Fatal error: Uncaught Error: Class "PHPUnit\Framework\TestCase" not found in /home/airtimer/public_html/vendor/amzn/amazon-pay-module/Test/Unit/Observer/AddAmazonButtonTest.php:37 Stack trace: #0 {main} thrown in /home/airtimer/public_html/vendor/amzn/amazon-pay-module/Test/Unit/Observer/AddAmazonButtonTest.php on line 37