static Map<ProcessId, Map<String, Optional<String>>> getRandomProcessRacks(final int clientSize, final int nodeSize) {
        final List<String> racks = new ArrayList<>(nodeSize);
        for (int i = 0; i < nodeSize; i++) {
            racks.add(RACK_PREFIX + i);
        }
        final Random rand = getRandom();
        Collections.shuffle(racks, rand);
        final Map<ProcessId, Map<String, Optional<String>>> processRacks = new HashMap<>();
        for (int i = 1; i <= clientSize; i++) {
            final String rack = racks.get(i % nodeSize);
            processRacks.put(processIdForInt(i), mkMap(mkEntry("1", Optional.of(rack))));
        }
        return processRacks;
    }
Builds a ProcessId with a UUID by repeating the given number n. For valid n, it is guaranteed that the returned UUIDs satisfy
the same relation relative to others as their parameter n does: iff n < m, then uuidForInt(n) < uuidForInt(m)
streams/src/test/java/org/apache/kafka/streams/processor/internals/assignment/AssignmentTestUtils.java