// Test string without special characters
        String input = "Simple text without special characters";
        assertEquals(input, XmlUtil.escapeXml(input));
    }

    public void test_stripInvalidXMLCharacters_null() {
        // Test null input
        assertNull(XmlUtil.stripInvalidXMLCharacters(null));
    }

    public void test_stripInvalidXMLCharacters_empty() {
        // Test empty string