If you try to run a test like the following from NUnit, you will find that it does not work.
You get an InvalidOperationException telling you that “The calling thread must be STA, because many UI components require this”.
http://www.hedgate.net/articles/2007/01/08/instantiating-a-wpf-control-from-an-nunit-test/
System.InvalidOperationException: Beim aufrufenden Thread muss es sich um einen STA-Thread handeln, da dies für viele Komponenten der Benutzeroberfläche erforderlich ist.