test case for polymorphic inverse_of

polymorphic_inverse_test.rb

unless File.exist?('Gemfile')
  File.write('Gemfile', <<-GEMFILE)
    source 'https://rubygems.org'
    gem 'rails', github: 'rails/rails'
    gem 'arel', github: 'rails/arel'
    gem 'sqlite3'
  GEMFILE

  system 'bundle'
end

require 'bundler'
Bundler.setup(:default)

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 :users do |t|
  end

  create_table :comments do |t|
    t.integer :commentable_id
    t.string :commentable_type
    t.integer :user_id
  end
end

class User < ActiveRecord::Base
  has_many :comments, as: :commentable #, inverse_of: false # enable this to get test to pass
end

class Comment < ActiveRecord::Base
  belongs_to :commentable, polymorphic: true
  belongs_to :user
end

class BugTest < MiniTest::Unit::TestCase
  def test_polymorphic_inverse_of_with_matching_association_name
    user = User.create!
    commenting_user = User.create!
    comment = user.comments.create!
    comment.user = commenting_user
    comment.save
    assert_equal commenting_user.id, comment.user.id
    assert_equal commenting_user.id, user.comments.first.user_id
    assert_equal commenting_user.id, user.comments.first.user.id # this assertion fails in rails4.1 but passes in rails4.0
  end
end