Add a mechanism for validating meson output in tests

Expected stdout lines must match lines from the actual stdout, in the
same order. Lines with match type 're' are regex matched.

v2:
Ignore comment lines in expected_stdout

v3:
Automatically adjust path separators for location in expected output

v4:
Put expected stdout in test.json, rather than a separate file

1 files changed, 21 insertions, 0 deletions

diff --git a/docs/markdown/Contributing.md b/docs/markdown/Contributing.md
index 8a24e0b..34cd8ca 100644
--- a/docs/markdown/Contributing.md
+++ b/docs/markdown/Contributing.md
@@ -334,6 +334,27 @@ If a tool is specified, it has to be present in the environment, and the version
 requirement must be fulfilled match. Otherwise, the entire test is skipped
 (including every element in the test matrix).
 
+#### stdout
+
+The `stdout` key contains a list of dicts, describing the expected stdout.
+
+Each dict contains the following keys:
+
+- `line`
+- `match` (optional)
+
+Each item in the list is matched, in order, against the remaining actual stdout
+lines, after any previous matches. If the actual stdout is exhausted before
+every item in the list is matched, the expected output has not been seen, and
+the test has failed.
+
+The `match` element of the dict determines how the `line` element is matched:
+
+| Type      | Description             |
+| --------  | ----------------------- |
+| `literal` | Literal match (default) |
+| `re`      | regex match             |
+
 ### Skipping integration tests
 
 Meson uses several continuous integration testing systems that have slightly