@Override
    public void ignorableWhitespace(char[] ch, int start, int length) throws SAXException {
        filter(ch, start, length, ignorableWhitespaceOutput);
    }
@Test
    public void testInvalidSurrogates() throws SAXException {
        safe.ignorableWhitespace("\udb00\ubfff".toCharArray(), 0, 2);
        assertEquals("\ufffd\ubfff", output.toString());
    }