@Test
  public void testGetChild() {
    deleteFiles();
    region = DiskRegionHelperFactory.getAsyncPersistOnlyRegion(cache, diskProps);
    DiskRegion dr = ((LocalRegion) region).getDiskRegion();
    Oplog oplog = dr.testHook_getChild();
    long id = oplog.getOplogId();

    StatisticsFactory factory = region.getCache().getDistributedSystem();
    Oplog newOplog =
        new Oplog(id, dr.getOplogSet(), new DirectoryHolder(factory, dirs[0], 1000000, 0));
    dr.getDiskStore().getPersistentOplogs().setChild(newOplog);
    assertEquals(newOplog, dr.testHook_getChild());
    dr.setChild(oplog);
    assertEquals(oplog, dr.testHook_getChild());
    newOplog.close();
    newOplog = null;
    closeDown();
  }
Testing methods for SimpleDiskRegion.java api's

@since GemFire 5.1
geode-core/src/integrationTest/java/org/apache/geode/internal/cache/SimpleDiskRegionJUnitTest.java