'The object ``async_block_device_api`` refers to can be overridden by
supplying the ``_async_block_device_api`` keyword argument to the
initializer.'

def test_overridden(self):

    api = UnusableAPI()
    async_api = _SyncToThreadedAsyncAPIAdapter(_reactor=NonReactor(), _threadpool=NonThreadPool(), _sync=api)
    deployer = BlockDeviceDeployer(hostname=u'192.0.2.1', node_uuid=uuid4(), block_device_api=api, _async_block_device_api=async_api)
    self.assertIs(async_api, deployer.async_block_device_api)
