@Override public long currentTimeMicroseconds() {
    return ((platform.nanoTime() - baseTickNanos) / 1000) + baseEpochMicros;
  }
@Test void relativeTimestamp_incrementsAccordingToNanoTick() {
    TickClock clock = new TickClock(platform, 1000L /* 1ms */, 0L /* 0ns */);

    when(platform.nanoTime()).thenReturn(1000L); // 1 microsecond = 1000 nanoseconds

    assertThat(clock.currentTimeMicroseconds()).isEqualTo(1001L); // 1ms + 1us
  }