Example code to reproduce the issue: http://stackoverflow.com/q/14838196/316700

.gitignore

.rvmrc
*.sqlite

.rvmrc.example

rvm use --create ruby-1.9.3-p286@ar_callbacks

active_record_callback.rb

require "active_record"
require "minitest/unit"
require "minitest/autorun"
require "mocha/setup"

ActiveRecord::Base.establish_connection(
  :adapter  => "sqlite3",
  :database => "#{File.dirname(__FILE__)}/db.sqlite"
)

ActiveRecord::Schema.define :version => 0 do
  create_table :users, :force => true do |t|
    t.string :name
  end
end

class User < ActiveRecord::Base
  after_save :execute_after_save

  def execute_after_save
    Kernel.puts "Actual object still not saved" if changed?
  end
end

class ARCallbackTest < MiniTest::Unit::TestCase
  def test_changed_attribute_works_properly_if_called_after_save
    user = User.create!(:name => "Wadus Name")

    user.name = "Other Name"
    assert(user.changed?)

    user.save!
    assert(!user.changed?)
  end

  def test_no_call_puts_in_after_save
    user = User.create!(:name => "Wadus Name")
    user.name = "Other Name"
    Kernel.expects(:puts).never
    user.save!
  end
end

Gemfile

source :rubygems

gem "activerecord"
gem "sqlite3"
gem "mocha"

Gemfile.lock

GEM
  remote: http://rubygems.org/
  specs:
    activemodel (3.2.11)
      activesupport (= 3.2.11)
      builder (~> 3.0.0)
    activerecord (3.2.11)
      activemodel (= 3.2.11)
      activesupport (= 3.2.11)
      arel (~> 3.0.2)
      tzinfo (~> 0.3.29)
    activesupport (3.2.11)
      i18n (~> 0.6)
      multi_json (~> 1.0)
    arel (3.0.2)
    builder (3.0.4)
    i18n (0.6.1)
    metaclass (0.0.1)
    mocha (0.13.2)
      metaclass (~> 0.0.1)
    multi_json (1.5.0)
    sqlite3 (1.3.7)
    tzinfo (0.3.35)

PLATFORMS
  ruby

DEPENDENCIES
  activerecord
  mocha
  sqlite3