Mock webserver for tests with Jest

Question

I have a bit of a weird question: I have a program for scraping data from webpages (just the actual HTML pages, not API responses).

I need to write end-to-end tests for this program with the Jest library. In order to test the functionality consistently, I need to make sure that the referred web pages don't change, which would be almost impossible to achieve with resources on the web.

I wondered how good of a practice it is to spin up a new webserver locally with express/fastify/etc. to serve static HTML pages before running the tests and then shut the server down once the tests pass.

Are there any better ways to achieve what I mentioned? Thank you in advance!

Answer 1

For mock server you need npm msw So in your frontend you import it like this:

import {setupServer} from "msw/node";
import {rest} from 'msw'

and after you can create a const server in your function for tests:

const server = setupServer(
    rest.get('/check_signup_email/*', (req, res, ctx) => {
      return res(ctx.json({result: 'ok', emails: []}))
    })
  )
  beforeAll(() => server.listen())
  afterEach(() => server.resetHandlers())
  afterAll(() => server.close())

It is important to close your server after each test and reopened it before new test because if your don't close it differents tests coud be executed on the firsts variables so results could be false.s