How to use should_not_be_similar_if_mocks_are_different method of org.mockito.internal.invocation.InvocationsFinderTest class

I have finally found the solution for this problem.

We have used an anonymous class extending original Sbb class which was tested and in this extended class implementation of mentioned method was altered and throws expression was removed which caused the problem.

I should have read my colleagues code more carefully.

You can use a spy.

public class MyVideoService {

  private VideoService videoService;

  public MyVideoService(VideoService videoService) {
    this.videoService = videoService;
  }

  public void delete(String param) {
    videoService.deleteVideo(param);
  }
}

public class VideoService {
  public void deleteVideo(String param) {
  }
}

If you now want to test an object that uses MyVideoService. E.g.

public class ObjectThatUsesMyVideoService {

  private MyVideoService myVideoService;

  ObjectThatUsesMyVideoService(MyVideoService myVideoService) {
    this.myVideoService = myVideoService;
  }

  public void deleteVideo(String param) {
    myVideoService.delete(param);
  }
}

You can write a test like this

public class MyVideoServiceTest {

  @Test
  public void delete(){
    // VideoService is just a mock
    VideoService videoServiceMock = Mockito.mock(VideoService.class); 

    // Creating the real MyVideoService
    MyVideoService myVideoService = new MyVideoService(videoServiceMock);

    // Creating a spy proxy
    MyVideoService myVideoServiceSpy = Mockito.spy(myVideoService);

    ObjectThatUsesMyVideoService underTest = new ObjectThatUsesMyVideoService(myVideoServiceSpy);

    underTest .deleteVideo("SomeValue");

    // Verify that myVideoService was invoked
    Mockito.verify(myVideoServiceSpy, Mockito.times(1)).delete("SomeValue");

    // Verify that myVideoService invoked the VideoService
    Mockito.verify(videoServiceMock, Mockito.times(1)).deleteVideo("SomeValue");
  }
}

You can use Mockitos Answer.

doAnswer(new Answer() {
     @Override
     public Object answer(InvocationOnMock invocation) {
         Object[] args = invocation.getArguments();
         ByteArrayOutputStream baos = (ByteArrayOutputStream)args[0];
         //fill baos with data
         return null;
     }
 }).when(client).retrieveFile(baos);

However, if you have possibility to refactor the tested code, better is to make client return the OutputStream or some data that can be put to this Output stream. This is would be much better design.

Since none of your classes are final, you can use "pure mockito" without resorting to PowerMockito:

final CacheWrapper wrapper = Mockito.spy(new CacheWrapper());

Mockito.doThrow(something)
    .when(wrapper).putInSharedMemory(Matchers.any(), Matchers.any());

Note that "method arguments" to a stub are in fact argument matchers; you can put specific values (if not "surrounded" by a specific method it will make a call to .equals()). So, you can guide the stub's behavior differently for different arguments.

Also, no need for any kind of .replay() with Mockito, which is very nice!

Finally, be aware that you can doCallRealMethod() as well. After that, it depends on your scenarios...

(note: last mockito version available on maven is 1.10.17 FWIW)

I believe you missed the whole idea of unit testing and mocking.

1. When you are unit testing your UserService, you DO NOT want to use the real UserRepository implementation.
2. You mocked a UserRepository, you do not expect the mock object to immediately behave as the real one. You need to make up its behavior (aka stubbing).
3. You should rarely need to use Spring Runner in unit test.

In order to decide the behavior of the mock object, you gotta know the expected interaction of your system-under-test (SUT, which is the UserService in your case) and its dependencies (UserRepository)

In your case, the test should looks like (haven't compiled, just show you the idea)

public class UserServiceTest {

    @InjectMocks
    UserService userService;

    @Mock
    UserDao mockUserRepository;

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

    @Test
    public void testFindUser(){
        // Given
        User dummyUser = new User();
        when(mockUserRepository.findByLoginAndPassword(anyString(), anyString()).thenReturn(dummyUser);

        // When
        User result = userService.findUser("first", "teste");

        // Then
        // you are expecting service to return whatever returned by repo
        assertThat("result", result, is(sameInstance(dummUser)));

        // you are expecting repo to be called once with correct param
        verify(mockUserRepository).findByLoginAndPassword("first", "teste");
    }
}

How about

when( method-call ).thenReturn( value1, value2, value3 );

You can put as many arguments as you like in the brackets of thenReturn, provided they're all the correct type. The first value will be returned the first time the method is called, then the second answer, and so on. The last value will be returned repeatedly once all the other values are used up.

"Mock" your repository method calls. Also, use @InjectMocks instead @Autowired for TransactionService. And you can also use MockitoJUnitRunner. How to mock repository calls:

when(customerRepository.save(sender)).thenReturn(someSenderInstance);

To verify that mocked method call has been invoked use:

verify(customerRepository, times(1)).save(sender);

Also, remember one thing: You are testing services! Therefore, all calls to database should be mocked.

You haven't mocked the behavior of getId in externalDependencyObject therefore it is returning null and giving you the NPE when toString() is called on that null.

You need a when(externalDependencyObject.getId()).then...

I suggest to use Mockito Framework it is very easy to use and understand.

@Mock
private EntityManager entityManager; 

If you want to use any method that belongs to entityManager, you should call.

Mockito.when(METHOD_EXPECTED_TO_BE_CALLED).thenReturn(AnyObjectoftheReturnType);

When you run your test, any call previosly declared in the Mockito.when for the EntityManager will return the value put in the declaration..

Read full documentation here.

https://static.javadoc.io/org.mockito/mockito-core/2.12.0/org/mockito/Mockito.html#stubbing