assertFalse(i.hasNext());
    assertThrows(NoSuchElementException.class, () -> i.next());
  }

  @GwtIncompatible // too slow for GWT
  public void testPowerSetIteration_iteratorTester() {
    ImmutableSet<Integer> elements = ImmutableSet.of(1, 2);

    Set<Set<Integer>> expected = new LinkedHashSet<>();
    expected.add(ImmutableSet.<Integer>of());
    expected.add(ImmutableSet.of(1));