I am in charge of testing an enterprise web application that makes heavy use of AJAX. I need to build a system that allows continuous running of tests without human interve
You might be able to take advantage of some of the available JavaScript unit testing tools to assemble the sort of environment you need.
For example I've found that loading env.js in rhino gives an acceptable fake browser for testing most JavaScript. It falls short on certain DOM attributes, like elements sized relative to their window, but that hasn't been a serious problem in my experience.
See also: