Fatal error: Uncaught Error: Class 'PHPUnit\Framework\TestCase' not found in /home/esecureh/public_html/magdemo/vendor/magento/framework/Config/Test/Unit/Converter/Dom/FlatTest.php:15 Stack trace: #0 {main} thrown in /home/esecureh/public_html/magdemo/vendor/magento/framework/Config/Test/Unit/Converter/Dom/FlatTest.php on line 15