/**
* Initializes the spy.
*
* If no function is specified it will use the existing function.
*
* @param string $namespace The namespace for the mock function.
* @param string $name The function name of the mocked function.
* @param callable|null $function The mock function, or null for using the existing function.
*/
public function __construct($namespace, $name, callable $function = null)
{
parent::__construct($namespace, $name, $function ?: $name);
}