private void waitForSendersRunning() {
    vm4.invoke(() -> waitForSenderRunningState("ln"));
    vm5.invoke(() -> waitForSenderRunningState("ln"));
    vm6.invoke(() -> waitForSenderRunningState("ln"));
    vm7.invoke(() -> waitForSenderRunningState("ln"));
  }
Put entries in region after gateway sender is stopped. Count number of PQRM messages sent.
geode-wan/src/distributedTest/java/org/apache/geode/internal/cache/wan/parallel/ParallelGatewaySenderOperationsDistributedTest.java