Ensure that system.methodSignature returns an array of signatures.
protected function testMethodSignature() {
$url = url('xmlrpc.php', array(
'absolute' => TRUE,
));
$signature = xmlrpc($url, array(
'system.methodSignature' => array(
'system.listMethods',
),
));
$this
->assert(is_array($signature) && !empty($signature) && is_array($signature[0]), 'system.methodSignature returns an array of signature arrays.');
}