抽象父 class 中的 Mocking 依赖项

Question

I have the following set of classes:

public abstract class ParentClass {

    @Autowired
    private SomeService service;

    protected Item getItem() {
        return service.foo();
    }

    protected abstract doSomething();

}

@Component
public ChildClass extends ParentClass {
    private final SomeOtherService someOtherService;

    @Override
    protected doSomething() {
        Item item = getItem(); //invoking parent class method
        .... do some stuff
    }
}

Trying to test the Child class:

@RunWith(MockitoJUnitRunner.class)
public class ChildClassTest {

    @Mock
    private SomeOtherService somerOtherService;

    @Mock
    private SomerService someService; //dependency at parent class

    @InjectMocks
    private ChildClass childClass;

    public void testDoSomethingMethod() {
         Item item = new Item();
         when(someService.getItem()).thenReturn(item);
         childClass.doSomething();
    }
}

The matter is that I'm always getting a NullPointerException because the parent dependency (SomeService) is always null.

Also tried:

Mockito.doAnswer(new Answer() {
    @Override
    public Object answer(InvocationOnMock invocationOnMock) throws Throwable {
        return new Item();
    }
}).when(someService).getItem();

And using Spy, without any success.

Thanks for your hints.

Answer 1

One option is using ReflectionTestUtils class to inject the mock. In the code bellow I've executed the unit tests with JUnit 4.

@RunWith(MockitoJUnitRunner.class)
public class ChildClassTest {

@Mock
private SomeService someService;

@Test
public void test_something() {
    ChildClass childClass = new ChildClass();       
    ReflectionTestUtils.setField(childClass, "service", someService);
    
    when(someService.foo()).thenReturn("Test Foo");
    
    assertEquals("Child Test Foo", childClass.doSomething());
}

}