Getting Selenium to wait for Ajax requests

Update: See here for one caveat in using Ajax.activeRequestCount.

Using Selenium IDE to test Ajax, you can usually use a waitFor condition reflecting on DOM elements to tell you when Ajax calls have returned. However, if you just want to wait until all Ajax requests have returned without relying on testing against page elements, there is this approach:

Command: waitForCondition
Target:  selenium.browserbot.getUserWindow().Ajax.activeRequestCount == 0
Value:   10000

This works for Prototype based Ajax pages, e.g. standard Rails. If you're using a different JavaScript library, you'll need to use a different call; see here for some possibilities.

(For earlier versions of Selenium, you might need to use getCurrentWindow() instead.)