TestScheduler and timer, test never ends.

[pvinis]

Bug Report

Current Behavior
i have a timer and some other streams that touch this timer.

Reproduction
i dont know how to do stackblitz with jest tests.
you can take the following code and run jest test, or yarn test.

 it('do some testing', () => {
    const testScheduler = new TestScheduler((actual, expected) => expect(actual).toEqual(expected))
    testScheduler.run(helpers => {
      const { cold, expectObservable } = helpers

      const tick = timer(0, 1000, testScheduler).pipe(
        // take(18),
        share(),
      )
      const now = tick
      const bla = cold('---a-----b')
      const blu = bla.pipe(
        withLatestFrom(now),
        map(([b, n]) => b)
      )
      const output = blu
      const expected = '---a-----b'
      expectObservable(output).toBe(expected)
    })
  })

Expected behavior
I want to test the above code, and i would expect that after i have gotten the expected output up to the point i have it, then it would stop the test as a success. with the current test above, the test never finishes, because i guess the timer never stops?
if i uncomment the take, then the test passes.

Environment

• Runtime: node 8, react native 0.55
• RxJS version: 6.2

Possible Solution
N/A

Additional context/Screenshots
N/A

[cartant]

IMO, this is not a bug. Without the take, there is nothing to stop the timer. The bla source does not complete, so the test infrastructure remains subscribed to it and to the timer. The timer keeps emitting notifications, so, as far as the testing infrastructure is concerned, the test still appears to be running. Forever.

[pvinis]

but the idea of the marble tests is that I say the expected output and check it. after the timeframe of the expectation, there is no need for the scheduler to keep running. so it could stop everything, right?

[cartant]

The test scheduler will see that the output matches the expectation, but it also has an observable that's still emitting. It cannot know that it won't receive more notifications, upon receipt of which the received output would not match the expected output.

If your source observable completed - i.e. ended with| - the test would behave as you're expecting it to.

[pvinis]

hm ok. so the expected should end with | and bla should also end with |. I will try that in a few hours and report back. is there another way I could make this happen as I want? maybe a takeuntil with some kind end observable? probably no..

[cartant]

Anything that stops the timer should work - like the take call you commented out.

Basically, you cannot leave an observable emitting and expect the test to end. Observables don't necessarily have to complete, but each time the timer emits, it schedules its next emission and that's the problem. The test infrastructure won't end the test until there are no more scheduled actions.

[pvinis]

indeed adding | did allow the test to finish. thank you. i dont know why i didnt think of trying that..