Hack to disable transactional fixtures on a per-test basis in rails 3.2

transactional_fixture_disabler.rb

module TransactionalFixtureDisabler

  def self.included(klass)
    klass.teardown :restore_transactional_fixture_status
  end

  # call this at the top of your test if you need to disable
  # transactional fixtures. this might be the case if:
  #   - you're testing after_commit or after_rollback callbacks
  #     on models
  #   - you're using more than one db connection some case
  #     (e.g. pushing some slow SELECTS to replicated db)
  #
  # the module takes care of all the cleanup and restores
  # transactional fixtures to the default. note that if you
  # want to speed things up a bit, you can specify the
  # particular tables or activerecord models that should have
  # their data deleted after your test has executed.
  #
  # NOTE: this will rollback any changes you make in a setup method
  #       (unless you call this method within your setup method)
  #       (it does an early rollback to remove the wrapper transaction)
  #
  # things_to_delete is an optional hash:
  #   :models_to_delete => array of classes to delete data for
  #   :tables_to_delete => array of table names to delete data for
  # optional. default => hand-crafted list of a lot of tables
  #
  # usage examples:
  #
  # class MyTest < ActiveSupport::TestCase
  #   test "my class does something important to every table" do
  #     disable_transactional_fixtures
  #     # run tests that require fixtures off...
  #   end
  #
  #   test "my test that touches only two tables, one activerecord, one not" do
  #     disable_transactional_fixtures :models_to_delete => [MyModel],
  #                                    :tables_to_delete => ['another_table_name']
  #     # run tests that require fixtures off
  #   end
  # end
  #-----------------------------------------------------------------------------
  def disable_transactional_fixtures(things_to_delete = {})
    if @_transactional_fixture_disabler_activated
      raise "transactional fixtures already disabled for this test!"
    end

    @_transactional_fixture_disabler_activated = true
    teardown_fixtures # activerecord gem: lib/active_record/fixtures.rb
    @_original_transactional_fixture_status = self.class.use_transactional_fixtures
    self.class.use_transactional_fixtures = false
    @_things_to_delete = things_to_delete
  end

  def restore_transactional_fixture_status
    if @_transactional_fixture_disabler_activated
      if @_original_transactional_fixture_status
        delete_everything @_things_to_delete

        # when we've finally gotten rid of all fixtures, can probably get
        # rid of this
        setup_fixtures
      end
      self.class.use_transactional_fixtures = @_original_transactional_fixture_status
      @_transactional_fixture_disabler_activated = false
    end
  end

end

NOTE: you'll have to provide your own delete_everything method...ours goes through the list of models and table names and truncates the corresponding tables, by default doing all of them.