Does withStateMachine work with switching subscribers?

[Matthias Seemann]

When I run the expectStreamEvents unit tests on this simple withStateMachine example the last 3 of 5 tests fail:

  describe "propagates all values", ->
    expectStreamEvents(
      -> series(1, [1, 2, 3]).withStateMachine(0, (acc, evt) ->
        if evt.isEnd
          [undefined, [evt]]
        else if evt.hasValue
          [[], [evt, new Bacon.Next(evt.value * evt.value)]])
      [1, 1, 2, 4, 3, 9])

The example is supposed to output the square alongside the value for each source value. Which works fine for a single subscriber, however:

propagates all values
         (switching subscribers) / (switching subscribers with unsub) / (switching aggressively)
           outputs expected values in order:

      AssertionError: expected [ Array(3) ] to deeply equal [ Array(6) ]
      + expected - actual

       [
         1
      +  1
         2
      +  4
         3
      +  9
       ]

[Juha Paananen]

Well, this is no surprise really. Some streams are unstable in the face of switching subscribers on-the-fly. It means that the newly added subscriber doesn't get added between events occurings "simultaneously".

[Juha Paananen]

Because of this, some tests are flagged as unstable or semiunstable, as in here: https://github.com/baconjs/bacon.js/blob/master/spec/specs/bus.coffee#L45

[Juha Paananen]

So, it's known behavior. Not super nice, but you're not supposed to be doing this kind of subscriber-switching mid-event.

[Matthias Seemann]

you're not supposed to be doing this kind of subscriber-switching mid-event.

Yes, I think so too.

I just was not sure how far to go with unit test situations when I wanted to introduce an additional stream combination function to Bacon. I.e. how bullet-proof it should be...

Thanks again for the fast reply!