在 Spring Boot 中使用模拟存储库测试 void 服务方法？

Question

My Spring Boot application provides the following service which increments a counter on the User entity and persists it to the database.

@Service
public class MyService {
    
    @Autowired
    UserRepo userRepo;
    
    public void incrementLoginFailures(String email) throws UserNotFoundException {
        final User user = userRepo.findByEmail(email).orElseThrow(UserNotFoundException::new);
        user.incrementLoginFailures();
        userRepo.save(user);
    }
}

Now I'd like to write a JUnit 5 test for this, preferrably mocking the respository but I guess I have some trouble understanding the concept of mocking here.

As you can see, the service method incrementLoginFailures() does not return anything so I don't know how I could check that the login counter on the User entity was actually incremented. Do I need to write an integration test for this kind of check which actually spins up a database?

@ExtendWith(MockitoExtension.class)
public class UserServiceTest {

  @InjectMocks
  private UserService userService;

  @Mock
  private UserRepo userRepo;

  @Test
  public void shouldIncrement() {
    userService.incrementLoginFailures("foo@bar.com");
    Assertions.assertEquals(1, xyz);  // from what source would xyz come from?
  }
}

Answer 1

In your test method before calling userService.incrementLoginFailures("foo@bar.com");you will need to mock the return values of the methods called on userRepo something like below:

@ExtendWith(MockitoExtension.class)
public class UserServiceTest {

  @InjectMocks
  private UserService userService;

  @Mock
  private UserRepo userRepo;

  @Test
  public void shouldIncrement() {
    User user = new User();//please initialize as per your requirement
    when(userRepo.findByEmail("foo@bar.com")).thenReturn(user);
    userService.incrementLoginFailures("foo@bar.com");//this method will make changes to the user object
    Assertions.assertEquals(1, user.getLoginFailures());
  }
}

Answer 2

I recommend returning the user object from the method to help with testing. To setup mock repository behavior, use Mockito.when and return a new user POJO. Then assert the login failure count is 1 on the returned object.

Answer 3

You should only test your own code and in unit test the code for that unit. So not for example if Spring data repository save() works. You can test it but you should trust that it works.

If done correct you should have a unit test that asserts that user.incrementLoginFailures() works as it should.

// Unit test for the user
@Test
public void shouldIncrement() {
    User user = new User();
    // In here when you have just initialized user you might know that 
    // the initial count is zero but it is overall better to assert 
    // the logic for any value / case
    int originalLoginFailures = user.getLoginFailures();
    user.incrementLoginFailures();
    assertEquals(originalLoginFailures + 1, user.getLoginFailures());
 }

That is actually what you need to know in addition that the data is saved to the database.

So you might have a unit test for UserService (or is it MyService?) that asserts that userIncrementLoginFailures() and userRepo.save() is called for user with email foo@bar.com when userService.incrementLoginFailures("foo@bar.com") is called.

That would be done with verify , like:

@InjectMocks
private MyService userService;
@Mock
private UserRepo userRepo;
@Mock
private User user; 

@Test
public void shouldIncrementAndSave() throws UserNotFoundException {
    when(userRepo.findByEmail("foo@bar.com")).thenReturn(Optional.of(user));
    userService.incrementLoginFailures("foo@bar.com");
    verify(user).incrementLoginFailures();
    verify(userRepo).save(user);
}

You could test that user.incrementLoginFailures() works in here also, but because you tested it in your user unit test it is not necessarily needed but is a redundant test and tests a logic that does not belong to unit tested, namely UserService .