fixing observable

I am trying to fix observable,

I've added a failing test to demonstrate is not working as expected. The test is expecting `OnNext` to be called in 2 seconds.

For what I can figure out so far `FakeAsyncSubject` is not working as expected, `onNext` body is never executed because completion is null, `OnComplete` will throw and exception because final will be null.

Do you think this is a good approach shall I continue to investigate and come up with a fix?
I've update the tests and removed Moq