无法模拟集合对象

Question

How do I mock this particular snippet?

Collection<SeoUrlParam> params = getUrlState().getParameters();

I have already mocked

urlState = mock(UrlState.class);

But I am not sure how to mock the params collection of type which is infact a class

Answer 1

You probably don't want to mock the collection. You want somewhat real data to exist in the collection, and let the code operate it from there instead.

Now, with the way your call is laid out, it may be the case that you have two mock objects - one to produce the mock result of getUrlState() , and one to actually return a collection from getParameters() .

I'm not sure of the type you're using for either of those calls, so I'll wing it. The principle applies, though.

// Assuming you have the appropriate mock for getUrlState defined
SeoUrlParamHolder parameterHolderMock = mock(SeoUrlParamHolder.class);
Collection<SeoUrlParam> dummyData = Collections.singletonList(new SeoUrlParam());

when(urlState.getUrlState()).thenReturn(parameterHolderMock);
when(parameterHolderMock.getParamters()).thenReturn(dummyData);

Answer 2

Don't mock collection objects. Collections themselves don't generally have enough logic in them to make it worthwhile to stub the logic out.

Treat your collections as value objects, and create real collections as needed. If you want to mock the individual objects inside the collection, that's fine, and a practice that I thoroughly recommend.