diff --git a/nova/test.py b/nova/test.py
index 4f3554d6826b..562bd2516ebd 100644
--- a/nova/test.py
+++ b/nova/test.py
@@ -66,7 +66,6 @@ from nova.tests import fixtures as nova_fixtures
 from nova.tests.unit import matchers
 from nova import utils
 from nova.virt import images
-from nova.virt import node
 
 CONF = cfg.CONF
 
@@ -302,7 +301,6 @@ class TestCase(base.BaseTestCase):
 
         # Reset our local node uuid cache (and avoid writing to the
         # local filesystem when we generate a new one).
-        node.LOCAL_NODE_UUID = None
         self.useFixture(nova_fixtures.ComputeNodeIdFixture())
 
     def _setup_cells(self):
diff --git a/nova/tests/fixtures/nova.py b/nova/tests/fixtures/nova.py
index 54ef4d2b8d2d..76dc63755d8a 100644
--- a/nova/tests/fixtures/nova.py
+++ b/nova/tests/fixtures/nova.py
@@ -65,6 +65,7 @@ from nova.scheduler import weights
 from nova import service
 from nova.tests.functional.api import client
 from nova import utils
+from nova.virt import node
 
 CONF = cfg.CONF
 LOG = logging.getLogger(__name__)
@@ -1855,6 +1856,7 @@ class ComputeNodeIdFixture(fixtures.Fixture):
     def setUp(self):
         super().setUp()
 
+        node.LOCAL_NODE_UUID = None
         self.useFixture(fixtures.MockPatch(
             'nova.virt.node.read_local_node_uuid',
             lambda: None))
diff --git a/nova/tests/functional/integrated_helpers.py b/nova/tests/functional/integrated_helpers.py
index 2dd840259f7b..ca6fd48e8cab 100644
--- a/nova/tests/functional/integrated_helpers.py
+++ b/nova/tests/functional/integrated_helpers.py
@@ -1230,8 +1230,6 @@ class _IntegratedTestBase(test.TestCase, PlacementInstanceHelperMixin):
         self.glance = self.useFixture(nova_fixtures.GlanceFixture(self))
         self.policy = self.useFixture(nova_fixtures.RealPolicyFixture())
 
-        self.useFixture(nova_fixtures.ComputeNodeIdFixture())
-
         self.notifier = self.useFixture(
             nova_fixtures.NotificationFixture(self))
 
@@ -1303,8 +1301,6 @@ class ProviderUsageBaseTestCase(test.TestCase, PlacementInstanceHelperMixin):
         self.placement = self.useFixture(func_fixtures.PlacementFixture()).api
         self.useFixture(nova_fixtures.AllServicesCurrent())
 
-        self.useFixture(nova_fixtures.ComputeNodeIdFixture())
-
         self.notifier = self.useFixture(
             nova_fixtures.NotificationFixture(self))
 
diff --git a/nova/tests/unit/virt/test_node.py b/nova/tests/unit/virt/test_node.py
index cc99268eb440..668b7625203c 100644
--- a/nova/tests/unit/virt/test_node.py
+++ b/nova/tests/unit/virt/test_node.py
@@ -72,7 +72,8 @@ class TestNodeIdentity(testtools.TestCase):
 
     def test_generate_local_node_uuid_unexpected_write_fail(self):
         with mock.patch('builtins.open') as mock_open:
-            mock_open.return_value.write.side_effect = IndexError()
+            mock_write = mock_open.return_value.__enter__.return_value.write
+            mock_write.side_effect = IndexError()
             e = self.assertRaises(exception.InvalidNodeConfiguration,
                                   node.write_local_node_uuid, 'foo')
             self.assertIn('Unable to write uuid to %s' % (
diff --git a/nova/virt/node.py b/nova/virt/node.py
index e567ad28e2a2..4cb3d0a57365 100644
--- a/nova/virt/node.py
+++ b/nova/virt/node.py
@@ -35,7 +35,8 @@ def write_local_node_uuid(node_uuid):
     # Try to create the identity file and write our uuid into it. Fail
     # if the file exists (since it shouldn't if we made it here).
     try:
-        open(fn, 'x').write(node_uuid)
+        with open(fn, 'x') as f:
+            f.write(node_uuid)
     except FileExistsError:
         # If the file exists, we must either fail or re-survey all the
         # potential files. If we just read and return it, it could be