roman_numerals_spec.rb

require 'fixnum'

describe Fixnum, 'when converting to Roman numerals' do
  context "up to 5" do
    it "represents units with I" do
      1.to_roman_numerals.should == 'I'
      2.to_roman_numerals.should == 'II'
      3.to_roman_numerals.should == 'III'
    end

    it 'represents 4 with IV' do
      4.to_roman_numerals.should == 'IV'
    end
  end

  context "at 5" do
    it "is represented by V" do
      5.to_roman_numerals.should == 'V'
    end
  end

  context "beyond 5" do
    it "appends extra units to the end" do
      6.to_roman_numerals.should == 'VI'
      7.to_roman_numerals.should == 'VII'
      8.to_roman_numerals.should == 'VIII'
    end

    it "represents 9 with IX" do
      9.to_roman_numerals.should == 'IX'
    end
  end

  context "10" do
    it "is represented by X" do
      10.to_roman_numerals.should == 'X'
    end
  end

  context "beyond 10" do
    it "appends fives and units to the end" do
      11.to_roman_numerals.should == 'XI'
      14.to_roman_numerals.should == 'XIV'
      15.to_roman_numerals.should == 'XV'
      16.to_roman_numerals.should == 'XVI'
    end

    it "represents 19 with IXX" do
      19.to_roman_numerals.should == 'IXX'
    end
  end

  context "beyond 20" do
    it "represented by multiples of X, appending fives and units to the end" do
      21.to_roman_numerals.should == 'XXI'
      25.to_roman_numerals.should == 'XXV'
    end
  end
end