Mockito RETURNS_SMART_NULLS answer weird behavior

Question

I'm using the annotation @Mock(answer=Answers.RETURNS_SMART_NULL) with Mockito 1.9.5 in order to get some SmartNullPointerException when some unexpected mock calls occurs.

Unfortunately, the test pass, even without mocking at least one important call. To be clear : My point is not to find by myself what I'm missing but to fail the test because I didn't mock the methods. I would want to do it without using Mockito.verifyNoMoreInteractions(...)

My test :

@RunWith(MockitoJUnitRunner.class)
public class ContextServiceImplTest {

    @Mock(answer = Answers.RETURNS_SMART_NULLS)
    private IAccountDAO accountDaoMock; 
    @Mock(answer = Answers.RETURNS_SMART_NULLS)
    private IRuleService ruleServiceMock;
    @Mock(answer = Answers.RETURNS_SMART_NULLS)
    private ISensorDAO sensorDAOMock;

    private ContextServiceImpl contextService;

    @Before
    public void before() {
        contextService = new ContextServiceImpl(accountDaoMock, ruleServiceMock, sensorDAOMock);
    }

    @Test
    public void fillSensor() throws Exception {
        // given
        String givenSensorId = "123"
        final EventDTO givenEvent = new EventDTO();
        givenEvent.setSensorId(givenSensorId)

        // when
        final Context context = contextService.getContext(givenEvent);

        // then (should fail and throw explicit exception

    }

The code to be tested :

public class ContextServiceImpl {
    ...

    public Context getContext(final EventDTO event) throws Exception {
        final String sMethodName = "getContext";
        final String sensorId = event.getSensorId();
        Context context = new Context();

        try {
            final Sensor sensor = sensorDAO.findById(sensorId);
            context.setSensor(sensor);
            return context;
        } catch (final NoResultException nre) {
            throw new BusinessException(ValidationCode.UNSUPPORTED_VALUE, "sensorId");
        } catch (final PersistenceException pe) {
            throw new TechnicalException(TechnicalCode.DATABASE_ACCESS_PROBLEM);
    }
}

Thanks for your comments / advices / explainations.

Answer 1

You need to call a method on the null object sensor for the test to fail.

It seems like you are never using the null object sensor. This means you won't get any NullPointerExceptions (smart or not)

you could do an

AssertEquals(context.getSensor().someMethod(), expectedResult);

or just a

context.getSensor().someMethod();

to get an exception. But

AssertNotNull(context.getSensor());

won't be sufficient to get the SmartNullPointerException