@Test
    public void testFetchSkipsBlackedOutNodes() {
        buildFetcher();

        assignFromUser(singleton(tp0));
        subscriptions.seek(tp0, 0);
        Node node = initialUpdateResponse.brokers().iterator().next();

        client.backoff(node, 500);
        assertEquals(0, sendFetches());

        time.sleep(500);
        assertEquals(1, sendFetches());
    }
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