Ruby

Resque

A Redis-backed library for creating background jobs, placing those jobs on multiple queues, and processing them later.

Active Record

A Ruby library for working with Relational SQL Databases, like MySQL and Postgres. It provides an Object Relational Mapping. 

Brakeman

A security scanner. Checks Ruby on Rails applications for security vulnerabilities. Looks at the source code of an application.

Bundler

Ensures Ruby applications run the same code on every machine. Tracks and installs the exact gems and versions that are needed.

Capistrano

Remote server automation and deployment tool written in Ruby. Capistrano automates the process of making a new version of an application available on one or more web servers.

Capybara

Automation library that provides a means for controlling a browser. Simulates scenarios for user stories and automates web application testing for behavior-driven software development.

Crystal

A dynamic, functional language designed for building scalable and maintainable applications. Leverages the Erlang VM, known for the running low-latency, distributed and fault-tolerant systems, while also being successfully used in web development and the embedded software domain.

ERB

ERB (Embedded Ruby) is a templating system in Ruby that allows developers to embed Ruby code within text templates. It's commonly used for dynamically generating HTML, XML, or other markup languages. ERB has been part of the Ruby standard library since Ruby 1.8.0.

EventMachine

Fast, simple event-processing library for Ruby programs. The most popular library for concurrent computing in the Ruby programming language.

FactoryBot

A software library for the Ruby. Provides factory methods to create test fixtures for automated software testing.

Grape

REST-like API micro-framework for Ruby. It's designed to run on Rack or complement existing web application frameworks such as Rails and Sinatra by providing a simple DSL to easily develop RESTful APIs.

Jekyll

A simple, static site, blog-aware generator perfect for personal, project, or organization sites.

JRuby

Implementation of the Ruby programming language atop the Java Virtual Machine, written largely in Java. JRuby has built-in support for Rails, RSpec, Rake, and RubyGems.

Minitest

Testing tool for Ruby. Provides a complete suite of testing facilities for writing tests to verify expectations from a code base. Supports TDD, BDD, mocking, and benchmarking.

Padrino

Ruby framework built upon the Sinatra microframework. Created to make it easy to code more advanced web applications. It leverages convention and automation to accomplish larger building tasks.

Passenger

A fast and robust web server and application server for Ruby, Python, Node.js and Meteor apps. It makes deploying in production much easier and is scalable.

Phoenix

Advance MVC web framework which implements the server-side MVC pattern. Many of its components and concepts are familiar to those who experience in other web frameworks like: 

• Ruby on Rails
• Python’s
• Django.

Rake

Software task management and build automation tool. It allows the user to specify tasks and describe dependencies as well as to group tasks in a namespace. Tasks and dependencies are specified in standard Ruby syntax.

RSpec

Testing tool for Ruby, created for behavior-driven development (BDD). Focused on writing software that emphasizes the importance of self-documenting, executable tests that drive the development process from requirements analysis through acceptance testing. Has a very rich and powerful DSL (domain-specific language).

RuboCop

Ruby static code analyzer and code formatter. 

Ruby

A dynamic, object-oriented, general-purpose programming language with a focus on simplicity and productivity. It has an elegant syntax that is natural to read and easy to write.

RubyGems

Package manager for the Ruby programming language that provides a standard format for distributing Ruby programs and libraries (in a self-contained format called a "gem"). Designed to easily manage the installation of gems, and a server for distributing them.

Ruby Arrays

A list of items in order (like mangoes, apples, and oranges). Every slot in the list acts like a variable: you can see what object a particular slot points to, and you can make it point to a different object.

Ruby deployment

Passenger, Capistrano.

Ruby frameworks

Rails/Ruby on Rails, Sinatra, Padrino, JRuby.