As announced in April, we are replacing Selenium tests written in Ruby with tests in Node.js. Now is the last responsible moment to make the move. There will be two more reminders, in September and October. In the meantime, only critical problems will be resolved in the Ruby stack. After October we will no longer maintain it. You can follow task T139740 for more information. Extensive documentation is available at mediawiki.org. If you need help with the migration, I am available for pairing and code review (zfilipin in Gerrit, zeljkof in #wikimedia-releng).