use PHPUnit\Framework\TestCase;

 class SomeClass extends TestCase
 {
     public function test()
     {
-        $this->assertSame(200, $this->client->getResponse()->getStatusCode());
+        $this->assertResponseIsSuccessful();
     }
 }

 use Symfony\Bundle\FrameworkBundle\Test\WebTestCase;

 final class SomeClass extends WebTestCase
 {
     public function test()
     {
-        $response = self::getClient()->getResponse();
-
-        $this->assertSame(301, $response->getStatusCode());
-        $this->assertSame('https://example.com', $response->headers->get('Location'));
+        $this->assertResponseStatusCodeSame(301);
+        $this->assertResponseRedirects('https://example.com');
     }
 }

 use Symfony\Bundle\FrameworkBundle\Controller\Controller;

 class BaseController extends Controller
 {
     function indexAction()
     {
-        $this->render('appBundle:Landing\Main:index.html.twig');
+        $this->render('@app/Landing/Main/index.html.twig');
     }
 }