@Override
      protected Iterator<Integer> newTargetIterator() {
        return Iterators.cycle(asList(1, 2));
      }
    }.test();
  }

  @GwtIncompatible // slow (~5s)
  public void testConcatNoIteratorsYieldsEmpty() {
    new EmptyIteratorTester() {
      @Override
      protected Iterator<Integer> newTargetIterator() {
        return Iterators.concat();
      }
    }.test();
  }

      @Override
      protected Iterator<Integer> newTargetIterator() {
        return Iterators.cycle(asList(1, 2));
      }
    }.test();
  }

  @GwtIncompatible // slow (~5s)
  public void testConcatNoIteratorsYieldsEmpty() {
    new EmptyIteratorTester() {
      @Override
      protected Iterator<Integer> newTargetIterator() {
        return Iterators.concat();
      }
    }.test();
  }

    final Set<Set<Integer>> powerSet = powerSet(elements);
    new IteratorTester<Set<Integer>>(6, UNMODIFIABLE, expected, KNOWN_ORDER) {
      @Override
      protected Iterator<Set<Integer>> newTargetIterator() {
        return powerSet.iterator();
      }
    }.test();
  }

  public void testPowerSetIteration_iteratorTester_fast() {
    ImmutableSet<Integer> elements = ImmutableSet.of(1, 2);