SettableFuture<String> nested = SettableFuture.create();
    assertTrue(future.setFuture(nested));
    // Later attempts to set the future should return false.
    assertFalse(future.set("x"));
    assertFalse(future.setException(new Exception("bar")));
    assertFalse(future.setFuture(SettableFuture.create()));
    // Check that the future has been set properly.
    assertFalse(future.isDone());

   *   <li>{@link Cancellation} terminal state, {@code cancel} was called.
   *   <li>{@link Failure} terminal state, {@code setException} was called.
   *   <li>{@link DelegatingToFuture} intermediate state, {@code setFuture} was called.
   *   <li>{@link #NULL} terminal state, {@code set(null)} was called.
   *   <li>Any other non-null value, terminal state, {@code set} was called with a non-null
   *       argument.
   * </ul>
   */

              + "Did you mean to return immediateFuture(null)? %s",
          callable);
    }

    @Override
    void setValue(ListenableFuture<V> value) {
      CombinedFuture.this.setFuture(value);
    }

    @Override
    String toPendingString() {
      return callable.toString();
    }
  }

  @WeakOuter

       * even with the above null checks.)
       */
      timeoutFutureRef = null;
      if (delegate.isDone()) {
        timeoutFuture.setFuture(delegate);
      } else {
        try {
          @RetainedLocalRef ScheduledFuture<?> timer = timeoutFuture.timer;
          timeoutFuture.timer = null; // Don't include already elapsed delay in delegate.toString()

    assertThat(futureResult.toString())
        .matches(
            "CombinedFuture@\\w+\\[status=PENDING,"
                + " setFuture=\\[SettableFuture@\\w+\\[status=PENDING]]]");

    // Future complete
    resultOfCombiner.set(createCombinedResult(getDone(futureInteger), getDone(futureBoolean)));

    assertThat(futureResult.toString())
        .matches(
            "CombinedFuture@\\w+\\[status=PENDING,"
                + " setFuture=\\[SettableFuture@\\w+\\[status=PENDING]]]");

    // Future complete
    resultOfCombiner.set(createCombinedResult(getDone(futureInteger), getDone(futureBoolean)));