MSW seems to be unreliably working with Cypress

Hi there,

after struggling for too long with this … asking here

Describe the bug

The worker sometimes starts sometimes not, and the request are sometimes intercepted others not.

This only happen when the app is tested with cypress

I’m only using a simple cy.visit('/')

and the console sometimes shows the

sometimes not

other times it show the worker has started but the requests are not intercepted

ie. this does not show

I’m starting the worker like this :

if (process.env.NODE_ENV === 'development') {
  const { worker } = require('./services/mocks');
  worker.start();
}

Note: the requests I’m mentioning are requests that are sent when the React App (CRA) starts

Environment

• msw:0.19.4
• nodejs: 14.1
• npm: 6.14

Please also provide your browser version.

chrome 83

Expected behavior

Consistent starting and interceptin of requests while working w/ Cypress

thanks a lot

[MaxDNG]

Hi All,

I have been facing the same issue. MSW indicated it was enabled but the requests were only caught with a force refresh and when the service worker was installed.

It turns out the issue was likely coming from the default registerServiceWorker provided in create-react-app. It was set to serviceWorker.unregister() and thus was calling

navigator.serviceWorker.ready.then(registration => {
  registration.unregister();
});

I’m no expert in service workers but I assume it was messing up with MSW.

TL;DR: remove or comment out the default registerWorker from CRA:

// import * as serviceWorker from './serviceWorker.js';
// serviceWorker.unregister();

[thomasmery]

Hi,

I’m sorry

I have ahed to switch to other matters and have had no time at all

I will have to come back to it but I don’t know when that will be

feel free to close if that’s convenient for you, I’ll re-open or make another issue when I can

thanks!

On Fri, Jul 3, 2020 at 10:06 AM Artem Zakharchenko [e-mail] wrote:

Hey. Did you have any luck in debugging this issue?

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