add a place for functional test to block specific regressions

We get some bugs reported in by users which we can replicate and fix
most easily in a full stack way. Having a dedicated place to put these
seems like a good idea. They are in no way an attempt to test all the
things, they are specific tests that demonstrate a bug, and ensure
that once that particular bug is fixed, it will not come back.

Change-Id: Idfd8680133197beabaf6e1ac8df7490c2a345b17
Related-Bug: #1522536

nova/tests/functional/regressions/README.rst

@@ -0,0 +1,24 @@
+================================
+ Tests for Specific Regressions
+================================
+
+When we have a bug reported by end users that we can write a full
+stack reproduce on, we should. And we should keep a regression test
+for that bug in our tree. It can be deleted at some future date if
+needed, but largely should not be changed.
+
+Writing Regression Tests
+========================
+
+- These should be full stack tests which inherit from
+  nova.test.TestCase directly. (This is to prevent coupling with other tests).
+
+- They should setup a full stack cloud in their setUp via fixtures
+
+- They should each live in a file which is named test_bug_######.py
+
+Writing Tests Before the Bug is Fixed
+=====================================
+
+TODO describe writing and landing tests before the bug is fixed as a
+reproduce.

nova/tests/functional/regressions/test_bug_1522536.py

@@ -0,0 +1,70 @@
+# Copyright 2016 HPE, Inc.
+#
+# 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.
+
+from oslo_config import cfg
+
+import nova.scheduler.utils
+import nova.servicegroup
+from nova import test
+from nova.tests import fixtures as nova_fixtures
+from nova.tests.functional.api import client
+from nova.tests.unit import cast_as_call
+import nova.tests.unit.image.fake
+from nova.tests.unit import policy_fixture
+
+CONF = cfg.CONF
+
+
+class TestServerGet(test.TestCase):
+    REQUIRES_LOCKING = True
+
+    def setUp(self):
+        super(TestServerGet, self).setUp()
+        self.useFixture(policy_fixture.RealPolicyFixture())
+        api_fixture = self.useFixture(nova_fixtures.OSAPIFixture(
+            api_version='v2.1'))
+
+        self.api = api_fixture.api
+
+        # the image fake backend needed for image discovery
+        nova.tests.unit.image.fake.stub_out_image_service(self)
+
+        self.start_service('conductor', manager=CONF.conductor.manager)
+        self.flags(scheduler_driver='chance_scheduler')
+        self.start_service('scheduler')
+        self.network = self.start_service('network')
+        self.compute = self.start_service('compute')
+
+        self.useFixture(cast_as_call.CastAsCall(self.stubs))
+        self.addCleanup(nova.tests.unit.image.fake.FakeImageService_reset)
+
+        self.image_id = self.api.get_images()[0]['id']
+        self.flavor_id = self.api.get_flavors()[0]['id']
+
+    def test_id_overlap(self):
+        """Regression test for bug #1522536.
+
+        Before fixing this bug, getting a numeric id caused a 500
+        error because it treated the numeric value as the db index,
+        fetched the server, but then processing of extensions blew up.
+
+        Since we have fixed this bug it returns a 404, which is
+        expected. In future a 400 might be more appropriate.
+        """
+        server = dict(name='server1',
+                      imageRef=self.image_id,
+                      flavorRef=self.flavor_id)
+        self.api.post_server({'server': server})
+        self.assertRaises(client.OpenStackApiNotFoundException,
+                          self.api.get_server, 1)