Mockito - 深存根

Question

I am using Mockito to test my classes. I am trying to use Deep stubbing as I didn't a way on injecting a Mock inside another mock object in Mockito.

class MyService{

    @Resource
    SomeHelper somehelper;

    public void create()
    {
        //....
        somehelper.invokeMeth(t);
    }
}

class SomeHelper{
    @Resource
    private WebServiceTemplate webServiceTemplate;

    public void invokeMeth(T t)
    {
        try{
            //...
            webServiceTemplate.marshalSendAndReceive(t);
        }catch (final WebServiceIOException e) {
            throw new MyAppException("Service not running");
        }
    }
}

Now I am trying to Unit test the MyService class's create() method. I have injected a mock for SomeHelper as follows

@Mock(answer = Answers.RETURNS_DEEP_STUBS)
SomeHelper somehelper;

What I want now is when the invokeMeth() method gets called on the mocked somehelper object it calls the real method in this case.

when(somehelper.invokeMeth(isA(RequestObject.class)))
    .thenCallRealMethod();

I was expecting the webServiceTemplate not be null in this case.

However I get a Nullpointer exception when the code tries to execute the line

webServiceTemplate.marshalSendAndReceive(t);

Any clue how I can get access to a deep mock object (ie mock within a mock - in this case webserviceTemplete mock inside somehelper mock) and then apply a when condition to throw a WebserviceIOException ? I want this so that I can test the MyService.create() to check it behaves properly when a WebServiceIOException is thrown down the code.

Answer 1

Yes of course, you are mixing real objects and mocks. Plus using the thenCallRealMethod lloks like a partial mock, it feels wrong here, it's no wonder the javadoc of this method talks about that as well.

I definatelty should stress you than, design wise, having a mock that returns a mock is often a smell. More precisely you are breaking the Demeter Law , or not following the Tell, Don't Ask principle.

Any looking at your code I don't why the code would need to mock WebServiceTemplate . You want to unit test MyService , and I don't see a relationship to WebServiceTemplate . Instead you should focus on the interactions with you helper only. And unit test SomeHelper separately where you'll be able to check the interactions between SomeHelper and WebServiceTemplate .

Here's a little example of how I see the thing:

public void ensure_helper_is_used_to_invoke_a_RequestObject() {
  // given a service that has an helper collaborator
  ... other fixture if necessary

  // when
  myService.behaviorToTest();

  // then
  verify(someHelperMock).invokeMeth(isA(RequestObject.class));
}

How those that look for your real use case ?

Hope that helps