code: public static void assertXpathNotExists(String xPathExpression, 
                                              Document inDocument)
          throws XpathException {
          XpathEngine simpleXpathEngine = XMLUnit.newXpathEngine();
          NodeList nodeList = simpleXpathEngine.getMatchingNodes(
                                                                 xPathExpression, inDocument);
          int matches = nodeList.getLength();
          assertEquals("Should be zero matches for Xpath " + 
                       xPathExpression, 0, matches);
      }
docs: Assert that a specific XPath does NOT exist in some given XML
  @param xPathExpression
  @param inDocument
  @see XpathEngine which provides the underlying evaluation mechanism