We normally use the Bobby tool to evaluate accessibility for web applications. We are implementing adaptive portlets with Plumtree which do not utilize URL clicks - has anyone got any tips on automating the accessibility testing process for rich user experience technologies, such as Plumtree.
I'm not familiar with Plumtree but if it renders the UI using HTML then Bobby should be OK. If it uses flash or applets etc then Bobby should be able to analyse the underlying HTML and you can suplement this with manual checks.
You should also (as recommended by the WAI) be performing some manual checks including viewing the application using a screen-reader and text-browser.
How much automated and manual testing you need to do will depend upon the compliance level you are hoping to achieve.