Selenium 0.92 doesn't work in IE over VPN or Dialup

I've been writing user interface tests for my current web project using Selenium. I really dig the fact that it uses JavaScript to manipulate the browser. I'm working on building a Language Pattern, where my unit tests read like a simple domain language -- it involves distilling Selenese output into a set of reusable classes.

I ran into a really frustrating snag during a late-night coding session and I started to freak out a bit -- my Selenium tests just magically stopped working! Instead of getting the Selenium framed window, my site was serving 404 messages. At first I thought the plumbing code that I had written was somehow serving the wrong URL.

I quickly switched my tests to FireFox and was relieved to see them working fine -- and under the same URL. Since my client uses IE 6, dropping Internet Explorer support for UI tests would be a deal breaker. I was surprised to see the tests work when I switched the URL from localhost:80 to localhost:4444, which is the port Selenium's proxy server runs on. The light in my head started to glow...

The aha moment came when I switched back to FireFox: I noticed that none of my FireFox plugins were loaded and that the Proxy server setting had been enabled to route localhost:80 through localhost:4444. Selenium is controlling registry settings for the browser, meaning that some setting was missing in IE. Although Internet Explorer had been configured to use my Selenium proxy-server settings, it ignores these values when on dial-up and VPN connections. You need to specify a different proxy server through an Advanced settings menu.

Both FireFox and Internet explorer use PAC files, which are used to automatically detect the configuration settings for your proxy server. Selenium generates a new PAC file between executions, so you'll quickly find that manually fixing it becomes a pain. To fix, create your own pac file and wire the setting in yourself.

Here's a snap of my connections dialog:

And the contents of my selenium-proxy.pac file:

function FindProxyForURL(url, host) {
        return 'PROXY localhost:4444; DIRECT';
}