Fatal error: Uncaught Error: Class "PHPUnit\Framework\TestCase" not found in /var/www/html/drupal/vendor/oomphinc/composer-installers-extender/tests/src/Installers/InstallerTest.php:12 Stack trace: #0 {main} thrown in /var/www/html/drupal/vendor/oomphinc/composer-installers-extender/tests/src/Installers/InstallerTest.php on line 12