Mocking a Drupal 7 core function with namespaces

moduleName.test.php

<?php
namespace Same\As\Class\Testing 
{

  function drupal_valid_token($token = NULL) 
  {
    return ($token == "expected value);
  }
  
  class moduleNameTestSuite extendsDrupalWebTestCase 
  {
    //static public function getInfo() ...
  
    public function setUp() 
    {
      parent::setUp(array('moduleName'));
    }
  
    public function testValidate() 
    {
      $testData = array(/*...*/);
      $object = new moduleNameClass($testData);
      $this->assertEqual($object->key, $testData['key'];
    }
  }
}

namespace 
{
  moduleNameGlobalTest extends \Same\As\Class\Testing\moduleNameTestSuite 
  {
  }
}