challenger.rb

require 'net/http'
require 'json'
require 'uri'

uri = URI.parse "http://www.letsrevolutionizetesting.com/challenge.json"

loop do
  response = JSON.parse(Net::HTTP.get_response(uri).body)
  puts response
  break unless response["follow"]
  new_uri = URI.parse response["follow"]
  new_id = URI.decode_www_form(new_uri.query).assoc("id").last
  uri.query = "id=#{new_id}"
end