使用Mockito isEmpty的模拟列表总是返回false，即使大小为0

Question

I'm playing with Mockito (1.9.5) and stuck at first simple test case:

List mockedList = mock(ArrayList.class);
assertEquals(0, mockedList.size()); // Passed
assertTrue(mockedList.isEmpty()); // Failed

Can anyone explain why isEmpty() here returns false while the size() returns 0?

Answer 1

I think this happens because mockito doesn't know the semantic meaning of isEmpty() and when it encounters a boolean method mocks it with a default value that is false . Same think happens with size() but the default value here is 0 .

Basically, you need to define the expected behaviour of your mocked object. If you don't, it will return default values.