def sell_in_equal_0():
backsetage = Backstage("VIP", 1, 15)
backsetage.update_quality()
assert backsetage.updated_item() == ("VIP", 0, 0)
def sell_in_plus_1():
backsetage = Backstage("VIP", 12, 10)
backsetage.update_quality()
assert backsetage.updated_item() == ("VIP", 11, 11)
def sell_in_plus_3():
backsetage = Backstage("VIP", 5, 15)
backsetage.update_quality()
assert backsetage.updated_item() == ("VIP", 4, 18)