Best way to simulate offline mode while developing?

[cmacdonnacha]

I've been using MSW to mock my test data while developing locally. It's been great so far but I was wondering how I can simulate "offline mode" to see how my app responds to failed requests. Is it possible to use the Network tab in Chrome dev tools to do so?

[kettanaito]

Hey, @cmacdonnacha.

You can simulate an offline mode using the res.networkError() utility.

rest.get('/user', (req, res, ctx) => {
  return res.networkError('Your error message')
})

Read more about res.networkError().

This produces an analogous response error as when requesting a resource while being offline.

[cmacdonnacha]

@kettanaito Do you think it would be a good idea to update these docs to include this code? This way it's clear to the reader how they can use both network errors and regular 200 responses within a handler

Example:

rest.get('/books', (req, res, ctx) => {
    if (!navigator.onLine) {
    return res.networkError('You are offline')
  }

  return res(ctx.json([{ name: 'The Great Gatsby' }]));
})

[kettanaito]

I think this is already mentioned in the conditional response section. The fact that the condition may be anything: a custom logic, or a reference whether the page is offline—those are implied. I don't think we need an explicit example for this, but if many people find this necessary I don't mind adding it in the future (still, probably as a recipe).

[cmacdonnacha]

Yea I'm good with that, this was likely more me not being thorough enough reading through all the docs. The docs are really well put together and easy to follow, only piece of feedback I'd have is that it would be great if there was some search functionality.

[kettanaito]

We are working on a redesigned website that is going to include a search. We know it's painful to find the information in the current docs, and we will improve the experience.

[timdeschryver]

I just wanted to add that if you use the same handler in tests that run on Node.JS, you will have to provide a mock for navigator . Because I think that Node.JS doesn't have a navigator instance, and that it only exists in a browser context.