DocumentUtil.encodeUrl(null);
            fail("Should throw NullPointerException");
        } catch (NullPointerException e) {
            // Expected
        }
    }

    public void test_encodeUrl_unicode() {
        assertEquals("%3F", DocumentUtil.encodeUrl("あ"));
        assertEquals("%3F%3F%3F", DocumentUtil.encodeUrl("あいう"));
    }

    public void test_complex_document_structure() {