Mockito mock returning Null value from repository

Question

I'm trying to test my service implementation with JUNIT5. I don't quite understand whats going wrong but my UserRepository doesn't seem to be returning a value.

I have tested to see if the UserRepository has been used with: verify(repository, times(1)); And the response was "Wanted but not invoked...Actually, there were zero interactions with this mock"

Here is the Test Class:

@ExtendWith(MockitoExtension.class)
public class UserServiceTest {

    @Mock
    UserRepository repository;
    @InjectMocks
    UserServiceImpl userServiceImpl;

    UserModel inputUserModel;

    @BeforeEach
    public void setUp() throws Exception {
        inputUserModel = new UserModel();
        inputUserModel.setEmail("testemail@gmail.com");
        inputUserModel.setFirstName("john");
        inputUserModel.setLastName("doe");
        inputUserModel.setPassword("test");
        inputUserModel.setMatchPassword("test");

        User inputUser = User.builder()
                .email(inputUserModel.getEmail())
                .firstName(inputUserModel.getFirstName())
                .lastName(inputUserModel.getLastName())
                .password(inputUserModel.getPassword())
                .timeCreated(Timestamp.valueOf(LocalDateTime.now(ZoneId.systemDefault()))).userID(1)
                .build();

        User outputUser = User.builder().
                email(inputUserModel.getFirstName()).
                password(inputUserModel.getLastName()).
                lastName(inputUserModel.getFirstName())
                .firstName(inputUserModel.getFirstName())

                .timeCreated(Timestamp.valueOf(LocalDateTime.now(ZoneId.systemDefault()))).userID(1).build();

        Mockito.when(repository.save(inputUser)).thenReturn(outputUser);

    }

    @Test
    public void whenSaveUser_ThenUserHasID(){

        Assertions.assertEquals(1, userServiceImpl.saveUser(inputUserModel).getUserID());
    }
}

The error that I am getting:

org.mockito.exceptions.misusing.PotentialStubbingProblem: 
Strict stubbing argument mismatch. Please check:
 - this invocation of 'save' method:
    repository.save(
    User(userID=0, email=testemail@gmail.com, timeCreated=2022-12-14 03:18:24.0435578, password=test, firstName=john, lastName=doe)
);
    -> at com.jschwery.securitydemo.service.Implementations.UserServiceImpl.saveUser(UserServiceImpl.java:37)
 - has following stubbing(s) with different arguments:
    1. repository.save(
    User(userID=1, email=testemail@gmail.com, timeCreated=2022-12-14 03:18:24.0235563, password=test, firstName=john, lastName=doe)
);

My Service Class that I'm creating the test for:

public class UserServiceImpl implements UserService {

    UserRepository  userRepository;

    @Autowired
    public UserServiceImpl(UserRepository repository){
        this.userRepository = repository;
    }

    @Override
    public User saveUser(UserModel userModel) {
        if(!Objects.equals(userModel.getPassword(), userModel.getMatchPassword())){
            throw new UserException("Passwords do not match");
        }
        User user = User.builder().
                email(userModel.getEmail()).
                firstName(userModel.getFirstName()).
                lastName(userModel.getLastName()).
                password(userModel.getPassword()).
                timeCreated(Timestamp.valueOf(LocalDateTime.now(ZoneId.systemDefault()))).build();
        User returnedUser = userRepository.save(user);
        System.out.println(returnedUser.getEmail());
        System.out.println("userID" + returnedUser.getUserID());
        return returnedUser;
    }
}

Thanks for reading! :)

The `userId` attribute has value 0 in the actual call, and 1 in the stub. — Benoit, Dec 14 '22 at 09:54

score 1 · Accepted Answer · answered Dec 14 '22 at 10:26

I guess that your User class has an equals/hashCode defined either on the userID field or on all fields. When you mock your repository in your setUp method, you define what the method should do when it is called with the exact object that you specified, comparing the given object to the object specified in the mock by calling the equals/hashCode method.

You define the User object in your setUp method to have the userID 1 but in your UserServiceImpl the userID is not ever set (as it is generated by the persistence layer). Therefore the equals/hashCode check to determine if Mockito should execute the stub logic will never be called because the object passed by the UserServiceImpl will never be equals to the one that you defined in your mock.

There are several ways how you can solve this.

1) Integration test

My advice would be to convert your Unit-Test to a @SpringBootTest. There is no value in testing mocked behaviour. If this test was an integration test, you would test that the repository inserts the User into the database and generates an ID with your assertion.

2) Unit test

If you want to mock the repository, you should use an any() matcher for the input argument and then do what the repository would do, namely set the id:

  when(repository.save(any(User.class))).thenAnswer(invocation -> {
            final User entity = invocation.getArgument(0);
            ReflectionTestUtils.setField(entity, "userID", RandomUtils.nextLong());
            return entity;
        });

I would then assert, that the userID is not null, as the userID will be randomly generated as it would in production:

@ExtendWith(MockitoExtension.class)
public class UserServiceTest {

    @Mock
    private UserRepository repository;

    @InjectMocks
    private UserServiceImpl userServiceImpl;

    @Test
    void saveUser_userHasID(){
        // Arrange
        final UserModel inputUserModel = new UserModel();
        inputUserModel.setEmail("testemail@gmail.com");
        inputUserModel.setFirstName("john");
        inputUserModel.setLastName("doe");
        inputUserModel.setPassword("test");
        inputUserModel.setMatchPassword("test");

        when(repository.save(any(User.class))).thenAnswer(invocation -> {
            final User entity = invocation.getArgument(0);
            ReflectionTestUtils.setField(entity, "userID", RandomUtils.nextLong());
            return entity;
        });

        // Act
        final User user = userServiceImpl.saveUser(inputUserModel);

        // Assert
        assertThat(user.getUserID()).isNotNull();
    }
}

I highly recommend to use AssertJ for your assertions as it offers fluent asssertions and way more assertion methods than JUnit.

score 0 · Answer 2 · answered Dec 14 '22 at 12:36

tl;dr

Spring data can't generate a userID through a simple unit test with a mock, you will need a spring context running in an Integration test.

Details

There are two fields leading to the error you are having : UserID and timeCreated.

For the timeCreated field : in your test you create a inputUser object that you use for your mock. the problem is that this object inputUser is NOT the one used by your method under test saveUser(UserModel userModel) you could clearly see the that the timestamp differs in the erreor between the two objects.
For the UserID field : again you give your expect your mock to use the inputUser object. this object has userID = 1. but in the real method saveUser(UserModel userModel) this field is not set explicitly so the default value will be set to 0 you could see that also in the error.

Now since your test case whenSaveUser_ThenUserHasID is meant to verify that a saved record has an ID, you can't do it with a mock. The ID is generated by the Spring Data you are using and yo make it run, you should use and Integration test to run your spring context in your test in order for your spring data to be able to generate an ID for your user, here is a previous question that will be helpful for you to do so. With this, you will neither need the inputUser in your test nor the mock. (You can use @DataJpaTest from JUnit 5 or @SpringBootTest...)

Mockito mock returning Null value from repository

2 Answers2

1) Integration test

2) Unit test

tl;dr

Details