Fatal error: Uncaught Error: Class 'PHPUnit\Framework\TestCase' not found in E:\xampp\htdocs\www\key1\vendor\sebastian\exporter\tests\ExporterTest.php:18 Stack trace: #0 {main} thrown in E:\xampp\htdocs\www\key1\vendor\sebastian\exporter\tests\ExporterTest.php on line 18