Zeit now.sh and CircleCI config

circle.yml

machine:
  environment:
    PATH: "${PATH}:${HOME}/${CIRCLE_PROJECT_REPONAME}/node_modules/.bin"
  node:
    version: 7.10.0

dependencies:
  override:
    - yarn
  cache_directories:
    - ~/.cache/yarn
  pre:
    - yarn global add now

test:
  override:
    - yarn test

deployment:
  development:
    branch: master
    commands:
      - now -t ${NOW_TOKEN}
      - now -t ${NOW_TOKEN} alias foo-dev
  production:
    branch: production
    commands:
      - now -t ${NOW_TOKEN}
      - now -t ${NOW_TOKEN} alias foo

now.json

{
  "alias": [
    "foo",
    "foo-dev"
  ],
  "forwardNpm": true
}

This setup tells CircleCI to use yarn instead of npm.
It installs now globally, overrides the default test script with yarn test.
It deploy from two branches master and production.
To use now alias without now alias set, the alias property needs to be set in now.json.
I also use forwardNpm flag, so now uses .npmrc to access the private modules.

NOW_TOKEN was generated on the https://now.sh and is set as an env variable on CircleCI dashboard.