An example Circle CI workflow for a Ruby on Rails app

config.yml

version: 2
jobs:
  checkout_and_deps:
    docker:
      - image: circleci/ruby:2.5.1-node-browsers

    steps:
      - checkout

      - run:
          name: Get the Gemfile.lock from the master branch
          command: |
            git show master:Gemfile.lock > MasterGemfile.lock

      - restore_cache:
          keys:
            - v1-dependencies-gem-{{ checksum "Gemfile.lock" }}
            - v1-dependencies-gem-{{ checksum "MasterGemfile.lock" }}
            - v1-dependencies-gem-

      - run:
          name: bundle install
          command: |
            bundle check --path vendor/bundle || bundle install --jobs=4 --retry=3 --path vendor/bundle

      - run:
          name: Dependencies security audit
          command: |
            bundle exec bundle-audit check --update

      - run:
          name: Clean up gems before we save
          command: |
            bundle clean

      - save_cache:
          key: v1-dependencies-gem-{{ checksum "Gemfile.lock" }}
          paths:
            - vendor/bundle

      - restore_cache:
          keys:
            - v1-rubocop-cache-{{ checksum ".rubocop.yml" }}-{{ .Branch }}
            - v1-rubocop-cache-{{ checksum ".rubocop.yml" }}-master
            - v1-rubocop-cache-{{ checksum ".rubocop.yml" }}

      - run:
          name: Rubocop
          command: bundle exec rubocop --parallel

      - save_cache:
          key: v1-rubocop-cache-{{ checksum ".rubocop.yml" }}-{{ .Branch }}-{{ epoch }}
          paths:
            - ../.cache/rubocop_cache

  run_tests:
    docker:
      - image: circleci/ruby:2.5.1-node-browsers
        environment:
          RAILS_ENV: test
          PGHOST: 127.0.0.1
          PGUSER: root
          PARALLEL_TEST_PROCESSORS: 4
      - image: redis:3.0
      - image: circleci/postgres:10.3-ram
        environment:
          POSTGRES_USER: root

    steps:
      - checkout

      - restore_cache:
          keys:
            - v1-dependencies-gem-{{ checksum "Gemfile.lock" }}

      - run:
          name: Setup bundler path
          command: |
            bundle check --path vendor/bundle

      - restore_cache:
          keys:
            - v1-bootsnap-cache-{{ checksum "Gemfile.lock" }}-{{ .Branch }}
            - v1-bootsnap-cache-{{ checksum "Gemfile.lock" }}-master

      # must be in run_tests step because requires a connection to Redis
      - run:
          name: Eager load classes to check for issues
          command: |
              bundle exec rails runner 'Rails.application.eager_load!'

      - run:
          name: Validate clockwork.rb
          command: |
            bundle exec ruby ./clockwork.rb

      - run:
          name: Wait for postgres
          command: dockerize -wait tcp://localhost:5432 -timeout 1m

      - run:
          name: Wait for redis
          command: dockerize -wait tcp://localhost:6379 -timeout 1m

      - run:
          name: Install Postgres Client
          command: |
            sudo sh -c 'echo "deb http://apt.postgresql.org/pub/repos/apt/ `lsb_release -cs`-pgdg main" >> /etc/apt/sources.list.d/pgdg.list'
            wget --quiet -O - https://www.postgresql.org/media/keys/ACCC4CF8.asc | sudo apt-key add -
            sudo apt update
            sudo apt install postgresql-client-10

      - run:
          name: Database Checksum
          command: |
            find db -type f -exec md5sum {} \; | sort -k 2 > db_dir_checksums.txt
            echo $PARALLEL_TEST_PROCESSORS >> db_dir_checksums.txt
            psql postgres -A -t -c 'SELECT version()' >> db_dir_checksums.txt

      - run:
          name: Cat db_dir_checksums.txt
          command: |
            cat db_dir_checksums.txt

      - restore_cache:
          keys:
            - v1-database-schema-{{ checksum "db_dir_checksums.txt" }}

      - run:
          name: Database Setup
          command: |
            if [ -e postgres_dump.sql ]
            then
              echo "Restoring databases dump"
              psql -U postgres -f postgres_dump.sql
            else
              echo "Setting up databases"
              bundle exec rake parallel:setup
              echo "Dumping databases"
              pg_dumpall > postgres_dump.sql
            fi

      - save_cache:
          key: v1-database-schema-{{ checksum "db_dir_checksums.txt" }}
          paths:
            - postgres_dump.sql

      - run:
          name: Create test results directory
          command: |
            mkdir tmp/test-results

      - restore_cache:
          keys:
            - v1-test-times-{{ .Branch }}
            - v1-test-times-master

      # run tests!
      - run:
          name: Run specs
          command: |
            bundle exec parallel_test  \
              -t rspec \
              --runtime-log tmp/test-results/parallel_runtime_rspec.log \
              -- --format progress \
              --format RspecJunitFormatter \
              --out tmp/test-results/rspec.xml \
              --format ParallelTests::RSpec::RuntimeLogger \
              --out tmp/test-results/parallel_runtime_rspec.log \
              -- $(circleci tests glob "spec/**/*_spec.rb" | circleci tests split --split-by=timings)

      - save_cache:
          key: v1-test-times-{{ .Branch }}-{{ epoch }}
          paths:
            - tmp/test-results/parallel_runtime_rspec.log

      - save_cache:
          key: v1-bootsnap-cache-{{ checksum "Gemfile.lock" }}-{{ .Branch }}-{{ epoch }}
          paths:
            - tmp/bootsnap_cache

      # collect reports
      - store_test_results:
          path: tmp/test-results

      - store_artifacts:
          path: tmp/test-results
          destination: test-results

      - store_artifacts:
          path: coverage

workflows:
  version: 2
  test_and_deploy:
    jobs:
      - checkout_and_deps
      - run_tests:
          requires:
            - checkout_and_deps