Mock path properly in test code for wrapped action.

Error checking code added elsewhere now means Things
must have a `path` property or we can't generate the
Thing Description. I've added this manually in test code, so we
don't need a server.

Author: rwb27

tests/test_actions.py

@@ -183,6 +183,7 @@ def decorated(
 
     # Check we can make the thing and it has a valid TD
     example = Example()
+    example.path = "/example"
     example.validate_thing_description()