Add test for extensions api

Change-Id: I973bae24d6cae98bc19e1799a51838c82de4cb7d

venus/tests/unit/api/test_extensions.py

@@ -0,0 +1,22 @@
+# Copyright 2023 Inspur
+#
+# 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.
+
+import unittest
+from venus.api import extensions
+
+
+class TestExtensions(unittest.TestCase):
+    def setUp(self):
+        self.extensions = extensions
+        super(TestExtensions, self).setUp()