New Post: Unit Testing the View Model

You could always have your own method call in the OnViewLoaded() that does all of the logic.

protected override OnViewLoaded()
{
     MyLogic();
}

public void MyLogic()
{
     //Do stuff
}

You can then unit test MyLogic.
You should also be able to use ViewModelBinder.Bind(ViewModel, view, context). It calls AttachView() which has the handler that calls OnViewLoaded().