Enhancement: Run mutation tests with infection/infection

.gitattributes

@@ -6,6 +6,7 @@
 /.gitignore                     export-ignore
 /.php_cs                        export-ignore
 /composer-require-checker.json  export-ignore
+/infection.json                 export-ignore
 /Makefile                       export-ignore
 /psalm-baseline.xml             export-ignore
 /psalm.xml                      export-ignore

.github/CONTRIBUTING.md

@@ -83,6 +83,18 @@ $ make tests
 
 to run all the tests.
 
+## 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.
+
 ## Extra lazy?
 
 Run

.github/settings.yml

@@ -17,6 +17,7 @@ branches:
           - "Code Coverage (7.4, locked)"
           - "Coding Standards (7.4, locked)"
           - "Dependency Analysis (7.4, locked)"
+          - "Mutation Tests (7.4, locked)"
           - "Static Code Analysis (7.4, locked)"
           - "Tests (7.4, highest)"
           - "Tests (7.4, locked)"

.github/workflows/integrate.yaml

@@ -9,8 +9,6 @@ on: # yamllint disable-line rule:truthy
       - "main"
 
 env:
-  MIN_COVERED_MSI: 92
-  MIN_MSI: 92
   PHP_EXTENSIONS: "mbstring"
 
 jobs:
@@ -264,3 +262,45 @@ jobs:
         env:
           CODECOV_TOKEN: "${{ secrets.CODECOV_TOKEN }}"
         run: "bash <(curl -s https://codecov.io/bash)"
+
+  mutation-tests:
+    name: "Mutation Tests"
+
+    runs-on: "ubuntu-latest"
+
+    strategy:
+      matrix:
+        php-version:
+          - "7.4"
+
+        dependencies:
+          - "locked"
+
+    steps:
+      - name: "Checkout"
+        uses: "actions/checkout@v2.4.0"
+
+      - name: "Install PHP with extensions"
+        uses: "shivammathur/setup-php@2.16.0"
+        with:
+          coverage: "xdebug"
+          extensions: "${{ env.PHP_EXTENSIONS }}"
+          php-version: "${{ matrix.php-version }}"
+
+      - name: "Determine composer cache directory"
+        uses: "./.github/actions/composer/composer/determine-cache-directory"
+
+      - name: "Cache dependencies installed with composer"
+        uses: "actions/cache@v2.1.7"
+        with:
+          path: "${{ 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 ${{ matrix.dependencies }} dependencies with composer"
+        uses: "./.github/actions/composer/composer/install"
+        with:
+          dependencies: "${{ matrix.dependencies }}"
+
+      - name: "Run mutation tests with Xdebug and infection/infection"
+        run: "vendor/bin/infection --configuration=infection.json"

Makefile

@@ -1,6 +1,3 @@
-MIN_COVERED_MSI:=92
-MIN_MSI:=92
-
 .PHONY: it
 it: coding-standards static-code-analysis tests ## Runs the coding-standards, static-code-analysis, and tests targets
 
@@ -24,6 +21,11 @@ dependency-analysis: vendor ## Runs a dependency analysis with maglnet/composer-
 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: static-code-analysis
 static-code-analysis: vendor ## Runs a static code analysis with vimeo/psalm
 	mkdir -p .build/psalm

composer.json

@@ -24,13 +24,15 @@
     "ergebnis/license": "^1.1.0",
     "ergebnis/php-cs-fixer-config": "^3.4.0",
     "fakerphp/faker": "^1.17.0",
+    "infection/infection": "~0.25.5",
     "phpunit/phpunit": "^9.5.11",
     "psalm/plugin-phpunit": "~0.16.1",
     "vimeo/psalm": "^4.16.1"
   },
   "config": {
     "allow-plugins": {
-      "composer/package-versions-deprecated": true
+      "composer/package-versions-deprecated": true,
+      "infection/extension-installer": true
     },
     "platform": {
       "php": "7.4.26"