Add unit test to the modules: 
dubbo-registry/dubbo-registry-multicast
   dubbo-registry/dubbo-registry-redis
  dubbo-registry/dubbo-registry-zookeeper 
if (urls.isEmpty()) {
            List<URL> cacheUrls = getCacheUrls(url);
            if (cacheUrls != null && !cacheUrls.isEmpty()) {
                urls.addAll(cacheUrls);
            }
        }
        if (urls.isEmpty()) {
            for (URL u : getRegistered()) {
                if (UrlUtils.isMatch(url, u)) {
                    urls.add(u);
                }
            }
        }
        if (Constants.ANY_VALUE.equals(url.getServiceInterface())) {
            for (URL u : getSubscribed().keySet()) {
                if (UrlUtils.isMatch(url, u)) {
                    urls.add(u);
                }
            }
        }
        return urls;
    }
    public MulticastSocket getMutilcastSocket() {
        return mutilcastSocket;
    }
    public Map<URL, Set<URL>> getReceived() {
        return received;
    }
}