@Test
public void sendPhysicalTime() {

  // a clock that always moves forward
  final long[] epoch = {System.currentTimeMillis() * 1000L};
  final DefaultVersionService.Clock clock = () -> epoch[0]++;
  DefaultVersionService v = new DefaultVersionService(clock);
  final DefaultVersionService.HybridLogicalTimestamp send = v.nextVersion();
  final DefaultVersionService.HybridLogicalTimestamp send1 = v.nextVersion();
  // when the physical clock makes progress, the logical time increases and the counters don't
  assertTrue(send.logicalTime() < send1.logicalTime());
  assertEquals(send.counter(), send1.counter());
  assertEquals(send.counter(), send1.counter());
}