javascript - 开 Jest 不承认 promise 中的 spy 电话

Question

我想测试一个在 promise 中调用函数的方法。

article-api.js(简化)

articleMiddleware(next) {
    return fetch(articleApiListUrl, { headers, method, body })
        .then(() => next({ some: 'data'}));

}

这是article-api.js的简化版本，完整代码可以在这里看到: https://gist.github.com/LukasBombach/7bd9cce28d3a3b905fb8a408b37de3a9

我想看看 next 是否被 { some: 'data'} 调用了。我用 fetch-mock模拟我的获取请求

article-api.spec.js(简体)

describe('article api middleware', () => {

    it('creates ARTICLE_SUCCESS when fetching an article has been done', () => {
        fetchMock.post('*', { some: 'data' });
        return articleMiddleware(next)
            .then(expect(next).toBeCalledWith({ some: 'data' }))
            .then(() => fetchMock.restore());

    });

});

这是 article-api.spec.js 的简化版本，完整代码可以在这里看到: https://gist.github.com/LukasBombach/178f591f516fe13c24fb0a4f02c4676c

我得到的是

Expected mock function to have been last called with: [{ some: 'data' }] But it was not called.

如果你查看两个要点中的完整代码，你会发现我的代码有点不同，那里的错误消息是

expect(received).toBe(expected)

Expected value to be (using ===):
  2
Received:
  1

这是因为 next(action) 在第一个 gist 的第 17 行中调用了 next (同步)，但是 next 在 promise 中永远不会被调用。

Answer 1

这里是只使用"jest": "^24.8.0"的解决方案，不需要使用fetch-mock，可以自己手动mock。

文章-api.js:

const fetch = require('node-fetch');

function articleMiddleware(next) {
  const articleApiListUrl = 'https://github.com/mrdulin';
  const headers = {};
  const method = 'get';
  const body = {};

  return fetch(articleApiListUrl, { headers, method, body }).then(() => next({ some: 'data' }));
}

exports.articleMiddleware = articleMiddleware;

article-api.spec.js:

jest.mock('node-fetch');

const fetch = require('node-fetch');
const { articleMiddleware } = require('./article-api');

describe('articleMiddleware', () => {
  it('t1', async () => {
    fetch.mockResolvedValueOnce({});
    const next = jest.fn();
    await articleMiddleware(next);
    expect(fetch).toBeCalledWith('https://github.com/mrdulin', { headers: {}, method: 'get', body: {} });
    expect(next).toBeCalledWith({ some: 'data' });
  });
});

100% 覆盖率的单元测试结果:

 PASS  src/stackoverflow/42676657/article-api.spec.js
  articleMiddleware
    ✓ t1 (9ms)

----------------|----------|----------|----------|----------|-------------------|
File            |  % Stmts | % Branch |  % Funcs |  % Lines | Uncovered Line #s |
----------------|----------|----------|----------|----------|-------------------|
All files       |      100 |      100 |      100 |      100 |                   |
 article-api.js |      100 |      100 |      100 |      100 |                   |
----------------|----------|----------|----------|----------|-------------------|
Test Suites: 1 passed, 1 total
Tests:       1 passed, 1 total
Snapshots:   0 total
Time:        3.131s

这是完整的演示:https://github.com/mrdulin/jest-codelab/tree/master/src/stackoverflow/42676657