But it's not system events though (which BTW is just wrapper over observer service so we do no guarantees there). All of these module `window/events` and `browser/events`, `event/utils` use `event/core` for registering and emitting events which have their own tests that do verify FIFO order. Of course we could test that in every module that makes use of `event/core` but then there was no real point of writing tests for `event/core` IMO.