def test_specialOfferCombinationsMinimisePrice(self):
    self.assertEqual(checkout('AAAAAAAAA'), ((checkout('AAAAA') + checkout('AAA')) + checkout('A')))
def test_specialOfferCombinationsMinimisePrice(self):
    self.assertEqual(checkout('AAAAAAAAA'), ((checkout('AAAAA') + checkout('AAA')) + checkout('A')))