Fatal error: Uncaught Error: Class "Drupal\Tests\BrowserTestBase" not found in /home/fnbrshareacopy/public_html/modules/contrib/panelizer/tests/src/Functional/LayoutBuilderMigrationTest.php:14 Stack trace: #0 {main} thrown in /home/fnbrshareacopy/public_html/modules/contrib/panelizer/tests/src/Functional/LayoutBuilderMigrationTest.php on line 14