List<List<Integer>> partitions = partition(source, 2);
    assertEquals(1, partitions.size());
    assertEquals(singletonList(1), partitions.get(0));
  }

  public void testPartition_2_1() {
    List<Integer> source = asList(1, 2);
    List<List<Integer>> partitions = partition(source, 1);
    assertEquals(2, partitions.size());
    assertEquals(singletonList(1), partitions.get(0));