test_task:
  container:
    matrix:
      image: ruby:2.5
      image: ruby:2.4
  bundle_cache:
    folder: /usr/local/bundle
    populate_script: bundle update
  test_script: bundle exec rake

test_task:
  container:
    matrix:
      image: ruby:2.5
      image: ruby:2.4
  bundle_cache:
    folder: /usr/local/bundle
    fingerprint_script: echo $RUBY_VERSION
    populate_script: bundle update
  test_script: bundle exec rake

Store cached for different Ruby version separatly
Store cached for different Ruby version separatly