Testing on Headless CI Systems (Travis CI, Jenkins)

    First, install Xvfb. It’s a virtual framebuffer, implementing the X11 display server protocol - it performs all graphical operations in memory without showing any screen output, which is exactly what we need.

    On Travis, your .travis.yml should look roughly like this:

    1. addons:
    3.       - xvfb
    6.   - Xvfb :99 -screen 0 1024x768x24 > /dev/null 2>&1 &

    CircleCI is awesome and has Xvfb and $DISPLAY already set up, so no further configuration is required.