We at www.leankoala.com do a lot of tests (65.000.000 since the beginning of the year). Most of them involve the Selenium Webdriver.
On the one hand, we love that tool. It is the de-facto standard for browser testing and works with almost every browser and every programming language. On the other hand, it is sometimes unstable, some errors are very hard to debug and with only Webdriver, a lot of things are not solvable.
After understanding how the Webdriver works we came to a solution to handle such problems. Selenium is not able to do that. That’s right. But Selenium is able to inject google chrome extension before running. So you are able to write the code you want to be called before inside such an extension and it will run up front.
This way we solved most of our requirements at www.leankoala.com.