Rxjs: Mocking fromEvent in rxjs6

[rsirs]

Spy on fromEvent haven't been called

spyOn(Observable, 'fromEvent')
expect(Observable.fromEvent).toHaveBeenCalled();

Above mentioned piece of code is not working for rxjs6 version but working on rxjs5

Work arounds to make this work but failed

import {fromEvent} from 'rxjs'

let Obj = { observableFromEvent: fromEvent }
spyOn(Obj, 'observableFromEvent')
expect(observableFromEvent).toHaveBeenCalled();

/* jasmine test case failed with spy hasn't been called */

```js
import * as rxjs form 'rxjs'

spyOn(rxjs, 'fromEvent')
expect(rxjs.fromEvent).toHaveBeenCalled();

/* Test case failed with no setter or non writable fromEvent */

[benlesh]

So you want to spy on fromEvent?

You should be able to just import everything, and spy on that:

import * as rxjs from 'rxjs';

spyOn(rxjs, 'fromEvent')

[rsirs]

@benlesh I already did but, Jasmine is complaining [method_name] is not declared writable or has no setter since es6 imports are constants. any other workaround ?

[aniruddhadas9]

After using @benlesh idea, I am getting below

    Error: <spyOn> : fromEvent is not declared writable or has no setter
    Usage: spyOn(<object>, <methodName>)
        at Object.<anonymous> src/app/app.component.spec.ts:215:7)
        at TestBed.push../node_modules/@angular/core/fesm5/testing.js.TestBed.execute node_modules/@angular/core/fesm5/testing.js:1074:1)
        at Object.<anonymous> node_modules/@angular/core/fesm5/testing.js:1225:29)
        at Object.<anonymous> node_modules/zone.js/dist/fake-async-test.js:593:1)
        at ZoneDelegate.push../node_modules/zone.js/dist/zone.js.ZoneDelegate.invoke node_modules/zone.js/dist/zone.js:388:1)
        at ProxyZoneSpec.push../node_modules/zone.js/dist/proxy.js.ProxyZoneSpec.onInvoke node_modules/zone.js/dist/proxy.js:128:1)
        at ZoneDelegate.push../node_modules/zone.js/dist/zone.js.ZoneDelegate.invoke node_modules/zone.js/dist/zone.js:387:1)

[kksevta]

Getting same error after importing everything.

[csaszika]

just use jasmine marbles for that, you can do it like that:

const myEvents = hot('--a-', { a: event });
const expected = cold('--b', { b: result });

expect(component.someSource$).toBeObservable(expected);

[bfaulk96]

@hannaraczek Observable.fromEvent() is from RXJS 5, they switched to just fromEvent() in RXJS 6... As this question is specifically for getting RXJS 6 to work, that is not a viable solution here.

[martinsik]

I know this is a lame solution but maybe just wrapping fromEvent would be enough (I didn't test this):

import {fromEvent as realFromEvent} from 'rxjs'

...

it('test', () => {
  let called = false;
  const fromEvent = (...args: any[]) => {
    const o = realFromEvent(...args);
    called = true;
    return o;
  };

  ... 

  expect(called).toBeTruthy(); // or whatever...
})