tdd.rb

class RomanNumeralGenerator
  TABLE = {
    1000 => "M",
    900  => "CM",
    500  => "D",
    400  => "CD",
    100  => "C",
    90   => "XC",
    50   => "L",
    40   => "XL",
    10   => "X",
    9    => "IX",
    5    => "V",
    4    => "IV",
    1    => "I",
  }

  def convert(arabic_numeral)
    roman_numeral = ""

    TABLE.each do |arabic, roman|
      while arabic_numeral >= arabic
        roman_numeral << roman
        arabic_numeral -= arabic
      end
    end

    return roman_numeral
  end

end

require 'test/unit'

class RomanNumeralGeneratorTest < Test::Unit::TestCase

  def setup
    @converter = RomanNumeralGenerator.new
  end

  def test_1999_returns_mcmxcix
    assert_equal "MCMXCIX", @converter.convert(1999)
  end

  def test_twenty_returns_xx
    assert_equal "XX", @converter.convert(20)
  end

  def test_nineteen_returns_xix
    assert_equal "XIX", @converter.convert(19)
  end

  def test_sixteen_returns_xvi
    assert_equal "XVI", @converter.convert(16)
  end

  def test_fifteen_returns_xv
    assert_equal "XV", @converter.convert(15)
  end

  def test_fourteen_returns_xiv
    assert_equal "XIV", @converter.convert(14)
  end

  def test_eleven_returns_xi
    assert_equal "XI", @converter.convert(11)
  end

  def test_ten_returns_x
    assert_equal "X", @converter.convert(10)
  end

  def test_nine_returns_ix
    assert_equal "IX", @converter.convert(9)
  end

  def test_eight_returns_viii
    assert_equal "VIII", @converter.convert(8)
  end

  def test_seven_returns_vii
    assert_equal "VII", @converter.convert(7)
  end

  def test_six_returns_vi
    assert_equal "VI", @converter.convert(6)
  end

  def test_five_returns_v
    assert_equal "V", @converter.convert(5)
  end

  def test_four_returns_iv
    assert_equal "IV", @converter.convert(4)
  end

  def test_three_returns_iii
    assert_equal "III", @converter.convert(3)
  end

  def test_two_returns_ii
    assert_equal "II", @converter.convert(2)
  end

  def test_one_returns_i
    assert_equal "I", @converter.convert(1)
  end

end