Sunday, January 1, 2012

Suppressing Firefox favicon Requests from WebDriver

Right now, WebTestingExplorer only works with Firefox. There are a couple of reasons for that which I won't go into here. Anyway, we decided to wire our HTTP requests to go through a proxy by default. This allows us to look for specific status codes, presumably "undesirable" ones like the 500-series, or possibly 404's.

When we did this and pointed the tool at a specific URL, the first thing we noticed was Firefox firing off a bunch of requests to various locations on the target site fishing around for the favicon, most of which (kind of by definition) ended with a 404. I'm surprised that for as long as I have used Firefox attached to a proxy for testing and debugging, I had never taken note of this before. In this case, it's really annoying -- after all, one of the points of using the proxy in the first place was to verify that all requests came back with a valid response.

The first thing I considered was adding special-case code for all favicon requests in the handlers for the proxy. That seemed kind of lame, so the second thing I thought about was looking for a way to suppress the requests in the first place. It turns out that there are Firefox preferences for this -- and -- as described here.

I have two main points left for this post. First, I wanted to show the code for how set these preferences in Selenium WebDriver when you build your FirefoxProfile:

final FirefoxProfile profile = new FirefoxProfile();

// The following preferences control Firefox's default behavior of sending
// requests for favicon.ico, which results in lots of bogus 404's for sites
// that don't have favicons. 
FirefoxDriver driver = new FirefoxDriver(profile);

Second, I will pitch my opinion that in most automated testing scenarios, you probably ought to be suppressing favicon requests from Firefox, even if your site actually has one. A good way to do this is to save the preferences into a custom Firefox profile used for automated testing. If you don't already have one of those, you should. I will try to provide some tips on how to maintain and use one of those in a future post.

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