How to use the stevedore.extension.ExtensionManager.make_test_instance function in stevedore

def _fake_extension_manager(self, ext):
        return extension.ExtensionManager.make_test_instance(
            [extension.Extension('test', None, None, ext), ])

def get_insert_pre_hourly_cmpt_mgr():
        return ExtensionManager.make_test_instance([Extension(
            'prepare_data',
            'monasca_transform.component.insert.prepare_data:PrepareData',
            PrepareData(),
            None),
            Extension('insert_data',
                      'tests.functional.component.insert.dummy_insert:'
                      'DummyInsert',
                      DummyInsert(),
                      None),
            Extension('insert_data_pre_hourly',
                      'tests.functional.component.insert.'
                      'dummy_insert_pre_hourly:'
                      'DummyInsertPreHourly',
                      DummyInsertPreHourly(),
                      None),
        ])

self.stubs.Set(db, 'instance_info_cache_delete', self.do_nothing)
        self.stubs.Set(db, 'instance_destroy', self.do_nothing)
        self.stubs.Set(db, 'instance_system_metadata_get',
                       self.fake_db_instance_system_metadata_get)
        self.stubs.Set(db, 'block_device_mapping_get_all_by_instance',
                       lambda context, instance: {})
        self.stubs.Set(db, 'instance_update_and_get_original',
                       lambda *args, **kwargs: (self.instance, self.instance))
        self.stubs.Set(flavors, 'extract_flavor', self.fake_extract_flavor)

        # Set up to capture the notification messages generated by the
        # plugin and to invoke our notifier plugin.
        self.notifications = []

        ext_mgr = extension.ExtensionManager.make_test_instance(
            extensions=[
                extension.Extension('test',
                                    None,
                                    None,
                                    self.Pollster(),
                                ),
            ],
        )
        self.ext_mgr = ext_mgr
        self.gatherer = nova_notifier.DeletedInstanceStatsGatherer(ext_mgr)
        # Initialize the global _gatherer in nova_notifier to use the
        # gatherer in this test instead of the gatherer in nova_notifier.
        nova_notifier.initialize_gatherer(self.gatherer)

        # Terminate the instance to trigger the notification.
        with contextlib.nested(

def _make_test_manager(self, plugin):
        return extension.ExtensionManager.make_test_instance(
            [extension.Extension('test_plugin', None, test_plugin, None)])

def get_setter_cmpt_mgr():
        return ExtensionManager.make_test_instance([Extension(
            'set_aggregated_metric_name',
            'monasca_transform.component.setter.'
            'set_aggregated_metric_name:SetAggregatedMetricName',
            SetAggregatedMetricName(),
            None),
            Extension('set_aggregated_period',
                      'monasca_transform.component.setter.'
                      'set_aggregated_period:SetAggregatedPeriod',
                      SetAggregatedPeriod(),
                      None),
            Extension('rollup_quantity',
                      'monasca_transform.component.setter.'
                      'rollup_quantity:RollupQuantity',
                      RollupQuantity(),
                      None)
        ])

def get_usage_cmpt_mgr():
        return ExtensionManager.make_test_instance([Extension(
            'fetch_quantity',
            'monasca_transform.component.usage.'
            'fetch_quantity:'
            'FetchQuantity',
            FetchQuantity(),
            None),
            Extension(
            'fetch_quantity_util',
            'monasca_transform.component.usage.'
            'fetch_quantity_util:'
            'FetchQuantityUtil',
            FetchQuantityUtil(),
            None),
            Extension(
                'calculate_rate',
                'monasca_transform.component.usage.'

def _empty_extension_manager(self):
        return extension.ExtensionManager.make_test_instance([])