删除话题 最后断言 404 失败？

预期的是404 为啥会返回200呢？？

Expected status code 404 but received 200.
Failed asserting that false is true.

/home/vagrant/Code/Laravel/vendor/laravel/framework/src/Illuminate/Foundation/Testing/TestResponse.php:78
/home/vagrant/Code/Laravel/tests/Feature/TopicApiTest.php:104

FAILURES!
Tests: 7, Assertions: 22, Failures: 1.

public function testDeleteTopic()
    {
        $topic = $this->makeTopic();
        $response = $this->JWTActingAs($this->user)
            ->json('DELETE', '/api/topics/'.$topic->id);
        $response->assertStatus(204);

        $response = $this->json('GET', '/api/topics/'.$topic->id);
        $response->assertStatus(404);
    }