assertTrue(result.contains("2021") || result.contains("Jan") || result.contains("1609459200000"));
    }

    // Test appendTimestamp method
    public void test_appendTimestamp() {
        StringBuilder buf = new StringBuilder();

        monitorTarget.appendTimestamp(buf);
        String result = buf.toString();
        assertTrue(result.startsWith("\"timestamp\":\""));
        assertTrue(result.endsWith("\""));