@Override
    public void run() {
      ((LocalRegion) region).getDiskRegion().flushForTesting();
      synchronized (region) {
        region.notify();
        hasBeenNotified = true;
      }
    }
DiskRegOplog1OverridingOplog2JUnitTest: Disk Region test : oplog1 flush overriding oplog2 flush

This test will hold the flush of oplog1 and flush oplog2 before it. After that oplog1 is
allowed to flush. A get of an entry which was first put in oplog1 and then in oplog2 should
result in the get being done from oplog2.
geode-core/src/integrationTest/java/org/apache/geode/internal/cache/DiskRegOplogSwtchingAndRollerJUnitTest.java