def test_mixedItemsAreSumed(self):
    self.assertEqual(checkout('ABCCABADDA'), ((((checkout('BB') + checkout('AAA')) + checkout('A')) + checkout('CC')) + checkout('DD')))
def test_mixedItemsAreSumed(self):
    self.assertEqual(checkout('ABCCABADDA'), ((((checkout('BB') + checkout('AAA')) + checkout('A')) + checkout('CC')) + checkout('DD')))