ci: add mutation testing with Infection and the Stryker dashboard

.github/workflows/mutation.yml

@@ -0,0 +1,49 @@
+---
+
+name: Mutation Tests
+
+on:  # yamllint disable-line rule:truthy
+  pull_request:
+  push:
+    branches: [1.x]
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.head_ref || github.ref }}
+  cancel-in-progress: ${{ github.event_name == 'pull_request' }}
+
+permissions:
+  contents: read
+
+jobs:
+  mutation:
+    timeout-minutes: 15
+    runs-on: ubuntu-latest
+    steps:
+      - name: 📦 Check out the codebase
+        uses: actions/checkout@v6
+        with:
+          persist-credentials: false
+
+      - name: 🛠️ Setup PHP
+        uses: shivammathur/setup-php@v2
+        with:
+          php-version: '8.4'
+          coverage: xdebug
+
+      - name: 📥 Install dependencies with composer
+        uses: ramsey/composer-install@v3
+        with:
+          dependency-versions: highest
+
+      # Not the Phar: its bundled testo/bridge-infection writes the unscoped `\Infection\StreamWrapper\IncludeInterceptor`
+      # into the mutant bootstrap, while the Phar ships the class as `Infected\...`, so every mutant fails with
+      # "class not found". Infection needs PHP 8.3+, so it is required here only, not in composer.json.
+      - name: 🧬 Install Infection
+        run: |
+          composer config allow-plugins.infection/extension-installer true
+          composer require --dev --no-interaction --no-progress infection/infection testo/bridge-infection
+
+      - name: 🧪 Run mutation testing
+        run: vendor/bin/infection --threads=max --logger-github --show-mutations=0 --min-msi=85
+        env:
+          STRYKER_DASHBOARD_API_KEY: ${{ github.event_name == 'push' && secrets.STRYKER_DASHBOARD_API_KEY || '' }}

README.md

@@ -14,6 +14,7 @@
 
 [![Psalm Level](https://shepherd.dev/github/roadrunner-php/version-checker/level.svg)](https://shepherd.dev/github/roadrunner-php/version-checker)
 [![Type Coverage](https://shepherd.dev/github/roadrunner-php/version-checker/coverage.svg)](https://shepherd.dev/github/roadrunner-php/version-checker)
+[![Mutation testing badge](https://img.shields.io/endpoint?url=https%3A%2F%2Fbadge-api.stryker-mutator.io%2Fgithub.com%2Froadrunner-php%2Fversion-checker%2F1.x)](https://dashboard.stryker-mutator.io/reports/github.com/roadrunner-php/version-checker/1.x)
 
 </div>
 

infection.json5

@@ -0,0 +1,16 @@
+{
+    "$schema": "https://raw.githubusercontent.com/infection/infection/master/resources/schema.json",
+    "source": {
+        "directories": ["src"]
+    },
+    "testFramework": "testo",
+    "tmpDir": "runtime",
+    "timeout": 10,
+    "logs": {
+        "text": "runtime/infection.log",
+        "github": true,
+        "stryker": {
+            "report": "1.x"
+        }
+    }
+}