# File lib/fog/aws/requests/elb/register_instances_with_load_balancer.rb, line 36
        def register_instances_with_load_balancer(instance_ids, lb_name)
          raise Fog::AWS::ELB::NotFound unless load_balancer = self.data[:load_balancers][lb_name]
          instance_ids = [*instance_ids]
          instances = instance_ids.map do |instance|
            raise Fog::AWS::ELB::InvalidInstance unless Fog::Compute::AWS::Mock.data[@region][@aws_access_key_id][:instances][instance]
            {'InstanceId' => instance}
          end

          response = Excon::Response.new
          response.status = 200

          load_balancer['Instances'] = load_balancer['Instances'] | instances.dup

          response.body = {
            'ResponseMetadata' => {
              'RequestId' => Fog::AWS::Mock.request_id
            },
            'RegisterInstancesWithLoadBalancerResult' => {
              'Instances' => instances
            }
          }

          response
        end