@Override
  public ScheduledFuture<?> scheduleAtFixedRate(Runnable command, long initialDelay, long period, TimeUnit unit) {
    return delegate.scheduleAtFixedRate(command, initialDelay, period, unit);
  }
@Test
  public void scheduleAtFixedRate() {
    underTest.scheduleAtFixedRate(runnable, initialDelay, period, SECONDS);
    verify(executorService).scheduleAtFixedRate(runnable, initialDelay, period, SECONDS);
  }