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