<?php
/**
 * CakePHP(tm) : Rapid Development Framework (http://cakephp.org)
 * Copyright (c) Cake Software Foundation, Inc. (http://cakefoundation.org)
 *
 * Licensed under The MIT License
 * For full copyright and license information, please see the LICENSE.txt
 * Redistributions of files must retain the above copyright notice
 *
 * @copyright     Copyright (c) Cake Software Foundation, Inc. (http://cakefoundation.org)
 * @link          http://cakephp.org CakePHP(tm) Project
 * @since         3.3.0
 * @license       http://www.opensource.org/licenses/mit-license.php MIT License
 */
namespace App\Test\TestCase;

use App\Application;
use Cake\Error\Middleware\ErrorHandlerMiddleware;
use Cake\Http\MiddlewareStack;
use Cake\Routing\Middleware\AssetMiddleware;
use Cake\Routing\Middleware\RoutingMiddleware;
use Cake\TestSuite\IntegrationTestCase;

/**
 * ApplicationTest class
 */
class ApplicationTest extends IntegrationTestCase
{

    /**
     * testMiddleware
     *
     * @return void
     */
    public function testMiddleware()
    {
        $app = new Application(dirname(dirname(__DIR__)) . '/config');
        $middleware = new MiddlewareStack();

        $middleware = $app->middleware($middleware);

        $this->assertInstanceOf(ErrorHandlerMiddleware::class, $middleware->get(0));
        $this->assertInstanceOf(AssetMiddleware::class, $middleware->get(1));
        $this->assertInstanceOf(RoutingMiddleware::class, $middleware->get(2));
    }
}

Add tests for Application class.
Add tests for Application class.
