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diff --git a/docs/devel/testing.rst b/docs/devel/testing.rst new file mode 100644 index 0000000..0ca1a2d --- /dev/null +++ b/docs/devel/testing.rst @@ -0,0 +1,486 @@ +=============== +Testing in QEMU +=============== + +This document describes the testing infrastructure in QEMU. + +Testing with "make check" +========================= + +The "make check" testing family includes most of the C based tests in QEMU. For +a quick help, run ``make check-help`` from the source tree. + +The usual way to run these tests is: + +.. code:: + + make check + +which includes QAPI schema tests, unit tests, and QTests. Different sub-types +of "make check" tests will be explained below. + +Before running tests, it is best to build QEMU programs first. Some tests +expect the executables to exist and will fail with obscure messages if they +cannot find them. + +Unit tests +---------- + +Unit tests, which can be invoked with ``make check-unit``, are simple C tests +that typically link to individual QEMU object files and exercise them by +calling exported functions. + +If you are writing new code in QEMU, consider adding a unit test, especially +for utility modules that are relatively stateless or have few dependencies. To +add a new unit test: + +1. Create a new source file. For example, ``tests/foo-test.c``. + +2. Write the test. Normally you would include the header file which exports + the module API, then verify the interface behaves as expected from your + test. The test code should be organized with the glib testing framework. + Copying and modifying an existing test is usually a good idea. + +3. Add the test to ``tests/Makefile.include``. First, name the unit test + program and add it to ``$(check-unit-y)``; then add a rule to build the + executable. Optionally, you can add a magical variable to support ``gcov``. + For example: + +.. code:: + + check-unit-y += tests/foo-test$(EXESUF) + tests/foo-test$(EXESUF): tests/foo-test.o $(test-util-obj-y) + ... + gcov-files-foo-test-y = util/foo.c + +Since unit tests don't require environment variables, the simplest way to debug +a unit test failure is often directly invoking it or even running it under +``gdb``. However there can still be differences in behavior between ``make`` +invocations and your manual run, due to ``$MALLOC_PERTURB_`` environment +variable (which affects memory reclamation and catches invalid pointers better) +and gtester options. If necessary, you can run + +.. code:: + make check-unit V=1 + +and copy the actual command line which executes the unit test, then run +it from the command line. + +QTest +----- + +QTest is a device emulation testing framework. It can be very useful to test +device models; it could also control certain aspects of QEMU (such as virtual +clock stepping), with a special purpose "qtest" protocol. Refer to the +documentation in ``qtest.c`` for more details of the protocol. + +QTest cases can be executed with + +.. code:: + + make check-qtest + +The QTest library is implemented by ``tests/libqtest.c`` and the API is defined +in ``tests/libqtest.h``. + +Consider adding a new QTest case when you are introducing a new virtual +hardware, or extending one if you are adding functionalities to an existing +virtual device. + +On top of libqtest, a higher level library, ``libqos``, was created to +encapsulate common tasks of device drivers, such as memory management and +communicating with system buses or devices. Many virtual device tests use +libqos instead of directly calling into libqtest. + +Steps to add a new QTest case are: + +1. Create a new source file for the test. (More than one file can be added as + necessary.) For example, ``tests/test-foo-device.c``. + +2. Write the test code with the glib and libqtest/libqos API. See also existing + tests and the library headers for reference. + +3. Register the new test in ``tests/Makefile.include``. Add the test executable + name to an appropriate ``check-qtest-*-y`` variable. For example: + + ``check-qtest-generic-y = tests/test-foo-device$(EXESUF)`` + +4. Add object dependencies of the executable in the Makefile, including the + test source file(s) and other interesting objects. For example: + + ``tests/test-foo-device$(EXESUF): tests/test-foo-device.o $(libqos-obj-y)`` + +Debugging a QTest failure is slightly harder than the unit test because the +tests look up QEMU program names in the environment variables, such as +``QTEST_QEMU_BINARY`` and ``QTEST_QEMU_IMG``, and also because it is not easy +to attach gdb to the QEMU process spawned from the test. But manual invoking +and using gdb on the test is still simple to do: find out the actual command +from the output of + +.. code:: + make check-qtest V=1 + +which you can run manually. + +QAPI schema tests +----------------- + +The QAPI schema tests validate the QAPI parser used by QMP, by feeding +predefined input to the parser and comparing the result with the reference +output. + +The input/output data is managed under the ``tests/qapi-schema`` directory. +Each test case includes four files that have a common base name: + + * ``${casename}.json`` - the file contains the JSON input for feeding the + parser + * ``${casename}.out`` - the file contains the expected stdout from the parser + * ``${casename}.err`` - the file contains the expected stderr from the parser + * ``${casename}.exit`` - the expected error code + +Consider adding a new QAPI schema test when you are making a change on the QAPI +parser (either fixing a bug or extending/modifying the syntax). To do this: + +1. Add four files for the new case as explained above. For example: + + ``$EDITOR tests/qapi-schema/foo.{json,out,err,exit}``. + +2. Add the new test in ``tests/Makefile.include``. For example: + + ``qapi-schema += foo.json`` + +check-block +----------- + +``make check-block`` is a legacy command to invoke block layer iotests and is +rarely used. See "QEMU iotests" section below for more information. + +GCC gcov support +---------------- + +``gcov`` is a GCC tool to analyze the testing coverage by instrumenting the +tested code. To use it, configure QEMU with ``--enable-gcov`` option and build. +Then run ``make check`` as usual. There will be additional ``gcov`` output as +the testing goes on, showing the test coverage percentage numbers per analyzed +source file. More detailed reports can be obtained by running ``gcov`` command +on the output files under ``$build_dir/tests/``, please read the ``gcov`` +documentation for more information. + +QEMU iotests +============ + +QEMU iotests, under the directory ``tests/qemu-iotests``, is the testing +framework widely used to test block layer related features. It is higher level +than "make check" tests and 99% of the code is written in bash or Python +scripts. The testing success criteria is golden output comparison, and the +test files are named with numbers. + +To run iotests, make sure QEMU is built successfully, then switch to the +``tests/qemu-iotests`` directory under the build directory, and run ``./check`` +with desired arguments from there. + +By default, "raw" format and "file" protocol is used; all tests will be +executed, except the unsupported ones. You can override the format and protocol +with arguments: + +.. code:: + + # test with qcow2 format + ./check -qcow2 + # or test a different protocol + ./check -nbd + +It's also possible to list test numbers explicitly: + +.. code:: + + # run selected cases with qcow2 format + ./check -qcow2 001 030 153 + +Cache mode can be selected with the "-c" option, which may help reveal bugs +that are specific to certain cache mode. + +More options are supported by the ``./check`` script, run ``./check -h`` for +help. + +Writing a new test case +----------------------- + +Consider writing a tests case when you are making any changes to the block +layer. An iotest case is usually the choice for that. There are already many +test cases, so it is possible that extending one of them may achieve the goal +and save the boilerplate to create one. (Unfortunately, there isn't a 100% +reliable way to find a related one out of hundreds of tests. One approach is +using ``git grep``.) + +Usually an iotest case consists of two files. One is an executable that +produces output to stdout and stderr, the other is the expected reference +output. They are given the same number in file names. E.g. Test script ``055`` +and reference output ``055.out``. + +In rare cases, when outputs differ between cache mode ``none`` and others, a +``.out.nocache`` file is added. In other cases, when outputs differ between +image formats, more than one ``.out`` files are created ending with the +respective format names, e.g. ``178.out.qcow2`` and ``178.out.raw``. + +There isn't a hard rule about how to write a test script, but a new test is +usually a (copy and) modification of an existing case. There are a few +commonly used ways to create a test: + +* A Bash script. It will make use of several environmental variables related + to the testing procedure, and could source a group of ``common.*`` libraries + for some common helper routines. + +* A Python unittest script. Import ``iotests`` and create a subclass of + ``iotests.QMPTestCase``, then call ``iotests.main`` method. The downside of + this approach is that the output is too scarce, and the script is considered + harder to debug. + +* A simple Python script without using unittest module. This could also import + ``iotests`` for launching QEMU and utilities etc, but it doesn't inherit + from ``iotests.QMPTestCase`` therefore doesn't use the Python unittest + execution. This is a combination of 1 and 2. + +Pick the language per your preference since both Bash and Python have +comparable library support for invoking and interacting with QEMU programs. If +you opt for Python, it is strongly recommended to write Python 3 compatible +code. + +Docker based tests +================== + +Introduction +------------ + +The Docker testing framework in QEMU utilizes public Docker images to build and +test QEMU in predefined and widely accessible Linux environments. This makes +it possible to expand the test coverage across distros, toolchain flavors and +library versions. + +Prerequisites +------------- + +Install "docker" with the system package manager and start the Docker service +on your development machine, then make sure you have the privilege to run +Docker commands. Typically it means setting up passwordless ``sudo docker`` +command or login as root. For example: + +.. code:: + + $ sudo yum install docker + $ # or `apt-get install docker` for Ubuntu, etc. + $ sudo systemctl start docker + $ sudo docker ps + +The last command should print an empty table, to verify the system is ready. + +An alternative method to set up permissions is by adding the current user to +"docker" group and making the docker daemon socket file (by default +``/var/run/docker.sock``) accessible to the group: + +.. code:: + + $ sudo groupadd docker + $ sudo usermod $USER -G docker + $ sudo chown :docker /var/run/docker.sock + +Note that any one of above configurations makes it possible for the user to +exploit the whole host with Docker bind mounting or other privileged +operations. So only do it on development machines. + +Quickstart +---------- + +From source tree, type ``make docker`` to see the help. Testing can be started +without configuring or building QEMU (``configure`` and ``make`` are done in +the container, with parameters defined by the make target): + +.. code:: + + make docker-test-build@min-glib + +This will create a container instance using the ``min-glib`` image (the image +is downloaded and initialized automatically), in which the ``test-build`` job +is executed. + +Images +------ + +Along with many other images, the ``min-glib`` image is defined in a Dockerfile +in ``tests/docker/dockefiles/``, called ``min-glib.docker``. ``make docker`` +command will list all the available images. + +To add a new image, simply create a new ``.docker`` file under the +``tests/docker/dockerfiles/`` directory. + +A ``.pre`` script can be added beside the ``.docker`` file, which will be +executed before building the image under the build context directory. This is +mainly used to do necessary host side setup. One such setup is ``binfmt_misc``, +for example, to make qemu-user powered cross build containers work. + +Tests +----- + +Different tests are added to cover various configurations to build and test +QEMU. Docker tests are the executables under ``tests/docker`` named +``test-*``. They are typically shell scripts and are built on top of a shell +library, ``tests/docker/common.rc``, which provides helpers to find the QEMU +source and build it. + +The full list of tests is printed in the ``make docker`` help. + +Tools +----- + +There are executables that are created to run in a specific Docker environment. +This makes it easy to write scripts that have heavy or special dependencies, +but are still very easy to use. + +Currently the only tool is ``travis``, which mimics the Travis-CI tests in a +container. It runs in the ``travis`` image: + +.. code:: + + make docker-travis@travis + +Debugging a Docker test failure +------------------------------- + +When CI tasks, maintainers or yourself report a Docker test failure, follow the +below steps to debug it: + +1. Locally reproduce the failure with the reported command line. E.g. run + ``make docker-test-mingw@fedora J=8``. +2. Add "V=1" to the command line, try again, to see the verbose output. +3. Further add "DEBUG=1" to the command line. This will pause in a shell prompt + in the container right before testing starts. You could either manually + build QEMU and run tests from there, or press Ctrl-D to let the Docker + testing continue. +4. If you press Ctrl-D, the same building and testing procedure will begin, and + will hopefully run into the error again. After that, you will be dropped to + the prompt for debug. + +Options +------- + +Various options can be used to affect how Docker tests are done. The full +list is in the ``make docker`` help text. The frequently used ones are: + +* ``V=1``: the same as in top level ``make``. It will be propagated to the + container and enable verbose output. +* ``J=$N``: the number of parallel tasks in make commands in the container, + similar to the ``-j $N`` option in top level ``make``. (The ``-j`` option in + top level ``make`` will not be propagated into the container.) +* ``DEBUG=1``: enables debug. See the previous "Debugging a Docker test + failure" section. + +VM testing +========== + +This test suite contains scripts that bootstrap various guest images that have +necessary packages to build QEMU. The basic usage is documented in ``Makefile`` +help which is displayed with ``make vm-test``. + +Quickstart +---------- + +Run ``make vm-test`` to list available make targets. Invoke a specific make +command to run build test in an image. For example, ``make vm-build-freebsd`` +will build the source tree in the FreeBSD image. The command can be executed +from either the source tree or the build dir; if the former, ``./configure`` is +not needed. The command will then generate the test image in ``./tests/vm/`` +under the working directory. + +Note: images created by the scripts accept a well-known RSA key pair for SSH +access, so they SHOULD NOT be exposed to external interfaces if you are +concerned about attackers taking control of the guest and potentially +exploiting a QEMU security bug to compromise the host. + +QEMU binary +----------- + +By default, qemu-system-x86_64 is searched in $PATH to run the guest. If there +isn't one, or if it is older than 2.10, the test won't work. In this case, +provide the QEMU binary in env var: ``QEMU=/path/to/qemu-2.10+``. + +Make jobs +--------- + +The ``-j$X`` option in the make command line is not propagated into the VM, +specify ``J=$X`` to control the make jobs in the guest. + +Debugging +--------- + +Add ``DEBUG=1`` and/or ``V=1`` to the make command to allow interactive +debugging and verbose output. If this is not enough, see the next section. + +Manual invocation +----------------- + +Each guest script is an executable script with the same command line options. +For example to work with the netbsd guest, use ``$QEMU_SRC/tests/vm/netbsd``: + +.. code:: + + $ cd $QEMU_SRC/tests/vm + + # To bootstrap the image + $ ./netbsd --build-image --image /var/tmp/netbsd.img + <...> + + # To run an arbitrary command in guest (the output will not be echoed unless + # --debug is added) + $ ./netbsd --debug --image /var/tmp/netbsd.img uname -a + + # To build QEMU in guest + $ ./netbsd --debug --image /var/tmp/netbsd.img --build-qemu $QEMU_SRC + + # To get to an interactive shell + $ ./netbsd --interactive --image /var/tmp/netbsd.img sh + +Adding new guests +----------------- + +Please look at existing guest scripts for how to add new guests. + +Most importantly, create a subclass of BaseVM and implement ``build_image()`` +method and define ``BUILD_SCRIPT``, then finally call ``basevm.main()`` from +the script's ``main()``. + +* Usually in ``build_image()``, a template image is downloaded from a + predefined URL. ``BaseVM._download_with_cache()`` takes care of the cache and + the checksum, so consider using it. + +* Once the image is downloaded, users, SSH server and QEMU build deps should + be set up: + + - Root password set to ``BaseVM.ROOT_PASS`` + - User ``BaseVM.GUEST_USER`` is created, and password set to + ``BaseVM.GUEST_PASS`` + - SSH service is enabled and started on boot, + ``$QEMU_SRC/tests/keys/id_rsa.pub`` is added to ssh's ``authorized_keys`` + file of both root and the normal user + - DHCP client service is enabled and started on boot, so that it can + automatically configure the virtio-net-pci NIC and communicate with QEMU + user net (10.0.2.2) + - Necessary packages are installed to untar the source tarball and build + QEMU + +* Write a proper ``BUILD_SCRIPT`` template, which should be a shell script that + untars a raw virtio-blk block device, which is the tarball data blob of the + QEMU source tree, then configure/build it. Running "make check" is also + recommended. + +Image fuzzer testing +==================== + +An image fuzzer was added to exercise format drivers. Currently only qcow2 is +supported. To start the fuzzer, run + +.. code:: + + tests/image-fuzzer/runner.py -c '[["qemu-img", "info", "$test_img"]]' /tmp/test qcow2 + +Alternatively, some command different from "qemu-img info" can be tested, by +changing the ``-c`` option. |