return powerSet.iterator();
      }
    }.test();
  }

  public void testPowerSetSize() {
    assertPowerSetSize(1);
    assertPowerSetSize(2, 'a');
    assertPowerSetSize(4, 'a', 'b');
    assertPowerSetSize(8, 'a', 'b', 'c');
    assertPowerSetSize(16, 'a', 'b', 'd', 'e');
    assertPowerSetSize(
        1 << 30, 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p',