machine:
  node:
    version:
      6.9.1
test:
  override:
    - npm run validate

machine:
  node:
    version:
      6.9.1
test:
  override:
    - yarn validate
dependencies:
  pre:
    # Install Yarn
    - sudo apt-key adv --fetch-keys http://dl.yarnpkg.com/debian/pubkey.gpg
    - echo "deb http://dl.yarnpkg.com/debian/ stable main" | sudo tee /etc/apt/sources.list.d/yarn.list
    - sudo apt-get update -qq
    - sudo apt-get install -y -qq yarn
  cache_directories:
    - ~/.yarn-cache
  override:
    - yarn install

Use yarn on Circle CI
Use yarn on Circle CI
