@Override
  public <T> UncommittedBundle<T> createRootBundle() {
    return UncommittedImmutableListBundle.create(null, StructuralKey.empty());
  }
@Test
  public void addElementsAtEndOfTimeThrows() {
    Instant timestamp = BoundedWindow.TIMESTAMP_MAX_VALUE;
    WindowedValue<Integer> value = WindowedValue.timestampedValueInGlobalWindow(1, timestamp);

    UncommittedBundle<Integer> bundle = bundleFactory.createRootBundle();
    thrown.expect(IllegalArgumentException.class);
    thrown.expectMessage(timestamp.toString());
    bundle.add(value);
  }