If you're interested, I've created a 'test harness' for the C++ WPILib, that allows you to run the robot code on your PC (and theoretically Mac/Linux are supported if someone makes the build files for it too). Theres a lot of stuff it supports doing, and a lot of stuff that it doesn't support yet. Hopefully if theres enough community support we can make it support just about everything.
Its been very helpful for me, even in its early stages -- I've used it to find bugs in my program and in WPILib as well. For more details/screenshots and of course the source code (GPL), see my blog:
http://www.virtualroadside.com/blog/...ness-released/