text: # 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 fixtures
  
  from keystone import auth
  from keystone.common import dependency
  from keystone.server import common
  
  
  class BackendLoader(fixtures.Fixture):
      """Initialize each manager and assigns them to an attribute."""
  
      def __init__(self, testcase):
          super(BackendLoader, self).__init__()
          self._testcase = testcase
  
      def setUp(self):
          super(BackendLoader, self).setUp()
  
          # TODO(blk-u): Shouldn't need to clear the registry here, but some
          # tests call load_backends multiple times. These should be fixed to
          # only call load_backends once.
          dependency.reset()
  
          self.clear_auth_plugin_registry()
          drivers, _unused = common.setup_backends()
  
          for manager_name, manager in drivers.items():
              setattr(self._testcase, manager_name, manager)
  
          self.addCleanup(self._testcase.cleanup_instance(*list(drivers.keys())))
  
          del self._testcase  # break circular reference
  
      def clear_auth_plugin_registry(self):
          auth.core.AUTH_METHODS.clear()
          auth.core.AUTH_PLUGINS_LOADED = False
  