Ask HN: How are you handling functional testing in the browser?

What tools and practices are you using to test your in-browser user interface and application flow for dynamically rendered content?

I've been rewriting a Rails web app using test-first methodology and am thrilled with the unit, functional, and integration testing features of rails. I've been working out from the models to the controllers and then to the views. This works great as long as the content is static, but once I hit the browser, I'm at a loss. Because I'm using jQuery, I'd be happy to find a solution that just automated use-case tests for Firefox (for example), and mop up issues in an ad-hoc manner for other browsers (no-cache issues on IE and the like.)