Fatal error: Uncaught Error: Class "PHPUnit\Framework\TestCase" not found in C:\xampp\htdocs\mflux\vendor\league\oauth1-client\tests\PlainTextSignatureTest.php:9 Stack trace: #0 {main} thrown in C:\xampp\htdocs\mflux\vendor\league\oauth1-client\tests\PlainTextSignatureTest.php on line 9