code: protected Document getXPathResultAsDocument(String select,
                                                  Document document)
          throws ConfigurationException, TransformerException, XpathException {
          DOMResult result = new DOMResult();
          performTransform(getCopyTransformation(select), document, result);
          return (Document) result.getNode();
      }
docs: Execute the copy-of transform and return the resulting Document.
  Used for XMLTestCase comparison
  @param select
  @param document
  @throws ConfigurationException
  @throws TransformerException
  @return the Document created by the copy-of transform.