diff --git a/csharp/GildedRoseTest.cs b/csharp/GildedRoseTest.cs
index 911df1be..d8ddd99c 100644
--- a/csharp/GildedRoseTest.cs
+++ b/csharp/GildedRoseTest.cs
@@ -7,12 +7,219 @@ namespace csharp
     public class GildedRoseTest
     {
         [Test]
-        public void foo()
+        public void UpdateQuality_LowersItemQualityBy1()
         {
-            IList<Item> Items = new List<Item> { new Item { Name = "foo", SellIn = 0, Quality = 0 } };
-            GildedRose app = new GildedRose(Items);
-            app.UpdateQuality();
-            Assert.AreEqual("fixme", Items[0].Name);
+            var item = new Item
+            {
+                Name = "test",
+                Quality = 5,
+                SellIn = 30
+            };
+
+            var items = new List<Item>(new[] { item });
+            var gRose = new GildedRose(items);
+
+            gRose.UpdateQuality();
+
+            Assert.That(item.Quality, Is.EqualTo(4));
+        }
+
+        [Test]
+        public void UpdateQuality_LowersItemSellInBy1()
+        {
+            var item = new Item
+            {
+                Name = "test",
+                Quality = 5,
+                SellIn = 30
+            };
+
+            var items = new List<Item>(new[] { item });
+            var gRose = new GildedRose(items);
+
+            gRose.UpdateQuality();
+
+            Assert.That(item.SellIn, Is.EqualTo(29));
+        }
+
+        [Test]
+        public void UpdateQuality_ItemWithZeroSellIn_LowersItemQualityBy2()
+        {
+            var item = new Item
+            {
+                Name = "test",
+                Quality = 5,
+                SellIn = 0
+            };
+
+            var items = new List<Item>(new[] { item });
+            var gRose = new GildedRose(items);
+
+            gRose.UpdateQuality();
+
+            Assert.That(item.Quality, Is.EqualTo(3));
+        }
+
+        [Test]
+        public void UpdateQuality_ItemWithZeroQuality_StayAtZeroQuality()
+        {
+            var item = new Item
+            {
+                Name = "test",
+                Quality = 0,
+                SellIn = 30
+            };
+
+            var items = new List<Item>(new[] { item });
+            var gRose = new GildedRose(items);
+
+            gRose.UpdateQuality();
+
+            Assert.That(item.Quality, Is.EqualTo(0));
+        }
+
+        [Test]
+        public void UpdateQuality_AgedBrie_IncreaseQualityBy1()
+        {
+            var item = new Item
+            {
+                Name = "Aged Brie",
+                Quality = 0,
+                SellIn = 30
+            };
+
+            var items = new List<Item>(new[] { item });
+            var gRose = new GildedRose(items);
+
+            gRose.UpdateQuality();
+
+            Assert.That(item.Quality, Is.EqualTo(1));
+        }
+
+        [Test]
+        public void UpdateQuality_AgedBrieWith50Quality_StayAt50Quality()
+        {
+            var item = new Item
+            {
+                Name = "Aged Brie",
+                Quality = 50,
+                SellIn = 30
+            };
+
+            var items = new List<Item>(new[] { item });
+            var gRose = new GildedRose(items);
+
+            gRose.UpdateQuality();
+
+            Assert.That(item.Quality, Is.EqualTo(50));
+        }
+
+        [Test]
+        public void UpdateQuality_Sulfuras_DoesNotDecreaseQuality()
+        {
+            var item = new Item
+            {
+                Name = "Sulfuras, Hand of Ragnaros",
+                Quality = 80,
+                SellIn = 30
+            };
+
+            var items = new List<Item>(new[] { item });
+            var gRose = new GildedRose(items);
+
+            gRose.UpdateQuality();
+
+            Assert.That(item.Quality, Is.EqualTo(80));
+        }
+
+        [Test]
+        public void UpdateQuality_Sulfuras_DoesNotDecreaseSellIn()
+        {
+            var item = new Item
+            {
+                Name = "Sulfuras, Hand of Ragnaros",
+                Quality = 80,
+                SellIn = 30
+            };
+
+            var items = new List<Item>(new[] { item });
+            var gRose = new GildedRose(items);
+
+            gRose.UpdateQuality();
+
+            Assert.That(item.SellIn, Is.EqualTo(30));
+        }
+
+        [Test]
+        public void UpdateQuality_BackstagePassesWithMoreThan10DaysLeft_IncreasesQualityBy1()
+        {
+            var item = new Item
+            {
+                Name = "Backstage passes to a TAFKAL80ETC concert",
+                Quality = 35,
+                SellIn = 11
+            };
+
+            var items = new List<Item>(new[] { item });
+            var gRose = new GildedRose(items);
+
+            gRose.UpdateQuality();
+
+            Assert.That(item.Quality, Is.EqualTo(36));
+        }
+
+        [Test]
+        public void UpdateQuality_BackstagePassesWith10DaysLeft_IncreasesQualityBy2()
+        {
+            var item = new Item
+            {
+                Name = "Backstage passes to a TAFKAL80ETC concert",
+                Quality = 35,
+                SellIn = 10
+            };
+
+            var items = new List<Item>(new[] { item });
+            var gRose = new GildedRose(items);
+
+            gRose.UpdateQuality();
+
+            Assert.That(item.Quality, Is.EqualTo(37));
+        }
+
+        [Test]
+        public void UpdateQuality_BackstagePassesWith5DaysLeft_IncreasesQualityBy3()
+        {
+            var item = new Item
+            {
+                Name = "Backstage passes to a TAFKAL80ETC concert",
+                Quality = 35,
+                SellIn = 5
+            };
+
+            var items = new List<Item>(new[] { item });
+            var gRose = new GildedRose(items);
+
+            gRose.UpdateQuality();
+
+            Assert.That(item.Quality, Is.EqualTo(38));
+        }
+
+        [Test]
+        public void UpdateQuality_BackstagePassesWith0DaysLeft_SetQualityToZero()
+        {
+            var item = new Item
+            {
+                Name = "Backstage passes to a TAFKAL80ETC concert",
+                Quality = 35,
+                SellIn = 0
+            };
+
+            var items = new List<Item>(new[] { item });
+            var gRose = new GildedRose(items);
+
+            gRose.UpdateQuality();
+
+            Assert.That(item.Quality, Is.EqualTo(0));
         }
     }
 }