Symfony\Component\HttpFoundation\Response::isNotFound PHP Method

    public function isNotFound()
    {
        return 404 === $this->statusCode;
    }

 public function testIsNotFound()
 {
     $response = new Response('', 404);
     $this->assertTrue($response->isNotFound());
     $response = new Response('', 200);
     $this->assertFalse($response->isNotFound());
 }