assertClosed(closeable1, closeable2);
  }

  public void testTransformAsync() throws Exception {
    ClosingFuture<String> closingFuture =
        ClosingFuture.from(immediateFuture("value"))
            .transformAsync(
                new AsyncClosingFunction<String, TestCloseable>() {
                  @Override
                  public ClosingFuture<TestCloseable> apply(DeferredCloser closer, String v)

   * Example usage:
   *
   * {@snippet :
   * ListenableFuture<RowKey> rowKeyFuture = indexService.lookUp(query);
   * ListenableFuture<QueryResult> queryFuture =
   *     transformAsync(rowKeyFuture, dataService::readFuture, executor);
   * }
   *
   * <p>When selecting an executor, note that {@code directExecutor} is dangerous in some cases. See