I never had to stub a call that accepts a functional interface/method reference as argument, so I just find out about the obvious incapacity for compare with "equals" these, aside from the reference comparison.
So how does one deal with this scenario during testing? Do we have to use any() either we want it or not?
Comparator<String> comparator = Comparator.naturalOrder();
when(myColaborator.isCalledWith(comparator)).thenReturn("foo"); //This is not gonna work as long as the real call does not use theat very same reference
It is necessary to verify its collaborator whether has recieved an exactly Comparator in a simple test case since such a communication protocol test in a book of GOOS describes whether they will work together correctly. and then skip checking the rest of tests by using any(Comparator.class). you can read it further in Martin's blog:
in the second test case is that I've relaxed the constraints on the expectation by using
withAnyArguments. The reason for this is that the first test checks that the number is passed to the warehouse, so the second test need not repeat that element of the test. If the logic of the order needs to be changed later, then only one test will fail, easing the effort of migrating the tests. As it turns out I could have leftwithAnyArgumentsout entirely, as that is the default.