AR-inherit.rb

# Activate the gem you are reporting the issue against.
gem 'activerecord', '4.2.5'
require 'active_record'
require 'minitest/autorun'
require 'logger'

# Ensure backward compatibility with Minitest 4
Minitest::Test = MiniTest::Unit::TestCase unless defined?(Minitest::Test)

# 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, force: true do |t|
    t.string :email
  end
  create_table :people, force: true do |t|
    t.string :email
  end
end

module M
  def email=(value)
    puts "shot!"
    super
  end
end

class User < ActiveRecord::Base
  include M
end

class Parent < ActiveRecord::Base
  self.abstract_class = true
  include M
end

class Person < Parent
end

class BugTest < Minitest::Test
  def test_first_or_create
    user = User.where(email: 'email@email.com').first_or_create!
    
    assert_equal 'email@email.com', user.email
  end

  def test_first_or_create2
    user = Person.where(email: 'email@email.com').first_or_create!
    
    assert_equal 'email@email.com', user.email
  end
end