code: protected void compare(Object expected, Object actual,
                             Node control, Node test, DifferenceListener listener, Difference difference)
          throws DifferenceFoundException {
          compare(expected, actual, control, test, listener, difference,
                  controlTracker, testTracker);
      }
docs: If the expected and actual values are unequal then inform the listener of
  a difference and throw a DifferenceFoundException.
  @param expected
  @param actual
  @param control
  @param test
  @param listener
  @param difference
  @throws DifferenceFoundException