updated network test to use correct interface if multiple present

molecule/testinfra/app/test_app_network.py

@@ -15,8 +15,10 @@ def test_app_iptables_rules(host):
     # Build a dict of variables to pass to jinja for iptables comparison
     kwargs = dict(
         mon_ip=os.environ.get('MON_IP', securedrop_test_vars.mon_ip),
-        default_interface=host.check_output("ip r | head -n 1 | "
-                                            "awk '{ print $5 }'"),
+        app_ip=os.environ.get('APP_IP', securedrop_test_vars.app_ip),
+        default_interface=host.check_output("ip r | grep -v default | "
+                                            "grep {} ".format(app_ip)
+                                            "awk '{ print $3 }'"),
         tor_user_id=host.check_output("id -u debian-tor"),
         securedrop_user_id=host.check_output("id -u www-data"),
         ssh_group_gid=host.check_output("getent group ssh | cut -d: -f3"),