    # File lib/action_controller/test_process.rb, line 450
        def xml_http_request(request_method, action, parameters = nil, session = nil, flash = nil)
          @request.env['HTTP_X_REQUESTED_WITH'] = 'XMLHttpRequest'
          @request.env['HTTP_ACCEPT'] =  [Mime::JS, Mime::HTML, Mime::XML, 'text/xml', Mime::ALL].join(', ')
          returning __send__(request_method, action, parameters, session, flash) do
            @request.env.delete 'HTTP_X_REQUESTED_WITH'
            @request.env.delete 'HTTP_ACCEPT'
          end
        end