code: public static void setControlParser(String className) {
          System.setProperty("javax.xml.parsers.DocumentBuilderFactory", className);
          controlBuilderFactory = null;
          controlBuilderFactory = getControlDocumentBuilderFactory();
      }
docs: Overide the DocumentBuilder to use to parse control documents.
  This is useful when comparing the output of two different
  parsers. Note: setting the control parser before any test cases
  are run will affect the test parser as well.