public static void AdvanceAfterElement <T>(this TestScheduler scheduler, ITestableObservable <T> events, int elementIndex, int timeAfter = 500)
 {
     scheduler.AdvanceTo(events.Messages.ElementAt(elementIndex).Time + Time.Tics(timeAfter));
 }
 public static void AdvanceJustAfterEnd <T>(this TestScheduler scheduler, ITestableObservable <T> events, int timeAfter = 500)
 {
     scheduler.AdvanceTo(events.Messages.Max(x => x.Time) + Time.Tics(timeAfter));
 }