StringBuilder buf = new StringBuilder();
        Supplier<Object> supplier = () -> "テスト 测试 테스트 🎉";

        monitorTarget.append(buf, "unicodeKey", supplier);
        // Unicode characters are escaped in JSON format
        assertEquals("\"unicodeKey\":\"\\u30C6\\u30B9\\u30C8 \\u6D4B\\u8BD5 \\uD14C\\uC2A4\\uD2B8 \\uD83C\\uDF89\"", buf.toString());
    }

    // Test append returns the same buffer instance