A CircleCI v2 config file (here using docker + JRuby image)

config.yml

version: 2
jobs:
  build:
    docker:
      # https://circleci.com/docs/2.0/circleci-images/#jruby
      # TODO: DRY version number with .ruby-version once we 
      # have a solution. See discussion at:
      # https://discuss.circleci.com/t/setting-docker-image-version-based-on-ruby-version/22119
      - image: circleci/jruby:9.1.14.0
        environment:
          COVER: "1"
          # SNIP
    steps:
      - checkout
      - restore_cache:
          keys:
            - gem-cache-{{ checksum "Gemfile.lock" }}
      # avoids CVEs
      - run: gem update --system
      - run: gem install bundler
      - run: bundle install --path vendor/bundle
      - save_cache:
            key: gem-cache-{{ checksum "Gemfile.lock" }}
            paths:
              - vendor/bundle
      - run: cp config/application.ci.yml config/application.yml
      - run: bundle exec rspec
      - run: bundle exec cucumber
      - run: bundle exec bundle-audit check --update