One of the exciting aspects of asp.net mvc is it’s inherent support for Test Driven Devleopment.
This post outlines how to make NUnit and RhinoMocks appear as options when generating a test project during creation of a new MVC app.
And an updated post for Preview 3
http://blogs.msdn.com/webdevtools/archive/2008/05/30/asp-net-mvc-preview-3-tooling-updates.aspx