Testing POST request in client side using Mockito

Question

I want to test the post method that should send a post request to "server" (So I want to mock the response from the server and check the response). Also, I want to test that the response contains http status OK in the body. Question: How should I do that with mockito?

My Post Method in the client (Client-side):

public class Client{
        public static void sendUser(){

        String url = "http://localhost:8080/user/add";

        HttpHeaders requestHeaders = new HttpHeaders();
        requestHeaders.setContentType(MediaType.APPLICATION_JSON);
        requestHeaders.setAccept(Arrays.asList(MediaType.APPLICATION_JSON));

        User test = new User();
        test.setName("test");
        test.setEmail("a@hotmail.com");
        test.setScore(205);

        RestTemplate restTemplate = new RestTemplate();
        HttpEntity<User> request = new HttpEntity<>(test);

        ResponseEntity<String> response = restTemplate.exchange(url, HttpMethod.POST, request, String.class);

        if(response.getStatusCode() == HttpStatus.OK){
            System.out.println("user response: OK");
        }

      }
  }

My Controller in another module (server-side):

@RestController
@RequestMapping("/user")
public class UserController
{
    @Autowired
    private UserRepository userRepository;

    @PostMapping("/add")
    public ResponseEntity addUserToDb(@RequestBody User user) throws Exception
    {
        userRepository.save(user);
        return ResponseEntity.ok(HttpStatus.OK);
    }

Test:

    @RunWith(SpringRunner.class)
@ActiveProfiles("test")
@SpringBootTest(classes = Client.class)
@AutoConfigureMockMvc
public class ClientTest
{

    private MockRestServiceServer mockServer;

    @Autowired
    private RestTemplate restTemplate; 

    @Autowired
    private MockMvc mockMvc;

    @Before
    public void configureRestMVC()
    {
        mockServer =
                MockRestServiceServer.createServer(restTemplate);
    }

    @Test
    public void testRquestUserAddObject() throws Exception
    {

        User user = new User("test", "mail", 2255);

        Gson gson = new Gson();

        String json = gson.toJson(user );

        mockServer.expect(once(), requestTo("http://localhost:8080/user/add")).andRespond(withSuccess());


        this.mockMvc.perform(post("http://localhost:8080/user/add")
                .content(json)
                .contentType(MediaType.APPLICATION_JSON))
                .andDo(print()).andExpect(status().isOk())
                .andExpect(content().json(json));
    }

}

And now i am getting this error:

org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'ClientTest': Unsatisfied dependency expressed through field 'restTemplate'; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type 'org.springframework.web.client.RestTemplate' available: expected at least 1 bean which qualifies as autowire candidate. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}

Answer 1

Based on your Client class , would like to suggest below changes so as to make it better testable :

    //  class
    public class Client {

        /*** restTemplate unique instance for every unique HTTP server. ***/
        @Autowired
        RestTemplate restTemplate;

        public ResponseEntity<String> sendUser() {

        String url = "http://localhost:8080/user/add";

        HttpHeaders requestHeaders = new HttpHeaders();
        requestHeaders.setContentType(MediaType.APPLICATION_JSON);
        requestHeaders.setAccept(Arrays.asList(MediaType.APPLICATION_JSON));

        User test = new User();
        test.setName("test");
        test.setEmail("a@hotmail.com");
        test.setScore(205);

        HttpEntity<User> request = new HttpEntity<>(test);

        ResponseEntity<String> response = restTemplate.exchange(url, HttpMethod.POST, request, String.class);

        if(response.getStatusCode() == HttpStatus.OK){
            System.out.println("user response: OK");
        }
        return response;
      }
  }

And then for above we Junit as :

@RunWith(MockitoJUnitRunner.class)
public class ClientTest {

  private String RESULT = "Assert result";

  @Mock
  private RestTemplate restTemplate;

  @InjectMocks
  private Client client;

  /**
   * any setting needed before load of test class
   */
  @Before
  public void setUp() {
    // not needed as of now
  }

  // testing an exception scenario
  @Test(expected = RestClientException.class)
  public void testSendUserForExceptionScenario() throws RestClientException {

    doThrow(RestClientException.class).when(restTemplate)
        .exchange(anyString(), any(HttpMethod.class), any(HttpEntity.class), any(Class.class));
    // expect RestClientException
    client.sendUser();
  }

  @Test
  public void testSendUserForValidScenario() throws RestClientException {

    // creating expected response
    User user= new User("name", "mail", 6609); 
    Gson gson = new Gson(); 
    String json = gson.toJson(user); 
    doReturn(new ResponseEntity<String>(json, HttpStatus.OK)).when(restTemplate)
        .exchange(anyString(), any(HttpMethod.class), any(HttpEntity.class), any(Class.class));
    // expect proper response
    ResponseEntity<String> response =
        (ResponseEntity<String>) client.sendUser();
    assertEquals(this.RESULT, HttpStatus.OK, response.getStatusCode());
  }
}

Basically in your sendResponse() function, we are doing as:

// we are getting URL , creating requestHeader
// finally creating HttpEntity<User> request 
// and then passing them restTemplate.exchange 
// and then restTemplate is doing its job to make a HTPP connection and getresponse...
// and then we are prinnting the response... somestuff 

Thus in its corresponding test we should also test only what the function is doing since the connection is being taken care by restTemplate and you're not overriding any working of restTemplate so we should not do anything for the same... rather just test our code/logic.

Lastly, to be sure imports looks like :

to be sure , imports will be like :

import org.springframework.http.HttpEntity; 
import org.springframework.http.HttpHeaders; 
import org.springframework.http.HttpMethod; 
import org.springframework.http.HttpStatus; 
import org.springframework.http.MediaType; 
import org.springframework.http.ResponseEntity; 
import org.springframework.web.client.RestTemplate;

Hope this helps.

Answer 2

Full code first (explanation is below):

import static org.springframework.test.web.client.ExpectedCount.manyTimes;
import static org.springframework.test.web.client.ExpectedCount.once;
import static org.springframework.test.web.client.match.MockRestRequestMatchers.requestTo;
import static org.springframework.test.web.client.response.MockRestResponseCreators.withSuccess;
import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.post;
import static org.springframework.test.web.servlet.result.MockMvcResultHandlers.print;
import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.content;
import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.status;

@RunWith(SpringRunner.class)
@ActiveProfiles("test")
@SpringBootTest
@AutoConfigureMockMvc
public class MyTestClass {

MockRestServiceServer mockServer;

    @Autowired
    private RestTemplate restTemplate;  //create a bean somewhere. It will be injected here. 

    @Autowired
    private MockMvc mockMvc;

    @Before
    public void configureRestMVC(){
        mockServer =
                MockRestServiceServer.createServer(restTemplate);
    }

    @Test
    public void test0() throws Exception {
        //this is where you would mock the call to endpoint and and response
        mockServer.expect(once(), requestTo("www.example.com/endpoint1"))
        .andRespond(withSuccess());
    ... 
    //here you will actually make a call to your controller. If the service class is making a post call to another endpoint outside, that you just mocked in above statement.
    this.mockMvc.perform(post("www.example2.com/example2endpoint")
                .content(asJsonString(new YouCustomObjectThatYouWantToPost))
                .contentType(MediaType.APPLICATION_JSON))
        .andDo(print()).andExpect(status().isOk())
        .andExpect(content().json(matchResponseAgainstThisObject()));
   }

You would need to use @AutoConfigureMockMvc annotation. The purpose behind is is to not start the server at all, but test only the layer below that, where Spring handles the incoming HTTP request and hands it off to your controller. That way, almost the full stack is used, and your code will be called exactly the same way as if it was processing a real HTTP request, but without the cost of starting the server. To do that we will use Spring's MockMvc, and we can ask for that to be injected for us by using the @AutoConfigureMockMvc annotation on the test class.

private MockRestServiceServer mockServer;

MockRestServiceServer is a main entry point for client-side REST testing. Used for tests that involve direct or indirect use of the RestTemplate. Provides a way to set up expected requests that will be performed through the RestTemplate as well as mock responses to send back thus removing the need for an actual server.

mockServer.expect(once(), requestTo("www.example.com/endpoint1"))
    .andRespond(withSuccess());

This is where you would setup mocking to outside calls. And setup expectations as well.

this.mockMvc.perform(post("www.example2.com/example2endpoint")..

This is where you would actually make a rest/api call to your own endpoint, the one that you defined in your controller. Spring will hit your endpoint, perform all the logic that you have in your controller/service layer, and when it comes to the part of actually making a call outside, will use mockServer that you just defined above. That way, it is totally offline. You never hit the actual outside service. Also, you will append your assertions on the same mockMvc.perform method.