webkit and rspec without x server


problems running capybara-webkit with the Headless gem, Xvfb and our ci server. We use this setup for automatic integration testing and javascript testing of our Ruby on Rails 3.2 app. During the tests it complains that

webkit_server: cannot connect to X server need to rspec to config as:

require File.expand_path("../../config/environment", __FILE__)
require 'rspec/rails'
require 'rspec/autorun'
require 'capybara/rspec'
require 'capybara/webkit'
require 'headless'

Capybara.register_driver :webkit do |app|
  Capybara::Driver::Webkit.new(app, :ignore_ssl_errors => true)

Capybara.javascript_driver = :webkit

# don't run on the local machine (since we don't have xvfb running locally)
if Rails.env.production?
    headless = Headless.new