mutation.yml

name: Mutation Testing

on:
  push:
    branches: [main]
  pull_request:
    branches: [main]
    types: [opened, synchronize, reopened, labeled]
  workflow_dispatch:
  schedule:
    # Run full mutation testing weekly on Sundays at 3 AM UTC
    - cron: '0 3 * * 0'

env:
  CARGO_TERM_COLOR: always

jobs:
  # Quick mutation testing on PRs (only changed files)
  # Opt-in only: add `run-mutation` label to the PR when needed.
  mutation-pr:
    runs-on: ubuntu-latest
    if: github.event_name == 'pull_request' && contains(github.event.pull_request.labels.*.name, 'run-mutation')
    steps:
      - uses: actions/checkout@v6
        with:
          fetch-depth: 0  # Need full history for --in-diff

      - uses: dtolnay/rust-toolchain@stable

      - name: Install protobuf
        run: |
          sudo apt-get update
          sudo apt-get install -y protobuf-compiler

      - name: Cache cargo
        uses: Swatinem/rust-cache@v2
        with:
          cache-on-failure: true

      - name: Install cargo-mutants
        run: cargo install cargo-mutants

      - name: Run mutation testing on changed files
        # Only test mutants in files changed in this PR
        # Runs only when PR has the `run-mutation` label
        continue-on-error: true
        run: |
          # Ensure base branch ref exists locally for reliable diffing
          git fetch origin "${{ github.base_ref }}":"refs/remotes/origin/${{ github.base_ref }}"

          # Collect changed Rust source files (exclude test-only and workflow files)
          changed_rs=$(git diff --name-only origin/${{ github.base_ref }}...HEAD -- '*.rs' | grep -v '_test\.rs$' || true)
          if [ -z "$changed_rs" ]; then
            echo "No Rust source files changed in this PR"
            exit 0
          fi

          # Build --file flags for each changed file
          file_args=""
          for f in $changed_rs; do
            file_args="$file_args --file $f"
          done

          echo "Running mutation testing for changed files:"
          echo "$changed_rs"
          cargo mutants $file_args

      - name: Upload mutation report
        uses: actions/upload-artifact@v4
        if: always()
        with:
          name: mutation-report-pr
          path: mutants.out/
          retention-days: 30

      - name: Comment PR with mutation results
        if: always() && github.event_name == 'pull_request'
        uses: actions/github-script@v7
        with:
          script: |
            const fs = require('fs');
            const path = require('path');

            // Try the expected path first
            let outcomesPath = path.join('mutants.out', 'outcomes.json');

            // If not found, search under the workspace so we can handle any
            // unexpected layout changes while still using the results.
            if (!fs.existsSync(outcomesPath)) {
              const workspace = process.env.GITHUB_WORKSPACE || process.cwd();

              /** @param {string} start */
              function findOutcomes(start) {
                const entries = fs.readdirSync(start, { withFileTypes: true });
                for (const entry of entries) {
                  const full = path.join(start, entry.name);
                  if (entry.isDirectory()) {
                    const found = findOutcomes(full);
                    if (found) return found;
                  } else if (entry.isFile() && entry.name === 'outcomes.json') {
                    return full;
                  }
                }
                return null;
              }

              const found = fs.existsSync(workspace) ? findOutcomes(workspace) : null;
              if (found) {
                console.log(`Found outcomes.json at ${found}`);
                outcomesPath = found;
              } else {
                console.log('No mutation outcomes file found (no outcomes.json anywhere under workspace)');
                await github.rest.issues.createComment({
                  issue_number: context.issue.number,
                  owner: context.repo.owner,
                  repo: context.repo.repo,
                  body: '## 🧬 Mutation Testing Results\n\nNo mutation outcomes file was found for this run. This usually means no mutants were generated for the changed files or mutation testing did not complete.'
                });
                return;
              }
            }

            const data = JSON.parse(fs.readFileSync(outcomesPath, 'utf8'));
            const outcomes = data.outcomes || [];
            const mutants = outcomes.filter(o => o.scenario !== 'Baseline');
            const total = mutants.length;
            const killed = mutants.filter(o => o.summary === 'CaughtMutant').length;
            const survived = mutants.filter(o => o.summary === 'MissedMutant').length;
            const timeout = mutants.filter(o => o.summary === 'Timeout').length;
            const score = total > 0 ? ((killed / total) * 100).toFixed(1) : 0;

            const survivorList = mutants
              .filter(o => o.summary === 'MissedMutant')
              .map(o => {
                const name = o.scenario?.Mutant?.name || 'unknown';
                return `- \`${name}\``;
              })
              .join('\n') || 'None';

            const body = [
              '## 🧬 Mutation Testing Results',
              '',
              '| Metric | Count |',
              '|--------|-------|',
              `| Total Mutants | ${total} |`,
              `| Killed | ${killed} |`,
              `| Survived | ${survived} |`,
              `| Timeout | ${timeout} |`,
              `| **Score** | **${score}%** |`,
              '',
              survived > 0 ? '**Note:** Some mutants survived. Consider improving tests for the changed code.' : 'All mutants killed!',
              '',
              '<details>',
              '<summary>Surviving Mutants</summary>',
              '',
              survivorList,
              '',
              '</details>'
            ].join('\n');

            await github.rest.issues.createComment({
              issue_number: context.issue.number,
              owner: context.repo.owner,
              repo: context.repo.repo,
              body: body
            });

  # Full mutation testing on main branch (baseline)
  mutation-baseline:
    runs-on: ubuntu-latest
    if: github.ref == 'refs/heads/main' || github.event_name == 'schedule' || github.event_name == 'workflow_dispatch'
    steps:
      - uses: actions/checkout@v6

      - uses: dtolnay/rust-toolchain@stable

      - name: Install protobuf
        run: |
          sudo apt-get update
          sudo apt-get install -y protobuf-compiler

      - name: Cache cargo
        uses: Swatinem/rust-cache@v2
        with:
          cache-on-failure: true

      - name: Install cargo-mutants
        run: cargo install cargo-mutants

      - name: Run full mutation testing
        run: cargo mutants
        # Note: Do NOT fail on low score initially (report only mode)
        continue-on-error: true

      - name: Upload mutation report
        uses: actions/upload-artifact@v4
        if: always()
        with:
          name: mutation-report-baseline
          path: |
            mutants.out/
          retention-days: 90

      - name: Upload HTML report to GitHub Pages
        if: github.ref == 'refs/heads/main' && always()
        uses: peaceiris/actions-gh-pages@v4
        with:
          github_token: ${{ secrets.GITHUB_TOKEN }}
          publish_dir: ./mutants.out/html
          destination_dir: mutation-testing

      - name: Generate mutation summary
        if: always()
        run: |
          echo "## Mutation Testing Summary" >> $GITHUB_STEP_SUMMARY
          echo "" >> $GITHUB_STEP_SUMMARY
          
          if [ -f mutants.out/outcomes.json ]; then
            total=$(jq '[.outcomes[] | select(.scenario != "Baseline")] | length' mutants.out/outcomes.json)
            killed=$(jq '[.outcomes[] | select(.scenario != "Baseline") | select(.summary == "CaughtMutant")] | length' mutants.out/outcomes.json)
            survived=$(jq '[.outcomes[] | select(.scenario != "Baseline") | select(.summary == "MissedMutant")] | length' mutants.out/outcomes.json)
            timeout=$(jq '[.outcomes[] | select(.scenario != "Baseline") | select(.summary == "Timeout")] | length' mutants.out/outcomes.json)
            unviable=$(jq '[.outcomes[] | select(.scenario != "Baseline") | select(.summary == "Unviable")] | length' mutants.out/outcomes.json)
            
            if [ "$total" -gt 0 ]; then
              score=$(echo "scale=1; ($killed / $total) * 100" | bc)
              echo "| Metric | Count |" >> $GITHUB_STEP_SUMMARY
              echo "|--------|-------|" >> $GITHUB_STEP_SUMMARY
              echo "| Total Mutants | $total |" >> $GITHUB_STEP_SUMMARY
              echo "| ✅ Killed | $killed |" >> $GITHUB_STEP_SUMMARY
              echo "| ❌ Survived | $survived |" >> $GITHUB_STEP_SUMMARY
              echo "| ⏱️ Timeout | $timeout |" >> $GITHUB_STEP_SUMMARY
              echo "| ⚪ Unviable | $unviable |" >> $GITHUB_STEP_SUMMARY
              echo "| **Mutation Score** | **$score%** |" >> $GITHUB_STEP_SUMMARY
              echo "" >> $GITHUB_STEP_SUMMARY
              
              if (( $(echo "$score >= 80" | bc -l) )); then
                echo "✅ **Excellent test quality!**" >> $GITHUB_STEP_SUMMARY
              elif (( $(echo "$score >= 50" | bc -l) )); then
                echo "⚠️ **Acceptable test quality, room for improvement.**" >> $GITHUB_STEP_SUMMARY
              else
                echo "🔴 **Poor test quality. Consider improving tests.**" >> $GITHUB_STEP_SUMMARY
              fi
            fi
          fi
          
          echo "" >> $GITHUB_STEP_SUMMARY
          echo "📊 [View Full Report](https://${{ github.repository_owner }}.github.io/${{ github.event.repository.name }}/mutation-testing/)" >> $GITHUB_STEP_SUMMARY