Very simple example of configuration for headless web testing with RSpec, Capybara, Poltergeist and PhantomJS.

From nepalez/ruby (Ubuntu 14.04 + MRI Ruby 2.1.2 + Rubygems + Bundler), add RSpec, Capybara, Poltergeist and PhantomJS.

Start container interactively, execute "rspec test.rb" in the container and examine directory for output result.

For example, From a Docker-enabled platform, such as Ubuntu 14.04, you might do the following:

1. cd ~
2. git clone https://github.com/unigeek/petulant-octo-hipster
3. cd petulant-octo-hipster
4. sudo docker build -t demo .
5. sudo docker run -i -t demo
6. rspec test.rb

You now expect to see: 1 example, 0 failures

...and issuing ls -al should expose a new screen capture named capture.png with a recent timestamp. You can copy this to the host by doing the following..

7. In another terminal / shell, issue sudo docker ps which might show something like this..

   CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES

   4686d8b1a5cc demo:latest bash 8 minutes ago Up 8 minutes goofy_sammet1

8. sudo docker cp 4686d8b1a5cc:/app/petulant-octo-hipster/capture.png ~