':func:`validate_signature_against_kwargs` raises an
``InvalidSignature`` exception if the function takes one argument, but
is passed an argument with a different name.'

def test_one_argument_validation_failure_differs(self):

    self.assertThat((lambda : validate_signature_against_kwargs(_one_argument_function, set(['bad']))), _raises_invalid_signature(missing_arguments=set(['arg']), unexpected_arguments=set(['bad'])))
