@Override
  public <T> UncommittedBundle<T> createRootBundle() {
    return underlying.createRootBundle();
  }
@Test
  public void rootBundleSucceeds() {
    UncommittedBundle<byte[]> root = factory.createRootBundle();
    byte[] array = new byte[] {0, 1, 2};
    root.add(WindowedValue.valueInGlobalWindow(array));
    CommittedBundle<byte[]> committed = root.commit(Instant.now());

    assertThat(
        committed.getElements(), containsInAnyOrder(WindowedValue.valueInGlobalWindow(array)));
  }