When running Selenium tests remotely with PHPUnit and Firefox, onChange events are not fired as they are when a user is operating the browser.

The solution to this seems to be to set the focusmanager.testmode option to true in Firefox's preferences (i.e. about:config), as suggested in a Selenium bug report.

However all the examples are using Selenium directly, while I am using PHPUnit which has its own API hiding the Selenium internals. I can't figure out how to set this Firefox option using PHPUnit, so I'm hoping someone else can tell me how this can be done!

(No, I can't go into about:config and set it myself manually because the tests create a new clean browser profile each time the tests are run, so any manual config changes are lost.)