AR bug with association named `record` : https://github.com/rails/rails/issues/12628

ar_association_named_record_bug.rb

unless File.exists?('Gemfile')
  File.write('Gemfile', <<-GEMFILE)
source 'https://rubygems.org'
gem 'rails', github: 'rails/rails'
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 :posts do |t|
  end

  create_table :comments do |t|
    t.integer :record_id
  end
end

class Post < ActiveRecord::Base
  has_many :comments
end

class Comment < ActiveRecord::Base
  belongs_to :record, class_name: 'Post'
end

class BugTest < Minitest::Test
  def test_save_failed
    comment = Comment.new
    assert comment.save
    assert comment.persisted?
  end
end

Fail on line 43 , comment is never persisted