Fatal error: Uncaught Error: Interface "Drupal\TestSite\TestSetupInterface" not found in /home/www/drupal8/test/core/tests/Drupal/TestSite/TestSiteInstallTestScript.php:10 Stack trace: #0 {main} thrown in /home/www/drupal8/test/core/tests/Drupal/TestSite/TestSiteInstallTestScript.php on line 10