@SuppressWarnings("unused") // https://errorprone.info/bugpattern/FutureReturnValueIgnored
    Future<?> possiblyIgnoredError =
        testExecutor.scheduleWithFixedDelay(DO_NOTHING, 100, 10, MINUTES);
    mock.assertLastMethodCalled("scheduleWithFixedDelay", 100, 10, MINUTES);

    @SuppressWarnings("unused") // https://errorprone.info/bugpattern/FutureReturnValueIgnored

    return delegate.scheduleAtFixedRate(wrapTask(command), initialDelay, period, unit);
  }

  @Override
  public final ScheduledFuture<?> scheduleWithFixedDelay(
      Runnable command, long initialDelay, long delay, TimeUnit unit) {
    return delegate.scheduleWithFixedDelay(wrapTask(command), initialDelay, delay, unit);
  }

   * submitted tasks and to collections of tasks submitted via {@code invokeAll}, {@code invokeAny},
   * {@code schedule}, {@code scheduleAtFixedRate}, and {@code scheduleWithFixedDelay}. In the case
   * of tasks submitted by {@code invokeAll} or {@code invokeAny}, tasks will run serially on the
   * calling thread. Tasks are run to completion before a {@code Future} is returned to the caller

    return delegate.scheduleAtFixedRate(wrapTask(command), initialDelay, period, unit);
  }

  @Override
  public final ScheduledFuture<?> scheduleWithFixedDelay(
      Runnable command, long initialDelay, long delay, TimeUnit unit) {
    return delegate.scheduleWithFixedDelay(wrapTask(command), initialDelay, delay, unit);
  }

    throw new UnsupportedOperationException("scheduleAtFixedRate is not supported.");
  }

  @Override
  public ListenableScheduledFuture<?> scheduleWithFixedDelay(
      Runnable command, long initialDelay, long delay, TimeUnit unit) {
    throw new UnsupportedOperationException("scheduleWithFixedDelay is not supported.");
  }

    throw new UnsupportedOperationException("scheduleAtFixedRate is not supported.");
  }

  @Override
  public ListenableScheduledFuture<?> scheduleWithFixedDelay(
      Runnable command, long initialDelay, long delay, TimeUnit unit) {
    throw new UnsupportedOperationException("scheduleWithFixedDelay is not supported.");
  }

      Runnable command, long initialDelay, long period, TimeUnit unit);

  /**
   * @since 15.0 (previously returned ScheduledFuture)
   */
  @Override
  ListenableScheduledFuture<?> scheduleWithFixedDelay(
      Runnable command, long initialDelay, long delay, TimeUnit unit);