test_script.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 'active_support/all'
require 'minitest/autorun'

# 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|
    t.string :stuff
  end
end

class Post < ActiveRecord::Base
  serialize :stuff, Hash
  store :stuff, accessors: [:thing]
end

class TestStuff < MiniTest::Test
  def test_stuff
    post = Post.new
    post.send(:write_attribute, :thing, 'things')
    assert_equal({ thing: 'things' }, post.stuff.symbolize_keys)
  end
end