@Override
      public void afterSettingOplogOffSet(long offset) {
        ((LocalRegion) region).getDiskRegion().forceRolling();
        // Let the operation thread yield to the Roller so that
        // it is able to obtain the iterator of the concurrrent region map
        // & thus get the reference to the entry which will contain
        // value as Token.Removed as the entry though removed from
        // concurrent
        // map still will be available to the roller
        Thread.yield();
        // Sleep for some time
        try {
          Thread.sleep(5000);
        } catch (InterruptedException e) {
          testFailed = true;
          failureCause = "No guarantee that test is succesful";
          fail("No guarantee that test is succesful");
        }
      }
This tests the bug which caused the oplogRoller to attempt to roll a removed entry whose value
is Token.Removed This bug can occur if a remove operation causes oplog switching & hence roller
thread gets notified, & the roller thread obtains the iterator of the concurrent region map
before the remove
geode-core/src/integrationTest/java/org/apache/geode/internal/cache/OplogJUnitTest.java