There has been an unofficial release of the ASP.NET MVC Source Code which is now available on the new ASP.NET CodePlex Project. It now includes unit tests (using Moq – will be blogging on that soon) and some support for testing controllers 
Scott Guthrie has posted everything you need to know about the refresh: ASP.NET MVC Source Refresh Preview. Well worth a read if you are into MVC or MVP!
