public void EmitsNewValueWheneverNewValueIsSet(TimeSpan timeSpan)
{
var observer = Substitute.For <IObserver <TimeSpan> >();
SettingsStorage.TimeSpanBeforeCalendarNotifications.Subscribe(observer);
SettingsStorage.SetTimeSpanBeforeCalendarNotifications(timeSpan);
Received.InOrder(() =>
{
observer.OnNext(TimeSpan.FromMinutes(10));
observer.OnNext(timeSpan);
});
}