ci: run PHPUnit Unit suite on push/PR (PHP 8.1–8.4)

.github/workflows/tests.yml

@@ -0,0 +1,43 @@
+name: Unit tests
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+
+jobs:
+  phpunit:
+    name: PHPUnit (PHP ${{ matrix.php }})
+    runs-on: ubuntu-latest
+
+    strategy:
+      fail-fast: false
+      matrix:
+        php: ['8.2', '8.3', '8.4']
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Setup PHP
+        uses: shivammathur/setup-php@v2
+        with:
+          php-version: ${{ matrix.php }}
+          coverage: none
+          tools: composer:v2
+
+      - name: Get Composer cache directory
+        id: composer-cache
+        run: echo "dir=$(composer config cache-files-dir)" >> "$GITHUB_OUTPUT"
+
+      - name: Cache Composer packages
+        uses: actions/cache@v4
+        with:
+          path: ${{ steps.composer-cache.outputs.dir }}
+          key: composer-${{ matrix.php }}-${{ hashFiles('composer.json') }}
+          restore-keys: composer-${{ matrix.php }}-
+
+      - name: Install dependencies
+        run: composer install --no-interaction --no-progress --prefer-dist
+
+      - name: Run unit tests
+        run: vendor/bin/phpunit --testsuite Unit