methods_and_recursion.rb

require 'minitest/spec'
require 'minitest/autorun'

describe Integer do
  describe "#in_words" do
    it "should return four for 4" do
      4.in_words.must_equal "four"
    end

    it "should return twenty seven for 27" do
      27.in_words.must_equal "twenty seven"
    end

    it "should return twenty seven for 102" do
      102.in_words.must_equal "one hundred two"
    end

    it "should return two hundred thirty eight for 238" do
      238.in_words.must_equal "two hundred thirty eight"
    end
  end
end

class Integer
  def in_words
    number_words = [
                    [1000, "thousand"],
                    [100, "one hundred"],
                    [30, "thirty"],
                    [20, "twenty"],
                    [19, "nineteen"],
                    [18, "eighteen"],
                    [17, "seventeen"],
                    [16, "sixteen"],
                    [15, "fifteen"],
                    [14, "fourteen"],
                    [13, "thirteen"],
                    [12, "twelve"],
                    [11, "eleven"],
                    [10, "ten"],
                    [9, "nine"],
                    [8, "eight"],
                    [7, "seven"],
                    [6, "six"],
                    [5, "five"],
                    [4, "four"],
                    [3, "three"],
                    [2, "two"],
                    [1, "one"]
                  ]

    output_word = []
    inbetween_number = self
    number_words.each do |number, word|
      if inbetween_number >= number
        output_word << word
        inbetween_number -= number
      end
    end
    output_word.join(" ")
  end
end