TDD Gilde Rose Kata in JS

shop.test.js

import Shop from "./Shop";
import Item from "./Item";

const MIN_QUALITY = 0;
const MAX_QUALITY = 50;

test("regular items' quality decreases every day", () => {
  const item = regularItem(1, 3);
  const shop = new Shop([item]);

  shop.updateQuality();

  expect(item.quality).toEqual(2);
  expect(item.sellIn).toEqual(0);
});

test("expired regular items' quality decreases twice as fast once sellIn has passed", () => {
  const item = regularItem(0, 3);
  const shop = new Shop([item]);

  shop.updateQuality();

  expect(item.quality).toEqual(1);
  expect(item.sellIn).toEqual(-1);
});

test("regular items' quality never decreases below the minimum quality", () => {
  const item = regularItem(5, 0);
  const shop = new Shop([item]);

  shop.updateQuality();

  expect(item.quality).toEqual(MIN_QUALITY);
  expect(item.sellIn).toEqual(4);
});

test("expired regular items' quality never decreases below the minimum quality", () => {
  const item = regularItem(0, 1);
  const shop = new Shop([item]);

  shop.updateQuality();

  expect(item.quality).toEqual(MIN_QUALITY);
  expect(item.sellIn).toEqual(-1);
});

test("aged brie increases quality by 1", () => {
  const item = agedBrie(5, 8);
  const shop = new Shop([item]);

  shop.updateQuality();

  expect(item.quality).toEqual(9);
  expect(item.sellIn).toEqual(4);
});

test("aged brie quality never increases over the maximun quality", () => {
  const item = agedBrie(5, MAX_QUALITY);
  const shop = new Shop([item]);

  shop.updateQuality();

  expect(item.quality).toEqual(MAX_QUALITY);
  expect(item.sellIn).toEqual(4);
});

test("expired aged brie quality never increases over the maximun quality", () => {
  const item = agedBrie(0, 49);
  const shop = new Shop([item]);

  shop.updateQuality();

  expect(item.quality).toEqual(MAX_QUALITY);
  expect(item.sellIn).toEqual(-1);
});

test("expired aged brie increases quality by 2", () => {
  const item = agedBrie(0, 8);
  const shop = new Shop([item]);

  shop.updateQuality();

  expect(item.quality).toEqual(10);
  expect(item.sellIn).toEqual(-1);
});

test("sulfuras never changes", () => {
  const item = sulfuras(1, 80);
  const shop = new Shop([item]);

  shop.updateQuality();

  expect(item.quality).toEqual(80);
  expect(item.sellIn).toEqual(1);
});

test("already expired sulfuras never changes", () => {
  const item = sulfuras(-1, 80);
  const shop = new Shop([item]);

  shop.updateQuality();

  expect(item.quality).toEqual(80);
  expect(item.sellIn).toEqual(-1);
});

test("backstage increase quality by 1 when sellIn is greater than 10", () => {
  const item = backstagePasses(11, 6);
  const shop = new Shop([item]);

  shop.updateQuality();

  expect(item.quality).toEqual(7);
  expect(item.sellIn).toEqual(10);
});

test("backstage increase quality by 2 when sellIn is inside [10, 5)", () => {
  const item1 = backstagePasses(10, 6);
  const item2 = backstagePasses(6, 20);
  const shop = new Shop([item1, item2]);

  shop.updateQuality();

  expect(item1.quality).toEqual(8);
  expect(item1.sellIn).toEqual(9);
  expect(item2.quality).toEqual(22);
  expect(item2.sellIn).toEqual(5);
});

test("backstage increase quality by 3 when sellIn is inside [5, 0)", () => {
  const item1 = backstagePasses(5, 6);
  const item2 = backstagePasses(1, 20);
  const shop = new Shop([item1, item2]);

  shop.updateQuality();

  expect(item1.quality).toEqual(9);
  expect(item1.sellIn).toEqual(4);
  expect(item2.quality).toEqual(23);
  expect(item2.sellIn).toEqual(0);
});

test("backstage quality drops to 0 after the concert", () => {
  const item = backstagePasses(0, 6);
  const shop = new Shop([item]);

  shop.updateQuality();

  expect(item.quality).toEqual(0);
  expect(item.sellIn).toEqual(-1);
});

test("backstage quality never increases over the maximun quality when increasing by 1", () => {
  const item = backstagePasses(11, MAX_QUALITY);
  const shop = new Shop([item]);

  shop.updateQuality();

  expect(item.quality).toEqual(MAX_QUALITY);
  expect(item.sellIn).toEqual(10);
});

test("backstage quality never increases over the maximun quality when increasing by 2", () => {
  const item = backstagePasses(8, 49);
  const shop = new Shop([item]);

  shop.updateQuality();

  expect(item.quality).toEqual(MAX_QUALITY);
  expect(item.sellIn).toEqual(7);
});

test("backstage quality never increases over the maximun quality when increasing by 3", () => {
  const item = backstagePasses(4, 48);
  const shop = new Shop([item]);

  shop.updateQuality();

  expect(item.quality).toEqual(MAX_QUALITY);
  expect(item.sellIn).toEqual(3);
});


function regularItem(sellIn, quality) {
  return new Item("foo", sellIn, quality);
}

function agedBrie(sellIn, quality) {
  return new Item("Aged Brie", sellIn, quality);
}

function sulfuras(sellIn, quality) {
  return new Item("Sulfuras, Hand of Ragnaros", sellIn, quality);
}

function backstagePasses(sellIn, quality) {
  return new Item("Backstage passes to a TAFKAL80ETC concert", sellIn, quality)
}