MockMvc returns null instead of object - spring

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);

Answer 1

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.