def test_already_exists(self):
        api = ApplicationNodeDeployer(u'example.com',
                                      docker_client=FakeDockerClient())
        application = Application(
            name=b'site-example.com',
            image=DockerImage(repository=u'clusterhq/flocker',
                              tag=u'release-14.0'),
            links=frozenset(),
        )

        result1 = StartApplication(
            application=application,
            node_state=EMPTY_NODESTATE
        ).run(api, state_persister=InMemoryStatePersister())
        self.successResultOf(result1)

        result2 = StartApplication(
            application=application,
            node_state=EMPTY_NODESTATE
        ).run(api, state_persister=InMemoryStatePersister())
        self.failureResultOf(result2, AlreadyExists)
``StartApplication.run`` returns a `Deferred` which errbacks with
dataset/ETHPy150Open ClusterHQ/flocker/flocker/node/test/test_container.py/StartApplicationTests.test_already_exists