At the time of writing the latest version of Firefox (version 13) has just been released. Bear in mind that a week ago I updated our Selenium bindings so that we could use Firefox 9+ for running our browser tests.
The latest release is another great release for the Firefox team, except there is software out there will be broken. The software in question I'm talking about is any code that uses Selenium 2.22.0 that was released 2012-05-29. It turns out the bindings only work for Firefox 12 or less.
For whatever reason any tests that used Selenium this morning just stopped working for us - and others. The tests in question caused the runner to hang as no window could be opened. I'm not sure what causes this, as the browser is essentially the same to the end user, bar some new features. Not being a Selenium developer I cannot comment how or why this has happened, nor can I suggest the Selenium team should be version agnostic.
Our solution in the end was simple. Turn off the auto updating and downgrade the browser. I've blogged about this in the past, but since Firefox 10 - the team are adopting a "silent" update process. This is great for end users. Imagine the countless man hours saved if IE6 had shipped with an auto update feature? The problem now seems to be in the hands of developers.
Another attempt to make this problem more obvious has been to add a check prior to our tests running to ensure that it can open a window. If this fails or hangs, we display a useful error message indicating that the browser in question is not compatible. This is due to the fact that it is not immediately obvious what the problem is. More confusion occurs when some machines will execute the tests with no problems at all.
Tools -> Options -> Advanced -> Update Tab
So if you use Selenium and Firefox - ditch the auto updating. Manually update your bindings and check compatability for now...