*/
    assertWithMessage(
            "Can't test the main listenInPoolThread path "
                + "if the input is already a ListenableFuture")
        .that(input)
        .isNotInstanceOf(ListenableFuture.class);
    ListenableFuture<String> listenable = listenInPoolThread(input);
    /*
     * This will occur before the waiting get() in the
     * listenInPoolThread-spawned thread completes:
     */

     */
    assertWithMessage(
            "Can't test the main listenInPoolThread path "
                + "if the input is already a ListenableFuture")
        .that(input)
        .isNotInstanceOf(ListenableFuture.class);
    ListenableFuture<String> listenable = listenInPoolThread(input);
    /*
     * This will occur before the waiting get() in the
     * listenInPoolThread-spawned thread completes:
     */

   * Future} instances to be upgraded to {@code ListenableFuture} after the fact.
   */
  public static <V extends @Nullable Object> ListenableFuture<V> listenInPoolThread(
      Future<V> future) {
    if (future instanceof ListenableFuture) {
      return (ListenableFuture<V>) future;
    }
    return new ListenableFutureAdapter<>(future);
  }

  /**