The Google Gmail system is a widely used AJAX application that presents some special problems for testing, not the least of which is the process of synchronizing a test playback. We're all familiar with the "Loading..." message...and the problem in setting up a test script is how to make the playback wait until the mail file is ready to be processed
The solution, as described in our Testing the Google Gmail Application writeup, is to synchronize on a visible text entity. As you'll see in the example script, this means having the test playback wait until the string "You are currently using" appears on the screen. Note that this synchronization is done 100% inside the browser (i.e. it does not require use of the desktop); this means two or more of these same scripts could be running in parallel if you wished (or need to).