### Question:
StepClock implements Clock { @Override public long wallTime() { return impl.wallTime() / step * step; } StepClock(Clock impl, long step); @Override long wallTime(); @Override long monotonicTime();  }### Answer:
@Test public void wallTime() { ManualClock mc = new ManualClock(); StepClock sc = new StepClock(mc, 10000); mc.setWallTime(5000); Assertions.assertEquals(0L, sc.wallTime()); mc.setWallTime(10000); Assertions.assertEquals(10000L, sc.wallTime()); mc.setWallTime(20212); Assertions.assertEquals(20000L, sc.wallTime()); }