old_contents: # vim: tabstop=4 shiftwidth=4 softtabstop=4
  #
  # Copyright (c) 2013 dotCloud, Inc.
  # All Rights Reserved.
  #
  #    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.
  
  from nova import test
  from nova.tests import utils
  from nova.tests.virt.test_virt_drivers import test_virt_drivers
  
  
  class DockerDriverTestCase(test_virt_drivers._VirtDriverTestCase, test.TestCase):
      def setUp(self):
          # Point _VirtDriverTestCase at the right module
          self.driver_module = 'nova.virt.docker.DockerDriver'
          super(DockerDriverTestCase, self).setUp()
          # Replace connection to Docker daemon with in-memory Mock object
          self.connection.use_mock_client()
  
      def _get_running_instance(self):
          instance_ref = utils.get_test_instance()
          network_info = utils.get_test_network_info(legacy_model=False)
          network_info[0]['network']['subnets'][0]['meta']['dhcp_server'] = \
              '1.1.1.1'
          image_info = utils.get_test_image_info(None, instance_ref)
          image_info['disk_format'] = 'raw'
          image_info['container_format'] = 'docker'
          self.connection.spawn(self.ctxt, instance_ref, image_info,
                                [], 'herp', network_info=network_info)
          return instance_ref, network_info
  
new_contents: # vim: tabstop=4 shiftwidth=4 softtabstop=4
  #
  # Copyright (c) 2013 dotCloud, Inc.
  # All Rights Reserved.
  #
  #    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.
  
  from nova import test
  from nova.tests import utils
  from nova.tests.virt.test_virt_drivers import test_virt_drivers
  
  
  class DockerDriverTestCase(test_virt_drivers._VirtDriverTestCase, test.TestCase):
      def setUp(self):
          # Point _VirtDriverTestCase at the right module
          self.driver_module = 'nova.virt.docker.DockerDriver'
          super(DockerDriverTestCase, self).setUp()
          # Replace connection to Docker daemon with in-memory Mock object
          self.connection.use_mock_client()
  
      #NOTE(bcwaldon): This exists only because _get_running_instance on the
      # base class will not let us set a custom disk/container_format.
      def _get_running_instance(self):
          instance_ref = utils.get_test_instance()
          network_info = utils.get_test_network_info(legacy_model=False)
          network_info[0]['network']['subnets'][0]['meta']['dhcp_server'] = \
              '1.1.1.1'
          image_info = utils.get_test_image_info(None, instance_ref)
          image_info['disk_format'] = 'raw'
          image_info['container_format'] = 'docker'
          self.connection.spawn(self.ctxt, instance_ref, image_info,
                                [], 'herp', network_info=network_info)
          return instance_ref, network_info
  
subject: Document why _get_running_instance is overridden