MockMvc returns null instead of object

Question

I am developing a microservice application and I need to test a post request to a controller. Testing manually works but the test case always returns null.

I've read many similar questions here in Stackoverflow and documentation but haven't figured out yet what I am missing.

Here is what I currently have and what I tried in order to make it work:

//Profile controller method need to be tested
@RequestMapping(path = "/", method = RequestMethod.POST)
public ResponseEntity<Profile> createProfile(@Valid @RequestBody User user, UriComponentsBuilder ucBuilder) {
    Profile createdProfile = profileService.create(user); // line that returns null in the test
    if (createdProfile == null) {
        System.out.println("Profile already exist");
        return new ResponseEntity<>(HttpStatus.CONFLICT);
    }
    HttpHeaders headers = new HttpHeaders();
    headers.setLocation(ucBuilder.path("/{name}").buildAndExpand(createdProfile.getName()).toUri());
    return new ResponseEntity<>(createdProfile , headers, HttpStatus.CREATED);
}

//ProfileService create function that returns null in the test case
public Profile create(User user) {
    Profile existing = repository.findByName(user.getUsername());
    Assert.isNull(existing, "profile already exists: " + user.getUsername());

    authClient.createUser(user); //Feign client request

    Profile profile = new Profile();
    profile.setName(user.getUsername());
    repository.save(profile);

    return profile;
}

// The test case
@RunWith(SpringRunner.class)
@SpringBootTest(classes = ProfileApplication.class)
@WebAppConfiguration
public class ProfileControllerTest {

    @InjectMocks
    private ProfileController profileController;

    @Mock
    private ProfileService profileService;

    private MockMvc mockMvc;

    private static final ObjectMapper mapper = new ObjectMapper();

    private MediaType contentType = MediaType.APPLICATION_JSON;

    @Before
    public void setup() {
        initMocks(this);
        this.mockMvc = MockMvcBuilders.standaloneSetup(profileController).build();
    }
    @Test
    public void shouldCreateNewProfile() throws Exception {

        final User user = new User();
        user.setUsername("testuser");
        user.setPassword("password");

        String userJson = mapper.writeValueAsString(user);

        mockMvc.perform(post("/").contentType(contentType).content(userJson))
                .andExpect(jsonPath("$.username").value(user.getUsername()))
                .andExpect(status().isCreated());

    }
}

Tried to add when/thenReturn before post but still returns 409 response with null object.

when(profileService.create(user)).thenReturn(profile);

Solution

You're using a mock profileService in your test, and you never tell that mock what to return. So it returns null.

You need something like

when(profileService.create(any(User.class)).thenReturn(new Profile(...));

Note that using

when(profileService.create(user).thenReturn(new Profile(...));

will only work if you properly override equals() (and hashCode()) in the User class, because the actual User instance that the controller receives is a serialized/deserialized copy of the user you have in your test, and not the same instance.