code: public static void assertXpathExists(String xPathExpression, 
                                           InputSource control)
          throws IOException, SAXException, XpathException {
          Document inDocument = XMLUnit.buildControlDocument(control);
          assertXpathExists(xPathExpression, inDocument);
      }
docs: Assert that a specific XPath exists in some given XML
  @param xPathExpression
  @param control
  @see XpathEngine which provides the underlying evaluation mechanism