Mocking Object that returns Java 8 Optional Object with Mockito returns Empty Optional

Question

I'm attempting to mock an object that returns a Java Optional object with Mockito:

SomeObject someObject = new SomeObject();
Mockito.when(someSpringJpaRepository.findById(Mockito.any(UUID.class))).thenReturn(Optional.of(someObject));

When someSpringJpaRepository.findById(UUID) is called, it returns Optional.empty.

I'm expecting the method findById() to return someObject.
Any reason why it's returning Optional.empty instead?

Here is the method:

public UUID saveOrder(OrderDTO orderDto) {

        Order order = new Order();
        if (orderDto.getId() != null) {
            Optional<Order> result = orderRepository.findById(orderDto.getId());
            if (result != null && result.isPresent()) {
                order = result.get(); // existing record

            } else {
                order.setId(UUID.randomUUID());
            }
        } else {
            // new record
            order.setId(UUID.randomUUID());
        }

        return order.getId();
    }

And here is the Junit:

@Test
    public void saveOrderTest(){

        @Autowired
        private OrderApiService orderApiService;
        @Mock
        private OrderRepository orderRepository;

        OrderDTO orderDto = new OrderDTO();
        UUID orderID = UUID.randomUUID();
        Order order = new Order();
        order.setId(orderID);

        orderDto.setId(orderID);
        Mockito.when(orderRepository.findById(Mockito.any(UUID.class))).thenReturn(Optional.of(order));
        assertNotNull(orderApiService.saveOrder(orderDto));
    }

Answer 1

Your @Mock in class is doing nothing. You created a separate instance of orderRepository which is not injected into your service class. To inject your mock into context use @MockBean

Difference between @Mock and @MockBean here

Answer 2

you can try to use spy method

Repository spyRepo = Mockito.spy(someSpringJpaRepository);
Mockito.doReturn(Optional.of(someObject)).when(spyRepo).findById(Mockito.any(UUID.class));