* to their desired timezone:
 * <pre>{@code
 * Instant now = MonotonicClock.now();
 * ZonedDateTime local = now.atZone(ZoneId.systemDefault());
 * }</pre>
 *
 * @see System#nanoTime()
 * @see Clock
 */
public class MonotonicClock extends Clock {
    private static final MonotonicClock CLOCK = new MonotonicClock();

    private final long startNanos;
    private final Instant startInstant;

    /**

    @Test
    @DisplayName("MonotonicClock singleton instance should always return the same instance")
    void testSingletonInstance() {
        MonotonicClock clock1 = MonotonicClock.get();
        MonotonicClock clock2 = MonotonicClock.get();

        assertSame(clock1, clock2, "Multiple calls to get() should return the same instance");
    }

    @Test
    @DisplayName("MonotonicClock should always use UTC timezone")

        }
    }

    /**
     * Returns new builder from scratch.
     */
    static Builder newBuilder() {
        return new Builder().withStartTime(MonotonicClock.now());
    }

    class Builder {
        private Map<String, String> userProperties;
        private Map<String, String> systemProperties;
        private Instant startTime;