private IImmutableList<int> Run(IGraph<FlowShape<int, int>, NotUsed> flow)
{
var task =
Source.From(Enumerable.Range(1, 5).Concat(Enumerable.Range(1, 5).ToList()))
.Via(flow)
.Limit(1000)
.RunWith(Sink.Seq<int>(), Materializer);
task.Wait(TimeSpan.FromSeconds(3)).Should().BeTrue();
return task.Result;
}