buf.append(",");
        monitorTarget.append(buf, "key3", () -> null);

        assertEquals("\"key1\":\"value1\",\"key2\":123,\"key3\":null", buf.toString());
    }

    // Test append with empty string
    @Test
    public void test_append_emptyString() {
        StringBuilder buf = new StringBuilder();
        Supplier<Object> supplier = () -> "";

     */
    static class MonitorTarget implements TimeoutTarget {

        /** The job log being monitored */
        private final JobLog jobLog;

        /**
         * Constructor for MonitorTarget.
         *
         * @param jobLog the job log to monitor
         */
        public MonitorTarget(final JobLog jobLog) {
            this.jobLog = jobLog;
        }