TestScheduler test

        [TestMethod]
        public void OnCompletedCalled()
        {
            TestScheduler scheduler = new TestScheduler();
            ReplaySubject<TcpClient> subject = new ReplaySubject<TcpClient>(scheduler);
            TcpListener listener = new TcpListener(IPAddress.Any, 11122);
            listener.Start();
            CancellationDisposable cancel = new CancellationDisposable();
            bool isOk = false;
            Func<IObservable<TcpClient>> asyncObs = Observable.FromAsyncPattern(listener.BeginAcceptTcpClient, listener.EndAcceptTcpClient);
            asyncObs().Where(x => x.Connected)
                .SubscribeOn(scheduler)
                .ObserveOn(scheduler)
                .Subscribe(
                subject.OnNext,
                cancel.Token);
            subject
                .SubscribeOn(scheduler)
                .ObserveOn(scheduler)
                .Subscribe(x => { }, () => { isOk = true; }, cancel.Token);
            cancel.Token.Register(subject.OnCompleted);
            cancel.Token.Register(listener.Stop);
            //cancel.Token.Register(() => { isOk = true; });
            cancel.Dispose();
            scheduler.AdvanceBy(1);
            Assert.IsTrue(isOk);
        }