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

        public void PrefixAndTail_must_handle_master_stream_cancellation()
        {
            this.AssertAllStagesStopped(() =>
            {
                var publisher = TestPublisher.CreateManualProbe<int>(this);
                var subscriber = TestSubscriber.CreateManualProbe<Tuple<IImmutableList<int>, Source<int, NotUsed>>>(this);

                Source.FromPublisher(publisher)
                    .PrefixAndTail(3)
                    .To(Sink.FromSubscriber(subscriber))
                    .Run(Materializer);

                var upstream = publisher.ExpectSubscription();
                var downstream = subscriber.ExpectSubscription();

                downstream.Request(1);

                upstream.ExpectRequest();
                upstream.SendNext(1);

                downstream.Cancel();
                upstream.ExpectCancellation();
            }, Materializer);
        }