require 'rubygems'
require 'rspec'

class Fixnum
  ROMANS = { M: 1000, CM: 900, D: 500, CD: 400, C: 100, XC: 90, L: 50, XL: 40, X: 10, IX: 9, V: 5, IV: 4, I: 1 }
  def to_roman
    ROMANS.detect do |roman, arabic|
      diff = self - arabic
      return "#{roman}#{diff.to_roman}" if diff >= 0
    end
  end
end

describe "Roman numerals" do
  it "transforms 1 to I" do
    1.to_roman.should == "I"
  end

  it "transforms 2 to II" do
    2.to_roman.should == "II"
  end

  it "transforms 3 to III" do
    3.to_roman.should == "III"
  end

  it "transforms 4 to IV" do
    4.to_roman.should == "IV"
  end

  it "transforms 5 to V" do
    5.to_roman.should == "V"
  end

  it "transforms 6 to VI" do
    6.to_roman.should == "VI"
  end

  it "transforms 7 to VII" do
    7.to_roman.should == "VII"
  end

  it "transforms 8 to VIII" do
    8.to_roman.should == "VIII"
  end

  it "transforms 9 to IX" do
    9.to_roman.should == "IX"
  end

  it "transforms 10 to X" do
    10.to_roman.should == "X"
  end

  it "transforms 11 to XI" do
    11.to_roman.should == "XI"
  end

  it "transforms 12 to XII" do
    12.to_roman.should == "XII"
  end

  it "transforms 14 to XIV" do
    14.to_roman.should == "XIV"
  end

  it "transforms 15 to XV" do
    15.to_roman.should == "XV"
  end

  it "transforms 19 to XIX" do
    19.to_roman.should == "XIX"
  end

  it "transforms 39 to XXXIX" do
    39.to_roman.should == "XXXIX"
  end

  it "transforms 40 to XL" do
    40.to_roman.should == "XL"
  end

  it "transforms 41 to XLI" do
    41.to_roman.should == "XLI"
  end

  it "transforms 50 to L" do
    50.to_roman.should == "L"
  end

  it "transforms 89 to LXXXIX" do
    89.to_roman.should == "LXXXIX"
  end

  it "transforms 90 to XC" do
    90.to_roman.should == "XC"
  end

  it "transforms 99 to XCIX" do
    99.to_roman.should == "XCIX"
  end

  it "transforms 100 to C" do
    100.to_roman.should == "C"
  end

  it "transforms 399 to CCCXCIX" do
    399.to_roman.should == "CCCXCIX"
  end

  it "transforms 400 to CD" do
    400.to_roman.should == "CD"
  end

  it "transforms 500 to D" do
    500.to_roman.should == "D"
  end

  it "transforms 899 to DCCCXCIX" do
    899.to_roman.should == "DCCCXCIX"
  end

  it "transforms 900 to CM" do
    900.to_roman.should == "CM"
  end

  it "transforms 1000 to M" do
    1000.to_roman.should == "M"
  end
end