inspector.rb

# When an RSpec test like this fails,
# 
#   @my_array.should == [@some_model, @some_model2]
# 
# RSpec will call inspect on each of the objects to "help" you figure out
# what went wrong. Well, inspect will usually dump a TON OF SHIT and make trying
# to figure out why `@my_array` is not made up of `@some_model` and `@some_model2`
# really really painful.
#
# This little module and technique helps get around that. It will redefine `inspect`
# when you include it in any object. 
# 
# You can define a whitelist of methods that inspect will dump, and it will always
# provide `object_id` at a minimum. 
# 
# To use it, drop it in spec/support/inspector.rb and class_eval the models that
# you need override `inspect` on!
#
# Thanks to Jeff at PivotalLabs Boulder for showing me the basic technique.
#
module Inspector
  
  def inspect
    string = "<#{self.class.name}:#{self.object_id} "
    fields = self.class.inspector_fields.map{|field| "#{field}: #{self.send(field)}"}
    string << fields.join(", ")
  end
  
  def self.included source
    $stdout.puts "Overriding inspect on #{source}"
    source.class_eval do
      def self.inspector *fields
        @inspector_fields = *fields
      end
      
      def self.inspector_fields
        @inspector_fields ||= []
      end
    end
  end
end

SomeModel.class_eval do
  include Inspector
  inspector :id, :title
end