roman_numerals_spec.rb

class RomanNumerals
  def self.to_roman(num)
    ('I' * num)
      .gsub('IIIII', 'V')
      .gsub('IIII', 'IV')
      .gsub('VV', 'X')
      .gsub('VIV', 'IX')
      .gsub('XXXXX', 'L')
      .gsub('XXXX', 'XL')
      .gsub('LL', 'C')
      .gsub('LXL', 'XC')
      .gsub('CCCCC', 'D')
      .gsub('CCCC', 'CD')
      .gsub('DD', 'M')
      .gsub('DCD', 'CM')
  end
end

describe RomanNumerals do
  def expect_roman_numerals_to_be(expected_roman_numerals, input)
    expect(RomanNumerals.to_roman(input)).to eq(expected_roman_numerals)
  end

  it 'can romanise numbers' do
    expect_roman_numerals_to_be('I', 1)
    expect_roman_numerals_to_be('II', 2)
    expect_roman_numerals_to_be('III', 3)
    expect_roman_numerals_to_be('IV', 4)
    expect_roman_numerals_to_be('V', 5)
    expect_roman_numerals_to_be('VI', 6)
    expect_roman_numerals_to_be('IX', 9)
    expect_roman_numerals_to_be('X', 10)
    expect_roman_numerals_to_be('XI', 11)
    expect_roman_numerals_to_be('XIV', 14)
    expect_roman_numerals_to_be('XL', 40)
    expect_roman_numerals_to_be('L', 50)
    expect_roman_numerals_to_be('XLIV', 44)
    expect_roman_numerals_to_be('XLVI', 46)
    expect_roman_numerals_to_be('LI', 51)
    expect_roman_numerals_to_be('XC', 90)
    expect_roman_numerals_to_be('C', 100)
    expect_roman_numerals_to_be('XCVI', 96)
    expect_roman_numerals_to_be('MMMCMXCIX', 3999)
    expect_roman_numerals_to_be('D', 500)
    expect_roman_numerals_to_be('CD', 400)
    expect_roman_numerals_to_be('CM', 900)
    expect_roman_numerals_to_be('M', 1000)

  end
end