diff --git a/app/gilded-rose.ts b/app/gilded-rose.ts
index ee55134..06f0222 100644
--- a/app/gilded-rose.ts
+++ b/app/gilded-rose.ts
@@ -1,69 +1,55 @@
 export class Item {
-    name: string;
-    sellIn: number;
-    quality: number;
+  name: string;
+  sellIn: number;
+  quality: number;
 
-    constructor(name, sellIn, quality) {
-        this.name = name;
-        this.sellIn = sellIn;
-        this.quality = quality;
-    }
+  constructor(name, sellIn, quality) {
+    this.name = name;
+    this.sellIn = sellIn;
+    this.quality = quality;
+  }
 }
 
 export class GildedRose {
-    items: Array<Item>;
+  items: Array<Item>;
 
-    constructor(items = [] as Array<Item>) {
-        this.items = items;
-    }
+  constructor(items = [] as Array<Item>) {
+    this.items = items;
+  }
+
+  updateQuality() {
+    for (let i = 0; i < this.items.length; i++) {
+      if (this.items[i].name != "Sulfuras, Hand of Ragnaros") {
+        let qualityDifference = 1;
+        if (this.items[i].name.includes("Conjured")) {
+          qualityDifference = 2;
+        }
+        if (this.items[i].sellIn <= 0) {
+          qualityDifference *= 2;
+        }
 
-    updateQuality() {
-        for (let i = 0; i < this.items.length; i++) {
-            if (this.items[i].name != 'Aged Brie' && this.items[i].name != 'Backstage passes to a TAFKAL80ETC concert') {
-                if (this.items[i].quality > 0) {
-                    if (this.items[i].name != 'Sulfuras, Hand of Ragnaros') {
-                        this.items[i].quality = this.items[i].quality - 1
-                    }
-                }
-            } else {
-                if (this.items[i].quality < 50) {
-                    this.items[i].quality = this.items[i].quality + 1
-                    if (this.items[i].name == 'Backstage passes to a TAFKAL80ETC concert') {
-                        if (this.items[i].sellIn < 11) {
-                            if (this.items[i].quality < 50) {
-                                this.items[i].quality = this.items[i].quality + 1
-                            }
-                        }
-                        if (this.items[i].sellIn < 6) {
-                            if (this.items[i].quality < 50) {
-                                this.items[i].quality = this.items[i].quality + 1
-                            }
-                        }
-                    }
-                }
-            }
-            if (this.items[i].name != 'Sulfuras, Hand of Ragnaros') {
-                this.items[i].sellIn = this.items[i].sellIn - 1;
-            }
-            if (this.items[i].sellIn < 0) {
-                if (this.items[i].name != 'Aged Brie') {
-                    if (this.items[i].name != 'Backstage passes to a TAFKAL80ETC concert') {
-                        if (this.items[i].quality > 0) {
-                            if (this.items[i].name != 'Sulfuras, Hand of Ragnaros') {
-                                this.items[i].quality = this.items[i].quality - 1
-                            }
-                        }
-                    } else {
-                        this.items[i].quality = this.items[i].quality - this.items[i].quality
-                    }
-                } else {
-                    if (this.items[i].quality < 50) {
-                        this.items[i].quality = this.items[i].quality + 1
-                    }
-                }
-            }
+        if (this.items[i].name != "Aged Brie" && this.items[i].name != "Backstage passes to a TAFKAL80ETC concert" && this.items[i].quality > 0) {
+          this.items[i].quality = this.items[i].quality >= qualityDifference ? (this.items[i].quality - qualityDifference) : 0;
         }
 
-        return this.items;
+        if (this.items[i].name == "Aged Brie" && this.items[i].quality < 50) {
+          this.items[i].quality = (this.items[i].quality + qualityDifference) <= 50 ? (this.items[i].quality + qualityDifference) : 50;
+        }
+
+        if (this.items[i].name == "Backstage passes to a TAFKAL80ETC concert" && this.items[i].quality < 50) {
+          if (this.items[i].sellIn > 10) {
+            this.items[i].quality += qualityDifference;
+          } else if (5 < this.items[i].sellIn && this.items[i].sellIn <= 10) {
+            this.items[i].quality = (this.items[i].quality + 2 * qualityDifference) <= 50 ? (this.items[i].quality + 2 * qualityDifference) : 50;
+          } else if (0 < this.items[i].sellIn && this.items[i].sellIn <= 5) {
+            this.items[i].quality = (this.items[i].quality + 3 * qualityDifference) <= 50 ? (this.items[i].quality + 3 * qualityDifference) : 50;
+          } else {
+            this.items[i].quality = 0;
+          }
+        }
+        this.items[i].sellIn -= 1;
+      }
     }
-}
\ No newline at end of file
+    return this.items;
+  }
+}
diff --git a/test/jest/gilded-rose.spec.ts b/test/jest/gilded-rose.spec.ts
index 613639f..938c1f2 100644
--- a/test/jest/gilded-rose.spec.ts
+++ b/test/jest/gilded-rose.spec.ts
@@ -1,25 +1,164 @@
-import { Item, GildedRose } from '@/gilded-rose';
+import { Item, GildedRose } from "@/gilded-rose";
 
-describe('Gilded Rose', () => {
-    it('should foo', () => {
-        // Arrange
-        const gildedRose = new GildedRose([new Item('foo', 0, 0)]);
+describe("Gilded Rose", () => {
+  it("should foo", () => {
+    // Arrange
+    const gildedRose = new GildedRose([new Item("foo", 0, 0)]);
 
-        // Act
-        const items = gildedRose.updateQuality();
+    // Act
+    const items = gildedRose.updateQuality();
 
-        // Assert
-        expect(items[0].name).toBe('bar');
-    });
+    // Assert
+    expect(items[0].name).toBe("foo");
+  });
 
-    it('sword quality drops by 1', () => {
-      // Arrange
-      const gildedRose = new GildedRose([new Item('Sword', 1, 1)]);
+  it("Sulfuras quality is 80 and it never alters", () => {
+    // Arrange
+    const gildedRose = new GildedRose([new Item("Sulfuras, Hand of Ragnaros", 1, 80)]);
 
-      // Act
-      const items = gildedRose.updateQuality();
+    // Act
+    const items = gildedRose.updateQuality();
 
-      // Assert
-      expect(items[0].quality).toBe(1);
-    })
+    // Assert
+    expect(items[0].quality).toBe(80);
+  });
+
+  it("Sulfuras SellIn date never alters", () => {
+    // Arrange
+    const gildedRose = new GildedRose([new Item("Sulfuras, Hand of Ragnaros", 8, 80)]);
+
+    // Act
+    const items = gildedRose.updateQuality();
+
+    // Assert
+    expect(items[0].sellIn).toBe(8);
+  });
+
+  it("SellIn date for items except Sulfuras decreases by 1", () => {
+    // Arrange
+    const gildedRose = new GildedRose([
+      new Item("Sword", 0, 80),
+      new Item("Aged Brie", 4, 3),
+      new Item("Backstage passes to a TAFKAL80ETC concert", 5, 5),
+    ]);
+
+    // Act
+    const items = gildedRose.updateQuality();
+
+    // Assert
+    expect(items[0].sellIn).toBe(-1);
+    expect(items[1].sellIn).toBe(3);
+    expect(items[2].sellIn).toBe(4);
+  });
+
+  it("sword quality drops by 1", () => {
+    // Arrange
+    const gildedRose = new GildedRose([new Item("Sword", 1, 1)]);
+
+    // Act
+    const items = gildedRose.updateQuality();
+
+    // Assert
+    expect(items[0].quality).toBe(0);
+  });
+
+  it("Aged Brie quality increases", () => {
+    const gildedRose = new GildedRose([new Item("Aged Brie", 1, 0)]);
+
+    const items = gildedRose.updateQuality();
+
+    expect(items[0].quality).toBe(1);
+  });
+
+  it("Backstage Pass quality increases by 2 when there are 10 days or less", () => {
+    const gildedRose = new GildedRose([
+      new Item("Backstage passes to a TAFKAL80ETC concert", 10, 5),
+      new Item("Backstage passes to a TAFKAL80ETC concert", 7, 5),
+    ]);
+
+    const items = gildedRose.updateQuality();
+
+    expect(items[0].quality).toBe(7);
+    expect(items[1].quality).toBe(7);
+  });
+
+  it("Backstage Pass quality increases by 3 when there are 5 days or less", () => {
+    const gildedRose = new GildedRose([
+      new Item("Backstage passes to a TAFKAL80ETC concert", 5, 5),
+      new Item("Backstage passes to a TAFKAL80ETC concert", 3, 5),
+    ]);
+
+    const items = gildedRose.updateQuality();
+
+    expect(items[0].quality).toBe(8);
+    expect(items[1].quality).toBe(8);
+  });
+
+  it("Backstage Pass item quality drops to 0 after the concert", () => {
+    const gildedRose = new GildedRose([
+      new Item("Backstage passes to a TAFKAL80ETC concert", 0, 5),
+    ]);
+
+    const items = gildedRose.updateQuality();
+
+    expect(items[0].sellIn).toBe(-1);
+    expect(items[0].quality).toBe(0);
+  });
+
+  it("quality is never negative", () => {
+    const gildedRose = new GildedRose([
+      new Item("Sword", 1, 0),
+      new Item("Conjured Mana Cake", -3, 0),
+    ]);
+
+    const items = gildedRose.updateQuality();
+
+    expect(items[0].quality).toBe(0);
+    expect(items[1].quality).toBe(0);
+  });
+
+  it("Aged Brie quality and Backstage Pass quality are never more than 50", () => {
+    const gildedRose = new GildedRose([
+      new Item("Aged Brie", 1, 50),
+      new Item("Backstage passes to a TAFKAL80ETC concert", 1, 50),
+    ]);
+
+    const items = gildedRose.updateQuality();
+
+    expect(items[0].quality).toBe(50);
+    expect(items[1].quality).toBe(50);
+  });
+
+  it("Once the sell by date has passed, Quality degrades twice as fast.", () => {
+    const gildedRose = new GildedRose([
+      new Item("Aged Brie", -2, 6),
+      new Item("Sword", 0, 2),
+      new Item("Sword", 0, 3),
+      new Item("Sword", -1, 1),
+    ]);
+
+    const items = gildedRose.updateQuality();
+
+    expect(items[0].quality).toBe(8);
+    expect(items[1].quality).toBe(0);
+    expect(items[2].quality).toBe(1);
+    expect(items[3].quality).toBe(0);
+  });
+
+  it('"Conjured" items degrade in Quality twice as fast as normal items.', () => {
+    const gildedRose = new GildedRose([
+      new Item("Conjured Mana Cake", 3, 6),
+      new Item("Conjured Mana Cake", 0, 4),
+      new Item("Conjured Mana Cake", -3, 3),
+    ]);
+
+    const items = gildedRose.updateQuality();
+
+    expect(items[0].sellIn).toBe(2);
+    expect(items[0].quality).toBe(4);
+    expect(items[1].sellIn).toBe(-1);
+    expect(items[1].quality).toBe(0);
+    expect(items[2].sellIn).toBe(-4);
+    expect(items[2].quality).toBe(0);
+  });
 });