@Test
void testGetRollUpPermutationsAsPositionsTagCountOne() {

    final Set<List<Integer>> perms = RollUpBitMask.getRollUpPermutationsAsPositions(1);
    assertThat(perms.size()).isEqualTo(2);
    assertThat(perms.contains(Collections.<Integer>emptyList())).isTrue();
    assertThat(perms.contains(Arrays.asList(0))).isTrue();
}