This package provides "mocks", fake functions that can be configured to return values or raise exceptions. It is possible to inspect their arguments after their execution. The API is greatly inspired by unittest.mock in Python.
There is no magic under the hood, it is "just" a reference to a function, but it makes it possible to have pleasant output like this in your tests:
expected f to be called once, but it was called 3 times
A wrapper for OUnit is available as mock-ounit.