Fatal error: Uncaught Error: Class "Drupal\FunctionalTests\Installer\InstallerTestBase" not found in /home/www/drupal8/test/core/modules/config_translation/tests/src/Functional/ConfigTranslationInstallTest.php:12 Stack trace: #0 {main} thrown in /home/www/drupal8/test/core/modules/config_translation/tests/src/Functional/ConfigTranslationInstallTest.php on line 12