bug-report.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 :cars, force: true  do |t|
  end

  create_table :engines, force: true  do |t|
    t.integer :car_id
  end
end

class Car < ActiveRecord::Base
  has_one :engine
end

class Engine < ActiveRecord::Base
  belongs_to :car
end

class BugTest < Minitest::Test
  def test_build_association
    car = Car.create!
    engine = car.create_engine

    assert_equal car.id, engine.car_id

    car.build_engine
    engine.reload

    assert_equal car.id, engine.car_id
  end
end