Collections2.permutations(Collections.<Integer>singletonList(1)).iterator();
    assertNextPermutation(newArrayList(1), permutations);
    assertNoMorePermutations(permutations);
  }

  public void testPermutationSetTwoElements() {
    Iterator<List<Integer>> permutations = Collections2.permutations(newArrayList(1, 2)).iterator();
    assertNextPermutation(newArrayList(1, 2), permutations);