how to test cheerio js

Question

this is my code and i don't know how to write test for it:

html.js

const getHtml = async (url) => {
  const { data } = await axios.get(url);
  return data;
};

const cheerioInit = async (url) => cheerio.load(await getHtml(url));

module.exports = {
  cheerioInit,
  getHtml 
};

i think i should mock this, but don't know how to do that. i wrote this but getting error:

const htmlJs = require("./html");

describe("html", () => {
  it("initializes cheerio js", () => {
    const mock = jest.spyOn(htmlJs, "cheerioInit");
    expect(mock).toHaveBeenCalled();
  });
});

this is error:

Answer 1

You can use jest.spyOn(object, methodName) to mock axios.get() method and its resolved value and mock cheerio.load() method with a fake implementation. After executing the getHtml and cheerioInit functions, make assertion for above mocks to check if they have been called with specific arguments.

E.g.

html.js:

const axios = require('axios');
const cheerio = require('cheerio');

const getHtml = async (url) => {
  const { data } = await axios.get(url);
  return data;
};

const cheerioInit = async (url) => cheerio.load(await getHtml(url));

module.exports = {
  cheerioInit,
  getHtml,
};

html.test.js:

const { getHtml, cheerioInit } = require('./html');
const axios = require('axios');
const cheerio = require('cheerio');

describe('html', () => {
  afterEach(() => {
    jest.restoreAllMocks();
  });
  describe('getHtml', () => {
    it('should get html', async () => {
      const getSpy = jest.spyOn(axios, 'get').mockResolvedValueOnce({ data: '<div>teresa teng</div>' });
      const actual = await getHtml('http://localhost:3000');
      expect(actual).toEqual('<div>teresa teng</div>');
      expect(getSpy).toBeCalledWith('http://localhost:3000');
    });
  });
  describe('cheerioInit', () => {
    it('should initializes cheerio', async () => {
      const loadSpy = jest.spyOn(cheerio, 'load').mockImplementation();
      const getSpy = jest.spyOn(axios, 'get').mockResolvedValueOnce({ data: '<div>teresa teng</div>' });
      await cheerioInit('http://localhost:3000');
      expect(loadSpy).toHaveBeenCalledWith('<div>teresa teng</div>');
    });
  });
});

unit test result:

 PASS  examples/66304918/html.test.js
  html
    getHtml
      ✓ should get html (3 ms)
    cheerioInit
      ✓ should initializes cheerio

----------|---------|----------|---------|---------|-------------------
File      | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s 
----------|---------|----------|---------|---------|-------------------
All files |     100 |      100 |     100 |     100 |                   
 html.js  |     100 |      100 |     100 |     100 |                   
----------|---------|----------|---------|---------|-------------------
Test Suites: 1 passed, 1 total
Tests:       2 passed, 2 total
Snapshots:   0 total
Time:        4.088 s