version: 2.1

orbs:
  # orbs are basically bundles of pre-written build scripts that work for common cases
  # https://github.com/CircleCI-Public/ruby-orb
  ruby: circleci/ruby@1.1

jobs:
  # skipping build step because Gemfile.lock is not included in the source
  # this makes the bundler caching step a noop
  test:
    parameters:
      ruby-version:
        type: string
    docker:
      - image: cimg/ruby:<< parameters.ruby-version >>
    steps:
      - checkout
      - ruby/install-deps:
          bundler-version: '1.17.2'
          with-cache: false
      - ruby/rspec-test

# strangely, there seems to be very little documentation about exactly how martix builds work.
# By defining a param inside your job definition, Circle CI will automatically spawn a job for
# unique param value passed via `matrix`. Neat!
# https://circleci.com/blog/circleci-matrix-jobs/
workflows:
  build_and_test:
    jobs:
      - test:
          matrix:
            parameters:
              # https://github.com/CircleCI-Public/cimg-ruby
              # only supports the last three ruby versions
              ruby-version: ["2.5", "2.6", "2.7"]