@Override
      public void run() {
        try {
          Thread.sleep(600);
        } catch (InterruptedException e) {
          errorCollector.addError(e);
        }
        list1 = HARegionQueue.createMessageListForTesting();
      }
This test tests remove operation is causing the insertion of sequence ID for existing
ThreadIdentifier object and concurrently the QRM thread is iterating over the Map to form the
Data Set for dispatch. There should not be any Data Loss

In this test, first we add x number of events for unique thread id for the same region then we
start two concurrent threads. One which does add to dispatched events map with sequence id's
greater than x but the same ThreadIds as previous. The second thread does createMessageList
(which removes from the dispatched events map) and stores the list

After the two threads have operated, createMessageList is called again and the data is stored
in another list.

The data in the list is populated on a map against the threadId.

It is then verified to see that all the sequence should be greater than x
geode-core/src/integrationTest/java/org/apache/geode/internal/cache/ha/HARegionQueueJUnitTest.java