cakephp/tests/test_app/TestApp/Controller/ComponentTestController.php

<?php
declare(strict_types=1);

/**
 * CakePHP(tm) : Rapid Development Framework (https://cakephp.org)
 * Copyright 2005-2011, Cake Software Foundation, Inc. (https://cakefoundation.org)
 *
 * Licensed under The MIT License
 * Redistributions of files must retain the above copyright notice.
 *
 * @copyright     Copyright 2005-2011, Cake Software Foundation, Inc. (https://cakefoundation.org)
 * @link          https://cakephp.org CakePHP(tm) Project
 * @since         3.0.0
 * @license       https://opensource.org/licenses/mit-license.php MIT License
 */
namespace TestApp\Controller;

use Cake\Controller\Controller;

/**
 * ComponentTestController class
 */
class ComponentTestController extends Controller
{
    public function initialize(): void
    {
        parent::initialize();

        $this->loadComponent('Flash');
    }

    public function flash()
    {
        return $this->response->withStringBody(json_encode([
            'flashKey' => $this->Flash->getConfig('key'),
        ]));
    }
}