diff --git a/tests.py b/tests.py
index 4195a55..0c66442 100755
--- a/tests.py
+++ b/tests.py
@@ -85,8 +85,8 @@ class YAMLTest(unittest.TestCase):
                     this_msg_expected = True
                     break
             if not this_msg_expected:
-                print(f"{self.yaml_filename}: Unexpected message: {m}", file=sys.stderr)
-                fail = True
+              print(f"{self.yaml_filename}: Unexpected message: {m}", file=sys.stderr)
+              fail = True
 
         count = 0
         if (
diff --git a/vpp/applier.py b/vpp/applier.py
new file mode 100644
index 0000000..6d729fe
--- /dev/null
+++ b/vpp/applier.py
@@ -0,0 +1,105 @@
+"""
+The functions in this file interact with the VPP API to modify certain
+interface metadata.
+"""
+
+from vpp.vppapi import VPPApi
+
+
+class Applier(VPPApi):
+    """The methods in the Applier class modify the running state in the VPP dataplane
+    and will ensure that the local cache is consistent after creations and
+    modifications."""
+
+    def __init__(self, address="/run/vpp/api.sock", clientname="vppcfg"):
+        VPPApi.__init__(self, address, clientname)
+        self.logger.info("VPP Applier: changing the dataplane is enabled")
+
+    def set_interface_ip_address(self, ifname, address, is_set=True):
+        pass
+
+    def delete_loopback(self, ifname):
+        pass
+
+    def delete_subinterface(self, ifname):
+        pass
+
+    def set_interface_l2_tag_rewrite(self, ifname, mode):
+        ## somewhere in interface.api see vtr_* fields
+        pass
+
+    def set_interface_l3(self, ifname):
+        pass
+
+    def delete_bridgedomain(self, instance):
+        pass
+
+    def delete_tap(self, ifname):
+        pass
+
+    def bond_remove_member(self, bondname, membername):
+        pass
+
+    def delete_bond(self, ifname):
+        pass
+
+    def create_vxlan_tunnel(self, instance, config, is_create=True):
+        """'config' is the YAML configuration for the vxlan_tunnels: entry"""
+        pass
+
+    def delete_subinterface(self, ifname):
+        pass
+
+    def set_interface_link_mtu(self, ifname, link_mtu):
+        pass
+
+    def lcp_delete(self, lcpname):
+        pass
+
+    def set_interface_packet_mtu(self, ifname, packet_mtu):
+        pass
+
+    def set_interface_state(self, ifname, state):
+        pass
+
+    def create_loopback_interface(self, instance, config):
+        """'config' is the YAML configuration for the loopbacks: entry"""
+        pass
+
+    def create_bond(self, instance, config):
+        """'config' is the YAML configuration for the bondethernets: entry"""
+        pass
+
+    def create_subinterface(self, parent_ifname, sub_id, config):
+        """'config' is the YAML configuration for the sub-interfaces: entry"""
+        pass
+
+    def create_tap(self, instance, config):
+        """'config' is the YAML configuration for the taps: entry"""
+        pass
+
+    def create_bridgedomain(self, instance, config):
+        """'config' is the YAML configuration for the bridgedomains: entry"""
+        pass
+
+    def lcp_create(self, ifname, host_if_name):
+        pass
+
+    def set_interface_mac(self, ifname, mac):
+        pass
+
+    def bond_add_member(self, bondname, membername):
+        pass
+
+    def sync_bridgedomain(self, instance, config):
+        """'config' is the YAML configuration for the bridgedomains: entry"""
+        pass
+
+    def set_interface_l2_bridge_bvi(self, instance, ifname):
+        pass
+
+    def set_interface_l2_bridge(self, instance, ifname):
+        pass
+
+    def set_interface_l2xc(self, rx_ifname, tx_ifname):
+        pass