A function that allows spying on ruby objects

spycraft.rb

class Watchable
  def do_something(foo, bar)
    puts "Did something with #{foo} and #{bar}"
  end
end

module Spycraft
  def self.spy(instance)
    instance.instance_eval do
      public_methods(false).each do |meth|
        old_method = method(meth)
        define_singleton_method meth do |*args|
          puts "[DEBUG] Called #{meth} with arguments: (#{args.map(&:inspect).join(', ')})"
          old_method.call(*args)
        end
      end
    end
  end
end
watchable = Watchable.new
Spycraft.spy(watchable)
watchable.do_something("FOO", "BAR")