## app/models/comment.rb
class Comment < ActiveRecord::Base

  def validate
    puts "CNK validating optional attributes"
    ["name", "email", "affiliation"].each do |attr_name|
      if send(attr_name+'_required') and self.send(attr_name).blank?
        errors.add(attr_name, "is required.")
      end
    end
  end

  def method_missing_with_setting_delegation(method, *args)
    puts "CNK looking for method "+method.to_s
    if method.to_s =~ /_required$/
      puts "CNK in method missing about to send to setting"
      # attempt to delegate to setting
      CommentSetting.instance.send(method, *args)
    else
      puts "CNK in method missing using the old one"
      # use old method_missing
      method_missing_without_setting_delegation method, *args
    end
  end

  alias_method_chain :method_missing, :setting_delegation

end

## This code works fine from the browser. If CommentSetting.instance.email_required is 'true', then comment must have an email address in email field.

## So for a test, created a factory method that gets included by test_helper.rb
module Factory
   def self.create_comment(attributes = {})
    default_attributes = {
      :name => 'Someone',
      :email => 'me@example.com',
      :affiliation => 'Undergrad',
      :creation_ip => '131.215.130.46',
      :anonymous => false,
      :body => 'Some basic comment.'
    }
    Comment.create(default_attributes.merge(attributes))
  end

end

##
require File.dirname(__FILE__) + '/../test_helper'

class CommentTest < ActiveSupport::TestCase
  def test_factory
    comment = Factory.create_comment
    # assert_not_valid comment
    puts comment.valid?
    puts comment.errors.inspect
  end

end

$ ruby test/unit/comment_test.rb
Loaded suite test/unit/comment_test
Started
CNK looking for method name=
CNK in method missing using the old one
false
#<ActiveRecord::Errors:0x9d26668 @base=#<Comment id: nil, name: "Someone", email: "me@example.com", affiliation: "Under\
grad", creation_ip: "131.215.130.46", anonymous: false, body: "Some basic comment.", approved: false, approved_by: nil,\
 approved_at: nil, updated_by: nil, created_at: nil, updated_at: nil>, @errors={}>
.
Finished in 0.431101 seconds.

1 tests, 0 assertions, 0 failures, 0 errors