private void validateSecondaryQueueSizeStat(String senderId, int queueSize) {
    InternalGatewaySender sender = findInternalGatewaySender(senderId);

    await()
        .untilAsserted(() -> {
          assertThat(sender.getStatistics().getUnprocessedEventMapSize())
              .as("Sender statistics unprocessed event map contents: "
                  + sender.getEventProcessor().printUnprocessedEvents())
              .isEqualTo(queueSize);
        });
  }
Since the sender is attached to a region and in use, it can not be destroyed. Hence, exception
is thrown by the sender API.
geode-wan/src/distributedTest/java/org/apache/geode/internal/cache/wan/serial/SerialGatewaySenderOperationsDistributedTest.java