Question

我在mobx商店中定义了一个操作，如下所示：

// CardsStore.js

import FetchData from './FetchData';

export default class CardsStore {

  @observable cards = [];

  @action fetchCards = async () => {
    try {
      this.cards = await FetchData();
    } catch (error) {
      // handling error
    }
  };

  ...
  other actions and computed values
  ...
}

这是FetchData的实现：

import EndpointService from 'app/services/EndpointService';

const endpointService = new EndpointService();

export default async function fetchData() {
  try {
      return await endpointService.getCards();
    } catch (e) {
    return 'caught';
  }
}

我在__mocks __文件夹中为FetchData创建了一个模拟模块，它没有调用端点服务，而是返回了一个像这样的硬编码数组：

// ./__mocks__/FetchData.js

const cards = [
  {
    id: 'some-id-1',
    name: 'Test1',
  },
  {
    id: 'some-id-2',
    name: 'Test2',
  },
];

export default function FetchData() {
  return new Promise((resolve, reject) => {
  process.nextTick(() =>
  cards ? resolve(cards) : reject({ error: 'Cards are not found.' })
   );
 });
}

在我的cards.test.js文件中，我对此进行了测试，并且可以正常工作：

import CardsStore from './CardsStore.js';

jest.mock('./FetchData');

const cards = [
  {
    id: 'some-id-1',
    name: 'Test1',
  },
  {
    id: 'some-id-2',
    name: 'Test2',
  },
];

describe('when fetch cards is called', () => {

  const cardsStore = new CardsStore();

  it('should load the cards', async () => {
    await cardsStore.fetchCards();
    expect(cardsStore.cards).toEqual(cards);
  });
});

问题是，如果我要测试其他操作addNewCard，则需要动态更改卡并添加新卡，然后检查期望的卡列表是否等于新卡（应该包含3张卡片）

我找不到动态更新./__mocks__/FetchData.js内的纸牌阵列的方法

Answer 1

使用jest.spyOn和mockReturnValue ...

jest.spyOn(cardsStore.prototype, "fetchCards").mockReturnValue(Promise.resolve(obj));

将 obj 替换为您要返回的内容

示例

describe('when fetch cards is called', () => {

  const cardsStore = new CardsStore();

  it('should load the cards', async () => {
    jest.spyOn(cardsStore.prototype, "fetchCards").mockReturnValue(Promise.resolve(obj));
    await cardsStore.fetchCards();
    expect(cardsStore.cards).toEqual(cards);
  });
});

如何创建具有动态返回值的笑话模拟实现

1 个答案: