public void AgeBrie() { var item = new Item { Name = GildedRose.AgedBrie, SellIn = 1, Quality = 47 }; var app = new GildedRose(null); // check increases by 1 when before sell in app.AgeBrie(item); Assert.AreEqual(48, item.Quality); Assert.AreEqual(0, item.SellIn); // check increases by 2 when after sell in app.AgeBrie(item); Assert.AreEqual(50, item.Quality); Assert.AreEqual(-1, item.SellIn); }