Teaching my 10yr old daughter about ROT-13

rot13.rb

class String
  def rot13
    tr 'abcdefghijklmnopqrstuvwxyz', 'nopqrstuvwxyzabcdefghijklm'
  end
end

describe 'String#rot13' do
  let (:message) { "the quick brown fox jumps over the lazy dog" }
  let (:encoded) { "gur dhvpx oebja sbk whzcf bire gur ynml qbt" }

  specify do
    message.rot13.should == encoded
  end

  specify do
    encoded.rot13.should == message
  end
end