public void AgeBackstagePass_LessThan10Days_LessThan5Days()
        {
            var item = new Item {
                Name = GildedRose.BackstagePasses, SellIn = 6, Quality = 1
            };
            var app = new GildedRose(null);

            app.AgeBackstagePass(item);

            Assert.AreEqual(3, item.Quality);
            Assert.AreEqual(5, item.SellIn);

            app.AgeBackstagePass(item);

            Assert.AreEqual(6, item.Quality);
            Assert.AreEqual(4, item.SellIn);
        }
        public void AgeBackstagePass_MoreThan10Days()
        {
            var item = new Item {
                Name = GildedRose.BackstagePasses, SellIn = 20, Quality = 1
            };
            var app = new GildedRose(null);

            app.AgeBackstagePass(item);

            Assert.AreEqual(2, item.Quality);
            Assert.AreEqual(19, item.SellIn);
        }