Cleanup mock patches on BaseTestCase tearDown()

Instead of cleaning up any remaining mock patches in each unit test that
uses them, do it once on BaseTestCase tearDown().

Change-Id: I121ba554e16d83fc5908bb85afee4940f42dc4eb
Closes-Bug: 1323214

oslotest/base.py

@@ -20,6 +20,7 @@ import os
 import tempfile
 
 import fixtures
+import mock
 import testtools
 
 _TRUE_VALUES = ('True', 'true', '1', 'yes')
@@ -35,6 +36,7 @@ class BaseTestCase(testtools.TestCase):
         self._fake_logs()
         self.useFixture(fixtures.NestedTempfile())
         self.useFixture(fixtures.TempHomeDir())
+        self.addCleanup(mock.patch.stopall)
 
     def _set_timeout(self):
         test_timeout = os.environ.get('OS_TEST_TIMEOUT', 0)

tests/unit/test_base.py

@@ -13,6 +13,7 @@
 #    under the License.
 
 import logging
+import unittest
 
 import mock
 import testtools
@@ -71,3 +72,23 @@ class TestBaseTestCase(testtools.TestCase):
         env_get_mock.assert_any_call('OS_LOG_CAPTURE')
         env_get_mock.assert_any_calls('OS_DEBUG')
         self.assertEqual(fixture_mock.call_count, 1)
+
+    def test_mock_patch_cleanup_on_teardown(self):
+        # create an object and save its reference
+        class Sub(object):
+            pass
+
+        obj = Sub()
+        obj.value = obj.backup = object()
+
+        # patch the object
+        mock.patch.object(obj, 'value').start()
+        self.assertNotEqual(obj.value, obj.backup)
+
+        # run a test case
+        loader = unittest.defaultTestLoader
+        suite = loader.loadTestsFromTestCase(self.FakeTestCase)
+        suite.run(unittest.TestResult())
+
+        # check that mock patches are cleaned up
+        self.assertEqual(obj.value, obj.backup)