Which version of Ruby to use with Rails?

To know which version of Ruby is safe to use with Rails one option is to look at the Travis configuration, for example, Rails 5.2: https://github.com/rails/rails/blob/ee1278cc841a883835918fbedb70add96c84543b/.travis.yml#L64-L69 Note the allowed_failures configuration: https://github.com/rails/rails/blob/172bb64ca8d3f1cf88ca7daa4f6a58436e577c69/.travis.yml#L145-L148 This works for Rubygems too: https://github.com/bblimke/webmock/blob/a3c8de2550122d0998cb47292be0bbd2e3f203bf/.travis.yml#L4-L14