hstore returns nil

test.rb

unless File.exist?('Gemfile')
  File.write('Gemfile', <<-GEMFILE)
    source 'https://rubygems.org'
    gem 'rails', github: 'rails/rails'
    gem 'arel', github: 'rails/arel'
    gem 'pg'
  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: 'postgresql', database: 'testapp_development', host: "localhost", username: 'postgres', password: 'admin')
ActiveRecord::Base.logger = Logger.new(STDOUT)

ActiveRecord::Schema.define do
  enable_extension "hstore"   # connection role must be a superuser
  
  drop_table :posts
  create_table :posts do |t|
    t.hstore :data
  end

  drop_table :comments
  create_table :comments do |t|
    t.integer :post_id
  end
end

class Post < ActiveRecord::Base
  has_many :comments
  store_accessor :data, :title
end

class Comment < ActiveRecord::Base
  belongs_to :post
end

class BugTest < Minitest::Test
  def test_hstore_duplication
    post = Post.new
    post.title = "A Great Post"
    duped = post.dup
    assert_equal post.title, duped.title
  end
end