CkeditorTestHooks.php

<?php

declare (strict_types=1);
namespace Drupal\ckeditor_test\Hook;

use Drupal\Core\Hook\Attribute\Hook;

/**
 * Hook implementations for ckeditor_test.
 */
class CkeditorTestHooks {
  
  /**
   * Implements hook_editor_info_alter().
   */
  public function editorInfoAlter(array &$editors) : void {
    // Drupal 9 used to have an editor called ckeditor. Copy the Unicorn editor
    // to it to be able to test upgrading to CKEditor 5.
    $editors['ckeditor'] = $editors['unicorn'];
  }

}