CoreDispatcher in a unit test with reactive extensions - unit-testing

Question

I have the following bit of code in my Windows 8 Store app:
public static void ConvertUpdateStreamToCollection<T>(this IObservable<UpdateInfo<T>> input, ObservableCollection<T> list)
{
input
.ObserveOnDispatcher()
.Subscribe(upInfo => UpdateList(upInfo, list));
}
That ObserveOnDispatcher is there b.c. this will often be called on a background thread, and when it updates the observable list I will need it to be on the UI dispatcher. To first order this looks like it works fine when I run the app.
But I wish to test this with unit tests. I'm using the built in MSTest. The ObserveOnDispatcher throws, however, complaining there is no valid Window from which to get a CoreDispatcher.
I've seen work arounds for WPF in other places in Stack overflow. But that looks like just something to make the dispatcher run. This error seems more fundamental. Is there a known workaround?

Answer 1

(edit: better formatting now that I have a keyboard instead of a phone)
There's another way to achieve the same functionality:
.ObserveOnDispatcher()
Is fairly equivalent to:
.ObserveOn(new DispatcherScheduler(Dispatcher.CurrentDispatcher))
Now, instead of that DispatcherScheduler, have a class like:
public static class Schedulers
{
public static IScheduler Dispatcher {get; internal set;}
}
And change usage to:
.ObserveOn(Schedulers.Dispatcher)
Example:
void Main()
{
// For normal usage, we'll set this to the proper DispatcherScheduler
Schedulers.Dispatcher = new DispatcherScheduler(Dispatcher.CurrentDispatcher);
// Do stuff
new Thingy().DoStuff();
// for testing usage, we'll set this to be the immediate scheduler
Schedulers.Dispatcher = Scheduler.Immediate;
// Do stuff
new Thingy().DoStuff();
}
public class Thingy
{
public void DoStuff()
{
var query = Observable.Range(0, 10).ObserveOn(Schedulers.Dispatcher);
query.Subscribe(Console.WriteLine);
}
}