Fatal error: Uncaught Error: Class 'PHPUnit\Framework\TestCase' not found in /home/esecureh/public_html/magdemo/vendor/magento/module-sales/Test/Unit/Observer/Backend/SubtractQtyFromQuotesObserverTest.php:18 Stack trace: #0 {main} thrown in /home/esecureh/public_html/magdemo/vendor/magento/module-sales/Test/Unit/Observer/Backend/SubtractQtyFromQuotesObserverTest.php on line 18