This is something probably obvious to everyone, but it wasn't to me, so just a note on this.

I like to keep my unit tests in the same class library as the actual generated classes.  On the surface, this seems normal, but the DataManager class requires configuration settings in an app.config file, and it stumped me for a bit.

Until I realized the obvious, that you can include an application configuration in a class library.  You don't actually need to create an application (windows or web forms) project to do this and so can proceed normally.