public void loadServiceMetadataSnapshot(ConcurrentMap<Service, ServiceMetadata> snapshot) {
        for (Service each : snapshot.keySet()) {
            Service  service = Service.newService(each.getNamespace(), each.getGroup(), each.getName(), each.isEphemeral());
            ServiceManager.getInstance().getSingleton(service);
        }
        ConcurrentMap<Service, ServiceMetadata> oldSnapshot = serviceMetadataMap;
        serviceMetadataMap = snapshot;
        oldSnapshot.clear();
    }
@Test
    void testLoadServiceMetadataSnapshot() {
        namingMetadataManager.loadServiceMetadataSnapshot(new ConcurrentHashMap<>());
        Map<Service, ServiceMetadata> serviceMetadataSnapshot = namingMetadataManager.getServiceMetadataSnapshot();
        
        assertEquals(0, serviceMetadataSnapshot.size());
    }