@Override
    public Map<Uuid, Set<Integer>> partitions() {
        return partitions;
    }
@Test
    public void testAttributes() {
        Map<Uuid, Set<Integer>> partitions = mkAssignment(
            mkTopicAssignment(Uuid.randomUuid(), 1, 2, 3)
        );
        Assignment assignment = new Assignment(partitions);
        assertEquals(partitions, assignment.partitions());
    }