clone_master.rb

begin
  require 'bundler/inline'
rescue LoadError => e
  $stderr.puts 'Bundler version 1.10 or later is required. Please update your Bundler'
  raise e
end

gemfile(true) do
  source 'https://rubygems.org'
  gem 'rails', github: 'rails/rails'
  gem 'arel', github: 'rails/arel'
  gem 'rack', github: 'rack/rack'
  gem 'sprockets', github: 'rails/sprockets'
  gem 'sprockets-rails', github: 'rails/sprockets-rails'
  gem 'sass-rails', github: 'rails/sass-rails'
  gem 'sqlite3'
end

require 'active_record'
require 'minitest/autorun'
require 'logger'

# This connection will do for database-independent bug reports.
ActiveRecord::Base.establish_connection(adapter: 'sqlite3', database: ':memory:')
ActiveRecord::Base.logger = Logger.new(STDOUT)

ActiveRecord::Schema.define do
  create_table :posts, force: true  do |t|
    t.string :name
  end
end

class Post < ActiveRecord::Base
end

class BugTest < Minitest::Test
  def test_cloning
    post = Post.create! :name => 'original'
    clone = post.dup

    assert_equal 'original', post.name
    assert_equal 'original', clone.name
    assert_equal({}, post.changed_attributes)

    clone.name = 'changed'
    assert_equal({}, post.changed_attributes)
    assert_equal({'name' => nil}, clone.changed_attributes)
  end
end