Add Show ' os-attach-interfaces ' policy tests

Change-Id: Ic6b2b8530b7f736a97270c1d278f2563719d0e53
diff --git a/patrole_tempest_plugin/tests/api/compute/test_server_misc_policy_actions_rbac.py b/patrole_tempest_plugin/tests/api/compute/test_server_misc_policy_actions_rbac.py
index 9ce4ba0..f15dd78 100644
--- a/patrole_tempest_plugin/tests/api/compute/test_server_misc_policy_actions_rbac.py
+++ b/patrole_tempest_plugin/tests/api/compute/test_server_misc_policy_actions_rbac.py
@@ -571,6 +571,20 @@
         self.interfaces_client.list_interfaces(
             self.server['id'])['interfaceAttachments']
 
+    @decorators.idempotent_id('1b9cf7db-dc50-48a2-8eb9-8c25af5e934a')
+    @testtools.skipUnless(CONF.compute_feature_enabled.interface_attach,
+                          "Interface attachment is not available.")
+    @utils.requires_ext(extension='os-attach-interfaces', service='compute')
+    @rbac_rule_validation.action(
+        service="nova",
+        rule="os_compute_api:os-attach-interfaces")
+    def test_show_interface(self):
+        """Test show interfaces, part of os-attach-interfaces."""
+        interface = self._attach_interface_to_server()
+        self.rbac_utils.switch_role(self, toggle_rbac_role=True)
+        self.interfaces_client.show_interface(
+            self.server['id'], interface['port_id'])['interfaceAttachment']
+
     @testtools.skipUnless(CONF.compute_feature_enabled.interface_attach,
                           "Interface attachment is not available.")
     @utils.requires_ext(extension='os-attach-interfaces', service='compute')