Enhancement: Run mutation tests with infection/infection

.gitattributes

@@ -6,6 +6,7 @@
 /.gitignore                     export-ignore
 /.php-cs-fixer.php              export-ignore
 /composer-require-checker.json  export-ignore
+/infection.json                 export-ignore
 /Makefile                       export-ignore
 /phpunit.xml.dist               export-ignore
 /psalm-baseline.xml             export-ignore

.github/CONTRIBUTING.md

@@ -34,6 +34,18 @@ make dependency-analysis
 
 to run a dependency analysis.
 
+## Mutation Tests
+
+We are using [`infection/infection`](https://github.com/infection/infection) to ensure a minimum quality of the tests.
+
+Enable `Xdebug` and run
+
+```sh
+make mutation-tests
+```
+
+to run mutation tests.
+
 ## Static Code Analysis
 
 We are using [`vimeo/psalm`](https://github.com/vimeo/psalm) to statically analyze the code.

.github/workflows/integrate.yaml

@@ -175,6 +175,53 @@ jobs:
       - name: "Run maglnet/composer-require-checker"
         run: ".phive/composer-require-checker check --config-file=$(pwd)/composer-require-checker.json"
 
+  mutation-tests:
+    name: "Mutation Tests"
+
+    runs-on: "ubuntu-latest"
+
+    strategy:
+      matrix:
+        php-version:
+          - "8.0"
+
+        dependencies:
+          - "locked"
+
+    steps:
+      - name: "Checkout"
+        uses: "actions/checkout@v3.3.0"
+
+      - name: "Set up PHP"
+        uses: "shivammathur/setup-php@2.24.0"
+        with:
+          coverage: "xdebug"
+          extensions: "none, ctype, dom, json, mbstring, phar, simplexml, tokenizer, xml, xmlwriter"
+          php-version: "${{ matrix.php-version }}"
+
+      - name: "Set up problem matchers for PHP"
+        run: "echo \"::add-matcher::${{ runner.tool_cache }}/php.json\""
+
+      - name: "Determine composer cache directory"
+        uses: "ergebnis/.github/actions/composer/determine-cache-directory@1.8.0"
+
+      - name: "Cache dependencies installed with composer"
+        uses: "actions/cache@v3.2.3"
+        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 ${{ matrix.dependencies }} dependencies with composer"
+        uses: "ergebnis/.github/actions/composer/install@1.8.0"
+        with:
+          dependencies: "${{ matrix.dependencies }}"
+
+      - name: "Run mutation tests with Xdebug and infection/infection"
+        env:
+          XDEBUG_MODE: "coverage"
+        run: "vendor/bin/infection --ansi --configuration=infection.json --logger-github"
+
   static-code-analysis:
     name: "Static Code Analysis"
 

Makefile

@@ -20,6 +20,11 @@ dependency-analysis: phive ## Runs a dependency analysis with maglnet/composer-r
 help: ## Displays this list of targets with descriptions
 	@grep -E '^[a-zA-Z0-9_-]+:.*?## .*$$' $(MAKEFILE_LIST) | sort | awk 'BEGIN {FS = ":.*?## "}; {printf "\033[32m%-30s\033[0m %s\n", $$1, $$2}'
 
+.PHONY: mutation-tests
+mutation-tests: vendor ## Runs mutation tests with infection/infection
+	mkdir -p .build/infection
+	vendor/bin/infection --configuration=infection.json
+
 .PHONY: phive
 phive: .phive## Installs dependencies with phive
 	mkdir -p .build/phive

composer.json

@@ -22,6 +22,7 @@
         "ergebnis/license": "^2.1.0",
         "ergebnis/php-cs-fixer-config": "^5.2.0",
         "fakerphp/faker": "^1.21.0",
+        "infection/infection": "~0.26.18",
         "phpunit/phpunit": "^9.5.28",
         "psalm/plugin-phpunit": "~0.18.4",
         "vimeo/psalm": "^5.6.0"
@@ -38,7 +39,8 @@
     },
     "config": {
         "allow-plugins": {
-            "ergebnis/composer-normalize": true
+            "ergebnis/composer-normalize": true,
+            "infection/extension-installer": true
         },
         "platform": {
             "php": "8.0.25"