@Override
    public void ignorableWhitespace(char[] ch, int start, int length) throws SAXException {
        filter(ch, start, length, ignorableWhitespaceOutput);
    }
@Test
    public void testInvalidWhitespace() throws SAXException {
        safe.ignorableWhitespace("ab\u0000".toCharArray(), 0, 3);
        safe.ignorableWhitespace("a\u0001c".toCharArray(), 0, 3);
        safe.ignorableWhitespace("\u0002bc".toCharArray(), 0, 3);
        assertEquals("ab\ufffda\ufffdc\ufffdbc", output.toString());
    }