'``BlockDeviceDeployer.discover_state`` returns a ``NodeState`` with one
``manifestations`` if the ``api`` reports one locally attached volume
and the volume\'s filesystem is mounted in the right place.'

def test_one_device(self):

    dataset_id = uuid4()
    volume = self.api.create_volume(dataset_id=dataset_id, size=LOOPBACK_MINIMUM_ALLOCATABLE_SIZE)
    self.api.attach_volume(volume.blockdevice_id, attach_to=self.this_node)
    device = self.api.get_device_path(volume.blockdevice_id)
    mount_point = self.deployer.mountroot.child(bytes(dataset_id))
    mount_point.makedirs()
    make_filesystem(device, block_device=True)
    mount(device, mount_point)
    assert_discovered_state(self, self.deployer, persistent_state=PersistentState(blockdevice_ownership={dataset_id: volume.blockdevice_id}), expected_discovered_datasets=[DiscoveredDataset(state=DatasetStates.MOUNTED, dataset_id=volume.dataset_id, blockdevice_id=volume.blockdevice_id, maximum_size=LOOPBACK_MINIMUM_ALLOCATABLE_SIZE, device_path=device, mount_point=mount_point)])
