Some time ago I read about (might be on DotNetRocks) a little gem coming out of Microsoft’s research lab called Pex, which is a framework for doing automated White Box Testing in .Net. It’s still in its early days (despite having been around for more than 2 years now) but packs a bag of potential judging by what I’ve seen of the demo materials and been able to use myself!
In short, Pex is able to analyze your methods and work out the boundary conditions, etc. and derive a series of tests that can be used to test your method with as high a coverage as possible. The download package also includes a lightweight framework for test stubs and detours (which basically allows you to replace any .Net method with your own delegate) called Stubs and Moles. It also comes with the ability to automatically generate test project for you in MSTest and NUnit though I haven’t tested out the NUnit generation as it didn’t support NUnit generation the last time I played around it.
I won’t go into detail on how to use it as there are a ton of documentation and demo material on its site and I have barely scratched the surface myself, but do check it out if you haven’t done so already!