Earlier this week, I was having trouble getting my tests to run in Travis CI. My use case was running Sublime Text inside of Travis CI. Unfortunately, I was running into issues that can only encounter in a display-less environment.

$ ./test.sh
(sublime_text:1080): Gtk-WARNING **: cannot open display: :0

From there, and reading enough articles about PhantomJS, I knew that I needed to run Xvfb to get around this.

# Inside of .travis.yml
before_script:
  - export DISPLAY=:99.0
  - sh -e /etc/init.d/xvfb start

However, after doing that I was met with another error and stuck for the rest of the night.

$ ./test.sh
Xlib:  extension "RANDR" missing on display ":99.0".

The next day, I began to research and discovered that Travis CI's tests are run inside of a Ubuntu 12.04 LTS 64 bit virtual machine. Additionally, there was documentation on versions of software.

I decided to mock this environment via Vagrant, a development environment management program. I created a Vagrant using the vanilla Ubuntu 64 bit base image.

Vagrant.configure("2") do |config|
  config.vm.box = "precise64"
  config.vm.box_url = "http://files.vagrantup.com/precise64.box"
end

Then, it was a series of thoughtful trial and error to get to the same error message. The important steps for me were:

# Install xvfb and libgtk2.0-0
sudo apt-get install xvfb
sudo apt-get install libgtk2.0-0

# Install `sublime_text`
wget 64bit-sublime-text.tar.bz2
tar xvf 64bit-sublime-text.tar.bz2
ln -s $PWD"/Sublime Text 2/sublime_text" /usr/bin/sublime_text

# Trial and error with Xvfb
xvfb -screen 0 1024x768x24
./test.sh

Once I got to the same error, I found the problem was the tests were running fine but not terminating Sublime Text. I added an exit statement to each test and Travis CI ran flawlessly.

As it turns out, you really are supposed to ignore the Xlib error for RANDR.

$ ./test.sh
Xlib: extension "RANDR" missing on display ":99.0".
.Xlib: extension "RANDR" missing on display ":99.0".
.Xlib: extension "RANDR" missing on display ":99.0".
.
----------------------------------------------------------------------
Ran 3 tests in 2.023s

OK