Nokogiri::Diff adds the ability to calculate the differences (added or removed nodes) between two XML/HTML documents.

This library contains some useful functionality to support the development of Ruby gems.

Spy is a mocking library. By default, it will raise an error if you attempt to stub a method that doesn't exist or call the stubbed method with the wrong arity.

Ruby Bindings for the GNU LibIDN library, an implementation of the Stringprep, Punycode and IDNA specifications. These are used to encode and decode internationalized domain + names according to the IDNA2003 specifications.

Included are the most important parts of the Stringprep, Punycode and IDNA APIs like performing Stringprep processings, encoding to and decoding from Punycode strings and converting entire domain names to and from the ACE encoded form.

Rack::Test is a small, simple testing API for Rack applications. It can be used on its own or as a reusable starting point for Web frameworks and testing libraries to build on.

Kramdown is a library for parsing and converting a superset of Markdown. It is completely written in Ruby, supports standard Markdown (with some minor modifications) and various extensions that have been made popular by the PHP Markdown Extra package and Maruku.

The concurrent-ruby-edge gem includes concurrent-ruby features that are under active development and may change frequently. They are expected not to keep backward compatibility (there may also lack tests and documentation), although semantic versions are obeyed though. Features developed in concurrent-ruby-edge are expected to move to concurrent-ruby when final.

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.

Tilt is a thin interface over a number of different Ruby template engines in an attempt to make their usage as generic as possible.

Pry is an IRB alternative and runtime developer console for Ruby. It features syntax highlighting, a plugin architecture, runtime invocation, and source and documentation browsing.

ChunkyPNG is a pure Ruby library that can read and write Portable Network Graphics (PNG) images without depending on an external image library. It tries to be memory efficient and reasonably fast. It has features such as:

• Decoding support for any image that the PNG standard allows. This includes all standard color modes, all bit depths, all transparency, and interlacing and filtering options.

• Encoding support for images of all color modes (true color, grayscale, and indexed) and transparency for all these color modes. The best color mode is chosen automatically, based on the amount of used colors.

• Read/write access to the image's pixels.

• Read/write access to all image metadata that is stored in chunks.

• Memory efficiency: fixnum are used, i.e. 4 or 8 bytes of memory per pixel, depending on the hardware).

• Performance: ChunkyPNG is reasonably fast for Ruby standards, by only using integer math and a highly optimized saving routine.

• Interoperability with RMagick.

ChunkyPNG is vulnerable to decompression bombs and can run out of memory when loading a specifically crafted PNG file. This is hard to fix in pure Ruby. Deal with untrusted images in a separate process, e.g., by using fork or a background processing library.

Puma is a simple, fast, threaded, and highly concurrent HTTP 1.1 server for Ruby/Rack applications. Puma is intended for use in both development and production environments. In order to get the best throughput, it is highly recommended that you use a Ruby implementation with real threads like Rubinius or JRuby.

shoulda is a meta-package combining shoulda-context and shoulda-matchers providing tools for writing tests.

This gem provides a DSL that makes it easy to write reports of various types in ruby. It eliminates the need to litter your source with puts statements, instead providing a more readable, expressive interface to your application.

This library provides a generic OAuth2 strategy for OmniAuth. It doesn't provide a way to gather user information, so should be used as a building block for authentication strategies.

crack provides really simple JSON and XML parsing, extracted from code in Merb and Rails.

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

Spinach is a high-level BDD framework that leverages the expressive Gherkin language to help you define executable specifications of your code.

The Listen gem listens to file modifications and notifies you about the changes.

cliver provides a way to detect missing command-line dependencies, including versions.

Pygmentize provides a simple way to call pygmentize from within a Ruby application.

The Polyglot library allows a Ruby module to register a loader for the file type associated with a filename extension, and it augments require to find and load matching files.

This package can speed up Test::Unit, RSpec, Cucumber, and Spinach tests by running them concurrently across multiple CPU cores.

Minitest-bacon extends minitest with bacon-like functionality, making it easier to migrate test suites from bacon to minitest.