fix-linter-test

name	fix-linter-test
description	Debug and fix a failing MegaLinter linter test. Use when a linter test fails in CI or locally.
allowed-tools	Read Grep Glob Bash Edit
argument-hint	["linter-name-or-test-output"]
model	sonnet

Debug the failing test for $ARGUMENTS.

Steps:

1. Find the test file in megalinter/tests/test_megalinter/linters/
2. Check if it's auto-generated (has @generated by .automation/build.py header) — if so, fix the descriptor YAML or fixtures, NOT the test file itself
3. Read the descriptor YAML in megalinter/descriptors/ to understand expected behavior (cli_lint_mode, config_file_name, cli_lint_errors_regex, file_extensions)
4. Check test fixtures in .automation/test/<test_folder>/:
   • Good files must pass the linter cleanly
   • Bad files must trigger errors matching cli_lint_errors_regex
   • File extensions must match file_extensions or file_names_regex in the descriptor
5. If a custom linter class exists in megalinter/linters/, review it for issues
6. Common failure causes:
   • Fixture file extensions don't match descriptor's file_extensions
   • cli_lint_errors_regex doesn't match actual linter output format
   • Missing config file referenced in config_file_name
   • cli_lint_mode mismatch (file vs list_of_files vs project)
   • Version pin broken or tool not installable in Dockerfile
   • Linter behavior differs between host OS and Docker container (Linux)
7. Reproduce in Docker (required — linters are not installed locally):

   LINTER="<descriptor_id_lowercase>_<linter_name>"
   docker buildx build --platform linux/amd64 --file linters/$LINTER/Dockerfile --tag $LINTER .
   docker run --rm --env TEST_CASE_RUN=true --env OUTPUT_DETAIL=detailed \
     --env TEST_KEYWORDS="${LINTER}_test" --env MEGALINTER_VOLUME_ROOT="." \
     --volume "$(pwd):/tmp/lint" $LINTER
   

   To run only a specific test method (e.g., test_failure):

   --env TEST_KEYWORDS="${LINTER}_test and test_failure"
   

8. In CI, filter tests via commit message body: TEST_KEYWORDS=<linter>_test
9. Update CHANGELOG.md only if the fix changes user-visible linter behavior (wrong error count, missed files, broken output). Add one line under Fixes in the beta section:

   - Fix <linter-name>: <what was wrong and what users now get>
   

   Do NOT add an entry for test-infrastructure-only fixes (fixture paths, test class regeneration, etc.).