private Cache createCache(Properties props) throws Exception {
    DistributedSystem ds = getSystem(props);
    ds.disconnect();
    ds = getSystem(props);
    Cache result = null;
    result = CacheFactory.create(ds);
    if (result == null) {
      throw new Exception("CacheFactory.create() returned null");
    }
    return result;
  }
Simulates old value null, entry null
geode-core/src/distributedTest/java/org/apache/geode/internal/cache/DeltaPropagationStatsDUnitTest.java