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fix-test-case

Testing & Quality
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Fix a specific failing test case in this repo by identifying the root cause, adding a minimal repro under tests/, explaining the cause, applying a targeted fix, re-running the test, and reporting any new failures uncovered.

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How to use this skill

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  2. Copy the prompt below and paste it into your agent.
  3. Review the proposed files and risks before you approve installation.
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I want to install this Agent Skill for this project in Codex.

Source SKILL.md: https://github.com/majiayu000/claude-skill-registry/blob/HEAD/skills/development/fix-test-case/SKILL.md

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Fix a failing test case

Scope

  • Work on one concrete failing test at a time.
  • Keep the repro small and isolated under tests/.
  • Do not try to fix failures that are due to changing the source layout; add them to EXPECTED_FAILURE.md instead.
  • If a failure is due to shifting line numbers or changed source content (literal tracebacks, linecache, etc.), add it to EXPECTED_FAILURE.md.

Workflow

  1. Reproduce the failure

    • Re-run the failing test directly (use the narrowest command possible, e.g. uvx pytest tests/test_file.py -k "test_name").
    • Capture the exact error, traceback, and any assertion mismatch.

  2. Identify the root cause

    • Inspect the failing code path and surrounding logic.
    • Map the failure back to the minimal incorrect behavior (state mismatch, wrong transform, missing edge case).
    • If needed, use the python-debug skill for pdb stepping or the python-monitoring-trace skill for a sys.monitoring trace.

  3. Always add a minimal repro under tests/

    • Create a new test file or extend the most relevant existing test file.
    • Keep the input as small as possible while still reproducing the failure.
    • Prefer integration-style tests consistent with existing tests/ conventions.

  4. Explain the cause

    • Summarize the bug in one or two sentences.
    • Point to the relevant code path and why it misbehaves.

  5. Implement the fix

    • Apply the smallest change that makes the repro pass.
    • Avoid unrelated refactors or behavior changes.
    • Never change the cpython source to fix a test.
    • The goal is to transform python to a minimal form, so do not selectively disable that to fix the tests.

  6. Re-run the test

    • Re-run the specific failing test and the new repro.
    • If it uncovers additional failures, summarize them and continue iterating.

  7. Final verification

    • Run the full required test commands (cargo test and uvx pytest tests/).

Output expectations

  • Provide a short cause explanation and the fix rationale.
  • List the exact tests re-run and the results.
  • If more failures appear, list them with a brief classification (ERROR/FAIL/TIMEOUT/CRASHED).