* ability to throw the correct exception in the future.
     */
    assertThrows(NoSuchElementException.class, empty::peek);
    assertThrows(NoSuchElementException.class, empty::peek);
  }

  public void testSneakyThrow() throws Exception {
    Iterator<Integer> iter =
        new AbstractIterator<Integer>() {
          boolean haveBeenCalled;

          @Override
          public Integer computeNext() {