Mockito.when().thenReturn() doesn't work or returns null

Question

During the test there is a NullPointerException thrown. I tried to debug it and the only thing I worked out was that eventOptional is always null. Just as if Mockito.when().thenReturn() didn't work. Can anybody help? Here's my code for a tested service and for the test itself:

@Service
public class EventService {

    @Autowired 
    public EventService(EventRepository eventRepository) {
        this.eventRepository = eventRepository;
    }
    //...
    public void updateEvent(EventDTO eventDTO) {
        Optional<Event> eventOptional = eventRepository.findOneById(eventDTO.getId());

        eventOptional.orElseThrow(() -> new BadRequestException(EVENT_NOT_FOUND));
        //...
    }
}

And the test class:

@RunWith(MockitoJUnitRunner.class)
public class EventServiceTest {

    @Mock
    private EventRepository eventRepository;
    @InjectMocks
    private EventService eventService;

    private Event sampleEventFromDb;

    @Before
    public void setUp() throws Exception {

        MockitoAnnotations.initMocks(this);
    }

    @Test
    public void shouldUpdateEventTestAndWithProperTime() throws Exception {
        EventDTO eventDTOMock = Mockito.mock(EventDTO.class);

        sampleEventFromDb = Event.builder()
            .name("name")
            .startDateTime(LocalDateTime.now())
            .placeName("place")
            .description("description")
            .publicEvent(true)
            .owner(new User())
            .build();

        Mockito.when(eventRepository.findOneById(anyString())).thenReturn(Optional.of(sampleEventFromDb));
        Mockito.when(eventDTOMock.getId()).thenReturn("1");

        eventService.updateEvent(eventDTOMock); //NullPointerException
        //...
    }
}

You dont need to do MockitoAnnotations.initMocks(this) if running the test with the MockitoJUnitRunner. Also make sure that the findOneById method is not declared as static, private or final. — mdewit, May 03 '16 at 18:37
@SotiriosDelimanolis, it is initialized by the runner and/or initMocks using reflection. And it is, in fact, initialized in this example—I've just checked. The funny thing is, works fine for me with TestNG, but fails with JUnit. This is certainly not a duplicate so I've voted to reopen. — Sergei Tachenov, May 03 '16 at 18:40
Actually when I just gave up on MockitoJunitRunner and mocked repository manually as well as initialized the service via its constructor - it works now perfectly. — HectorBarbossa, May 03 '16 at 18:44
@mdewit, looks like you hit the spot—removing either the runner or the `initMocks` call fixes the problem, but why? `initMocks` is not idempotent? — Sergei Tachenov, May 03 '16 at 18:44
@Sergey Tachenov That is interesting, I did not actually think it would fix the problem just thought it was unnecessary to use both. As MockitoAnnotations.initMocks only needs to be used if you want to run with a different runner than MockitoJUnitRunner (such as the Junit Parameterized runner). — mdewit, May 03 '16 at 18:51
@mdewit, neither did I. I've discovered it purely because I tried to run this first with TestNG and saw no problems. But then I thought, “Oh, but there is no JUnitRunner in TestNG, don't tell me...” — Sergei Tachenov, May 03 '16 at 18:52

score 14 · Answer 1 · answered Sep 12 '18 at 16:10

14

I got this same error, after trying a lot of things I fixed it by replacing the anyString() method with any()

Try this:

Mockito.when(eventRepository.findOneById(any())).thenReturn(Optional.of(sampleEventFromDb));

answered Sep 12 '18 at 16:10

Hugo Lezama

198
2
7

1

Wasted 4 hours on this - Not sure why it doesnt like anyString() , the library should have the method it wasnt supposed to work., replacing with any() worked. – Vinny May 22 '20 at 19:59
1

same here!!! with anyString() was working before and stopped working suddenly, changed it to any() and worked. Strange!!! – SumataPatil Jan 04 '21 at 18:40
1

you are my savior. Thanks a lot – chandu Aug 08 '22 at 13:03
after 3 days of damning Mockito and Spring testing, this answer gave me the magic solution. i <3 u – Andres Camilo Sierra Hormiga Jul 07 '23 at 13:03

score 8 · Accepted Answer · answered May 03 '16 at 18:48

8

Looks like the problem is that initMock is called twice: once by the runner and once by the setUp method. Running the test with the regular runner or removing the initMocks call from the setUp method fixes this problem.

answered May 03 '16 at 18:48

Sergei Tachenov

24,345
8
57
73

score 0 · Answer 3 · answered May 05 '22 at 14:07

0

Change anyList(), anyMap()..... to any(). After long debugging it is worked finally.

answered May 05 '22 at 14:07

Saravanakumar Arunachalam

11
3

Mockito.when().thenReturn() doesn't work or returns null

3 Answers3

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