Akka.Streams.Tests.Dsl.FlowPrefixAndTailSpec.PrefixAndTail_must_pass_along_early_cancellation C# (CSharp) Method

        public void PrefixAndTail_must_pass_along_early_cancellation()
        {
            this.AssertAllStagesStopped(() =>
            {
                var up = TestPublisher.CreateManualProbe<int>(this);
                var down = TestSubscriber.CreateManualProbe<Tuple<IImmutableList<int>, Source<int, NotUsed>>>(this);

                var flowSubscriber = Source.AsSubscriber<int>()
                    .PrefixAndTail(1)
                    .To(Sink.FromSubscriber(down))
                    .Run(Materializer);

                var downstream = down.ExpectSubscription();
                downstream.Cancel();
                up.Subscribe(flowSubscriber);
                var upSub = up.ExpectSubscription();
                upSub.ExpectCancellation();
            }, Materializer);
        }