protected static TopicPartition tp(String topic, int partition) {
        return new TopicPartition(topic, partition);
    }
This unit test performs sticky assignment for a scenario that round robin assignor handles poorly.
Topics (partitions per topic): topic1 (2), topic2 (1), topic3 (2), topic4 (1), topic5 (2)
Subscriptions:
 - consumer1: topic1, topic2, topic3, topic4, topic5
 - consumer2: topic1, topic3, topic5
 - consumer3: topic1, topic3, topic5
 - consumer4: topic1, topic2, topic3, topic4, topic5
Round Robin Assignment Result:
 - consumer1: topic1-0, topic3-0, topic5-0
 - consumer2: topic1-1, topic3-1, topic5-1
 - consumer3:
 - consumer4: topic2-0, topic4-0
Sticky Assignment Result:
 - consumer1: topic2-0, topic3-0
 - consumer2: topic1-0, topic3-1
 - consumer3: topic1-1, topic5-0
 - consumer4: topic4-0, topic5-1
clients/src/test/java/org/apache/kafka/clients/consumer/internals/AbstractStickyAssignorTest.java