improvements-2.x-dev/tests/modules/improvements_test/src/Controller/ImprovementsTestController.php

<?php

namespace Drupal\improvements_test\Controller;

use Drupal\Core\Controller\ControllerBase;
use Drupal\node\NodeInterface;

class ImprovementsTestController extends ControllerBase {

  public function alteredPageResult(): array {
    return [
      '#markup' => 'Markup from controller',
    ];
  }

  public function entityUuidAccessCheck(NodeInterface $node): array {
    return [
      '#markup' => 'Hello World!',
    ];
  }

}