How to provoke an error and success response on the same GET endpoint

[kevinmamaqi]

Is your feature request related to a problem? Please describe.
I use the library for testing purposes with jest and @testing-library/react. When I do a fetch request to a GET endpoint, how can I return once an error and once a success to test both states of my app?

Describe the solution you'd like
A flag.

Describe alternatives you've considered
Sending an extra parameter in the request to filter it in the endpoint.

[kettanaito]

Hey, @kevinmamaqi. You can use a runtime request handler to override which response is being returned for the same endpoint to test multiple states of your code.

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

const server = setupServer(
  // I recommend listing the success scenarios when declaring the server.
  rest.get('/resource', (req, res, ctx) => {
    return res(ctx.json({ id: 1 }))
  })
)

beforeAll(() => server.listen())
afterEach(() => server.resetHandlers())
afterAll(() => server.close())

it('handles a successful response', () => {
  // run your code (i.e. render components, execute functions)
  // without any additions, this test case will receive a successful response
  // defined above.
})

it('handles an error response', () => {
  server.use(
    // In this paticular test respond to the same request with a 404 response.
    rest.get('/resource', (req, res, ctx) => {
      return res(ctx.status(404))
    })
  )

  // run your code here.
  // within this test a "GET /resource" will receive a 404 error response
  // specified above.
})

Don't forget to call .resetHandlers() after each test so that the .use() overrides you add don't affect irrelevant tests.