coverage-check.yml

name: Coverage Check

on:
  pull_request:
    branches: [ "**" ]

permissions:
  contents: read
  pull-requests: read

jobs:
  coverage-check:
    runs-on: ubuntu-latest

    steps:
    - uses: actions/checkout@v4
      with:
        fetch-depth: 0

    - name: Set up Python
      uses: actions/setup-python@v4
      with:
        python-version: "3.12"

    - name: Install dependencies
      run: |
        python -m pip install --upgrade pip
        pip install -e ".[dev]"

    - name: Get base branch coverage
      run: |
        git checkout origin/mainline
        pip install -e ".[dev]"
        python -m pytest tests/ -m "not integration" --cov=src --cov-report=json:coverage-base.json --tb=no -q || true
        BASE_COVERAGE=$(python -c "import json; print(json.load(open('coverage-base.json'))['totals']['percent_covered'])")
        echo "BASE_COVERAGE=$BASE_COVERAGE" >> $GITHUB_ENV
        echo "Base branch coverage: $BASE_COVERAGE%"

    - name: Get PR coverage
      run: |
        git checkout ${{ github.event.pull_request.head.sha }}
        pip install -e ".[dev]"
        python -m pytest tests/ -m "not integration" --cov=src --cov-report=json:coverage-pr.json --tb=no -q || true
        PR_COVERAGE=$(python -c "import json; print(json.load(open('coverage-pr.json'))['totals']['percent_covered'])")
        echo "PR_COVERAGE=$PR_COVERAGE" >> $GITHUB_ENV
        echo "PR branch coverage: $PR_COVERAGE%"

    - name: Compare coverage and enforce increase
      run: |
        python -c "
        import sys
        base = float('${{ env.BASE_COVERAGE }}')
        pr = float('${{ env.PR_COVERAGE }}')
        diff = pr - base

        print(f'Coverage Report')
        print(f'Base coverage: {base:.2f}%')
        print(f'PR coverage: {pr:.2f}%')
        print(f'Coverage change: {diff:+.2f}%')
        print()

        if diff < -0.01:  # Allow small floating point differences
            print('❌ Coverage decreased! This PR reduces test coverage.')
            print('Please add tests to maintain or improve coverage.')
            sys.exit(1)
        elif diff > 0.01:
            print('✅ Coverage increased! Great job improving test coverage.')
        else:
            print('➡️ Coverage unchanged (within tolerance).')
        "