prevent leakage of FLAGS changes across tests

nova/flags.py

@@ -90,6 +90,12 @@ class FlagValues(gflags.FlagValues):
         self.ClearDirty()
         return args
 
+    def Reset(self):
+        gflags.FlagValues.Reset(self)
+        self.__dict__['__dirty'] = []
+        self.__dict__['__was_already_parsed'] = False
+        self.__dict__['__stored_argv'] = []
+
     def SetDirty(self, name):
         """Mark a flag as dirty so that accessing it will case a reparse."""
         self.__dict__['__dirty'].append(name)

nova/tests/flags_unittest.py

@@ -20,6 +20,8 @@ from nova import exception
 from nova import flags
 from nova import test
 
+FLAGS = flags.FLAGS
+flags.DEFINE_string('flags_unittest', 'foo', 'for testing purposes only')
 
 class FlagsTestCase(test.TrialTestCase):
     def setUp(self):
@@ -85,3 +87,13 @@ class FlagsTestCase(test.TrialTestCase):
 
         self.assert_('runtime_answer' in self.global_FLAGS)
         self.assertEqual(self.global_FLAGS.runtime_answer, 60)
+
+    def test_flag_leak_left(self):
+        self.assertEqual(FLAGS.flags_unittest, 'foo')
+        FLAGS.flags_unittest = 'bar'
+        self.assertEqual(FLAGS.flags_unittest, 'bar')
+
+    def test_flag_leak_right(self):
+        self.assertEqual(FLAGS.flags_unittest, 'foo')
+        FLAGS.flags_unittest = 'bar'
+        self.assertEqual(FLAGS.flags_unittest, 'bar')