// a bigger one
    checkHashCode(
        cartesianProduct(set(1, num, num + 1), set(2), set(3, num + 2), set(4, 5, 6, 7, 8)));
  }

  public void testPowerSetEmpty() {
    ImmutableSet<Integer> elements = ImmutableSet.of();
    Set<Set<Integer>> powerSet = powerSet(elements);
    assertEquals(1, powerSet.size());
    assertEquals(ImmutableSet.of(ImmutableSet.of()), powerSet);