produce and verify output in performEvent test

test/RequesterT.hs

@@ -1,3 +1,4 @@
+{-# LANGUAGE AllowAmbiguousTypes #-}
 {-# LANGUAGE CPP #-}
 {-# LANGUAGE BangPatterns #-}
 {-# LANGUAGE FlexibleContexts #-}
@@ -80,6 +81,7 @@ main = do
   let ![[Nothing, Nothing]] = os6 -- TODO re-enable this test after issue #233 has been resolved
   let !(Just [(-9223372036854775808,"2")]) = M.toList <$> head (head os7)
   let !(Just [(-9223372036854775808,"dcba")]) = M.toList <$> head (head os8)
+  let ![[Nothing,Just "0:1"],[Nothing,Just "1:2"],[Nothing,Just "2:3"]] = os9
   return ()
 
 unwrapApp :: forall t m a.
@@ -241,17 +243,26 @@ testMatchRequestsWithResponses pulse = mdo
       , \x -> has @Read r $ readMaybe x
       )
 
--- If a widget is destroyed, and simultaneously it tries to use performEvent, the event shouldn't be performed.
+-- If a widget is destroyed, and simultaneously it tries to use performEvent, the event does not get performed.
+-- TODO Determine whether this is actually the behavior we want.
 testMoribundPerformEvent
-  :: ( Adjustable t m
+  :: forall t m
+   . ( Adjustable t m
      , PerformEvent t m
      , MonadIO (Performable m)
+     , MonadHold t m
+     , Reflex t
      )
-  => Event t Int -> m (Event t ())
+  => Event t Int -> m (Event t String)
 testMoribundPerformEvent pulse = do
-  runWithReplace (performEvent $ liftIO . print <$> pulse) $ ffor pulse $ \i -> do
-    performEvent $ liftIO . print <$> pulse
-    pure ()
-  pure never
+  (outputInitial, outputReplaced) <- runWithReplace (performPrint 0 pulse) $ ffor pulse $ \i -> performPrint i pulse
+  switchHold outputInitial outputReplaced
+  where
+    performPrint i evt =
+      let outputEvt = ((show i <> ":") <>) . show <$> evt
+      in performEvent $ ffor outputEvt $ \output ->
+        let msg = show i <> ":" <> show output
+        in return output
+
 
 deriveArgDict ''TestRequest