UserService userServiceMock = Mockito.mock(UserService.class);
User user = new User("John");
Mockito.when(userServiceMock.createUser()).thenReturn(user);
Mockito.verify(userServiceMock, Mockito.times(1)).createUser();
@InjectMocks
private UserManager userManager;
@Mock
private UserService userService;
@Mock
private UserRepository userRepository;