sample.rb

class Version
  include Comparable

  attr_reader :major, :minor, :patch
  def initialize(version)
    @major, @minor, @patch =
      version.split('.').map(&:to_i)
  end

  def <=>(other)
    return nil unless other.is_a?(Version)

    [major <=> other.major,
     minor <=> other.minor,
     patch <=> other.patch,
    ].detect {|n| !n.zero?} || 0
  end
end

require 'minitest/autorun'

describe(Version) do
  describe("when parsing") do
    before do
      @version = Version.new('10.8.9')
    end
    it("creates three integers") do
      @version.major.must_equal(10)
      @version.minor.must_equal(8)
      @version.patch.must_equal(9)
    end
  end

  describe("when comparing") do
    before do
      @v1 = Version.new("2.1.1")
      @v2 = Version.new("2.3.0")
    end

    it("orders correctly") do
      @v1.wont_equal(@v2)
      @v1.must_be(:<, @v2)
    end
  end
end