code: public void elapseTime(long quantum, TimeUnit timeUnit)
      {
          Preconditions.checkArgument(quantum > 0, "Time quantum must be a positive number");
          Preconditions.checkState(!isShutdown, "Trying to elapse time after shutdown");
  
          elapseTime(toNanos(quantum, timeUnit), ticker);
      }
docs: Advance time by the given quantum.
  <p/>
  Scheduled tasks due for execution will be executed in the caller's thread.
  
  @param quantum the amount of time to advance
  @param timeUnit the unit of the quantum amount