest/googletest/test/googletest-options-test.cc
diff --git a/third_party/googletest/test/googletest-output-test-golden-lin.txt b/third_party/googletest/googletest/test/googletest-output-test-golden-lin.txt
index 1f24fb7..6ddf822 100644
--- a/third_party/googletest/test/googletest-output-test-golden-lin.txt
+++ b/third_party/googletest/googletest/test/googletest-output-test-golden-lin.txt
@@ -12,7 +12,7 @@ Expected equality of these values:
   3
 Stack trace: (omitted)
 
-[0;32m[==========] [mRunning 89 tests from 42 test suites.
+[0;32m[==========] [mRunning 90 tests from 43 test suites.
 [0;32m[----------] [mGlobal test environment set-up.
 FooEnvironment::SetUp() called.
 BarEnvironment::SetUp() called.
@@ -967,6 +967,15 @@ Stack trace: (omitted)
 googletest-output-test_.cc:#: Skipped
 
 [0;32m[  SKIPPED ] [mTestSuiteThatFailsToSetUp.ShouldNotRun
+[0;32m[----------] [m1 test from TestSuiteThatSkipsInSetUp
+googletest-output-test_.cc:#: Skipped
+Skip entire test suite
+Stack trace: (omitted)
+
+[0;32m[ RUN      ] [mTestSuiteThatSkipsInSetUp.ShouldNotRun
+googletest-output-test_.cc:#: Skipped
+
+[0;32m[  SKIPPED ] [mTestSuiteThatSkipsInSetUp.ShouldNotRun
 [0;32m[----------] [m1 test from PrintingFailingParams/FailingParamTest
 [0;32m[ RUN      ] [mPrintingFailingParams/FailingParamTest.Fails/0
 googletest-output-test_.cc:#: Failure
@@ -1043,10 +1052,11 @@ Failed
 Expected fatal failure.
 Stack trace: (omitted)
 
-[0;32m[==========] [m89 tests from 42 test suites ran.
+[0;32m[==========] [m90 tests from 43 test suites ran.
 [0;32m[  PASSED  ] [m31 tests.
-[0;32m[  SKIPPED ] [m1 test, listed below:
+[0;32m[  SKIPPED ] [m2 tests, listed below:
 [0;32m[  SKIPPED ] [mTestSuiteThatFailsToSetUp.ShouldNotRun
+[0;32m[  SKIPPED ] [mTestSuiteThatSkipsInSetUp.ShouldNotRun
 [0;31m[  FAILED  ] [m57 tests, listed below:
 [0;31m[  FAILED  ] [mNonfatalFailureTest.EscapesStringOperands
 [0;31m[  FAILED  ] [mNonfatalFailureTest.DiffForLongStrings
diff --git a/third_party/googletest/test/googletest-output-test.py b/third_party/googletest/googletest/test/googletest-output-test.py
index 6d80d53..6d80d53 100755
--- a/third_party/googletest/test/googletest-output-test.py
+++ b/third_party/googletest/googletest/test/googletest-output-test.py
diff --git a/third_party/googletest/test/googletest-output-test_.cc b/third_party/googletest/googletest/test/googletest-output-test_.cc
index f1facf5..e3560c0 100644
--- a/third_party/googletest/test/googletest-output-test_.cc
+++ b/third_party/googletest/googletest/test/googletest-output-test_.cc
@@ -1007,6 +1007,12 @@ class TestSuiteThatFailsToSetUp : public testing::Test {
 };
 TEST_F(TestSuiteThatFailsToSetUp, ShouldNotRun) { std::abort(); }
 
+class TestSuiteThatSkipsInSetUp : public testing::Test {
+ public:
+  static void SetUpTestSuite() { GTEST_SKIP() << "Skip entire test suite"; }
+};
+TEST_F(TestSuiteThatSkipsInSetUp, ShouldNotRun) { std::abort(); }
+
 // The main function.
 //
 // The idea is to use Google Test to run all the tests we have defined (some
diff --git a/third_party/googletest/test/googletest-param-test-invalid-name1-test.py b/third_party/googletest/googletest/test/googletest-param-test-invalid-name1-test.py
index 4886e49..4886e49 100644
--- a/third_party/googletest/test/googletest-param-test-invalid-name1-test.py
+++ b/third_party/googletest/googletest/test/googletest-param-test-invalid-name1-test.py
diff --git a/third_party/googletest/test/googletest-param-test-invalid-name1-test_.cc b/third_party/googletest/googletest/test/googletest-param-test-invalid-name1-test_.cc
index 004733a..004733a 100644
--- a/third_party/googletest/test/googletest-param-test-invalid-name1-test_.cc
+++ b/third_party/googletest/googletest/test/googletest-param-test-invalid-name1-test_.cc
diff --git a/third_party/googletest/test/googletest-param-test-invalid-name2-test.py b/third_party/googletest/googletest/test/googletest-param-test-invalid-name2-test.py
index bcd8ddf..bcd8ddf 100644
--- a/third_party/googletest/test/googletest-param-test-invalid-name2-test.py
+++ b/third_party/googletest/googletest/test/googletest-param-test-invalid-name2-test.py
diff --git a/third_party/googletest/test/googletest-param-test-invalid-name2-test_.cc b/third_party/googletest/googletest/test/googletest-param-test-invalid-name2-test_.cc
index 6d88a9c..6d88a9c 100644
--- a/third_party/googletest/test/googletest-param-test-invalid-name2-test_.cc
+++ b/third_party/googletest/googletest/test/googletest-param-test-invalid-name2-test_.cc
diff --git a/third_party/googletest/test/googletest-param-test-test.cc b/third_party/googletest/googletest/test/googletest-param-test-test.cc
index c9c5e78..c9c5e78 100644
--- a/third_party/googletest/test/googletest-param-test-test.cc
+++ b/third_party/googletest/googletest/test/googletest-param-test-test.cc
diff --git a/third_party/googletest/test/googletest-param-test-test.h b/third_party/googletest/googletest/test/googletest-param-test-test.h
index 6d77e10..6d77e10 100644
--- a/third_party/googletest/test/googletest-param-test-test.h
+++ b/third_party/googletest/googletest/test/googletest-param-test-test.h
diff --git a/third_party/googletest/test/googletest-param-test2-test.cc b/third_party/googletest/googletest/test/googletest-param-test2-test.cc
index 71727a6..71727a6 100644
--- a/third_party/googletest/test/googletest-param-test2-test.cc
+++ b/third_party/googletest/googletest/test/googletest-param-test2-test.cc
diff --git a/third_party/googletest/test/googletest-port-test.cc b/third_party/googletest/googletest/test/googletest-port-test.cc
index 32a2a7b..e0793ba 100644
--- a/third_party/googletest/test/googletest-port-test.cc
+++ b/third_party/googletest/googletest/test/googletest-port-test.cc
@@ -418,8 +418,8 @@ TYPED_TEST(RETest, ImplicitConstructorWorks) {
   const RE simple(TypeParam("hello"));
   EXPECT_STREQ("hello", simple.pattern());
 
-  const RE normal(TypeParam(".*(\\w+)"));
-  EXPECT_STREQ(".*(\\w+)", normal.pattern());
+  const RE normal(TypeParam(".*([[:alnum:]_]+)"));
+  EXPECT_STREQ(".*([[:alnum:]_]+)", normal.pattern());
 }
 
 // Tests that RE's constructors reject invalid regular expressions.
diff --git a/third_party/googletest/test/googletest-printers-test.cc b/third_party/googletest/googletest/test/googletest-printers-test.cc
index f44f29a..d5061be 100644
--- a/third_party/googletest/test/googletest-printers-test.cc
+++ b/third_party/googletest/googletest/test/googletest-printers-test.cc
@@ -54,6 +54,15 @@
 
 #include "gtest/gtest-printers.h"
 #include "gtest/gtest.h"
+#include "gtest/internal/gtest-port.h"
+
+#ifdef GTEST_HAS_ABSL
+#include "absl/strings/str_format.h"
+#endif
+
+#if GTEST_INTERNAL_HAS_STD_SPAN
+#include <span>  // NOLINT
+#endif  // GTEST_INTERNAL_HAS_STD_SPAN
 
 // Some user-defined types for testing the universal value printer.
 
@@ -119,6 +128,19 @@ void operator<<(::std::ostream& os, const StreamableInGlobal* /* x */) {
   os << "StreamableInGlobal*";
 }
 
+#ifdef GTEST_HAS_ABSL
+// A user-defined type with AbslStringify
+struct Point {
+  template <typename Sink>
+  friend void AbslStringify(Sink& sink, const Point& p) {
+    absl::Format(&sink, "(%d, %d)", p.x, p.y);
+  }
+
+  int x = 10;
+  int y = 20;
+};
+#endif
+
 namespace foo {
 
 // A user-defined unprintable type in a user namespace.
@@ -317,6 +339,11 @@ TEST(PrintEnumTest, EnumWithPrintTo) {
   EXPECT_EQ("invalid", Print(static_cast<EnumWithPrintTo>(0)));
 }
 
+#ifdef GTEST_HAS_ABSL
+// Tests printing a class that defines AbslStringify
+TEST(PrintClassTest, AbslStringify) { EXPECT_EQ("(10, 20)", Print(Point())); }
+#endif
+
 // Tests printing a class implicitly convertible to BiggestInt.
 
 TEST(PrintClassTest, BiggestIntConvertible) {
@@ -1157,6 +1184,17 @@ TEST(PrintStlContainerTest, Vector) {
   EXPECT_EQ("{ 1, 2 }", Print(v));
 }
 
+TEST(PrintStlContainerTest, StdSpan) {
+#if GTEST_INTERNAL_HAS_STD_SPAN
+  int a[] = {3, 6, 5};
+  std::span<int> s = a;
+
+  EXPECT_EQ("{ 3, 6, 5 }", Print(s));
+#else
+  GTEST_SKIP() << "Does not have std::span.";
+#endif  // GTEST_INTERNAL_HAS_STD_SPAN
+}
+
 TEST(PrintStlContainerTest, LongSequence) {
   const int a[100] = {1, 2, 3};
   const vector<int> v(a, a + 100);
@@ -1636,6 +1674,12 @@ TEST(PrintToStringTest, PrintReferenceToStreamableInGlobal) {
   EXPECT_STREQ("StreamableInGlobal", PrintToString(r).c_str());
 }
 
+#ifdef GTEST_HAS_ABSL
+TEST(PrintToStringTest, AbslStringify) {
+  EXPECT_PRINT_TO_STRING_(Point(), "(10, 20)");
+}
+#endif
+
 TEST(IsValidUTF8Test, IllFormedUTF8) {
   // The following test strings are ill-formed UTF-8 and are printed
   // as hex only (or ASCII, in case of ASCII bytes) because IsValidUTF8() is
diff --git a/third_party/googletest/test/googletest-setuptestsuite-test.py b/third_party/googletest/googletest/test/googletest-setuptestsuite-test.py
index 899531f..899531f 100755
--- a/third_party/googletest/test/googletest-setuptestsuite-test.py
+++ b/third_party/googletest/googletest/test/googletest-setuptestsuite-test.py
diff --git a/third_party/googletest/test/googletest-setuptestsuite-test_.cc b/third_party/googletest/googletest/test/googletest-setuptestsuite-test_.cc
index d20899f..d20899f 100644
--- a/third_party/googletest/test/googletest-setuptestsuite-test_.cc
+++ b/third_party/googletest/googletest/test/googletest-setuptestsuite-test_.cc
diff --git a/third_party/googletest/test/googletest-shuffle-test.py b/third_party/googletest/googletest/test/googletest-shuffle-test.py
index 61e3a15..61e3a15 100755
--- a/third_party/googletest/test/googletest-shuffle-test.py
+++ b/third_party/googletest/googletest/test/googletest-shuffle-test.py
diff --git a/third_party/googletest/test/googletest-shuffle-test_.cc b/third_party/googletest/googletest/test/googletest-shuffle-test_.cc
index b570c48..b570c48 100644
--- a/third_party/googletest/test/googletest-shuffle-test_.cc
+++ b/third_party/googletest/googletest/test/googletest-shuffle-test_.cc
diff --git a/third_party/googletest/test/googletest-test-part-test.cc b/third_party/googletest/googletest/test/googletest-test-part-test.cc
index 076e5be..076e5be 100644
--- a/third_party/googletest/test/googletest-test-part-test.cc
+++ b/third_party/googletest/googletest/test/googletest-test-part-test.cc
diff --git a/third_party/googletest/test/googletest-throw-on-failure-test.py b/third_party/googletest/googletest/test/googletest-throw-on-failure-test.py
index 106b004..106b004 100755
--- a/third_party/googletest/test/googletest-throw-on-failure-test.py
+++ b/third_party/googletest/googletest/test/googletest-throw-on-failure-test.py
diff --git a/third_party/googletest/test/googletest-throw-on-failure-test_.cc b/third_party/googletest/googletest/test/googletest-throw-on-failure-test_.cc
index 3b81a5a..3b81a5a 100644
--- a/third_party/googletest/test/googletest-throw-on-failure-test_.cc
+++ b/third_party/googletest/googletest/test/googletest-throw-on-failure-test_.cc
diff --git a/third_party/googletest/test/googletest-uninitialized-test.py b/third_party/googletest/googletest/test/googletest-uninitialized-test.py
index e5af7c8..e5af7c8 100755
--- a/third_party/googletest/test/googletest-uninitialized-test.py
+++ b/third_party/googletest/googletest/test/googletest-uninitialized-test.py
diff --git a/third_party/googletest/test/googletest-uninitialized-test_.cc b/third_party/googletest/googletest/test/googletest-uninitialized-test_.cc
index 88b61fc..88b61fc 100644
--- a/third_party/googletest/test/googletest-uninitialized-test_.cc
+++ b/third_party/googletest/googletest/test/googletest-uninitialized-test_.cc
diff --git a/third_party/googletest/test/gtest-typed-test2_test.cc b/third_party/googletest/googletest/test/gtest-typed-test2_test.cc
index f2eae12..f2eae12 100644
--- a/third_party/googletest/test/gtest-typed-test2_test.cc
+++ b/third_party/googletest/googletest/test/gtest-typed-test2_test.cc
diff --git a/third_party/googletest/test/gtest-typed-test_test.cc b/third_party/googletest/googletest/test/gtest-typed-test_test.cc
index 0cc8b21..0cc8b21 100644
--- a/third_party/googletest/test/gtest-typed-test_test.cc
+++ b/third_party/googletest/googletest/test/gtest-typed-test_test.cc
diff --git a/third_party/googletest/test/gtest-typed-test_test.h b/third_party/googletest/googletest/test/gtest-typed-test_test.h
index f3ef0a5..f3ef0a5 100644
--- a/third_party/googletest/test/gtest-typed-test_test.h
+++ b/third_party/googletest/googletest/test/gtest-typed-test_test.h
diff --git a/third_party/googletest/test/gtest-unittest-api_test.cc b/third_party/googletest/googletest/test/gtest-unittest-api_test.cc
index 2ea6927..2ea6927 100644
--- a/third_party/googletest/test/gtest-unittest-api_test.cc
+++ b/third_party/googletest/googletest/test/gtest-unittest-api_test.cc
diff --git a/third_party/googletest/test/gtest_all_test.cc b/third_party/googletest/googletest/test/gtest_all_test.cc
index 615b29b..615b29b 100644
--- a/third_party/googletest/test/gtest_all_test.cc
+++ b/third_party/googletest/googletest/test/gtest_all_test.cc
diff --git a/third_party/googletest/test/gtest_assert_by_exception_test.cc b/third_party/googletest/googletest/test/gtest_assert_by_exception_test.cc
index f507eac..f507eac 100644
--- a/third_party/googletest/test/gtest_assert_by_exception_test.cc
+++ b/third_party/googletest/googletest/test/gtest_assert_by_exception_test.cc
diff --git a/third_party/googletest/test/gtest_dirs_test.cc b/third_party/googletest/googletest/test/gtest_dirs_test.cc
index 1a5b63d..1a5b63d 100644
--- a/third_party/googletest/test/gtest_dirs_test.cc
+++ b/third_party/googletest/googletest/test/gtest_dirs_test.cc
diff --git a/third_party/googletest/test/gtest_environment_test.cc b/third_party/googletest/googletest/test/gtest_environment_test.cc
index 122eaf3..122eaf3 100644
--- a/third_party/googletest/test/gtest_environment_test.cc
+++ b/third_party/googletest/googletest/test/gtest_environment_test.cc
diff --git a/third_party/googletest/test/gtest_help_test.py b/third_party/googletest/googletest/test/gtest_help_test.py
index 85a0c33..38fc90f 100755
--- a/third_party/googletest/test/gtest_help_test.py
+++ b/third_party/googletest/googletest/test/gtest_help_test.py
@@ -43,11 +43,22 @@ import sys
 from googletest.test import gtest_test_utils
 
 
+FREEBSD = ('FreeBSD', 'GNU/kFreeBSD')
+NETBSD = ('NetBSD',)
+OPENBSD = ('OpenBSD',)
+
+
+def is_bsd_based_os() -> bool:
+  """Determine whether or not the OS is BSD-based."""
+  if os.name != 'posix':
+    return False
+
+  return os.uname()[0] in (FREEBSD + NETBSD + OPENBSD)
+
+
 IS_DARWIN = os.name == 'posix' and os.uname()[0] == 'Darwin'
 IS_LINUX = os.name == 'posix' and os.uname()[0] == 'Linux'
 IS_GNUHURD = os.name == 'posix' and os.uname()[0] == 'GNU'
-IS_GNUKFREEBSD = os.name == 'posix' and os.uname()[0] == 'GNU/kFreeBSD'
-IS_OPENBSD = os.name == 'posix' and os.uname()[0] == 'OpenBSD'
 IS_WINDOWS = os.name == 'nt'
 
 PROGRAM_PATH = gtest_test_utils.GetTestExecutablePath('gtest_help_test_')
@@ -96,7 +107,7 @@ HELP_REGEX = re.compile(
 )
 
 
-def RunWithFlag(flag):
+def run_with_flag(flag):
   """Runs gtest_help_test_ with the given flag.
 
   Returns:
@@ -116,17 +127,14 @@ def RunWithFlag(flag):
 class GTestHelpTest(gtest_test_utils.TestCase):
   """Tests the --help flag and its equivalent forms."""
 
-  def TestHelpFlag(self, flag):
+  def test_prints_help_with_full_flag(self):
     """Verifies correct behavior when help flag is specified.
 
     The right message must be printed and the tests must
     skipped when the given flag is specified.
-
-    Args:
-      flag:  A flag to pass to the binary or None.
     """
 
-    exit_code, output = RunWithFlag(flag)
+    exit_code, output = run_with_flag('--help')
     if HAS_ABSL_FLAGS:
       # The Abseil flags library prints the ProgramUsageMessage() with
       # --help and returns 1.
@@ -136,7 +144,7 @@ class GTestHelpTest(gtest_test_utils.TestCase):
 
     self.assertTrue(HELP_REGEX.search(output), output)
 
-    if IS_DARWIN or IS_LINUX or IS_GNUHURD or IS_GNUKFREEBSD or IS_OPENBSD:
+    if IS_DARWIN or IS_LINUX or IS_GNUHURD or is_bsd_based_os():
       self.assertIn(STREAM_RESULT_TO_FLAG, output)
     else:
       self.assertNotIn(STREAM_RESULT_TO_FLAG, output)
@@ -146,53 +154,27 @@ class GTestHelpTest(gtest_test_utils.TestCase):
     else:
       self.assertNotIn(DEATH_TEST_STYLE_FLAG, output)
 
-  def TestUnknownFlagWithAbseil(self, flag):
-    """Verifies correct behavior when an unknown flag is specified.
-
-    The right message must be printed and the tests must
-    skipped when the given flag is specified.
-
-    Args:
-      flag:  A flag to pass to the binary or None.
-    """
-    exit_code, output = RunWithFlag(flag)
-    self.assertEqual(1, exit_code)
-    self.assertIn('ERROR: Unknown command line flag', output)
-
-  def TestNonHelpFlag(self, flag):
+  def test_runs_tests_without_help_flag(self):
     """Verifies correct behavior when no help flag is specified.
 
     Verifies that when no help flag is specified, the tests are run
     and the help message is not printed.
-
-    Args:
-      flag:  A flag to pass to the binary or None.
     """
 
-    exit_code, output = RunWithFlag(flag)
+    exit_code, output = run_with_flag(None)
     self.assertNotEqual(exit_code, 0)
     self.assertFalse(HELP_REGEX.search(output), output)
 
-  def testPrintsHelpWithFullFlag(self):
-    self.TestHelpFlag('--help')
-
-  def testRunsTestsWithoutHelpFlag(self):
-    """Verifies correct behavior when no help flag is specified.
-
-    Verifies that when no help flag is specified, the tests are run
-    and the help message is not printed.
-    """
-
-    self.TestNonHelpFlag(None)
-
-  def testRunsTestsWithGtestInternalFlag(self):
+  def test_runs_tests_with_gtest_internal_flag(self):
     """Verifies correct behavior when internal testing flag is specified.
 
     Verifies that the tests are run and no help message is printed when
     a flag starting with Google Test prefix and 'internal_' is supplied.
     """
 
-    self.TestNonHelpFlag(INTERNAL_FLAG_FOR_TESTING)
+    exit_code, output = run_with_flag(INTERNAL_FLAG_FOR_TESTING)
+    self.assertNotEqual(exit_code, 0)
+    self.assertFalse(HELP_REGEX.search(output), output)
 
 
 if __name__ == '__main__':
diff --git a/third_party/googletest/test/gtest_help_test_.cc b/third_party/googletest/googletest/test/gtest_help_test_.cc
index 18b5f3c..18b5f3c 100644
--- a/third_party/googletest/test/gtest_help_test_.cc
+++ b/third_party/googletest/googletest/test/gtest_help_test_.cc
diff --git a/third_party/googletest/test/gtest_json_test_utils.py b/third_party/googletest/googletest/test/gtest_json_test_utils.py
index 86a5925..86a5925 100644
--- a/third_party/googletest/test/gtest_json_test_utils.py
+++ b/third_party/googletest/googletest/test/gtest_json_test_utils.py
diff --git a/third_party/googletest/test/gtest_list_output_unittest.py b/third_party/googletest/googletest/test/gtest_list_output_unittest.py
index afd521d..afd521d 100644
--- a/third_party/googletest/test/gtest_list_output_unittest.py
+++ b/third_party/googletest/googletest/test/gtest_list_output_unittest.py
diff --git a/third_party/googletest/test/gtest_list_output_unittest_.cc b/third_party/googletest/googletest/test/gtest_list_output_unittest_.cc
index 92b9d4f..92b9d4f 100644
--- a/third_party/googletest/test/gtest_list_output_unittest_.cc
+++ b/third_party/googletest/googletest/test/gtest_list_output_unittest_.cc
diff --git a/third_party/googletest/test/gtest_main_unittest.cc b/third_party/googletest/googletest/test/gtest_main_unittest.cc
index 29cd551..29cd551 100644
--- a/third_party/googletest/test/gtest_main_unittest.cc
+++ b/third_party/googletest/googletest/test/gtest_main_unittest.cc
diff --git a/third_party/googletest/test/gtest_no_test_unittest.cc b/third_party/googletest/googletest/test/gtest_no_test_unittest.cc
index d4f88db..d4f88db 100644
--- a/third_party/googletest/test/gtest_no_test_unittest.cc
+++ b/third_party/googletest/googletest/test/gtest_no_test_unittest.cc
diff --git a/third_party/googletest/test/gtest_pred_impl_unittest.cc b/third_party/googletest/googletest/test/gtest_pred_impl_unittest.cc
index 033e2d9..033e2d9 100644
--- a/third_party/googletest/test/gtest_pred_impl_unittest.cc
+++ b/third_party/googletest/googletest/test/gtest_pred_impl_unittest.cc
diff --git a/third_party/googletest/test/gtest_premature_exit_test.cc b/third_party/googletest/googletest/test/gtest_premature_exit_test.cc
index 1a0c5ea..1a0c5ea 100644
--- a/third_party/googletest/test/gtest_premature_exit_test.cc
+++ b/third_party/googletest/googletest/test/gtest_premature_exit_test.cc
diff --git a/third_party/googletest/test/gtest_prod_test.cc b/third_party/googletest/googletest/test/gtest_prod_test.cc
index ede81a0..ede81a0 100644
--- a/third_party/googletest/test/gtest_prod_test.cc
+++ b/third_party/googletest/googletest/test/gtest_prod_test.cc
diff --git a/third_party/googletest/test/gtest_repeat_test.cc b/third_party/googletest/googletest/test/gtest_repeat_test.cc
index f67b788..f67b788 100644
--- a/third_party/googletest/test/gtest_repeat_test.cc
+++ b/third_party/googletest/googletest/test/gtest_repeat_test.cc
diff --git a/third_party/googletest/test/gtest_skip_check_output_test.py b/third_party/googletest/googletest/test/gtest_skip_check_output_test.py
index b30a165..b30a165 100755
--- a/third_party/googletest/test/gtest_skip_check_output_test.py
+++ b/third_party/googletest/googletest/test/gtest_skip_check_output_test.py
diff --git a/third_party/googletest/test/gtest_skip_environment_check_output_test.py b/third_party/googletest/googletest/test/gtest_skip_environment_check_output_test.py
index 388a4e9..388a4e9 100755
--- a/third_party/googletest/test/gtest_skip_environment_check_output_test.py
+++ b/third_party/googletest/googletest/test/gtest_skip_environment_check_output_test.py
diff --git a/third_party/googletest/test/gtest_skip_in_environment_setup_test.cc b/third_party/googletest/googletest/test/gtest_skip_in_environment_setup_test.cc
index 5f21c27..5f21c27 100644
--- a/third_party/googletest/test/gtest_skip_in_environment_setup_test.cc
+++ b/third_party/googletest/googletest/test/gtest_skip_in_environment_setup_test.cc
diff --git a/third_party/googletest/test/gtest_skip_test.cc b/third_party/googletest/googletest/test/gtest_skip_test.cc
index e1b8d65..e1b8d65 100644
--- a/third_party/googletest/test/gtest_skip_test.cc
+++ b/third_party/googletest/googletest/test/gtest_skip_test.cc
diff --git a/third_party/googletest/test/gtest_sole_header_test.cc b/third_party/googletest/googletest/test/gtest_sole_header_test.cc
index e8e22a8..e8e22a8 100644
--- a/third_party/googletest/test/gtest_sole_header_test.cc
+++ b/third_party/googletest/googletest/test/gtest_sole_header_test.cc
diff --git a/third_party/googletest/test/gtest_stress_test.cc b/third_party/googletest/googletest/test/gtest_stress_test.cc
index af8e757..af8e757 100644
--- a/third_party/googletest/test/gtest_stress_test.cc
+++ b/third_party/googletest/googletest/test/gtest_stress_test.cc
diff --git a/third_party/googletest/test/gtest_test_macro_stack_footprint_test.cc b/third_party/googletest/googletest/test/gtest_test_macro_stack_footprint_test.cc
index 45f368b..45f368b 100644
--- a/third_party/googletest/test/gtest_test_macro_stack_footprint_test.cc
+++ b/third_party/googletest/googletest/test/gtest_test_macro_stack_footprint_test.cc
diff --git a/third_party/googletest/test/gtest_test_utils.py b/third_party/googletest/googletest/test/gtest_test_utils.py
index 964fa9f..964fa9f 100755
--- a/third_party/googletest/test/gtest_test_utils.py
+++ b/third_party/googletest/googletest/test/gtest_test_utils.py
diff --git a/third_party/googletest/test/gtest_testbridge_test.py b/third_party/googletest/googletest/test/gtest_testbridge_test.py
index 0d58758..0d58758 100755
--- a/third_party/googletest/test/gtest_testbridge_test.py
+++ b/third_party/googletest/googletest/test/gtest_testbridge_test.py
diff --git a/third_party/googletest/test/gtest_testbridge_test_.cc b/third_party/googletest/googletest/test/gtest_testbridge_test_.cc
index c2c000d..c2c000d 100644
--- a/third_party/googletest/test/gtest_testbridge_test_.cc
+++ b/third_party/googletest/googletest/test/gtest_testbridge_test_.cc
diff --git a/third_party/googletest/test/gtest_throw_on_failure_ex_test.cc b/third_party/googletest/googletest/test/gtest_throw_on_failure_ex_test.cc
index 25d7c79..25d7c79 100644
--- a/third_party/googletest/test/gtest_throw_on_failure_ex_test.cc
+++ b/third_party/googletest/googletest/test/gtest_throw_on_failure_ex_test.cc
diff --git a/third_party/googletest/test/gtest_unittest.cc b/third_party/googletest/googletest/test/gtest_unittest.cc
index 77d968a..67d776e 100644
--- a/third_party/googletest/test/gtest_unittest.cc
+++ b/third_party/googletest/googletest/test/gtest_unittest.cc
@@ -67,11 +67,27 @@ TEST(CommandLineFlagsTest, CanBeAccessedInCodeOnceGTestHIsIncluded) {
 #include <string>
 #include <type_traits>
 #include <unordered_set>
+#include <utility>
 #include <vector>
 
 #include "gtest/gtest-spi.h"
 #include "src/gtest-internal-inl.h"
 
+struct ConvertibleGlobalType {
+  // The inner enable_if is to ensure invoking is_constructible doesn't fail.
+  // The outer enable_if is to ensure the overload resolution doesn't encounter
+  // an ambiguity.
+  template <
+      class T,
+      std::enable_if_t<
+          false, std::enable_if_t<std::is_constructible<T>::value, int>> = 0>
+  operator T() const;  // NOLINT(google-explicit-constructor)
+};
+void operator<<(ConvertibleGlobalType&, int);
+static_assert(sizeof(decltype(std::declval<ConvertibleGlobalType&>()
+                              << 1)(*)()) > 0,
+              "error in operator<< overload resolution");
+
 namespace testing {
 namespace internal {
 
@@ -173,7 +189,7 @@ class TestEventListenersAccessor {
   }
 
   static void SuppressEventForwarding(TestEventListeners* listeners) {
-    listeners->SuppressEventForwarding();
+    listeners->SuppressEventForwarding(true);
   }
 };
 
@@ -4097,7 +4113,7 @@ TEST(ExpectThrowTest, DoesNotGenerateUnreachableCodeWarning) {
 
   EXPECT_THROW(throw 1, int);
   EXPECT_NONFATAL_FAILURE(EXPECT_THROW(n++, int), "");
-  EXPECT_NONFATAL_FAILURE(EXPECT_THROW(throw 1, const char*), "");
+  EXPECT_NONFATAL_FAILURE(EXPECT_THROW(throw n, const char*), "");
   EXPECT_NO_THROW(n++);
   EXPECT_NONFATAL_FAILURE(EXPECT_NO_THROW(throw 1), "");
   EXPECT_ANY_THROW(throw 1);
diff --git a/third_party/googletest/test/gtest_xml_outfile1_test_.cc b/third_party/googletest/googletest/test/gtest_xml_outfile1_test_.cc
index 19aa252..19aa252 100644
--- a/third_party/googletest/test/gtest_xml_outfile1_test_.cc
+++ b/third_party/googletest/googletest/test/gtest_xml_outfile1_test_.cc
diff --git a/third_party/googletest/test/gtest_xml_outfile2_test_.cc b/third_party/googletest/googletest/test/gtest_xml_outfile2_test_.cc
index 4a76429..4a76429 100644
--- a/third_party/googletest/test/gtest_xml_outfile2_test_.cc
+++ b/third_party/googletest/googletest/test/gtest_xml_outfile2_test_.cc
diff --git a/third_party/googletest/test/gtest_xml_outfiles_test.py b/third_party/googletest/googletest/test/gtest_xml_outfiles_test.py
index d17cc0c..d17cc0c 100755
--- a/third_party/googletest/test/gtest_xml_outfiles_test.py
+++ b/third_party/googletest/googletest/test/gtest_xml_outfiles_test.py
diff --git a/third_party/googletest/test/gtest_xml_output_unittest.py b/third_party/googletest/googletest/test/gtest_xml_output_unittest.py
index 422569e..422569e 100755
--- a/third_party/googletest/test/gtest_xml_output_unittest.py
+++ b/third_party/googletest/googletest/test/gtest_xml_output_unittest.py
diff --git a/third_party/googletest/test/gtest_xml_output_unittest_.cc b/third_party/googletest/googletest/test/gtest_xml_output_unittest_.cc
index 0ab3302..0ab3302 100644
--- a/third_party/googletest/test/gtest_xml_output_unittest_.cc
+++ b/third_party/googletest/googletest/test/gtest_xml_output_unittest_.cc
diff --git a/third_party/googletest/test/gtest_xml_test_utils.py b/third_party/googletest/googletest/test/gtest_xml_test_utils.py
index 74e0f4a..74e0f4a 100755
--- a/third_party/googletest/test/gtest_xml_test_utils.py
+++ b/third_party/googletest/googletest/test/gtest_xml_test_utils.py
diff --git a/third_party/googletest/test/production.cc b/third_party/googletest/googletest/test/production.cc
index 0f69f6d..0f69f6d 100644
--- a/third_party/googletest/test/production.cc
+++ b/third_party/googletest/googletest/test/production.cc
diff --git a/third_party/googletest/test/production.h b/third_party/googletest/googletest/test/production.h
index 4dec8d4..4dec8d4 100644
--- a/third_party/googletest/test/production.h
+++ b/third_party/googletest/googletest/test/production.h
diff --git a/third_party/googletest/googletest_deps.bzl b/third_party/googletest/googletest_deps.bzl
new file mode 100644
index 0000000..e25f5a1
--- /dev/null
+++ b/third_party/googletest/googletest_deps.bzl
@@ -0,0 +1,22 @@
+"""Load dependencies needed to use the googletest library as a 3rd-party consumer."""
+
+load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
+
+def googletest_deps():
+    """Loads common dependencies needed to use the googletest library."""
+
+    if not native.existing_rule("com_googlesource_code_re2"):
+        http_archive(
+            name = "com_googlesource_code_re2",  # 2023-03-17T11:36:51Z
+            sha256 = "cb8b5312a65f2598954545a76e8bce913f35fbb3a21a5c88797a4448e9f9b9d9",
+            strip_prefix = "re2-578843a516fd1da7084ae46209a75f3613b6065e",
+            urls = ["https://github.com/google/re2/archive/578843a516fd1da7084ae46209a75f3613b6065e.zip"],
+        )
+
+    if not native.existing_rule("com_google_absl"):
+        http_archive(
+            name = "com_google_absl",  # 2023-08-01T14:59:13Z
+            sha256 = "d2c09bf3b3aba57ad87a56082020bee2948445407756e92ddaf3595396086853",
+            strip_prefix = "abseil-cpp-22091f4c0d6626b3ef40446ce3d4ccab19425ca3",
+            urls = ["https://github.com/abseil/abseil-cpp/archive/22091f4c0d6626b3ef40446ce3d4ccab19425ca3.zip"],
+        )
author	David Benjamin <davidben@google.com>	2023-09-01 21:23:01 -0400
committer	Boringssl LUCI CQ <boringssl-scoped@luci-project-accounts.iam.gserviceaccount.com>	2023-09-05 21:11:19 +0000
commit	fa343af32b77f5f005a651656732ae3f0b526774 (patch)
tree	d477a6527b92aa2fc074a263493581670dcd0df7 /third_party
parent	db1e9877fdabaf88494e2314cd527f09d5790281 (diff)
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