has_one_through_problem.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 '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|
  end

  create_table :comments, force: true do |t|
    t.integer :post_id
  end

  create_table :replies, force: true do |t|
    t.integer :comment_id
  end
end

class Post < ActiveRecord::Base
  has_one :comment
  has_one :reply, through: :comment
end

class Comment < ActiveRecord::Base
  belongs_to :post
  has_one :reply
end

class Reply < ActiveRecord::Base
  belongs_to :comment
end

class BugTest < Minitest::Test
  def test_association_stuff
    post = Post.new
    post.comment = Comment.new
    post.comment.reply = Reply.new

    assert_equal post.reply, post.comment.reply
  end
end