ci: add mutation testing using infection/infection

Author: lotyp

.github/workflows/testing.yml

@@ -131,3 +131,56 @@ jobs:
 
       - name: 🧪 Run unit tests using pestphp/pest
         run: composer test
+
+  mutation-testing:
+    timeout-minutes: 16
+    runs-on: ${{ matrix.os }}
+    concurrency:
+      cancel-in-progress: true
+      group: mutation-testing-${{ github.workflow }}-${{ github.event.pull_request.number || github.ref }}
+    strategy:
+      fail-fast: true
+      matrix:
+        os:
+          - ubuntu-latest
+        php-version:
+          - '8.1'
+        dependencies:
+          - locked
+    steps:
+      - name: 📦 Check out the codebase
+        uses: actions/checkout@v4.1.5
+
+      - name: 🛠️ Setup PHP
+        uses: shivammathur/setup-php@2.30.4
+        with:
+          php-version: ${{ matrix.php-version }}
+          extensions: mbstring, pdo, pdo_sqlite
+          ini-values: error_reporting=E_ALL
+          coverage: xdebug
+
+      - name: 🛠️ Setup problem matchers
+        run: echo "::add-matcher::${{ runner.tool_cache }}/php.json"
+
+      - name: 🤖 Validate composer.json and composer.lock
+        run: composer validate --ansi --strict
+
+      - name: 🔍 Get composer cache directory
+        uses: wayofdev/gh-actions/actions/composer/get-cache-directory@v3.1.0
+
+      - name: ♻️ Restore cached dependencies installed with composer
+        uses: actions/cache@v4.0.2
+        with:
+          path: ${{ env.COMPOSER_CACHE_DIR }}
+          key: php-${{ matrix.php-version }}-composer-${{ matrix.dependencies }}-${{ hashFiles('composer.lock') }}
+          restore-keys: php-${{ matrix.php-version }}-composer-${{ matrix.dependencies }}-
+
+      - name: 📥 Install "${{ matrix.dependencies }}" dependencies
+        uses: wayofdev/gh-actions/actions/composer/install@v3.1.0
+        with:
+          dependencies: ${{ matrix.dependencies }}
+
+      - name: 🧪 Run mutation testing using Xdebug and infection/infection
+        run: composer infect:ci
+        env:
+          STRYKER_DASHBOARD_API_KEY: ${{ secrets.STRYKER_DASHBOARD_API_KEY }}

composer.json

@@ -26,7 +26,10 @@
         "phpstan/phpstan-deprecation-rules": "^1.2",
         "phpstan/phpstan-phpunit": "^1.4",
         "phpstan/phpstan-strict-rules": "^1.6",
-        "phpunit/phpunit": "^10.5"
+        "phpunit/phpunit": "^10.5",
+        "psalm/plugin-phpunit": "~0.19.0",
+        "roave/infection-static-analysis-plugin": "^1.35",
+        "vimeo/psalm": "^5.23.1"
     },
     "autoload": {
         "psr-4": {
@@ -41,6 +44,7 @@
     "config": {
         "allow-plugins": {
             "ergebnis/composer-normalize": true,
+            "infection/extension-installer": true,
             "pestphp/pest-plugin": true,
             "phpstan/extension-installer": true
         },