Expanded class hierarchy of UpdateKernel in Drupal 9
- class \Drupal\Core\DrupalKernel implements \Symfony\Component\HttpKernel\TerminableInterface, DrupalKernelInterface uses InstallerRedirectTrait
- class \Drupal\Core\Installer\InstallerKernel
- class \Drupal\Core\Test\TestKernel
- class \Drupal\Core\Test\TestRunnerKernel
- class \Drupal\Core\Update\UpdateKernel