new_contents: # Licensed under the Apache License, Version 2.0 (the "License"); you may
  # not use this file except in compliance with the License. You may obtain
  # a copy of the License at
  #
  #      http://www.apache.org/licenses/LICENSE-2.0
  #
  # Unless required by applicable law or agreed to in writing, software
  # distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
  # WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
  # License for the specific language governing permissions and limitations
  # under the License.
  
  import mock
  
  from nova import context
  from nova import objects
  from nova import test
  from nova.tests import fixtures as nova_fixtures
  from nova.tests.functional.libvirt import base
  
  from oslo_serialization import jsonutils
  
  
  class TestVolumeDisconnectDuringPreLiveMigrationRollback(base.ServersTestBase):
      """Regression test for bug #1899835
  
      This regression test aims to ensure that no attempt is made to disconnect
      volumes from the destination host of a live migration if a failure is
      encountered early when creating the new volume attachment during
      pre_live_migration ahead of any volumes actually being connected.
      """
      # Default self.api to the self.admin_api as live migration is admin only
      ADMIN_API = True
      microversion = 'latest'
  
      def setUp(self):
          super().setUp()
          self.start_compute(hostname='src')
          self.start_compute(hostname='dest')
  
      def test_disconnect_volume_called_during_pre_live_migration_failure(self):
          server = {
              'name': 'test',
              'imageRef': '',
              'flavorRef': 1,
              'networks': 'none',
              'host': 'src',
              'block_device_mapping_v2': [{
                  'source_type': 'volume',
                  'destination_type': 'volume',
                  'boot_index': 0,
                  'uuid': nova_fixtures.CinderFixture.IMAGE_BACKED_VOL
              }]
          }
  
          with test.nested(
              mock.patch.object(
                  self.computes['src'].driver, 'get_volume_connector'),
              mock.patch.object(
                  self.computes['src'].driver, '_connect_volume'),
          ) as (
              mock_src_connector, mock_src_connect
          ):
              server = self.api.post_server({'server': server})
              self._wait_for_state_change(server, 'ACTIVE')
  
          # Assert that we called the src connector and connect mocks
          mock_src_connector.assert_called_once()
          mock_src_connect.assert_called_once()
  
          # Fetch the connection_info from the src
          ctxt = context.get_admin_context()
          bdm = objects.BlockDeviceMapping.get_by_volume_id(
              ctxt, nova_fixtures.CinderFixture.IMAGE_BACKED_VOL,
              instance_uuid=server['id'])
          src_connection_info = jsonutils.loads(bdm.connection_info)
  
          with test.nested(
              mock.patch.object(
                  self.computes['dest'].driver, 'get_volume_connector'),
              mock.patch.object(
                  self.computes['dest'].driver, '_connect_volume'),
              mock.patch.object(
                  self.computes['dest'].driver, '_disconnect_volume'),
              mock.patch(
                  'nova.volume.cinder.API.attachment_create',
                  side_effect=test.TestingException)
          ) as (
              mock_dest_connector, mock_dest_connect, mock_dest_disconnect,
              mock_attachment_create
          ):
              # Attempt to live migrate and ensure it is marked as failed
              self._live_migrate(server, 'failed')
  
          # Assert that we called the dest connector and attachment_create mocks
          mock_dest_connector.assert_called_once()
          mock_attachment_create.assert_called_once()
  
          # Assert that connect_volume hasn't been called on the dest
          mock_dest_connect.assert_not_called()
  
          # FIXME(lyarwood): This is bug #1899835, disconnect_volume shouldn't be
          # called on the destination host without connect_volume first being
          # called and especially using with the connection_info from the source
          mock_dest_disconnect.assert_called_with(
              mock.ANY, src_connection_info, mock.ANY, encryption=mock.ANY)
  
subject: Add regression test for bug #1899835