DevelTestController.php

<?php

namespace Drupal\devel_test\Controller;

use Drupal\Core\Controller\ControllerBase;
use Symfony\Component\DependencyInjection\ContainerInterface;

/**
 * Returns responses for devel module routes.
 */
class DevelTestController extends ControllerBase {
    
    /**
     * {@inheritdoc}
     */
    public static function create(ContainerInterface $container) : static {
        $instance = parent::create($container);
        $instance->stringTranslation = $container->get('string_translation');
        return $instance;
    }
    
    /**
     * Returns a simple page output.
     *
     * @return array
     *   A render array.
     */
    public function simplePage() : array {
        return [
            '#markup' => $this->t('Simple page'),
        ];
    }

}