Add fixture for plugin directory

This is needed to stop stubbing out _get_plugin_directory
from neutron unit tests, thus preserving testing isolation.

Change-Id: Ic94b264068955c67d71b86fe54825b9fba4533ac

neutron_lib/fixture.py

@@ -0,0 +1,31 @@
+# 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 neutron_lib.plugins import directory
+
+
+class PluginDirectoryFixture(fixtures.Fixture):
+
+    def __init__(self, plugin_directory=None):
+        super(PluginDirectoryFixture, self).__init__()
+        self.plugin_directory = (
+            plugin_directory or directory._PluginDirectory())
+
+    def _setUp(self):
+        self._orig_directory = directory._PLUGIN_DIRECTORY
+        directory._PLUGIN_DIRECTORY = self.plugin_directory
+        self.addCleanup(self._restore)
+
+    def _restore(self):
+        directory._PLUGIN_DIRECTORY = self._orig_directory

neutron_lib/tests/_base.py

@@ -29,7 +29,7 @@ import testtools
 from neutron_lib._i18n import _
 from neutron_lib import constants
 from neutron_lib import exceptions
-from neutron_lib.plugins import directory
+from neutron_lib import fixture
 
 from neutron_lib.tests import _post_mortem_debug as post_mortem_debug
 from neutron_lib.tests import _tools as tools
@@ -117,7 +117,7 @@ class BaseTestCase(testtools.TestCase):
 
     def setUp(self):
         super(BaseTestCase, self).setUp()
-        self.setup_test_directory_instance()
+        self.useFixture(fixture.PluginDirectoryFixture())
 
         # Enabling 'use_fatal_exceptions' allows us to catch string
         # substitution format errors in exception messages.
@@ -183,12 +183,6 @@ class BaseTestCase(testtools.TestCase):
         self.addOnException(self.check_for_systemexit)
         self.orig_pid = os.getpid()
 
-    def setup_test_directory_instance(self):
-        """Give a private copy of the directory to each test."""
-        self._plugin_directory = directory._PluginDirectory()
-        mock.patch.object(directory, '_get_plugin_directory',
-                          return_value=self._plugin_directory).start()
-
     def get_new_temp_dir(self):
         """Create a new temporary directory.
 

neutron_lib/tests/unit/test_fixture.py

@@ -0,0 +1,31 @@
+# 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 oslotest import base
+
+from neutron_lib import fixture
+from neutron_lib.plugins import directory
+
+
+class PluginDirectoryFixtureTestCase(base.BaseTestCase):
+
+    def setUp(self):
+        super(PluginDirectoryFixtureTestCase, self).setUp()
+        self.directory = mock.Mock()
+        self.useFixture(fixture.PluginDirectoryFixture(
+            plugin_directory=self.directory))
+
+    def test_fixture(self):
+        directory.add_plugin('foo', 'foo')
+        self.assertTrue(self.directory.add_plugin.called)

releasenotes/notes/directory-fixture-083c5c5f365670d6.yaml

@@ -0,0 +1,17 @@
+---
+features:
+  - |
+    Introduced neutron_lib.fixture, and added fixture for plugin
+    directory ``PluginDirectoryFixture``. An example below:
+
+    .. code-block:: python
+
+        from neutron_lib.plugins import directory
+        from neutron_lib import fixture
+
+
+        def setup_test_directory_instance(self):
+            """Give a private copy of the directory to each test."""
+            self._plugin_directory = directory._PluginDirectory()
+            self.useFixture(fixture.PluginDirectoryFixture(
+                plugin_directory=self._plugin_directory))