That would defeat the whole point of this test on Desktop.
We explicitely wait during `open` event in order to call close during this `open` event dispatch.
That's the trick to prevent other addons/loader-module-instances from receiving any `open` event.

I can easily agree this test is extremelly focused and maybe too detailed? We might drop part of the concurrent loader code and just ensure that we don't get any exception when calling close during open event in both loaders.

See https://bugzilla.mozilla.org/show_bug.cgi?id=843500 for more info