I'm now testing selenium or watir with the headless extension (https://github.com/leonid-shevtsov/headless). It works fine on ubuntu. But i will integrated in the turnkey lamp, but there are some difficulties to get firefox running.

Thanks for help!

Here a summary to get watir working on turnkey lamp:

Install Firefox:

echo -e "\ndeb http://downloads.sourceforge.net/project/ubuntuzilla/mozilla/apt all main" | tee -a /etc/apt/sources.list.d/sources.list > /dev/null
apt-key adv --recv-keys --keyserver keyserver.ubuntu.com C1289A29
apt-get update
apt-get install libgtk-3-0
apt-get install firefox-mozilla-build

Download and install geckodriver from here: https://github.com/mozilla/geckodriver/releases

Install Watir:

apt-get install ruby ruby-dev
gem install watir

Install headless:

apt-get install xvfb
gem install headless

Now you can use firefox for headless web testing with ruby like this:

require "rubygems"
require "headless"
require "watir"

# start firefox headless
headless = Headless.new
headless.start

browser = Watir::Browser.new :firefox
browser.goto "http://www.google.de"
html = browser.html

...

headless.destroy

This is working fine. I'm now trying to get it workking with google chrome ...

I found now a way to use chrome/chromium for web testing.

Install chrome:

sh -c 'echo "deb http://dl.google.com/linux/chrome/deb/ stable main" >> /etc/apt/sources.list.d/google-chrome.list'
wget -q -O - https://dl-ssl.google.com/linux/linux_signing_key.pub | apt-key add -
apt-get update
apt-get install google-chrome-stable

Install chromium:

apt-get install chromium

You need both google-chrome and chromium. Google-chrome is not running, but is neccessary for the gnomedriver for watir. Chromium is running with parameter --no-sandbox:

chromium --no-sandbox

Download and install chromedriver from here: https://sites.google.com/a/chromium.org/chromedriver/

Install watir and headless.

Now you can use chrome for headless web testing (with disabled image download) with ruby like this:

require "rubygems"
require "headless"
require "watir"

# start chrome headless
headless = Headless.new
headless.start

# chrome disable load images
profile = Selenium::WebDriver::Chrome::Profile.new
profile['webkit.webprefs.loads_images_automatically'] = false

# start Browser
browser = Watir::Browser.new :chrome, :profile => profile, :switches => %w[--no-sandbox]
browser.goto "http://www.google.de"
html = browser.html

...

headless.destroy

Works fine ... and it's quite faster than firefox ...