public Optional<InstanceMetadata> getInstanceMetadata(Service service, String metadataId) {
        ConcurrentMap<String, InstanceMetadata> instanceMetadataMapForService = instanceMetadataMap.get(service);
        if (null == instanceMetadataMapForService) {
            return Optional.empty();
        }
        return Optional.ofNullable(instanceMetadataMapForService.get(metadataId));
    }
@Test
    void testGetInstanceMetadata() {
        Optional<InstanceMetadata> instanceMetadata = namingMetadataManager.getInstanceMetadata(service, METADATA_ID);
        
        assertTrue(instanceMetadata.isPresent());
        assertNotNull(instanceMetadata.get());
    }