add unit test to verify existing code functionality

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

@@ -1,9 +1,100 @@
-import { Item, GildedRose } from '@/gilded-rose';
+import { Item, GildedRose } from "@/gilded-rose";
 
-describe('Gilded Rose', () => {
-  it('should foo', () => {
-    const gildedRose = new GildedRose([new Item('foo', 0, 0)]);
+describe("Gilded Rose", () => {
+  it("should degrade quality", () => {
+    const gildedRose = new GildedRose([new Item("foo", 1, 1)]);
     const items = gildedRose.updateQuality();
-    expect(items[0].name).toBe('fixme');
+    expect(items[0].quality).toBe(0);
+  });
+  it("should tick down sell in", () => {
+    const gildedRose = new GildedRose([new Item("foo", 1, 1)]);
+    const items = gildedRose.updateQuality();
+    expect(items[0].sellIn).toBe(0);
+  });
+  it("should handle multiple items", () => {
+    const gildedRose = new GildedRose([
+      new Item("one", 1, 1),
+      new Item("two", 2, 3),
+    ]);
+    const items = gildedRose.updateQuality();
+    expect(items.length).toBe(2);
+    expect(items[0].name).toBe("one");
+    expect(items[0].quality).toBe(0);
+    expect(items[0].sellIn).toBe(0);
+    expect(items[1].name).toBe("two");
+    expect(items[1].quality).toBe(2);
+    expect(items[1].sellIn).toBe(1);
+  });
+  it("should degrade twice as fast past sell in date", () => {
+    const gildedRose = new GildedRose([new Item("foo", 0, 3)]);
+    const items = gildedRose.updateQuality();
+    expect(items[0].sellIn).toBe(-1);
+    expect(items[0].quality).toBe(1);
+  });
+  it("should not have negative quality for expired items", () => {
+    const gildedRose = new GildedRose([new Item("foo", 0, 0)]);
+    const items = gildedRose.updateQuality();
+    expect(items[0].sellIn).toBe(-1);
+    expect(items[0].quality).toBe(0);
+  });
+  it("should not have negative quality for non expired items", () => {
+    const gildedRose = new GildedRose([new Item("foo", 1, 0)]);
+    const items = gildedRose.updateQuality();
+    expect(items[0].sellIn).toBe(0);
+    expect(items[0].quality).toBe(0);
+  });
+  it("should tick up quality for Aged Brie", () => {
+    const gildedRose = new GildedRose([new Item("Aged Brie", 1, 0)]);
+    const items = gildedRose.updateQuality();
+    expect(items[0].sellIn).toBe(0);
+    expect(items[0].quality).toBe(1);
+  });
+  it("should not exceed a quality of 50", () => {
+    const gildedRose = new GildedRose([new Item("Aged Brie", 1, 50)]);
+    const items = gildedRose.updateQuality();
+    expect(items[0].sellIn).toBe(0);
+    expect(items[0].quality).toBe(50);
+  });
+  it("should not tick down sell in or quality if the item is Sulfuras", () => {
+    const gildedRose = new GildedRose([
+      new Item("Sulfuras, Hand of Ragnaros", 1, 2),
+    ]);
+    const items = gildedRose.updateQuality();
+    expect(items[0].sellIn).toBe(1);
+    expect(items[0].quality).toBe(2);
+  });
+  describe("backstage pass", () => {
+    it("should tick up quality with more than 10 days of sell in", () => {
+      const gildedRose = new GildedRose([
+        new Item("Backstage passes to a TAFKAL80ETC concert", 11, 2),
+      ]);
+      const items = gildedRose.updateQuality();
+      expect(items[0].sellIn).toBe(10);
+      expect(items[0].quality).toBe(3);
+    });
+    it("should tick up quality twice with less than 10 days of sell in", () => {
+      const gildedRose = new GildedRose([
+        new Item("Backstage passes to a TAFKAL80ETC concert", 10, 2),
+      ]);
+      const items = gildedRose.updateQuality();
+      expect(items[0].sellIn).toBe(9);
+      expect(items[0].quality).toBe(4);
+    });
+    it("should tick up quality thrice with less than 5 days of sell in", () => {
+      const gildedRose = new GildedRose([
+        new Item("Backstage passes to a TAFKAL80ETC concert", 5, 2),
+      ]);
+      const items = gildedRose.updateQuality();
+      expect(items[0].sellIn).toBe(4);
+      expect(items[0].quality).toBe(5);
+    });
+    it("should have 0 quality when sell in date has passed", () => {
+      const gildedRose = new GildedRose([
+        new Item("Backstage passes to a TAFKAL80ETC concert", 0, 2),
+      ]);
+      const items = gildedRose.updateQuality();
+      expect(items[0].sellIn).toBe(-1);
+      expect(items[0].quality).toBe(0);
+    });
   });
 });