As of Firefox 46, the extension based version FirefoxDriver will no longer work. This is because of the new Add-on policy that Mozilla is enforcing to try help protect end users from installers inserting add ons that are not what the user wants. This version is due for release next week.

This does not mean that your tests need to stop working entirely as there are options to keep them working.

Marionette

Firstly, you can use Marionette, the Mozilla version of FirefoxDriver to drive Firefox. This has been in Firefox since about 24 as we, slowly working against Mozilla priorities, getting it up to Selenium level. Currently Marionette is passing ~85% of the Selenium test suite.

I have written up some documentation on how to use Marionette on MDN

I am not expecting everything to work but below is a quick list that I know doesn't work.

• No support for self-signed certificates
• No support for actions
• No support logging endpoint
• I am sure there are other things we don't remember

It would be great if we could raise bugs.

Firefox 45 ESR

If you don't want to worry about Marionette, the other option is to downgrade to Firefox 45, preferably the ESR as it won't update to 46 and will update in about 6-9 months time to Firefox 52 when you will need to use Marionette.

Marionette will be turned on by default from Selenium 3, which is currently being worked on by the Selenium community. Ideally when Firefox 52 comes around you will just update to Selenium 3 and, fingers crossed, all works as planned.

http://www.theautomatedtester.co.uk/blog/2016/selenium-webdriver-and-firefox-46.html