numeral_kata.rb

require 'rspec'
require 'securerandom'

describe("Roman numeral conversion") do

  def expect_numeral_to_become_number(numeral,number)
    expect(convert_numeral(numeral)).to(eql(number))
  end

  it "should return 1 for I" do
    expect_numeral_to_become_number("I",1)
  end
  it "should return 2 for II" do
    expect_numeral_to_become_number("II",2)
  end
  it "should return 3 for III" do
    expect_numeral_to_become_number("III",3)
  end
  it "should return 4 for IV" do
    expect_numeral_to_become_number("IV",4)
  end
  it "should return 5 for V" do
    expect_numeral_to_become_number("V",5)
  end
  it "should return 6 for VI" do
    expect_numeral_to_become_number("VI",6)
  end
end

NUMERAL_TO_ARABIC = {
  "I"   => 1,
  "IV"  => 4,
  "V"   => 5,
  "VI" => 6
}

# Given a string containing a roman numeral,
# returns the arabic number
#
# @param numeral [String] numeral to turn to arabic
# @return [Numeric]
def convert_numeral(numeral)
  return NUMERAL_TO_ARABIC[numeral]if NUMERAL_TO_ARABIC[numeral]
  array = numeral.split("")
  array.count
end