code: public static void assertXpathEvaluatesTo(String expectedValue,
                                                String xpathExpression,
                                                InputSource control)
          throws SAXException, IOException,
                 XpathException {
          Document document = XMLUnit.buildControlDocument(control);
          assertXpathEvaluatesTo(expectedValue, xpathExpression, document);
      }
docs: Assert the value of an Xpath expression in an XML document.
  @param expectedValue
  @param xpathExpression
  @param control
  @throws SAXException
  @throws IOException
  @see XpathEngine which provides the underlying evaluation mechanism