javascript - Jest 模拟未覆盖函数或返回错误

Question

我正在尝试为 csvtojson 编写一个 Jest 模拟测试，但出现错误:

TypeError: Cannot read property 'subscribe' of undefined

api.js:

import csv = require('csvtojson')
const request = require('request')

export const getApiData = url => {
  return csv()
   .fromStream(request.get(url)
   .subscribe(json => json)
}

api.test.js

import { getApiData } from '../api';
const csv = require('csvtojson');

jest.mock('csvtojson', () => {
  const fromStream = jest.fn();
  const subscribe = jest.fn(() => new Promise(resolve => setTimeout(resolve, 0)));
  const result = { fromStream, subscribe };
  return jest.fn(() => result);
});
jest.mock('request', () => {
  return { get: jest.fn() };
});
describe('getApiData', () => {
  beforeEach(() => {
    getApiData('http://test.com');
  });
  describe('csv', () => {
    expect(csv).toHaveBeenCalled();
  });
});

然后我测试了它，如果我从 getApiData 函数中删除 fromStream 它可以工作，但后来我的报道显示 json => json尚未被调用。

我真的很困惑。有人可以帮忙吗？

Answer 1

这是单元测试解决方案:

api.js:

const csv = require('csvtojson');
const request = require('request');

export const getApiData = url => {
  return csv()
    .fromStream(request.get(url))
    .subscribe(json => json);
};

api.test.js:

import { getApiData } from './api';
const csv = require('csvtojson');
const request = require('request');

jest.mock('csvtojson', () => {
  const mCsvtojson = {
    fromStream: jest.fn().mockReturnThis(),
    subscribe: jest.fn()
  };
  return jest.fn(() => mCsvtojson);
});
jest.mock('request', () => {
  return { get: jest.fn() };
});

describe('getApiData', () => {
  it('csv', done => {
    const mResponse = { name: 'UT' };
    let observer;
    csv()
      .fromStream()
      .subscribe.mockImplementationOnce(onSuccess => {
        observer = onSuccess;
      });
    request.get.mockResolvedValueOnce(mResponse);
    getApiData('http://test.com');
    const mJSON = {};
    expect(observer(mJSON)).toEqual({});
    expect(request.get).toBeCalledWith('http://test.com');
    expect(csv).toHaveBeenCalled();
    expect(csv().fromStream).toBeCalledWith(expect.any(Object));
    done();
  });
});

100%覆盖率的单元测试结果:

PASS  src/stackoverflow/58842143/api.test.js (10.249s)
  getApiData
    ✓ csv (8ms)

----------|----------|----------|----------|----------|-------------------|
File      |  % Stmts | % Branch |  % Funcs |  % Lines | Uncovered Line #s |
----------|----------|----------|----------|----------|-------------------|
All files |      100 |      100 |      100 |      100 |                   |
 api.js   |      100 |      100 |      100 |      100 |                   |
----------|----------|----------|----------|----------|-------------------|
Test Suites: 1 passed, 1 total
Tests:       1 passed, 1 total
Snapshots:   0 total
Time:        12.139s

源代码:https://github.com/mrdulin/jest-codelab/tree/master/src/stackoverflow/58842143