m stands for metal, a better test/unit and minitest test runner that can run tests by line number.

Liquid is a template language written in Ruby. It is used to load dynamic content on storefronts.

The test-queue module is a parallel test runner, built using a centralized queue to ensure optimal distribution of tests between workers. It is specifically optimized for Continuous Integration (CI) environments: build statistics from each run are stored locally and used to sort the queue at the beginning of the next run.

This library allows rendering Scalable Vector Graphics (SVG) graphics directly into a Portable Document Format (PDF) document using the Prawn module.

YARD is a documentation generation tool for the Ruby programming language. It enables the user to generate consistent, usable documentation that can be exported to a number of formats very easily, and also supports extending for custom Ruby constructs such as custom class level definitions.

Net::SCP is a pure-Ruby implementation of the SCP client protocol.

This package provides a Ruby module that provides a two-phase lock with a counter.

The SafeYAML gem provides an alternative implementation of YAML.load suitable for accepting user input in Ruby applications.

This library provides a high-level API that wraps the ZeroMQ networking library using the Ruby foreign function interface (FFI). It is a pure Ruby wrapper, hence is compatible with any Ruby runtime that has support for FFI.

Daemons provides a way to wrap existing Ruby scripts to be run as a daemon and to be controlled by simple start/stop/restart commands.

Timeout provides a way to auto-terminate a potentially long-running operation if it hasn't finished in a fixed amount of time.

This package provides a session management implementation for Rack.

The ptools (power tools) library extends Ruby's core File class with many additional methods modelled after common POSIX tools, such as File.which for finding executables, File.tail to print the last lines of a file, File.wc to count words, and so on.

childprocess provides a gem to control external programs running in the background, in Ruby.

Mercenary is a lightweight and flexible library for writing command-line apps in Ruby.

Skinny is a simple, upgradable WebSockets for Ruby, using the Thin library.

MultiXml provides swappable XML backends utilizing either LibXML, Nokogiri, Ox, or REXML.

mkmf-lite is a light version of Ruby's mkmf.rb designed for use as a library. It does not create packages, builds, or log files of any kind. Instead, it provides mixin methods that you can use in FFI or tests to check for the presence of header files, constants, and so on.

Pg is the Ruby interface to the PostgreSQL RDBMS. It works with PostgreSQL 9.3 and later.

Aruba is an extension for Cucumber, RSpec and Minitest for testing command-line applications. It supports applications written in any language.

ruby-hydra is a Ruby library for working with hyphenation patterns.

The sexp_processor package is derived from ParseTree, but contrary to ParseTree, it includes all the generic S-exp processing tools. Amongst the included tools are Sexp, SexpProcessor and Environment

The Hashery is a tight collection of Hash-like classes. Included are the auto-sorting Dictionary class, the efficient LRUHash, the flexible OpenHash and the convenient KeyHash. Nearly every class is a subclass of the CRUDHash which defines a CRUD (Create, Read, Update and Delete) model on top of Ruby's standard Hash making it possible to subclass and augment to fit any specific use case.

Temple is an abstraction and framework for compiling templates to pure Ruby.