Fatal error: Uncaught Error: Class "PHPUnit\Framework\TestCase" not found in /opt/lampp/htdocs/myhospitalnow/mhn-doctors-ms/vendor/nicmart/tree/test/Unit/Visitor/PostOrderVisitorTest.php:23 Stack trace: #0 {main} thrown in /opt/lampp/htdocs/myhospitalnow/mhn-doctors-ms/vendor/nicmart/tree/test/Unit/Visitor/PostOrderVisitorTest.php on line 23