In my experience, Mockito never actually gets to that point, because my program has called an unmocked stub, tried to use the return result, and NPEd in an obscure and hard-to-debug manner before verification call.
In my experience with Mockito and unit tests I haven't ever ran into this. However it seems like a very valid concern, and I could definitely see it causing problems.
I wonder if it is possible to use reflection and have mockito throw an exception if a stub method is called.
Not really. You can set a custom default answer and you can write a method that creates mocks with that answer, but there are enough rough edges that it ends up amounting to writing your own test framework. Much easier to just use EasyMock.
I wonder if it is possible to use reflection and have mockito throw an exception if a stub method is called.