How to write a jest test that will pass if return value is array of objects?

Question

I'm learning unit tests, and I've covered pretty much the basics.

Now I'm trying to test my scraper. My initial function involves multiple scrapers, but i wanted to check if each scraper works properly. The output of the test (to test be successful) should be if the return has an [{},{},...,{}] - array of objects. I really cant know what is inside of the objects(data is always different), but it's always a array of objects.

Now what my question is: How to properly do this? I've tried in multiple ways, and my test always fails. Closes that I've been is this solution:

const santScraper = require('../scraping/scrapers/sant-scraper');

test('Does scraper works properly', async () => {
  await expect(santScraper(1)).toBe({});
});

But my output is this:

FAIL  tests/santScraper.test.js
  × Does scraper works properly (20 ms)

  ● Does scraper works properly

    expect(received).toBe(expected) // Object.is equality

    - Expected  - 1
    + Received  + 1

    - Object {}
    + Promise {}

      2 |
      3 | test('Does scraper works properly', async () => {
    > 4 |   await expect(santScraper(1)).toBe({});
        |                                ^
      5 | });
      6 |

      at Object.<anonymous> (tests/santScraper.test.js:4:32)

Test Suites: 1 failed, 1 total
Tests:       1 failed, 1 total
Snapshots:   0 total
Time:        2.016 s
Ran all test suites.
npm ERR! Test failed.  See above for more details.

I really dont know what is pointing to.

Also here is my scraper:

//const data_functions = require('../data-functions/data-functions');
const axios = require('axios'); //npm package - promise based http client
const cheerio = require('cheerio'); //npm package - used for web-scraping in server-side implementations
const data_functions = require('../data-functions/data-functions');

//santScaper function which as paramater needs count which is sent in the scraping-service file.
const santScraper = async (count) => {
  const url = `https://www.sant.ba/pretraga/prodaja-1/tip-2/cijena_min-20000/stranica-${count}`;

  const santScrapedData = [];
  try {
    await load_url(url, santScrapedData);
  } catch (error) {
    console.log(error);
  }
};

//Function that does loading URL part of the scraper, and starting of process for fetching raw data.
const load_url = async (url, santScrapedData) => {
  await axios.get(url).then((response) => {
    const $ = cheerio.load(response.data);
    get_article_html_nodes($).each((index, element) => {
      process_single_article($, index, element, santScrapedData);
    });

    data_functions.mergeData(santScrapedData);
    return santScrapedData; //this is where I return array of objects
  });
};

// Part where raw html data is fetched but in div that we want.
const get_article_html_nodes = ($) => {
  return $('div[class="col-xxs-12 col-xss-6 col-xs-6 col-sm-6 col-lg-4"]');
};

//Here is all logic for getting data that we want, from the raw html.
const process_single_article = ($, index, element, santScrapedData) => {
  const getLink = $(element).find('a[class="re-image"]').attr('href');
  const getDescription = $(element).find('a[class="title"]').text();
  const getPrice = $(element)
    .find('div[class="prices"] > h3[class="price"]')
    .text()
    .replace(/\.| ?KM$/g, '')
    .replace(',', '.');
  const getPicture = $(element).find('img').attr('data-original');
  const getSquaremeters = $(element)
    .find('span[class="infoCount"]')
    .first()
    .text()
    .replace(',', '.')
    .split('m')[0];
  const pricepersquaremeter =
    parseFloat(getPrice) / parseFloat(getSquaremeters);

  santScrapedData[index] = {
    id: getLink.substring(42, 46),
    link: getLink,
    description: getDescription,
    price: Math.round(getPrice),
    picture: getPicture,
    squaremeters: Math.round(getSquaremeters),
    pricepersquaremeter: Math.round(pricepersquaremeter),
  };
};

module.exports = santScraper;

Answer 1

You can make use of typeof in this case like so:-

test('Does scraper works properly', async () => {
  await expect(typeof santScraper(1)).toBe('object');
});

Although if it's always the Promise object you want to check against, you can get more specific using instanceof like so:-

test('Does scraper works properly', async () => {
  await expect(santScraper(1) instanceof Promise).toBe(true);
});