Fatal error: Uncaught Error: Class 'PHPUnit\Framework\TestCase' not found in E:\xampp\htdocs\vendor\sebastian\diff\tests\Utils\UnifiedDiffAssertTraitIntegrationTest.php:21 Stack trace: #0 {main} thrown in E:\xampp\htdocs\vendor\sebastian\diff\tests\Utils\UnifiedDiffAssertTraitIntegrationTest.php on line 21