[Groxx]

Nothing is irrelevant for a testing platform. For instance, how does it handle a canvas tag? It'd be useful to be able to dump out frames as images. A user agent string could be used by javascript to do any number of things, so I would hope it's modifiable.

As to the libraries to make things cross-browser compatible, knowing which browser it tries to emulate would be essential to knowing which lines of code would be executed through this tool. If you can't test the IE-specific code, what's the use if you're developing for IE?