Cypress: Support for EventSource

Created on 8 Nov 2018 · 8Comments · Source: cypress-io/cypress

I would like to see the EventSource support because we use it extensively in our app.

Current behavior:

cy.route doesn't identify EventSource requests and there is no way to watch them reliably now.

Desired behavior:

Either cy.route should support it or we should have another API for EventSource.

proposal 💡 network feature

Source

buremba

👍4

Most helpful comment

I've come up with a solution to mock EventSources in a Cypress test:
You can use a package similar to https://github.com/gcedo/eventsourcemock

In your main file of your application, you can then add:

import EventSource, { sources } from 'eventsourcemock';

if (window['Cypress']) {
  // Add mocked EventSources to Cypress run
  Object.defineProperty(window, 'EventSource', { value: EventSource });
  Object.defineProperty(window, 'mockEventSources', { value: sources });
}

And in your test, you can use:

cy.window().its('mockEventSources' as any).then(mockEventSources => {
  cy.readFile('cypress/fixtures/<your fixture here>').then(fixture => {
    mockEventSources['<your name here>'].emit(
      messageEvent.type,
      messageEvent
    );
  });
});

I hope this helps some people.

EDIT If you don't want to add to your application's main file, you can also use the solution from #2349

orjandesmet on 7 May 2019

👍2

All 8 comments

Also, is there any workaround now?

buremba on 8 Nov 2018

👍2

Same problem here:)

sashashakun on 7 Feb 2019

👍2

Hey @buremba & @sashashakun, is the cy.route() not working during cypress open, cypress run, or both?

What is the current behavior of Cypress when trying to use cy.route() with EventSource? Does it error? Just not match the route?

jennifer-shehane on 7 Feb 2019

@jennifer-shehane
I think it does not match the route.

The console states: GET http://localhost:3000/sse-stream/HL01 net::ERR_EMPTY_RESPONSE
That is the path for my EventStream.
The cy.route configuration is:

cy.route(
      'GET',
      `sse-stream/HL01`,
      'fixture:load-carrier-arrived.json'
    );

Update
based on some digging around I found that EventSource can't accept custom headers.
I've noticed that cypress sets request headers on XHR, but not on EventSource.
I even wonder if it's actually possible. A stream is not the same as a simple XHR.
Would there be a way to override the EventSource with some JavaScript stream?

orjandesmet on 15 Apr 2019

I've come up with a solution to mock EventSources in a Cypress test:
You can use a package similar to https://github.com/gcedo/eventsourcemock

In your main file of your application, you can then add:

import EventSource, { sources } from 'eventsourcemock';

if (window['Cypress']) {
  // Add mocked EventSources to Cypress run
  Object.defineProperty(window, 'EventSource', { value: EventSource });
  Object.defineProperty(window, 'mockEventSources', { value: sources });
}

And in your test, you can use:

cy.window().its('mockEventSources' as any).then(mockEventSources => {
  cy.readFile('cypress/fixtures/<your fixture here>').then(fixture => {
    mockEventSources['<your name here>'].emit(
      messageEvent.type,
      messageEvent
    );
  });
});

I hope this helps some people.

EDIT If you don't want to add to your application's main file, you can also use the solution from #2349

orjandesmet on 7 May 2019

👍2

Hi.
As I understood from #2054 support for EventSource got to be already done?
But for me it does not work https://github.com/cypress-io/cypress/pull/2054#issuecomment-627225977

I can not use any "mock" things because it is real server requests and I need data from it.

drumslave-git on 13 May 2020

👍1

https://www.loom.com/share/0372a1ebc7094b4db6e6a2c1b92e1c9d

Doesn't work for me either

petrican on 21 May 2020

Hey @buremba & @sashashakun, is the cy.route() not working during cypress open, cypress run, or both?

What is the current behavior of Cypress when trying to use cy.route() with EventSource? Does it error? Just not match the route?

When running my tests, waiting for an sse, the wait never finishes successfully:
cy.route times out for me with "No request ever occurred."
cy.route2 times out for me with "No response ever occurred."

As @drumslave-git mentioned, i too need access to the response/events or at least a way to tell when the sse has received the first event to continue. Hope this information helps, feel free to reach out for further informations or advice on how to proceed with this.

Thanks,
Marcel