- Bundler - Bundler maintains a consistent environment for ruby applications. It tracks an application's code and the rubygems it needs to run, so that an application will always have the exact gems (and versions) that it needs to run.
- rabl - General ruby templating with json, bson, xml, plist and msgpack support
- jbuilder - JSON builder shipped with Rails.
- builder XML builder shipped with Rails.
- Puma - A Ruby/Rack web server built for concurrency. Shipped with Rails.
- SimpleCov - SimpleCov is a code coverage analysis tool for Ruby 1.9.
- bootstrap - Bootsnap preloads your Rails app so that your normal development tasks such as console, server, generate, and specs/tests is faster.
- factory_bot - factory_bot is a fixtures replacement with a straightforward definition syntax, support for multiple build strategies (saved instances, unsaved instances, attribute hashes, and stubbed objects), and support for multiple factories for the same class (user, admin_user, and so on), including factory inheritance.
- Sass - This gem provides official integration for Ruby on Rails projects with the Sass stylesheet language.
- Sidekiq - Redis-backed Ruby library for creating background jobs, placing them on multiple queues, and processing them later. Provide an admin interface.
- Heroku - Hosting provider for Ruby, Node.js, Clojure, Java, Python and Scala
- Forward - Forward your localhost to a publicly-accessible url
- Mandrill - Transactional email based on MailChimp infrastructure
- CircleCI - CI/CD. Test PR before merge, run deployment script when merged in master, ...
- Gitlab - Provide private and public git repositories with CI/CD integrated for free
- Ruby on Rails Guides - These guides are designed to make you immediately productive with Rails, and to help you understand how all of the pieces fit together.
- Better Specs - Collection of "best practices" that other developers learn through years of experience.