How to inject only one mock inside Service class with normal instantiation to other instances?

Question

Assume i have implemented next service class:

@Service
@RequiredArgsConstructor
@Transactional
public class ItemService {

    private final ItemRepository itemRepository;
    private final ItemCreatorFactory itemCreatorFactory;
    private final CommonClient commonClient;
    private final HelperService helperService;
    private final PrivilegeUtil privilegeUtil;

    public void addItem() {
        //How to only mock this in tests and other defaults to normal Autowired injection
        if(!privilegeUtil.isAdmin("bla bla")) {
             Throw new InvalidOperationException("Only super admin can insert data.");
        }
        helperService.doSomeRealLogic();
        commonClient.callAnotherExternalAPI();
        itemRepository.save(myObject);
    }
    // other methods
}

And i need to test insert new item in database, but before that i am doing some extra logic and if its fine so i can insert safely in database.

Now i need to use mockito so i mock only privilegeUtil class but i need all other instances inside ItemService class to be normally Autowired without mocking it.

So i go for next test class:

@RunWith(SpringRunner.class)
public class ItemTests {

    @Before
    public void setUp() throws Exception {
        MockitoAnnotations.initMocks(this);
    }

    @InjectMocks//Only mocks privilegeUtil but other instances is all null :(
    private ItemService itemService;//So how i get autowired item service instance but only mock privilegeUtil instance inside it and all other instances go for normal instantiation ???

    @Mock
    private PrivilegeUtil privilegeUtil;

    @Test
    public void testAddNewItem() {
        String email = "[email protected]";

        Mockito.when(privilegeUtil.isSuperAdmin(email)).thenReturn(true);
        
        //Here i need to test adding item normally
        //But only skip checking isSuperAdmin part inside addItem method
        itemService.addItem(itemRequest, email);
    }

}

So how i get autowired item service instance but only mock privilegeUtil instance inside it and all other instances go for normal instantiation ???

Is that possible? and if not so what you can suggest?

Answer 1

Yes, this is possible. As you are mentioning you test some database related logic, I guess it makes sense to use @DataJpaTest to let Spring create a sliced context for you with all JPA/database related components.

You can then already autowire your repository inside your test.

What's left is to manually create all other normal beans using e.g. @TestConfiguration. Those classes you want to mock, annotate them with @MockBean so that Spring places a mocked version into the sliced context.

@RunWith(SpringRunner.class)
@DataJpaTest
public class ItemTests {

  @TestConfiguration
  static class TestConfig {

    @Bean
    public ItemCreatorFactory itemCreatorFactory() {
      return new ItemCreatorFactory();
    }

   // .. manually create all other beans

  }

  @Autowired
  private ItemRepository itemRepository;

  @Autowired
  private ItemCreatorFactory itemCreatorFactory;

  @Autowired
  private CommonClient commonClient;

  @Autowired
  private HelperService helperService;

  @MockBean
  private PrivilegeUtil privilegeUtil;

  @Before
  public void setUp() throws Exception {
     this.itemService = new ItemService(itemRepository, itemCreatorFactory, commonClient, helperService, mockedPrivilegeUtil);
  }

  @Test
  public void testAddNewItem() {
      String email = "[email protected]";
      
      Mockito.when(privilegeUtil.isSuperAdmin(email)).thenReturn(true);
    
      itemService.addItem(itemRequest, email);
  }

}

... and then you can finally manually instantiate your ItemService and pass all your instances to the constructor.