Fatal error: Uncaught Error: Class 'TYPO3\CMS\ComposerTest\Installer\InstallerTestCase' not found in /var/www/typo3/vendor/typo3/cms-composer-installers/tests/Installer/ExtensionInstallerTest.php:21 Stack trace: #0 {main} thrown in /var/www/typo3/vendor/typo3/cms-composer-installers/tests/Installer/ExtensionInstallerTest.php on line 21