Refactor test_ipam functional testing module

Use existing testing ifrastructure to better integrate with the rest of
Neutron tests. This change allows test_ipam module to work with future
db engine facade changes.

Change-Id: I6c95cce56f36dd0c97f727c337ef6af04bc13a40
Related-Bug: 1520719

neutron/tests/functional/db/test_ipam.py

@@ -14,7 +14,6 @@
 #    under the License.
 
 from oslo_config import cfg
-from oslo_db.sqlalchemy import session
 import testtools
 
 from neutron.api.v2 import attributes
@@ -22,42 +21,32 @@ from neutron.common import constants
 from neutron.common import exceptions as n_exc
 from neutron import context
 from neutron.db import db_base_plugin_v2 as base_plugin
-from neutron.db import model_base
 from neutron.db import models_v2
 from neutron.ipam.drivers.neutrondb_ipam import db_models as ipam_models
 from neutron.tests import base
 from neutron.tests.common import base as common_base
+from neutron.tests.unit import testlib_api
 
 
-def get_admin_test_context(db_url):
-    """
-    get_admin_test_context is used to provide a test context. A new session is
-    created using the db url specified
-    """
-    ctx = context.Context(user_id=None,
-                          tenant_id=None,
-                          is_admin=True,
-                          overwrite=False)
-    facade = session.EngineFacade(db_url, mysql_sql_mode='STRICT_ALL_TABLES')
-    ctx._session = facade.get_session(autocommit=False, expire_on_commit=True)
-    return ctx
-
-
-class IpamTestCase(object):
+class IpamTestCase(base.BaseTestCase):
     """
     Base class for tests that aim to test ip allocation.
     """
+    use_pluggable_ipam = False
 
-    def configure_test(self, use_pluggable_ipam=False):
-        model_base.BASEV2.metadata.create_all(self.engine)
+    def setUp(self):
+        super(IpamTestCase, self).setUp()
         cfg.CONF.set_override('notify_nova_on_port_status_changes', False)
-        if use_pluggable_ipam:
+        self.useFixture(testlib_api.SqlFixture())
+        if self.use_pluggable_ipam:
             self._turn_on_pluggable_ipam()
         else:
             self._turn_off_pluggable_ipam()
         self.plugin = base_plugin.NeutronDbPluginV2()
-        self.cxt = get_admin_test_context(self.engine.url)
-        self.addCleanup(self.cxt._session.close)
+        self.cxt = context.Context(user_id=None,
+                                   tenant_id=None,
+                                   is_admin=True,
+                                   overwrite=False)
         self.tenant_id = 'test_tenant'
         self.network_id = 'test_net_id'
         self.subnet_id = 'test_sub_id'
@@ -219,33 +208,17 @@ class IpamTestCase(object):
             ip_avail_ranges_expected)
 
 
-class TestIpamMySql(common_base.MySQLTestCase, base.BaseTestCase,
-                    IpamTestCase):
-
-    def setUp(self):
-        super(TestIpamMySql, self).setUp()
-        self.configure_test()
+class TestIpamMySql(common_base.MySQLTestCase, IpamTestCase):
+    pass
 
 
-class TestIpamPsql(common_base.PostgreSQLTestCase,
-                   base.BaseTestCase, IpamTestCase):
-
-    def setUp(self):
-        super(TestIpamPsql, self).setUp()
-        self.configure_test()
+class TestIpamPsql(common_base.PostgreSQLTestCase, IpamTestCase):
+    pass
 
 
-class TestPluggableIpamMySql(common_base.MySQLTestCase,
-                             base.BaseTestCase, IpamTestCase):
-
-    def setUp(self):
-        super(TestPluggableIpamMySql, self).setUp()
-        self.configure_test(use_pluggable_ipam=True)
+class TestPluggableIpamMySql(common_base.MySQLTestCase, IpamTestCase):
+    use_pluggable_ipam = True
 
 
-class TestPluggableIpamPsql(common_base.PostgreSQLTestCase,
-                            base.BaseTestCase, IpamTestCase):
-
-    def setUp(self):
-        super(TestPluggableIpamPsql, self).setUp()
-        self.configure_test(use_pluggable_ipam=True)
+class TestPluggableIpamPsql(common_base.PostgreSQLTestCase, IpamTestCase):
+    use_pluggable_ipam = True