"Integrating NUnit with Ruby/Watir Unit Tests"
"Testing ASP.NET web applications can be a painful process. Wouldn't it be nice to have a unit testing framework that covered both the API and the web UI testing in an integrated fashion?"
That's how Travis Illig starts to explain (download links included) what he built to help with this issue, and point to his CodeProject article, in which he gives all the gory details of NUnit, Watir and Ruby integration. Built on top of a proof of concept by Scott Hanselman, Travis seems to have built something which many people will find useful, provided they know how to code in Ruby, that is.