assertEquals("\"unicodeKey\":\"\\u30C6\\u30B9\\u30C8 \\u6D4B\\u8BD5 \\uD14C\\uC2A4\\uD2B8 \\uD83C\\uDF89\"", buf.toString());
    }

    // Test append returns the same buffer instance
    public void test_append_returnsSameBuffer() {
        StringBuilder buf = new StringBuilder();
        Supplier<Object> supplier = () -> "test";

        StringBuilder result = monitorTarget.append(buf, "key", supplier);