Using @Spy and @Autowired together

Question

I have a Service Class with 3 methods, Service class is also using some @Autowired annotations. Out of 3 methods, I want to mock two methods but use real method for 3rd one.

Problem is:

1. If I am using @Autowired with @Spy, all three real method implementation is being called.
2. If I am using @Spy only, call to real method is return with Null pointer as there is no initialisation of Autowired objects.

Answer 1

I know about these two options:

1. Use @SpyBean annotation from spring-boot-test as the only annotation

@Autowired
@InjectMocks
private ProductController productController;

@SpyBean
private ProductService productServiceSpy;

2. Use Java reflection to "autowire" the spy object, e.g. ReflectionTestUtils

@Autowired
private ProductController productController;

@Autowired
private ProductService productService;

@Before
public void setUp() {
    ProductService productServiceSpy = Mockito.spy(productService);
    ReflectionTestUtils.setField(productController, "productService", productServiceSpy);
}

Answer 2

I was surprised myself but it does work for us. We have plenty places like:

@Spy
@Autowired
private FeatureService featureService;

I think I know why you are facing this problem. It's not about injection, it's about when(bloMock.doSomeStuff()).thenReturn(1) vs doReturn(1).when(bloMock).doSomeStuff(). See: http://www.stevenschwenke.de/spyingWithMockito

The very important difference is that the first option will actually call the doSomeStuff()- method while the second will not. Both will cause doSomeStuff() to return the desired 1.