Testing in Spring project - injecting repository into service with Mockito

Question

I'm trying to understand how to use Mockito in a Spring project, but I'm a bit stuck with the following:

I'm about to test a service with a real (in-memory) repository. I'm mocking every other object that's being used by that service. If I understand correctly, annotating an object with @Mock will be mocked, @Spy will use a real object, and with @InjectMocks will kind of "autowire" these annotated objects. However, I think I misunderstood @Spy because the following code is not working (seems like a mock object is inserted, neither a DB interaction, neither a NullPointerException comes up):

@SpringBootTest
@RunWith(SpringRunner.class)
public class UserServiceTests {

    @Spy
    @Autowired
    private UserRepository userRepository;

    @Mock
    private MessageService messageService;

    @InjectMocks
    private UserService userService = new UserServiceImpl();

    @Test
    public void testUserRegistration() {
        userService.registerUser("[email protected]");

        Assert.assertEquals("There is one user in the repository after the first registration.", 1, userRepository.count());
    }
}

If I remove the @Spy annotation and insert the repository in the service with reflection, it works:

ReflectionTestUtils.setField(userService, "userRepository", userRepository);

This seems inconvenient, and I'm pretty sure that @Spy is meant to do this. Can anyone point out what I'm missing/misunderstanding?

Edit: one more thing - with the @Spy annotation I'm not getting a NullPointerException on save, but it seems like a mock object is inserted instead of the real repository.

Edit 2: I think this is the answer for my confusion:

SpringBoot Junit bean autowire

Why do you have Autowired and Spy? Could you expand on "not working"? — jonrsharpe
– jonrsharpe, Commented Jul 26, 2018 at 7:12
Pretty sure you should be using @Mock above your repository — Tom Withers
– Tom Withers, Commented Jul 26, 2018 at 7:13
If at all practical, it's better to use constructor injection for precisely this reason--you don't need Spring for this test and can simply create and pass a mock to new UserServiceImpl(mockUserRepository). — chrylis -cautiouslyoptimistic-
– chrylis -cautiouslyoptimistic-, Commented Jul 26, 2018 at 7:14
@chrylis this would mean that I have to modify all the services, because field injection is used everywhere, and I'd like to avoid that. — Peter
– Peter, Commented Jul 26, 2018 at 7:20
@ThomasWithers I'm trying to use an in-memory db for testing, Mock wouldn't do what I want, would it? — Peter
– Peter, Commented Jul 26, 2018 at 7:21

Andrew Regan · Accepted Answer · 2019-09-12 09:18:38Z

2

The problem is that you probably @Autowired some services/repositories in UserService like these:

public class UserServiceImpl() {

  @Autowired
  private UserRepository userRepository;
  @Autowired
  private MessageService messageService;

  // ... all the stuff
}

Mockito tries to inject mocks through constructor or setters which are not available. Try to redesign your class UserServiceImpl, so it has constructor like:

public class UserServiceImpl() {

  private final UserRepository userRepository;
  private final MessageService messageService;

  @Autowired
  public UserServiceImpl(UserRepository userRepository, MessageService messageService) {
    this.userRepository = userRepository;
    this.messageService = messageService;
  }

Then you can instantiate the service in @Before with the constructor using those mocks.

edited Sep 12, 2019 at 9:18

Andrew Regan

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answered Jul 26, 2018 at 7:22

Woxis17

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5 Comments

Peter Over a year ago

So the @Spy and @Autowired annotations on the repository in the test are correct by the way, my only problem is the field autowiring?

Woxis17 Over a year ago

If you setup in-memory database in test context in the configuration, then I don't see a reason to use @Spy on the repository, since it is already a mock of real database. And yes I think that the only problem with that is field autowiring instead of constructor/setter. Also I'll highly recommend to use constructor injections.

Woxis17 Over a year ago

Also, now I see that you are missing MockitoAnnotations.initMocks(this) in @Before

Peter Over a year ago

I actually missed the existence of @MockBean annotation and basically I wanted to do it manually by combining some. :)

Peter Over a year ago

Also if I try to exclude the Spring parts from the test as much as I can and use MockitoJUnitRunner instead of SpringRunner I won't need to watch out for these if I'm correct.

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