Selenium is a great way to automate your browser testing.
Recently we had a customer write in asking about how to test browser extensions with Selenium.
After some research and a few changes mainly for message size, we have it working.
Since we are using webdriver.Remote you need to get the extension to our servers. You do that by including the extension in the chrome options or the firefox profile. In both cases the binary extension ends up being sent along in the capabilities in base64 encoding.