mutation.yml

name: Mutation Testing

# Mutation testing is slow (it re-runs the test suite per mutant), so it runs
# nightly and on demand — never on pull requests — to avoid PR latency. It is
# informational/non-blocking: the score is reported to the run summary and the
# HTML report is uploaded as an artifact.

on:
  schedule:
    - cron: "0 4 * * *" # nightly, 04:00 UTC
  workflow_dispatch:
    inputs:
      mutate:
        description: "Optional glob to scope mutation (e.g. src/tokens/**/*.ts)"
        required: false
        type: string

concurrency:
  group: mutation-${{ github.ref }}
  cancel-in-progress: true

jobs:
  stryker:
    name: Stryker (packages/pipeline)
    runs-on: ubuntu-latest
    timeout-minutes: 90
    steps:
      - uses: actions/checkout@v4

      - name: Setup Node.js
        uses: actions/setup-node@v4
        with:
          node-version: "20"

      - name: Install pnpm
        uses: pnpm/action-setup@v4
        with:
          version: 9

      - name: Install dependencies
        run: pnpm install --frozen-lockfile

      - name: Run Stryker mutation testing
        working-directory: packages/pipeline
        run: |
          # Run from packages/pipeline so the pnpm-linked node_modules resolve in
          # the Stryker sandbox; the config lives at the repo root.
          if [ -n "${{ github.event.inputs.mutate }}" ]; then
            npx stryker run ../../stryker.conf.json --mutate "${{ github.event.inputs.mutate }}"
          else
            npx stryker run ../../stryker.conf.json
          fi

      - name: Mutation score summary
        if: always()
        working-directory: packages/pipeline
        run: |
          node -e '
            const fs = require("fs");
            const path = "reports/mutation/mutation-report.json";
            if (!fs.existsSync(path)) { console.log("No mutation report produced."); process.exit(0); }
            const report = JSON.parse(fs.readFileSync(path, "utf-8"));
            const counts = { Killed: 0, Survived: 0, Timeout: 0, NoCoverage: 0, RuntimeError: 0, CompileError: 0, Ignored: 0 };
            for (const file of Object.values(report.files || {})) {
              for (const m of file.mutants || []) counts[m.status] = (counts[m.status] || 0) + 1;
            }
            const detected = counts.Killed + counts.Timeout;
            const valid = detected + counts.Survived + counts.NoCoverage;
            const score = valid ? ((detected / valid) * 100).toFixed(2) : "n/a";
            const out = [
              "## Mutation testing (packages/pipeline)",
              "",
              `**Mutation score: ${score}%**` + (score === "n/a" ? "" : ` (target 80%, opt-in)`),
              "",
              "| Status | Count |",
              "| --- | --- |",
              ...Object.entries(counts).map(([k, v]) => `| ${k} | ${v} |`),
            ].join("\n");
            fs.appendFileSync(process.env.GITHUB_STEP_SUMMARY || "/dev/stdout", out + "\n");
            console.log(`Mutation score: ${score}%`);
          '

      - name: Upload mutation report
        if: always()
        uses: actions/upload-artifact@v4
        with:
          name: mutation-report
          path: packages/pipeline/reports/mutation/
          if-no-files-found: ignore
          retention-days: 14