@Before
  public void setUp() throws Exception {
    Properties properties = new Properties();
    properties.setProperty(MCAST_PORT, "0");
    properties.setProperty(LOCATORS, "");
    distributedSystem = DistributedSystem.connect(properties);
    cache = CacheFactory.create(distributedSystem);
    AttributesFactory factory = new AttributesFactory();
    factory.setScope(Scope.DISTRIBUTED_ACK);
    factory.setDataPolicy(DataPolicy.PERSISTENT_REPLICATE);
    RegionAttributes regionAttributes = factory.create();
    testRegion = cache.createRegion("TestRegion1", regionAttributes);
    CacheObserverHolder.setInstance(new CacheObserverListener());
  }
Test methods to ensure that disk Clear is apparently atomic to region clear.

Data on disk should reflect data in memory. A put while clear is going on should wait for clear
and if it is successfully recorded in memory than it should be recorded on disk. Else if not
successfully recorded in memory than should not be recorded on disk

TODO: use DiskRegionTestingBase and DiskRegionHelperFactory
geode-core/src/integrationTest/java/org/apache/geode/internal/cache/DiskRegionClearJUnitTest.java