Docker image contains all necessary for visual testing.
See example.py to know how to write basic test
and bin/nosetests.sh to know how to run it.
For first time run bin/nosetests.sh example.py --with-save-baseline and create baseline.
Another time run bin/nosetests.sh example.py to compare current state against baseline.
Use host.local to access your localhost or take advantage of your hosts file.
For more details visit Needle, Selenium and Nose documentations.