Fatal error: Uncaught Error: Class 'PHPUnit\Framework\TestCase' not found in /mnt/volume_lon1_01/backend/admin/vendor/sebastian/environment/tests/OperatingSystemTest.php:17 Stack trace: #0 {main} thrown in /mnt/volume_lon1_01/backend/admin/vendor/sebastian/environment/tests/OperatingSystemTest.php on line 17