'``create_api_service`` returns an object providing ``IService``.'

def test_returns_service(self):

    reactor = MemoryReactor()
    endpoint = TCP4ServerEndpoint(reactor, 6789)
    verifyObject(IService, create_api_service(ConfigurationPersistenceService(reactor, FilePath(self.mktemp())), ClusterStateService(reactor), endpoint, ClientContextFactory()))
