Fixtures Load Error

When I run the following file:    require 'active_record/fixtures'   require 'Order'        class LoadOrdersData < ActiveRecord::Migration       def self.up         down           f = Fixtures.new(Orders.connection, # a database connection                           "orders", # table name                            Order, # model class                            File.join(File.dirname(__FILE__), "dev_data/orders"))           f.insert_fixtures     end

    def self.down       Order.delete_all     end   end

I am getting the following error:

LoadError: no such file to load — active_record/fixtures

method require in 003_load_orders_data.rb at line 1 at top level in 003_load_orders_data.rb at line 1

I ran the rake rails:freeze:edge but it gives the same error message. How can I fix this error? TIA.