private MockClient.RequestMatcher fetchRequestMatcher(
            short expectedVersion,
            TopicIdPartition tp,
            long expectedFetchOffset,
            Optional<Integer> expectedCurrentLeaderEpoch
    ) {
        return fetchRequestMatcher(
                expectedVersion,
                singletonMap(tp, new PartitionData(
                        tp.topicId(),
                        expectedFetchOffset,
                        FetchRequest.INVALID_LOG_START_OFFSET,
                        fetchSize,
                        expectedCurrentLeaderEpoch
                )),
                emptyList()
        );
    }
This validates that no records are fetched for partitions that are waiting for the
onPartitionsAssigned callback to complete. Note that this markPendingOnAssignedCallback
functionality is only used from the {@link AsyncKafkaConsumer}.
clients/src/test/java/org/apache/kafka/clients/consumer/internals/FetchRequestManagerTest.java