Using @Spy and @Autowired together

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.

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);
}

Using @Spy together with @Autowired works until you want to verify interaction between that spy and a different component that spy is injected into. What I found to work for me was the following approach found at https://dzone.com/articles/how-to-mock-spring-bean-version-2

@Configuration
public class AddressServiceTestConfiguration {
    @Bean
    @Primary
    public AddressService addressServiceSpy(AddressService addressService) {
        return Mockito.spy(addressService);
    }
}

This turns your autowired component into a spy object, which will be used by your service and can be verified in your tests.