'L{_collectWarnings} returns the result of calling the callable passed to
it with the parameters given.'

def test_callsFunction(self):

    arguments = []
    value = object()
    def f(*args, **kwargs):
        arguments.append((args, kwargs))
        return value
    result = _collectWarnings((lambda x: None), f, 1, 'a', b=2, c='d')
    self.assertEqual(arguments, [((1, 'a'), {'b': 2, 'c': 'd'})])
    self.assertIdentical(result, value)
