public void A_Flow_with_SelectAsync_must_signal_NPE_when_task_is_completed_with_null()
{
var c = TestSubscriber.CreateManualProbe<string>(this);
Source.From(new[] {"a", "b"})
.SelectAsync(4, _ => Task.FromResult(null as string))
.To(Sink.FromSubscriber(c)).Run(Materializer);
var sub = c.ExpectSubscription();
sub.Request(10);
c.ExpectError().Message.Should().StartWith(ReactiveStreamsCompliance.ElementMustNotBeNullMsg);
}