Don't worry, I asked my cat. He said add a Universal Test project anyway (the one with the dummy UI). This also adds a skeleton class which references some obscure extension SDK libraries for unit testing, so you get the familiar [TestXXX] attributes to put on test classes and methods.
However, it's not all hugs and puppies ... once you set the project to build and deploy, it opens a Universal app window which says "Tests Running", but there is no output anywhere from my WriteLines and it just sits there with clue about how to make it do anything. So I suppose I'm using it wrong and will have to study documentation for another hour to figure out how to make "Hello world" display somewhere. *GK*
