Which gems are great for Ruby-on-Rails (RoR) development?

Ruby on Rails (RoR) is a trendy, rather new software framework on the brink of usefulness for professional development. The modular character of this framework allows users to easily contribute software packages in the form of Ruby Gems, which provide invaluable help with the professional deployment of RoR-software.

The following gems are, in my experience, most valuable:

1) Gems for Development

• Brakeman

Download here. Brakeman is an open source vulnerability scanner specifically designed for Ruby on Rails applications. It statically analyzes Rails application code to find security issues at any stage of development.

• Rubocop

Download here. A robust Ruby code analyzer, based on the community Ruby style guide. It helps with efficiently finding code passages of possible brisance.

2) Gems for Testing

• RSPec

Download here.RSpec is testing tool for the Ruby programming language. Born under the banner of Behaviour-Driven Development, it is designed to make Test-Driven Development a productive and enjoyable experience.

• Factory Girl

Download here. A library for efficiently setting up Ruby objects as test data.

• Faker

Download here. Faker, a port of Data::Faker from Perl, is used to easily generate fake data: names, addresses, phone numbers, etc.

• Guard-Rspec

Download here. Guard is a command line tool to easily handle events on file system modifications. Helps with systematically testing RoR code.

• Simplecov

Download here. Code coverage for Ruby 1.9+ with a powerful configuration library and automatic merging of coverage across test suites. It helps with determining how much of your code is covered by tests.

3) Gems for Deployment

• capistrano

Download here. A remote server automation and deployment tool written in Ruby.