Rails Issue #20867

issue-20867.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 '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 :books, force: true  do |t|
    t.integer :chapters_count
    t.timestamps
  end

  create_table :chapters, force: true  do |t|
    t.integer :book_id
  end
end

class Book < ActiveRecord::Base
  has_many :chapters
end

class Chapter < ActiveRecord::Base
  belongs_to :book, counter_cache: true, touch: true
end

class BugTest < Minitest::Test
  def test_updated_at_changes
    book = Book.create!
    book.chapters << Chapter.create!
    book.chapters << Chapter.create!

    updated_at = book.updated_at

    chapter = book.chapters.last
    chapter.book_id = nil
    chapter.save

    refreshed_updated_at = book.updated_at

    assert updated_at != refreshed_updated_at
  end
end