CanCanCan Issue

cancan_bug.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' # use correct rails version
  gem 'cancancan', '3.2.0' # use correct cancancan version
  gem 'sqlite3' # use another DB if necessary
  gem 'byebug'
end

require 'active_record'
require 'cancancan'
require 'cancan/model_adapters/active_record_adapter'
require 'cancan/model_adapters/active_record_4_adapter'
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)

# create your tables here
ActiveRecord::Schema.define do
  create_table :parents, force: true  do |t|
  end

  create_table :children, force: true  do |t|
  end

  create_table :users, force: true do |t|
  end
end

class Parent < ActiveRecord::Base
end

class Child < Parent
end

class User < ActiveRecord::Base
end

class Ability
  include CanCan::Ability

  def initialize(user)
    can :manage, Parent
    cannot :manage, Child
  end
end

class BugTest < Minitest::Test
  def test_bug
    user = User.create!
    ability = Ability.new(user)
    assert_equal ability.can?(:index, Child), false
    assert_equal ability.can?(:index, Parent), true
  end
end