Fatal error: Uncaught Error: Class "Drupal\KernelTests\KernelTestBase" not found in /home/fnbrshareacopy/public_html/modules/contrib/page_manager/tests/src/Kernel/SerializationTest.php:19 Stack trace: #0 {main} thrown in /home/fnbrshareacopy/public_html/modules/contrib/page_manager/tests/src/Kernel/SerializationTest.php on line 19