Circle CI Config for Ember.js project with Yarn, and Latest Firefox

circle.ci.ember.firefox.yml

version: 2
jobs:
  build:
    working_directory: ~/selleo-mail-log
    docker:
      - image: circleci/node:latest-browsers
    steps:
      - checkout
      - restore_cache:
          key: dependency-cache-{{ checksum "package.json" }}
      - run:
          name: Download Latest Firefox
          command: "[ -d ~/firefox ] || ( wget -O ~/ff-latest.tar.bz2 'https://download.mozilla.org/?product=firefox-latest&os=linux64&lang=en-US' && tar xjf ~/ff-latest.tar.bz2 -C ~/ )"
      - run: 
          name: Link Firefox
          command: sudo ln -sf ~/firefox/firefox /usr/bin/firefox
      - run:
          name: Install Yarn
          command: 'sudo curl -o- -L https://yarnpkg.com/install.sh | bash'
      - run:
          name: Install packages
          command: yarn install && node_modules/bower/bin/bower install
      - save_cache:
          key: dependency-cache-{{ checksum "package.json" }}
          paths:
            - ./node_modules
            - ./bower_components
            - ~/firefox
            - ~/.npm
            - ~/.yarn-cache
            - ~/.cache
      - run:
          name: Run tests
command: node_modules/ember-cli/bin/ember test