use setup block to config which classes to extend

spec/spec_helper.rb

@@ -6,17 +6,15 @@ require 'rspec/autorun'
 
 require 'active_model'
 require 'active_model/validations'
-# require 'active_record'
-# require 'action_controller'
-# require 'action_view'
-# require 'action_mailer'
-# require 'rspec/rails'
-
+require 'active_record'
 require 'timecop'
-require 'model_helpers'
 
 require 'validates_timeliness'
 
+ValidatesTimeliness.setup do |c|
+  c.extend_classes = [ ActiveModel::Validations, ActiveRecord::Base ]
+end
+
 Time.zone = 'Australia/Melbourne'
 
 LOCALE_PATH = File.expand_path(File.dirname(__FILE__) + '/../lib/validates_timeliness/locale/en.yml')
@@ -35,6 +33,8 @@ class Person
   end
 end
 
+require 'model_helpers'
+
 Rspec.configure do |c|
   c.mock_with :rspec
   c.before do