How to file Active Record bug report when you are using unpublished versions of gems. More details at https://gist.github.com/neerajdotname/5187216 .

Gemfile

source 'http://rubygems.org'

gem 'rails', github: 'rails/rails'
gem 'sqlite3'

unpublished_version.rb

require 'bundler'
Bundler.setup(:default)

require 'active_record'
require "minitest/autorun"
require 'minitest/pride'

ActiveRecord::Base.establish_connection(adapter: 'sqlite3', database: ':memory:')

ActiveRecord::Schema.define do
  create_table :posts, force: true do |t|
  end
  create_table :comments, force: true do |t|
    t.integer :post_id
  end
end

class Post < ActiveRecord::Base
  has_many :comments
end

class Comment < ActiveRecord::Base
  belongs_to :post
end

class HasManyBugTest < MiniTest::Unit::TestCase
  def setup
    @post = Post.create!
    @post.comments << Comment.create!
  end

  def test_association_stuff
    assert_equal 1, @post.comments.count
    assert_equal 1, Comment.count
    assert_equal @post.id, Comment.first.post.id
  end

  def teardown
  end
end