bug_test.rb

require 'bundler/inline'

gemfile(true) do
  source 'https://rubygems.org'
  gem 'activerecord', '5.1.0'
  gem 'sqlite3'
  gem 'byebug'
end

require 'active_record'
require 'minitest/autorun'
require 'logger'
require 'byebug'

# 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 :posts, force: true do |t|
    t.string :author
  end
end

class Post < ActiveRecord::Base
  after_commit :set_foo, on: :update

  attr_accessor :foo
  attr_reader :bar

  def _run_commit_callbacks
    super
  ensure
    @foo = nil
  end

  def set_foo
    if foo
      @bar = true
    end
  end
end


class BugTest < Minitest::Test
  def test_association_stuff
    post = Post.create!
    post.foo = true

    post.author = 'John Doe'
    post.touch
    post.save

    assert_equal true, post.bar
  end
end