What is it about client-side scripting that you want to test? You can already test any server-side code with HTTP::Recorder, including code that is called by JavaScript on the client, because the full HTTP interaction is captured. The only thing that you can't test with it is your JavaScript itself.
Comment on Re: Testing at the browser: a trip report. (Perl, Ruby, etc.)
I agree. But (for instance), I have an application that uses ActiveX and Javascript to implement custom RPCs between IE and the server. No HTTP involved. The whole application is invisible to HTTP::Recorder.
And when the JS is a couple of frames deep in the page, poking at it becomes troublesome.