    # File lib/fog/aws/requests/iam/add_user_to_group.rb, line 35
            def add_user_to_group(group_name, user_name)
              if data[:groups].has_key? group_name
                if data[:users].has_key? user_name

                  unless data[:groups][group_name][:members].include?(user_name)
                    data[:groups][group_name][:members] << user_name
                  end

                  Excon::Response.new.tap do |response|
                    response.status = 200
                    response.body = { 'RequestId' => Fog::AWS::Mock.request_id }
                  end
                else
                  raise Fog::AWS::IAM::NotFound.new("The user with name #{user_name} cannot be found.")
                end
              else
                raise Fog::AWS::IAM::NotFound.new("The group with name #{group_name} cannot be found.")
              end
            end