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

    await()
        .untilAsserted(() -> assertThat(sender.getEventQueueSize())
            .as("Sender event queue size")
            .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