@Test
  public void demonstrateBroadcast() {
    final Sink<Author, CompletionStage<Done>> writeAuthors = Sink.ignore();
    final Sink<Hashtag, CompletionStage<Done>> writeHashtags = Sink.ignore();

    // #flow-graph-broadcast
    RunnableGraph.fromGraph(
            GraphDSL.create(
                b -> {
                  final UniformFanOutShape<Tweet, Tweet> bcast = b.add(Broadcast.create(2));
                  final FlowShape<Tweet, Author> toAuthor =
                      b.add(Flow.of(Tweet.class).map(t -> t.author));
                  final FlowShape<Tweet, Hashtag> toTags =
                      b.add(
                          Flow.of(Tweet.class)
                              .mapConcat(t -> new ArrayList<Hashtag>(t.hashtags())));
                  final SinkShape<Author> authors = b.add(writeAuthors);
                  final SinkShape<Hashtag> hashtags = b.add(writeHashtags);

                  b.from(b.add(tweets)).viaFanOut(bcast).via(toAuthor).to(authors);
                  b.from(bcast).via(toTags).to(hashtags);
                  return ClosedShape.getInstance();
                }))
        .run(mat);
    // #flow-graph-broadcast
  }
  @Test
  public void complexGraph() throws Exception {
    // #complex-graph
    RunnableGraph.fromGraph(
        GraphDSL.create(
            builder -> {
              final Outlet<Integer> A = builder.add(Source.single(0)).out();
              final UniformFanOutShape<Integer, Integer> B = builder.add(Broadcast.create(2));
              final UniformFanInShape<Integer, Integer> C = builder.add(Merge.create(2));
              final FlowShape<Integer, Integer> D =
                  builder.add(Flow.of(Integer.class).map(i -> i + 1));
              final UniformFanOutShape<Integer, Integer> E = builder.add(Balance.create(2));
              final UniformFanInShape<Integer, Integer> F = builder.add(Merge.create(2));
              final Inlet<Integer> G = builder.add(Sink.<Integer>foreach(System.out::println)).in();

              builder.from(F).toFanIn(C);
              builder.from(A).viaFanOut(B).viaFanIn(C).toFanIn(F);
              builder.from(B).via(D).viaFanOut(E).toFanIn(F);
              builder.from(E).toInlet(G);
              return ClosedShape.getInstance();
            }));
    // #complex-graph

    // #complex-graph-alt
    RunnableGraph.fromGraph(
        GraphDSL.create(
            builder -> {
              final SourceShape<Integer> A = builder.add(Source.single(0));
              final UniformFanOutShape<Integer, Integer> B = builder.add(Broadcast.create(2));
              final UniformFanInShape<Integer, Integer> C = builder.add(Merge.create(2));
              final FlowShape<Integer, Integer> D =
                  builder.add(Flow.of(Integer.class).map(i -> i + 1));
              final UniformFanOutShape<Integer, Integer> E = builder.add(Balance.create(2));
              final UniformFanInShape<Integer, Integer> F = builder.add(Merge.create(2));
              final SinkShape<Integer> G = builder.add(Sink.foreach(System.out::println));

              builder.from(F.out()).toInlet(C.in(0));
              builder.from(A).toInlet(B.in());
              builder.from(B.out(0)).toInlet(C.in(1));
              builder.from(C.out()).toInlet(F.in(0));
              builder.from(B.out(1)).via(D).toInlet(E.in());
              builder.from(E.out(0)).toInlet(F.in(1));
              builder.from(E.out(1)).to(G);
              return ClosedShape.getInstance();
            }));
    // #complex-graph-alt
  }
 @Test
 public void closedGraph() throws Exception {
   // #embed-closed
   final RunnableGraph<NotUsed> closed1 = Source.single(0).to(Sink.foreach(System.out::println));
   final RunnableGraph<NotUsed> closed2 =
       RunnableGraph.fromGraph(
           GraphDSL.create(
               builder -> {
                 final ClosedShape embeddedClosed = builder.add(closed1);
                 return embeddedClosed; // Could return ClosedShape.getInstance()
               }));
   // #embed-closed
 }
  public void demonstrateADetachedGraphStage() throws Exception {
    // tests:
    CompletionStage<Integer> result1 =
        Source.from(Arrays.asList(1, 2, 3))
            .via(new TwoBuffer<>())
            .runFold(0, (acc, n) -> acc + n, mat);

    assertEquals(new Integer(6), result1.toCompletableFuture().get(3, TimeUnit.SECONDS));

    TestSubscriber.ManualProbe<Integer> subscriber = TestSubscriber.manualProbe(system);
    TestPublisher.Probe<Integer> publisher = TestPublisher.probe(0, system);
    RunnableGraph<NotUsed> flow2 =
        Source.fromPublisher(publisher).via(new TwoBuffer<>()).to(Sink.fromSubscriber(subscriber));

    flow2.run(mat);

    Subscription sub = subscriber.expectSubscription();
    // this happens even though the subscriber has not signalled any demand
    publisher.sendNext(1);
    publisher.sendNext(2);

    sub.cancel();
  }