Patch fake_libvirt_utils with fixtures.MonkeyPatch

If tests are not run in the default order nosetests runs them in it
is possible that the monkey patching of fake_libvirt utils is not
properly cleaned up. Use fixtures.MonkeyPatch to monkey patch
fake_libvirt_utils in test setUp ensuring the monkey patching is
reverted properly after each test.

Part of blueprint grizzly-testtools

Change-Id: Ie691cbc777c01fa8a5affa3271f36776ea9648b9

nova/tests/test_imagebackend.py

@@ -15,6 +15,7 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
+import fixtures
 import os
 
 from nova.openstack.common import cfg
@@ -48,7 +49,9 @@ class _ImageTestCase(test.TestCase):
                                          '_base')
         self.TEMPLATE_PATH = os.path.join(self.TEMPLATE_DIR, 'template')
 
-        imagebackend.libvirt_utils = fake_libvirt_utils
+        self.useFixture(fixtures.MonkeyPatch(
+            'nova.virt.libvirt.imagebackend.libvirt_utils',
+            fake_libvirt_utils))
 
     def test_cache(self):
         self.mox.StubOutWithMock(os.path, 'exists')

nova/tests/test_libvirt.py

@@ -18,6 +18,7 @@
 import copy
 import errno
 import eventlet
+import fixtures
 import json
 import mox
 import os
@@ -474,11 +475,11 @@ class CacheConcurrencyTestCase(test.TestCase):
         self.stubs.Set(os.path, 'exists', fake_exists)
         self.stubs.Set(utils, 'execute', fake_execute)
         self.stubs.Set(imagebackend.disk, 'extend', fake_extend)
-        imagebackend.libvirt_utils = fake_libvirt_utils
+        self.useFixture(fixtures.MonkeyPatch(
+            'nova.virt.libvirt.imagebackend.libvirt_utils',
+            fake_libvirt_utils))
 
     def tearDown(self):
-        imagebackend.libvirt_utils = libvirt_utils
-
         # Make sure the lock_path for this test is cleaned up
         if os.path.exists(self.lock_path):
             shutil.rmtree(self.lock_path)
@@ -559,8 +560,12 @@ class LibvirtConnTestCase(test.TestCase):
         self.flags(instances_path='')
         self.flags(libvirt_snapshots_directory='')
         self.call_libvirt_dependant_setup = False
-        libvirt_driver.libvirt_utils = fake_libvirt_utils
-        snapshots.libvirt_utils = fake_libvirt_utils
+        self.useFixture(fixtures.MonkeyPatch(
+            'nova.virt.libvirt.driver.libvirt_utils',
+            fake_libvirt_utils))
+        self.useFixture(fixtures.MonkeyPatch(
+            'nova.virt.libvirt.snapshots.libvirt_utils',
+            fake_libvirt_utils))
 
         def fake_extend(image, size):
             pass
@@ -581,7 +586,6 @@ class LibvirtConnTestCase(test.TestCase):
                 'instance_type_id': '5'}  # m1.small
 
     def tearDown(self):
-        libvirt_driver.libvirt_utils = libvirt_utils
         nova.tests.image.fake.FakeImageService_reset()
         super(LibvirtConnTestCase, self).tearDown()
 
@@ -2335,7 +2339,6 @@ class LibvirtConnTestCase(test.TestCase):
 
             self.create_fake_libvirt_mock()
             libvirt_driver.LibvirtDriver._conn.lookupByName = fake_lookup
-            libvirt_driver.libvirt_utils = fake_libvirt_utils
 
             conn = libvirt_driver.LibvirtDriver(fake.FakeVirtAPI(), False)
 
@@ -2387,7 +2390,6 @@ class LibvirtConnTestCase(test.TestCase):
             libvirt_driver.LibvirtDriver._conn.lookupByName = fake_lookup
             libvirt_driver.LibvirtDriver._flush_libvirt_console = _fake_flush
             libvirt_driver.LibvirtDriver._append_to_file = _fake_append_to_file
-            libvirt_driver.libvirt_utils = fake_libvirt_utils
 
             conn = libvirt_driver.LibvirtDriver(fake.FakeVirtAPI(), False)
 

nova/tests/test_virt_drivers.py

@@ -16,6 +16,7 @@
 
 import __builtin__
 import base64
+import fixtures
 import mox
 import netaddr
 import StringIO
@@ -77,12 +78,21 @@ class _FakeDriverBackendTestCase(test.TestCase):
         import nova.virt.libvirt.driver
         import nova.virt.libvirt.firewall
 
-        self.saved_libvirt_imagebackend = nova.virt.libvirt.driver.imagebackend
-        nova.virt.libvirt.driver.imagebackend = fake_imagebackend
-        nova.virt.libvirt.driver.libvirt = fakelibvirt
-        nova.virt.libvirt.driver.libvirt_utils = fake_libvirt_utils
-        nova.virt.libvirt.snapshots.libvirt_utils = fake_libvirt_utils
-        nova.virt.libvirt.firewall.libvirt = fakelibvirt
+        self.useFixture(fixtures.MonkeyPatch(
+            'nova.virt.libvirt.driver.imagebackend',
+            fake_imagebackend))
+        self.useFixture(fixtures.MonkeyPatch(
+            'nova.virt.libvirt.driver.libvirt',
+            fakelibvirt))
+        self.useFixture(fixtures.MonkeyPatch(
+            'nova.virt.libvirt.driver.libvirt_utils',
+            fake_libvirt_utils))
+        self.useFixture(fixtures.MonkeyPatch(
+            'nova.virt.libvirt.snapshots.libvirt_utils',
+            fake_libvirt_utils))
+        self.useFixture(fixtures.MonkeyPatch(
+            'nova.virt.libvirt.firewall.libvirt',
+            fakelibvirt))
 
         self.flags(rescue_image_id="2",
                    rescue_kernel_id="3",
@@ -115,12 +125,8 @@ class _FakeDriverBackendTestCase(test.TestCase):
         # Restore libvirt
         import nova.virt.libvirt.driver
         import nova.virt.libvirt.firewall
-        nova.virt.libvirt.driver.imagebackend = self.saved_libvirt_imagebackend
         if self.saved_libvirt:
             sys.modules['libvirt'] = self.saved_libvirt
-            nova.virt.libvirt.driver.libvirt = self.saved_libvirt
-            nova.virt.libvirt.driver.libvirt_utils = self.saved_libvirt
-            nova.virt.libvirt.firewall.libvirt = self.saved_libvirt
 
     def setUp(self):
         super(_FakeDriverBackendTestCase, self).setUp()