Fatal error: Uncaught Error: Class "PHPUnit\Framework\TestCase" not found in /home/crmcodingobjects/public_html/modules/Core/Tests/Unit/Mail/Headers/IdHeaderTest.php:18 Stack trace: #0 {main} thrown in /home/crmcodingobjects/public_html/modules/Core/Tests/Unit/Mail/Headers/IdHeaderTest.php on line 18