Test that no router namespace is created for DVR on compute node

Namespace should be only created if there is VM with router that is set
as a default gateway. Need to verify that there will be no namespace
created on the compute node where VM is connected to the external
network. The same network is used as the default gateway for the router

Change-Id: I4aa338a0eaa1d50f043129e7628a8693bfcc272b

tobiko/tests/scenario/neutron/test_router.py

@@ -130,3 +130,36 @@ class L3HARouterTest(RouterTest):
         for backup_agent in backup_agents:
             self._check_routers_namespace_on_host(
                 backup_agent['host'], state="backup")
+
+
+class NetworkWithNoServersStack(stacks.NetworkStackFixture):
+    pass
+
+
+@neutron.skip_unless_is_ovs()
+class DVRTest(testtools.TestCase):
+
+    router_stack = tobiko.required_setup_fixture(NetworkWithNoServersStack)
+    server_stack = tobiko.required_setup_fixture(
+            stacks.CirrosExternalServerStackFixture)
+
+    def setUp(self):
+        super(DVRTest, self).setUp()
+        if not self.router_stack.gateway_details.get('distributed'):
+            tobiko.skip_test('No DVR enabled')
+
+    def test_router_not_created_on_compute_if_no_instance_connected(self):
+        '''Test that no router namespace is created for DVR on compute node
+
+        Namespace should be only created if there is VM with router that is set
+        as a default gateway. Need to verify that there will be no namespace
+        created on the compute node where VM is connected to the external
+        network. The same network is used as the default gateway for the router
+        '''
+
+        router_namespace = f'qrouter-{self.router_stack.gateway_details["id"]}'
+        cirros_hypervisor = topology.get_openstack_node(
+                hostname=self.server_stack.hypervisor_host)
+        namespaces = ip.list_network_namespaces(
+            ssh_client=cirros_hypervisor.ssh_client)
+        self.assertNotIn(router_namespace, namespaces)