create_fixtures

# File activerecord/lib/active_record/fixtures.rb, line 591
      def create_fixtures(fixtures_directories, fixture_set_names, class_names = {}, config = ActiveRecord::Base, &block)
        fixture_set_names = Array(fixture_set_names).map(&:to_s)
        class_names.stringify_keys!

        # FIXME: Apparently JK uses this.
        connection = block_given? ? block : lambda { ActiveRecord::Base.connection }

        fixture_files_to_read = fixture_set_names.reject do |fs_name|
          fixture_is_cached?(connection.call, fs_name)
        end

        if fixture_files_to_read.any?
          fixtures_map = read_and_insert(
            Array(fixtures_directories),
            fixture_files_to_read,
            class_names,
            connection,
          )
          cache_fixtures(connection.call, fixtures_map)
        end
        cached_fixtures(connection.call, fixture_set_names)
      end