mutation.yml

name: Mutation testing (advisory)

# Advisory only. This never runs on pull_request or push, so it cannot block a
# merge. It runs on demand and once a week to surface tests that have stopped
# pinning down the rules engine's behaviour. See docs/mutation-testing.md.

on:
  workflow_dispatch:
  schedule:
    # Mondays at 06:00 UTC.
    - cron: "0 6 * * 1"

permissions:
  contents: read

jobs:
  mutmut:
    runs-on: ubuntu-latest
    # Belt and suspenders: even a non-zero exit must not fail the workflow.
    continue-on-error: true
    steps:
      - uses: actions/checkout@df4cb1c069e1874edd31b4311f1884172cec0e10 # v6
        with:
          persist-credentials: false
      - uses: actions/setup-python@a309ff8b426b58ec0e2a45f0f869d46889d02405 # v6
        with:
          python-version: "3.12"
      - run: python -m pip install -e ".[dev,mutation]"
      - name: Run mutation testing on the rules engine
        run: mutmut run || true
      - name: Summarize survivors
        if: always()
        run: |
          mutmut results || true
          mutmut export-cicd-stats || true
          if [ -f mutants/mutmut-cicd-stats.json ]; then
            {
              echo '### Mutation testing (advisory)'
              echo '```json'
              cat mutants/mutmut-cicd-stats.json
              echo '```'
            } >> "$GITHUB_STEP_SUMMARY"
          fi
      - name: Upload stats
        if: always()
        uses: actions/upload-artifact@043fb46d1a93c77aae656e7c1c64a875d1fc6a0a # v7.0.1
        with:
          name: mutation-stats
          path: mutants/mutmut-cicd-stats.json
          if-no-files-found: ignore