Convert Kanji numerical to roman numerical

kanji_to_number.rb

# Encoding: UTF-8

module KanjiToNumber
  MULTIPLIERS = {'十' => 10, '百' => 100, '千' => 1000, '万' => 10000}
  NUM_FOR_NUM = {'壱' => 1, '一' => 1, '１' => 1,
                 '弐' => 2, '二' => 2, '２' => 2,
                 '参' => 3, '三' => 3, '３' => 3,
                 '四' => 4, '４' => 4,
                 '五' => 5, '５' => 5,
                 '六' => 6, '６' => 6,
                 '七' => 7, '７' => 7,
                 '八' => 8, '８' => 8,
                 '九' => 9, '９' => 9,
                 '零' => 0, '〇' => 0, '０' => 0}

  def self.convert(kanji_number)
    full_number = 0
    current_number = 0

    kanji_number.each_char do |kanji|
      if NUM_FOR_NUM.has_key?(kanji)
        number = NUM_FOR_NUM[kanji]
        current_number = current_number * 10 + number
      elsif MULTIPLIERS.has_key?(kanji)
        if current_number == 0 # Implicit "one" before hundred or thousand for example
          full_number += MULTIPLIERS[kanji]
        else
          full_number += current_number * MULTIPLIERS[kanji]
        end
        current_number = 0
      end
    end
    full_number += current_number
  end
end

require 'minitest/autorun'
class KanjiToNumberTest < MiniTest::Unit::TestCase
  def test_convert
    assert_equal 2012, KanjiToNumber.convert('二千十二')
    assert_equal 2012, KanjiToNumber.convert('二〇一二')
    assert_equal 2012, KanjiToNumber.convert('二〇一二')

    assert_equal 2222, KanjiToNumber.convert('二千二百二十二')
    assert_equal 2022, KanjiToNumber.convert('二千二十二')
    assert_equal 2002, KanjiToNumber.convert('二千二')
    assert_equal 2000, KanjiToNumber.convert('二千')
    assert_equal 1000, KanjiToNumber.convert('千')

    assert_equal 2220, KanjiToNumber.convert('二千二百二十')
    assert_equal 2200, KanjiToNumber.convert('二千二百')
    assert_equal 2002, KanjiToNumber.convert('二千二')

    assert_equal 1222, KanjiToNumber.convert('千二百二十二')
    assert_equal 222, KanjiToNumber.convert('二百二十二')
    assert_equal 122, KanjiToNumber.convert('百二十二')

    assert_equal 321, KanjiToNumber.convert('三二一')
    assert_equal 4321, KanjiToNumber.convert('四三二一')

    assert_equal 10001, KanjiToNumber.convert('万一')
    assert_equal 10001, KanjiToNumber.convert('一万一')
    assert_equal 240001, KanjiToNumber.convert('２４万一')
    assert_equal 11110, KanjiToNumber.convert('万千百十')
  end
end