from unittest import mock, TestCase, TextTestRunner, TestLoader
 
class CallDiffingMock(mock.Mock):
    def assert_called_with(self, *args, **kwargs):
        self.assert_called()
        test = TestCase()
        test.assertTupleEqual(args, self.call_args.args)
        test.assertDictEqual(kwargs, self.call_args.kwargs)
 
class Test(TestCase):
    def test_call(self):
        f = CallDiffingMock()
        f(a=1, b=2)
        f.assert_called_with(a=1, b=2, c=3)
 
TextTestRunner().run(TestLoader().loadTestsFromTestCase(Test))

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