Wercker CI config file to run in a Node Box: nightwatch with mocha, firefox and a custom nightwatch.json that differs from the dev file, also installs java to run selenium

wercker-config-nightwatch-mocha.yml

box: node
build:
    steps:
        - script:
            name: setup
            code: |
              sudo apt-get update -y -qq
        - install-packages:
            packages: ruby ruby-dev bzr mercurial git wget
        - script:
            name: install firefox
            code: |-
              # sudo apt-get install --assume-yes build-essential curl wget libfreetype6-dev libfontconfig1-dev xvfb x11-xkb-utils xfonts-100dpi xfonts-75dpi xfonts-scalable xfonts-cyrillic x11-apps
              cd /usr/local
              wget http://ftp.mozilla.org/pub/mozilla.org/firefox/releases/45.0/linux-x86_64/en-US/firefox-45.0.tar.bz2
              tar xvjf firefox-45.0.tar.bz2
              sudo ln -s /usr/local/firefox/firefox /usr/bin/firefox
             
        - script:
            name: install java
            code: |-
              sudo apt-get --assume-yes install default-jre
              # sudo apt-get --assume-yes install default-jdk
        - script:
            name: test java
            code: |-
              type java || { echo "I expected java to be available after oracle-java7-installer installation. Aborting."; exit 1; }
        - script:
            name: start virtual display xvfb
            code: |-
              sudo apt-get --assume-yes install xvfb -y
              sleep 15
              export DISPLAY=:99.0
              sudo start-stop-daemon --start --quiet --pidfile /tmp/xvfb_99.pid --make-pidfile --background --exec /usr/bin/Xvfb -- :99 -screen 0 1024x768x24 -ac +extension GLX +render -noreset
              sleep 15
              xdpyinfo -display :0 >/dev/null 2>&1 && echo "In use" || echo "Free"

        - npm-install
    
        - script:
          name: set NODE_ENV == testing
          code: |-
            export NODE_ENV=testing
        - script:
          name: install nightwatch global
          code: |-
            npm install -g nightwatch

        - script:
          name: run nightwatch with ci config
          code: |-
            nightwatch --config ./nightwatch-ci.json

Can you also share the nightwatch-ci.json ?