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MSpec is a specialized framework that is syntax-compatible with RSpec 2 for basic things like describe, it blocks and before, after actions. MSpec contains additional features that assist in writing specs for Ruby implementations in ruby/spec.

MSpec attempts to use the simplest Ruby language features so that beginning Ruby implementations can run the Ruby specs. For example, no file from the standard library or RubyGems is necessary to run MSpec.

MSpec is not intended as a replacement for RSpec. MSpec attempts to provide a subset of RSpec's features in some cases and a superset in others. It does not provide all the matchers, for instance.

However, MSpec provides several extensions to facilitate writing the Ruby specs in a manner compatible with multiple Ruby implementations.

  1. MSpec offers a set of guards to control execution of the specs. These guards not only enable or disable execution but also annotate the specs with additional information about why they are run or not run.

  2. MSpec provides a different shared spec implementation specifically designed to ease writing specs for the numerous aliased methods in Ruby.

  3. MSpec provides various helper methods to simplify some specs, for example, creating temporary file names.

  4. MSpec has several specialized runner scripts that includes a configuration facility with a default project file and user-specific overrides.

  5. MSpec support "tagging", that is excluding specs known as failing on a particular Ruby implementation, and automatically adding and removing tags while running the specs.


MSpec requires Ruby 2.6 or more recent.


A Gemfile is provided. Use Bundler to install gem dependencies. To install Bundler, run the following:

gem install bundler

To install the gem dependencies with Bundler, run the following:

ruby -S bundle install


Use RSpec to run the MSpec specs. There are no plans currently to make the MSpec specs runnable by MSpec: #19.

After installing the gem dependencies, the specs can be run as follows:

ruby -S bundle exec rspec

To run an individual spec file, use the following example:

ruby -S bundle exec rspec spec/helpers/ruby_exe_spec.rb


See in ruby/spec for a list of matchers and how to use mspec.

Source Code



See the LICENSE in the source code.