read_yaml_fixture_files

# File activerecord/lib/active_record/fixtures.rb, line 667
      def read_yaml_fixture_files
        yaml_string = (Dir["#{@fixture_path}/**/*.yml"].select { |f|
          File.file?(f)
        } + [yaml_file_path]).map { |file_path| IO.read(file_path) }.join

        if yaml = parse_yaml_string(yaml_string)
          # If the file is an ordered map, extract its children.
          yaml_value =
            if yaml.respond_to?(:type_id) && yaml.respond_to?(:value)
              yaml.value
            else
              [yaml]
            end

          yaml_value.each do |fixture|
            raise Fixture::FormatError, "Bad data for #{@class_name} fixture named #{fixture}" unless fixture.respond_to?(:each)
            fixture.each do |name, data|
              unless data
                raise Fixture::FormatError, "Bad data for #{@class_name} fixture named #{name} (nil)"
              end

              fixtures[name] = ActiveRecord::Fixture.new(data, model_class)
            end
          end
        end
      end