nusoap simple server

The web browser is not calling the Web service - you could create a PHP client :

// Pull in the NuSOAP code
require_once('lib/nusoap.php');
// Create the client instance
$client = new soapclient('your server url');
// Call the SOAP method
$result = $client->call('hello', array('name' => 'StackOverFlow'));
// Display the result
print_r($result);

This should display Hello, StackOverFlow

Update

To create a WSDL you need to add the following :

$server->configureWSDL(<webservicename>, <namespace>);

Please change your code to,

<?php
//call library
require_once('nusoap.php');
$URL       = "www.test.com";
$namespace = $URL . '?wsdl';
//using soap_server to create server object
$server    = new soap_server;
$server->configureWSDL('hellotesting', $namespace);

//register a function that works on server
$server->register('hello');

// create the function
function hello($name)
{
    if (!$name) {
        return new soap_fault('Client', '', 'Put your name!');
    }
    $result = "Hello, " . $name;
    return $result;
}
// create HTTP listener
$server->service($HTTP_RAW_POST_DATA);
exit();
?>

You didnt Define namespace..

Please see simple example here :-

http://patelmilap.wordpress.com/2011/09/01/soap-simple-object-access-protocol/

You can also use nusoap_client

<?php
// Pull in the NuSOAP code
require_once('lib/nusoap.php');
// Create the client instance
$client = new nusoap_client('your server url'); // using nosoap_client
// Call the SOAP method
$result = $client->call('hello', array('name' => 'Pingu'));
// Display the result
print_r($result)
?>