Use the vendor phpunit executable

Author: Rahe

.github/workflows/ci.yml

@@ -30,7 +30,7 @@ jobs:
       with:
         php-version: ${{ matrix.php-versions }}
         coverage: xdebug #optional, setup coverage driver
-        tools: psalm, phpcbf, phpcs, phpunit:5.7.27
+        tools: psalm, phpcbf, phpcs
 
     - name: Install all depenencies
       run: composer update
@@ -39,4 +39,4 @@ jobs:
       run: bash bin/install-wp-tests.sh wordpress_test root root 127.0.0.1:3306 ${{ matrix.wp }} true
 
     - name: phpunit tests
-      run: phpunit
+      run: ./vendor/bin/phpunit