Akka.Streams.Tests.Dsl.FlowExpandSpec.Expand_must_work_on_a_variable_rate_chain C# (CSharp) Method

        public void Expand_must_work_on_a_variable_rate_chain()
        {
            var future = Source.From(Enumerable.Range(1, 100))
                .Select(x =>
                {
                    if (ThreadLocalRandom.Current.Next(1, 3) == 2)
                        Thread.Sleep(10);
                    return x;
                })
                .Expand(i => Enumerable.Repeat(i, 200).GetEnumerator())
                .RunAggregate(new HashSet<int>(), (agg, elem) =>
                {
                    agg.Add(elem);
                    return agg;
                }, Materializer);

            future.Wait(TimeSpan.FromSeconds(10)).Should().BeTrue();
            future.Result.ShouldAllBeEquivalentTo(Enumerable.Range(1, 100));
        }