Supplier<Object> supplier = () -> longString;

        monitorTarget.append(buf, "longKey", supplier);
        assertTrue(buf.toString().startsWith("\"longKey\":\""));
        assertTrue(buf.toString().contains("aaaaaaaaaa"));
        assertEquals(10000 + "\"longKey\":\"\"".length(), buf.toString().length());
    }

    // Test append with Unicode characters
    @Test
    public void test_append_unicodeCharacters() {