update test for each cases in requirements

TypeScript/app/gilded-rose.ts

@@ -35,24 +35,17 @@ export class GildedRose {
           itemQuality = itemQuality + 1;
           break;
         case itemName.includes('Backstage passes'):
-          itemQuality = itemQuality + 1;
           if (itemSellin < 11) {
             itemQuality = itemQuality + 2;
           } else if (itemSellin < 6) {
             itemQuality = itemQuality + 3;
           } else if (itemSellin < 0) {
             itemQuality = 0;
+          } else {
+            itemQuality = itemQuality + 1;
           }
           break;
         case itemName.includes('Conjured'):
-          if (itemQuality > 0) {
-            itemQuality = itemQuality - 1;
-          }
-          if (itemSellin < 0) {
-            itemQuality = itemQuality - itemQuality;
-          }
-          break;
-        default:
           if (itemQuality > 0) {
             itemQuality = itemQuality - 2;
           }
@@ -60,6 +53,14 @@ export class GildedRose {
             itemQuality = itemQuality - itemQuality * 2;
           }
           break;
+        default:
+          if (itemQuality > 0) {
+            itemQuality = itemQuality - 1;
+          }
+          if (itemSellin < 0) {
+            itemQuality = itemQuality - itemQuality;
+          }
+          break;
       }
       this.items[i].quality = itemQuality > 50 ? 50 : itemQuality;
       this.items[i].sellIn = itemSellin;

TypeScript/test/jest/gilded-rose.spec.ts

@@ -1,9 +1,39 @@
 import { Item, GildedRose } from '@/gilded-rose';
 
+let gildedRose;
 describe('Gilded Rose', () => {
+  beforeEach(() => {
+    gildedRose = new GildedRose([
+      new Item('foo', 0, 0),
+      new Item('Conjured item', 10, 8),
+      new Item('Sulfuras item', 0, 80),
+      new Item('Aged Brie item ', 10, 33),
+      new Item('Aged Brie item', 0, 50),
+      new Item('Backstage passes item', 8, 30),
+    ]);
+  })
   it('should foo', () => {
-    const gildedRose = new GildedRose([new Item('foo', 0, 0)]);
     const items = gildedRose.updateQuality();
     expect(items[0].name).toBe('foo');
   });
+  it('The quality of Conjured item should be degraded by twice', () => {
+    const items = gildedRose.updateQuality();
+    expect(items[1].quality).toBe(6);
+  });
+  it('The quality of Sulfuras item should remain unchanged', () => {
+    const items = gildedRose.updateQuality();
+    expect(items[2].quality).toBe(80);
+  });
+  it('Aged Brie item actually increases in Quality the older it gets', () => {
+    const items = gildedRose.updateQuality();
+    expect(items[3].quality).toBe(34);
+  });
+  it('The Quality of an item is never more than 50', () => {
+    const items = gildedRose.updateQuality();
+    expect(items[4].quality).toBe(50);
+  });
+  it('The Quality of Backstage passes item increases by 2 when there are 10 days or less', () => {
+    const items = gildedRose.updateQuality();
+    expect(items[5].quality).toBe(32);
+  });
 });