Coverage issues

Not making proxy object so get_size not required.

Extend tests to improve coverage

src/leveled_codec.erl

@@ -641,9 +641,7 @@ get_size(PK, Value) ->
             Size;
         ?STD_TAG ->
             {_Hash, Size} = MD,
-            Size;
-        ?HEAD_TAG ->
-            0
+            Size
     end.
 
 -spec get_keyandobjhash(tuple(), tuple()) -> tuple().