I ran across an interesting article entitled “Improving Test Coverage of Ajax Applications” in which the author likens the challenges of testing Ajax applications to that of testing traditional GUI apps. While some newer frameworks (like Selenium) are positioned to actually verify Ajax-ian behavior, they can lead to a false sense of security because of the complexity associated with the combination of actions in using a GUI.
While Ajax applications are definitely more snazzy than traditional web apps, because they can alter the traditional notion of page flow, one must put some extra thought into how the application will be verified.

February 27th, 2007 at 10:42 pm
Absolutely - Selenium and other tools are now available to help, but there are still real challenges in describing these new types of interactions. The old-school tools (SilkTest, QTP, HttpUnit, etc) either didn’t understand the concept of multiple user transactions in a single page or didn’t have the technology to deal with AJAX at all.
Selenium helps with the AJAX/multiple user transactions issue, but it still requires testers to express the desire to “click on button X, wait for Y to appear” in their tests. I think there is still room to make this easier to understand and test against, possibly by integrating with AJAX and/or web-based frameworks, and thereby understanding the interactions at a deeper level.