Cucumber running headless Selenium with Jenkins (the easy way)

Selenium is a great way to test your javascript from Cucumber. It opens up a browser and you actually see it clicking around, filling in fields and submitting forms right before your eyes. It’s cool.

Jenkins is a brilliant continuous integration and deployment tool. I recently set it up for a new project i’ve started. It checks for git commits, pulls the latest code, runs all the specs and cucumber scenarios, and if they all pass, it deploys the code to five different websites. It’s great because we just have to git push and all five websites will get updated.

But Jenkins runs all its commands on the command line, and it doesn’t actually have a display on which it can run a browser. This isn’t too big a problem. You can use Xvfb virtual frame buffer which can emulate a display for you.

The old way to do this was to configure Xvfb to make a display (we usually use 99 to avoid conflicts) and write little shell scripts to start and stop this display, and export an environment variable to make sure the display is used ………… YAWN!

Now enter the gem headless. It does all those boring things behind the scenes, making it much simpler. I got this tip from 8th light’s blog post Jenkins, RVM, and Selenium. To get headless Selenium you simply have to do the following:

Install Xvfb:

sudo apt-get install xvfb

Require headless in your Gemfile:

gem 'headless'

Add this little snippet to features/support/env.rb:

if ENV['HEADLESS'] == 'true'
  require 'headless'

  headless = Headless.new
  headless.start

  at_exit do
    headless.destroy
  end
end

Tag your cucumber scenarios with @javascript for those that require selenium.

Call cucumber like this:

HEADLESS=true cucumber

It Just Works™!

As an added bonus, when i’m working remotely i’m often tunelling via SSH to a shared screen on a remote server. I can use the same HEADLESS=true trick to run my selenium scenarios remotely.