diff --git a/nova/tests/functional/test_monkey_patch.py b/nova/tests/functional/test_monkey_patch.py
new file mode 100644
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+++ b/nova/tests/functional/test_monkey_patch.py
@@ -0,0 +1,45 @@
+# Copyright 2020 Red Hat, Inc.  All rights reserved.
+#
+#    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.
+
+# NOTE(artom) This file exists to test eventlet monkeypatching. How and what
+# eventlet monkeypatches can be controlled by environment variables that
+# are processed by eventlet at import-time (for exmaple, EVENTLET_NO_GREENDNS).
+# Nova manages all of this in nova.monkey_patch. Therefore, nova.monkey_patch
+# must be the first thing to import eventlet. As nova.tests.functional.__init__
+# imports nova.monkey_patch, we're OK here.
+
+import socket
+import traceback
+
+from nova import test
+
+
+class TestMonkeyPatch(test.TestCase):
+
+    def test_greendns_is_disabled(self):
+        """Try to resolve a fake fqdn. If we see greendns mentioned in the
+        traceback of the raised exception, it means we've not actually disabled
+        greendns. See the TODO and NOTE in nova.monkey_patch to understand why
+        greendns needs to be disabled.
+        """
+        raised = False
+        try:
+            socket.gethostbyname('goat.fake')
+        except Exception:
+            tb = traceback.format_exc()
+            # NOTE(artom) If we've correctly disabled greendns, we expect the
+            # traceback to not contain any reference to it.
+            self.assertNotIn('greendns.py', tb)
+            raised = True
+        self.assertTrue(raised)