Fatal error: Uncaught Error: Class "PHPUnit\Framework\TestCase" not found in C:\xampp\htdocs\r10csm\vendor\sebastian\diff\tests\LongestCommonSubsequenceTestCase.php:17 Stack trace: #0 {main} thrown in C:\xampp\htdocs\r10csm\vendor\sebastian\diff\tests\LongestCommonSubsequenceTestCase.php on line 17