A finished solution to the roman numeral kata (http://codingdojo.org/cgi-bin/wiki.pl?KataRomanNumerals) from the 24 April and 1 May 2013 coding dojos at the University of Minnesota, Morris. This works, but it really isn't terribly readable and we'd like to do something to improve that.

RomanNumeralConverter.groovy

class RomanNumeralConverter {

	def mappings = [[[1000 , "M"], [500 , "D"], [100 , "C"]],
		             [[100 , "C"], [50 , "L"], [10 , "X"]],
					 [[10 , "X"], [5 , "V"], [1 , "I"]]]

	def convert(integer) {
		String result = ""
	
		def pair = handleDigit("M","D", "C", 100, result, integer)
		pair = handleDigit("C","L", "X", 10, pair[0], pair[1])
		pair = handleDigit("X","V", "I", 1, pair[0], pair[1])
		result = pair[0]
		integer= pair[1]
		while (integer >= 1){
			result = result + "I"
			integer = integer - 1
		}
		return result
	}
	
	def handleDigit(tensPlace, fivesPlace, onesPlace, number, result, integer) {
		while (integer >= number*10){
			result = result + tensPlace
			integer = integer - number*10
		}
		while (integer >= number*9){
			result = result + onesPlace + tensPlace
			integer = integer - number*9
		}
		while (integer >= number*5){
			result = result + fivesPlace
			integer = integer - number*5
		}
		while (integer >= number*4){
			result = result + onesPlace + fivesPlace
			integer = integer - number*4
		}
		return [result, integer]
	}
}

RomanNumeralTests.groovy

import spock.lang.Specification

class RomanNumeralTests extends Specification {
  	def converter = new RomanNumeralConverter()
		def romanValues = [1:"I", 2:"II", 3:"III", 4:"IV", 5:"V", 8: "VIII", 9:"IX" , 10:"X", 40:"XL", 50:"L", 
			90:"XC", 99:"XCIX", 100:"C", 150:"CL", 500:"D", 800:"DCCC", 999: "CMXCIX", 1000:"M", 1050:"ML",
			1500:"MD", 1750:"MDCCL", 1800:"MDCCC", 2000:"MM", 3000:"MMM"]
		
		def "test the map romanValues"() {
			expect:
			romanValues.each{k,v ->
				assert(converter.convert(k)==v)
			}
		}
		
		
}