TF.newTuple(ImmutableList.of("a", "b", "NULL")),
TF.newTuple(ImmutableList.of("a", "NULL", "NULL")),
TF.newTuple(ImmutableList.of("NULL", "NULL", "NULL"))
);
RollupDimensions rd = new RollupDimensions("NULL");
DataBag bag = rd.exec(t);
assertEquals(bag.size(), expected.size());
for (Tuple tup : bag) {
assertTrue(expected.contains(tup));
}