protected function assertXPath(\DOMNode $domNode, $xpathExpression)
{
$ownerDocument = $domNode instanceof \DOMDOcument ? $domNode : $domNode->ownerDocument;
$xpath = new \DOMXPath($ownerDocument);
$this->assertTrue($xpath->evaluate("boolean({$xpathExpression})", $domNode), "XPath expression '{$xpathExpression}' resulted in an empty node set.");
}