public void KeepAlive_must_immediately_pull_upstream()
{
var upstream = TestPublisher.CreateProbe<int>(this);
var downstream = TestSubscriber.CreateProbe<int>(this);
Source.FromPublisher(upstream)
.KeepAlive(TimeSpan.FromSeconds(1), () => 0)
.RunWith(Sink.FromSubscriber(downstream), Materializer);
downstream.Request(1);
upstream.SendNext(1);
downstream.ExpectNext(1);
upstream.SendComplete();
downstream.ExpectComplete();
}