How to use the Rubygems version requirement verification checking system.

versions_spec.rb

require 'rspec'

module SatisfyMatcher
  class Matcher
    def initialize(requirements)
      @requirements = requirements
    end

    def matches?(version)
      @version = version

      Gem::Requirement.new(@requirements) =~ Gem::Version.new(@version)
    end

    def description
      "satisfy a #{@requirements.inspect} requirement"
    end

    def failure_message
      "#{@version} satisfied a #{@requirements.inspect} requirement"
    end

    def negative_failure_message
      "#{@version} unexpectedly satisfied a #{@requirements.inspect} requirement"
    end
  end

  def satisfy(version)
    Matcher.new(version)
  end
end

RSpec.configure do |config|
  config.include(SatisfyMatcher)
end

describe "Gem version checking" do
  context "a \"1.3.5\" gem" do
    subject { '1.3.5' }

    it { should satisfy('=1.3.5') }
    it { should satisfy('>=1.3') }
    it { should satisfy('>=1.3.5') }
    it { should satisfy('~>1.3.5') }
    it { should satisfy(%w[>1.0 <3.1]) }
    it { should_not satisfy('<1.3.5') }
  end
end