Zend\Diactoros\Response::getStatusCode PHP Method

    public function getStatusCode()
    {
        return $this->statusCode;
    }

 public function testRoutingFailureDueToHttpMethodCallsNextWithNotAllowedResponseAndError()
 {
     $request = new ServerRequest();
     $response = new Response();
     $result = RouteResult::fromRouteFailure(['GET', 'POST']);
     $this->router->match($request)->willReturn($result);
     $next = function ($request, $response, $error = false) {
         $this->assertEquals(405, $error);
         $this->assertEquals(405, $response->getStatusCode());
         return $response;
     };
     $app = $this->getApplication();
     $test = $app->routeMiddleware($request, $response, $next);
     $this->assertInstanceOf('Psr\\Http\\Message\\ResponseInterface', $test);
     $this->assertEquals(405, $test->getStatusCode());
     $allow = $test->getHeaderLine('Allow');
     $this->assertContains('GET', $allow);
     $this->assertContains('POST', $allow);
 }