Run specs against multiple Ruby versions in CircleCi

config.yml

#.circleci/config.yml

version: 2.1

executors:
  test_executor:
    docker:
      - image: circleci/ruby:${RUBY_VERSION}
    working_directory: ~/app

jobs:
  build:
    environment:
      RUBY_VERSION: << parameters.ruby_version >>
    executor: test_executor
    parameters:
      ruby_version:
        type: string
    steps:
      - checkout

      - restore_cache:
           key: bundle-{{ checksum "Gemfile.lock" }}
           
      - run: bundle check || bundle install --path vendor/bundle
      
      - run: rubocop
      
      - save_cache:
          key: bundle-{{ checksum "Gemfile.lock" }}
          paths:
            - ~/app/vendor/bundle
      - run:
          name: RSpec
          command: bundle exec rspec spec

workflows:
  build_and_test:
    jobs:
      - build:
          name: 'ruby 2.4.5'
          ruby_version: 2.4.5
      - build:
          name: 'ruby 2.5.5'
          ruby_version: 2.5.5
      - build:
          name: 'ruby 2.6.2'
          ruby_version: 2.6.2