Tests done, refactoring to be done.

app/gilded-rose.ts

@@ -25,6 +25,7 @@ export class GildedRose {
                         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
@@ -50,18 +51,19 @@ export class GildedRose {
                     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
+                                this.items[i].quality -= 1
                             }
                         }
                     } else {
-                        this.items[i].quality = this.items[i].quality - this.items[i].quality
+                        this.items[i].quality = 0
                     }
                 } else {
                     if (this.items[i].quality < 50) {
                         this.items[i].quality = this.items[i].quality + 1
                     }
                 }
             }
+
         }
 
         return this.items;

package.json

@@ -22,8 +22,8 @@
     "rimraf": "~3.0.2",
     "source-map-support": "^0.5.20",
     "ts-jest": "^27.0.7",
-    "ts-node": "^10.4.0",
+    "ts-node": "^10.9.2",
     "tsconfig-paths": "^3.11.0",
-    "typescript": "^4.4.4"
+    "typescript": "^4.9.5"
   }
 }

test/jest/gilded-rose.spec.ts

@@ -9,7 +9,7 @@ describe('Gilded Rose', () => {
         const items = gildedRose.updateQuality();
 
         // Assert
-        expect(items[0].name).toBe('bar');
+        expect(items[0].name).toBe('foo');
     });
 
     it('sword quality drops by 1', () => {
@@ -20,6 +20,90 @@ describe('Gilded Rose', () => {
       const items = gildedRose.updateQuality();
 
       // Assert
-      expect(items[0].quality).toBe(1);
+      expect(items[0].quality).toBe(0);
+    })
+
+    it('Brie', () => {
+      // Arrange
+      const gildedRose = new GildedRose([new Item('Brie', 1, 1)]);
+
+      // Act
+      const items = gildedRose.updateQuality();
+
+      // Assert
+      expect(items[0].quality).toBe(0);
+
+    })
+
+    it('Brie quality', () => {
+      // Arrange
+      const gildedRose = new GildedRose([new Item('Aged Brie', 1, 49)]);
+
+      // Act
+      const items = gildedRose.updateQuality();
+
+      // Assert
+      expect(items[0].quality).toBe(50);
+
+    })
+
+    it('TAFKAL80ETC', () => {
+      // Arrange
+      const gildedRose = new GildedRose([new Item('Backstage passes to a TAFKAL80ETC concert', 10, 49)]);
+
+      // Act
+      const items = gildedRose.updateQuality();
+
+      // Assert
+      expect(items[0].quality).toBe(50);
+
+    })
+
+    it('TAFKAL80ETC2', () => {
+      // Arrange
+      const gildedRose = new GildedRose([new Item('Aged Brie', 5, 51)]);
+
+      // Act
+      const items = gildedRose.updateQuality();
+
+      // Assert
+      expect(items[0].quality).toBe(51);
+
+    })
+
+    it('TAFKAL80ETC3', () => {
+      // Arrange
+      const gildedRose = new GildedRose([new Item('Backstage passes to a TAFKAL80ETC concert', 5, 48)]);
+
+      // Act
+      const items = gildedRose.updateQuality();
+
+      // Assert
+      expect(items[0].quality).toBe(50);
+
+    })
+
+    it('testx', () => {
+      // Arrange
+      const gildedRose = new GildedRose([new Item('Backstage passes to a TAFKAL80ETC concert', -10, 100)]);
+
+      // Act
+      const items = gildedRose.updateQuality();
+
+      // Assert
+      expect(items[0].quality).toBe(0);
+
+    })
+
+    it('testy', () => {
+      // Arrange
+      const gildedRose = new GildedRose([new Item('Elixir of the Mongoose', -1, 10)]);
+
+      // Act
+      const items = gildedRose.updateQuality();
+
+      // Assert
+      expect(items[0].quality).toBe(8);
+
     })
 });