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+---
+category: tool
+tool: ruby ecosystem
+contributors:
+    - ["Jon Smock", "http://github.com/jonsmock"]
+    - ["Rafal Chmiel", "http://github.com/rafalchmiel"]
+
+---
+
+People using Ruby generally have a way to install different Ruby versions,
+manage their packages (or gems), and manage their gem dependencies.
+
+## Ruby Managers
+
+Some platforms have Ruby pre-installed or available as a package. Most rubyists
+do not use these, or if they do, they only use them to bootstrap another Ruby
+installer or implementation. Instead rubyists tend to install a Ruby manager to
+install and switch between many versions of Ruby and their projects' Ruby
+environments.
+
+The following are the popular Ruby environment managers:
+
+* [RVM](https://rvm.io/) - Installs and switches between rubies. RVM also has
+  the concept of gemsets to isolate projects' environments completely.
+* [ruby-build](https://github.com/sstephenson/ruby-build) - Only installs
+  rubies. Use this for finer control over your rubies' installations.
+* [rbenv](https://github.com/sstephenson/rbenv) - Only switches between rubies.
+  Used with ruby-build.  Use this for finer control over how rubies load.
+* [chruby](https://github.com/postmodern/chruby) - Only switches between rubies.
+  Similar in spirit to rbenv. Unopinionated about how rubies are installed.
+
+## Ruby Versions
+
+Ruby was created by Yukihiro "Matz" Matsumoto, who remains somewhat of a
+[BDFL](https://en.wikipedia.org/wiki/Benevolent_Dictator_for_Life), although
+that is changing recently. As a result, the reference implementation of Ruby is
+called MRI (Matz' Reference Implementation), and when you hear a Ruby version,
+it is referring to the release version of MRI.
+
+The three major version of Ruby in use are:
+
+* 2.0.0 - Released in February 2013. Most major libraries and frameworks support
+  2.0.0.
+* 1.9.3 - Released in October 2011. This is the version most rubyists use
+  currently. Also [retired](https://www.ruby-lang.org/en/news/2015/02/23/support-for-ruby-1-9-3-has-ended/)
+* 1.8.7 - Ruby 1.8.7 has been
+  [retired](http://www.ruby-lang.org/en/news/2013/06/30/we-retire-1-8-7/).
+
+The change between 1.8.7 to 1.9.x is a much larger change than 1.9.3 to 2.0.0.
+For instance, the 1.9 series introduced encodings and a bytecode VM.  There
+are projects still on 1.8.7, but they are becoming a small minority, as most of
+the community has moved to at least 1.9.2 or 1.9.3.
+
+## Ruby Implementations
+
+The Ruby ecosystem enjoys many different implementations of Ruby, each with
+unique strengths and states of compatibility. To be clear, the different
+implementations are written in different languages, but *they are all Ruby*.
+Each implementation has special hooks and extra features, but they all run
+normal Ruby files well. For instance, JRuby is written in Java, but you do
+not need to know Java to use it.
+
+Very mature/compatible:
+
+* [MRI](https://github.com/ruby/ruby) - Written in C, this is the reference implementation of Ruby. By
+  definition it is 100% compatible (with itself). All other rubies
+maintain compatibility with MRI (see [RubySpec](#rubyspec) below).
+* [JRuby](http://jruby.org/) - Written in Java and Ruby, this robust implementation is quite fast.
+  Most importantly, JRuby's strength is JVM/Java interop, leveraging existing
+JVM tools, projects, and languages.
+* [Rubinius](http://rubini.us/) - Written primarily in Ruby itself with a C++ bytecode VM. Also
+  mature and fast. Because it is implemented in Ruby itself, it exposes many VM
+features into rubyland.
+
+Medium mature/compatible:
+
+* [Maglev](http://maglev.github.io/) - Built on top of Gemstone, a Smalltalk VM. Smalltalk has some
+  impressive tooling, and this project tries to bring that into Ruby
+development.
+* [RubyMotion](http://www.rubymotion.com/) - Brings Ruby to iOS development.
+
+Less mature/compatible:
+
+* [Topaz](http://topazruby.com/) - Written in RPython (using the PyPy toolchain), Topaz is fairly young
+  and not yet compatible. It shows promise to be a high-performance Ruby
+implementation.
+* [IronRuby](http://ironruby.net/) - Written in C# targeting the .NET platform, work on IronRuby seems
+  to have stopped since Microsoft pulled their support.
+
+Ruby implementations may have their own release version numbers, but they always
+target a specific version of MRI for compatability. Many implementations have
+the ability to enter different modes (for example, 1.8 or 1.9 mode) to specify
+which MRI version to target.
+
+## RubySpec
+
+Most Ruby implementations rely heavily on [RubySpec](http://rubyspec.org/). Ruby
+has no official specification, so the community has written executable specs in
+Ruby to test their implementations' compatibility with MRI.
+
+## RubyGems
+
+[RubyGems](http://rubygems.org/) is a community-run package manager for Ruby.
+RubyGems ships with Ruby, so there is no need to download it separately.
+
+Ruby packages are called "gems," and they can be hosted by the community at
+RubyGems.org. Each gem contains its source code and some metadata, including
+things like version, dependencies, author(s), and license(s).
+
+## Bundler
+
+[Bundler](http://bundler.io/) is a gem dependency resolver. It uses a project's
+Gemfile to find dependencies, and then fetches those dependencies' dependencies
+recursively. It does this until all dependencies are resolved and downloaded, or
+it will stop if a conflict has been found.
+
+Bundler will raise an error if it finds conflicting dependencies. For example,
+if gem A requires version 3 or greater of gem Z, but gem B requires version 2,
+Bundler will notify you of the conflict. This becomes extremely helpful as many
+gems refer to other gems (which refer to other gems), which can form a large
+dependency graph to resolve.
+
+# Testing
+
+Testing is a large part of Ruby culture. Ruby comes with its own Unit-style
+testing framework called minitest (Or TestUnit for Ruby version 1.8.x). There
+are many testing libraries with different goals.
+
+* [TestUnit](http://ruby-doc.org/stdlib-1.8.7/libdoc/test/unit/rdoc/Test/Unit.html) - Ruby 1.8's built-in "Unit-style" testing framework
+* [minitest](http://ruby-doc.org/stdlib-2.0.0/libdoc/minitest/rdoc/MiniTest.html) - Ruby 1.9/2.0's built-in testing framework
+* [RSpec](http://rspec.info/) - A testing framework that focuses on expressivity
+* [Cucumber](http://cukes.info/) - A BDD testing framework that parses Gherkin formatted tests
+
+## Be Nice
+
+The Ruby community takes pride in being an open, diverse, welcoming community.
+Matz himself is extremely friendly, and the generosity of rubyists on the whole
+is amazing.