Thank you for the link. The Patterns of xUnit Test Automation
site is very helpful in thinking about all of this and is not a site I had seen before.
I don't have a lot of duplication yet, since this project is still in the early stages of development, but I am expecting there to be quite a bit of "test fixture setup" that is repeated from one test to the next (mainly setup of mock objects or subroutine overrides), possibly with variations in the setup data between tests. I think you're right, though, this will be something that can be factored out.