'Replace a function for the duration of the test.
Use the monkey patch fixture to replace a function for the
duration of a test. Useful when you want to provide fake
methods instead of mocks during testing.
This should be used instead of self.stubs.Set (which is based
on mox) going forward.'

def stub_out(self, old, new):

    self.useFixture(fixtures.MonkeyPatch(old, new))
