# File lib/fog/aws/requests/auto_scaling/attach_instances.rb, line 39
        def attach_instances(auto_scaling_group_name, options = {})
          unexpected_options = options.keys - ExpectedOptions[:asg_name] - ExpectedOptions[:instance_ids]

          unless unexpected_options.empty?
            raise Fog::AWS::AutoScaling::ValidationError.new("Options #{unexpected_options.join(',')} should not be included in request")
          end

          unless self.data[:auto_scaling_groups].key?(auto_scaling_group_name)
            raise Fog::AWS::AutoScaling::ValidationError.new('AutoScalingGroup name not found - null')
          end

          response = Excon::Response.new
          response.status = 200
          response.body = {
            'ResponseMetadata' => { 'RequestId' => Fog::AWS::Mock.request_id }
          }
          response
        end