public Collection<String> getAllClientsRegisteredService(Service service) {
        return publisherIndexes.containsKey(service) ? publisherIndexes.get(service) : new ConcurrentHashSet<>();
    }
@Test
    void testGetAllClientsRegisteredService() {
        Collection<String> allClientsRegisteredService = clientServiceIndexesManager.getAllClientsRegisteredService(service);
        
        assertNotNull(allClientsRegisteredService);
        assertEquals(1, allClientsRegisteredService.size());
    }