CLI-556: Mutation testing (#915)

* CLI-556: Add mutation testing.

* remove broken tests

* fix phpstan

* xdebug_mode

* Revert "fix phpstan"

This reverts commit 2fa9e2e.

* Revert "remove broken tests"

This reverts commit ae08062.

* composer

* fix workflow

* cleanup

* cleanup

* fix filter

.github/workflows/mutation.yml

@@ -0,0 +1,32 @@
+name: Mutation Testing
+
+on: [pull_request]
+
+jobs:
+  tests:
+    runs-on: ubuntu-latest
+
+    name: Mutation Testing Code Review Annotations
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v2
+
+      - name: Setup PHP
+        uses: shivammathur/setup-php@v2
+        with:
+          php-version: 7.4
+          tools: composer:v2
+          extensions: pcov
+          coverage: pcov
+
+      - name: Install dependencies
+        run: |
+          composer install --no-progress --no-suggest --no-interaction
+
+      - name: Download Infection
+        run: composer infection-install
+
+      - name: Run Infection for added files only
+        run: |
+          git fetch --depth=1 origin $GITHUB_BASE_REF
+          php build/infection.phar -j2 --git-diff-filter=AM --git-diff-base=origin/$GITHUB_BASE_REF --logger-github --only-covered

composer.json

@@ -173,6 +173,12 @@
         "box-compile": [
             "php build/box.phar compile"
         ],
+        "infection-install": [
+            "curl -f -L https://github.com/infection/infection/releases/download/0.26.0/infection.phar -o build/infection.phar"
+        ],
+        "infection": [
+            "XDEBUG_MODE=coverage php build/infection.phar --threads=8"
+        ],
         "cs": "phpcs",
         "cbf": "phpcbf",
         "unit": "phpunit tests/phpunit -vvv",

infection.json

@@ -0,0 +1,11 @@
+{
+    "$schema": "https://raw.githubusercontent.com/infection/infection/0.26.0/resources/schema.json",
+    "source": {
+        "directories": [
+            "src"
+        ]
+    },
+    "mutators": {
+        "@default": true
+    }
+}