correctly install deps only when needed

Author: transistive

.github/workflows/tests.yml

@@ -33,6 +33,11 @@ jobs:
         with:
           path: /tmp/composer-cache
           key: ${{ runner.os }}-${{ hashFiles('**/composer.lock') }}
+      - uses: php-actions/composer@v6
+        with:
+          progress: yes
+          php_version: 8.0
+          version: 2
       - uses: php-actions/phpunit@v3
         with:
           configuration: phpunit.xml.dist