Update tests

src/AFRP.hs

@@ -23,6 +23,7 @@ module AFRP
   , lMerge
   , Pair(..)
   , Request(..)
+  , SerializeUTCTime(..)
   , edge
   , duration
   , tag
@@ -308,7 +309,7 @@ instance Monoid (Event a) where
   mempty = Tick
 
 hold :: (Serialize a, Eq a) => a -> Mealy m (Event a) a
-hold def = preMapAccum step def id
+hold def = mapAccum step def id
   where
     step prev = \case
       Tick -> prev