public void 一二三四集各買了一本_價格應為_320()
        {
            //arrange
            var cal = new PotterShoppingCart_Class();
            cal.BuyFirst(1);
            cal.BuySecond(1);
            cal.BuyThird(1);
            cal.BuyForth(1);

            //act
            var actual = cal.Caltotal();

            //assert
            var expected = 320;
            Assert.AreEqual(expected, actual);
        }
        public void 第一集_1_第二集_3_第三集_3_第四集_5_第五集_2_應為1165()
        {
            //arrange
            var cal = new PotterShoppingCart_Class();
            cal.BuyFirst(1);
            cal.BuySecond(3);
            cal.BuyThird(3);
            cal.BuyForth(5);
            cal.BuyFifth(2);

            //act
            var actual = cal.Caltotal();

            //assert
            var expected = 1165;
            Assert.AreEqual(expected, actual);
        }