I think I'm on the right track. I have commented out all test harness code and have changed the signature for bufferPopulated

bufferPopulated :: UAC -> IO Bool
bufferPopulated ev = do
  let eInput = ev <$ never
      eValidated = toVAC <$> eInput
  bBufferMap <- liftMoment ((buffer eValidated eClear) :: Moment    (Behavior BufferMap)) 
  let r2 = [(Just $ BufferMap $ M.insert (AID (Data.Text.pack "100")) (toVAC ev) (M.empty :: M.Map AID VAC))]
  r1 <- (interpret (eBuffer bBufferMap) []) :: IO [Maybe BufferMap])          
  return $ r1 == r2

I believe this should work, but here's the error

tests/Spec.hs:35:17:
    No instance for (MonadMoment IO) arising from a use of ‘liftMoment’
    In a stmt of a 'do' block:
      bBufferMap <- liftMoment
                      ((buffer eValidated eClear) :: Moment (Behavior   BufferMap))

Let's take a look at MonadMoment from Reactive.Banana.Combinators

class Monad m => MonadMoment m where
 An instance of the MonadMoment class denotes a computation that happens at one particular moment in time.
 Unlike the Moment monad, it need not be pure anymore.
 Methods
   liftMoment :: Moment a -> m a
 Instances
 MonadMoment MomentIO
 MonadMoment Moment

m can be any Monad, IO is a Monad. so liftMoment should lift the Moment Behavior (BufferMap) to IO Behavior (BufferMap) , why doesn't it. What's wrong with my reasoning?

On Fri, Nov 13, 2015 at 7:16 AM, Michael Litchard <michael@schmong.org> wrote:

Below is some test code I am writing for my game, the link to the entire codebase, the error message and some discussion

main :: IO ()
main = defaultMain
  [ testGroup "EventNetwork Input"
    [testBuffer "bBuffer" Populated]
  ]

testBuffer :: String -> BufferState -> Test
testBuffer name Populated =
  testCase name $ assert $ bufferPopulated (UAC (PlayerCommand (Move (ToPlanetName Mongo)) (AID (Data.Text.pack "100"))))
testBuffer name Empty =
  testCase name $ assert $ bufferEmptied (UAC (PlayerCommand (Move (ToPlanetName Mongo)) (AID (Data.Text.pack "100"))))

bufferPopulated :: UAC -> MomentIO Bool
bufferPopulated ev = do
  let eInput = ev <$ never
      eValidated = toVAC <$> eInput
  bBufferMap <- (buffer eValidated eClear) :: MomentIO (Behavior BufferMap)
  let r2 = [(Just $ BufferMap $ M.insert (AID (Data.Text.pack "100")) (toVAC ev) (M.empty :: M.Map AID VAC))]
  r1 <- liftIO $ ((interpret (eBuffer bBufferMap) []) :: IO [Maybe BufferMap])
  return $ r1 == r2

bufferEmptied :: UAC -> MomentIO Bool
bufferEmptied ev = undefined

eBuffer :: Behavior BufferMap -> Event a -> Event BufferMap
eBuffer bBufferMap nvr =
  bBufferMap <@ (() <$ nvr)

eClear = Clear <$ (() <$ never)


When I run stack build I get

tests/Spec.hs:26:19:
    No instance for (Test.HUnit.Base.Assertable (MomentIO Bool))
      arising from a use of ‘assert’
In the expression: assert
In the second argument of ‘($)’, namely
  ‘assert
   $ bufferPopulated
       (UAC
          (PlayerCommand (Move (ToPlanetName Mongo)) (AID (pack "100"))))’
In the expression:
  testCase name
  $ assert
    $ bufferPopulated
        (UAC
           (PlayerCommand (Move (ToPlanetName Mongo)) (AID (pack "100"))))

The problem lies with buffer. It relies on accumB which requires the MomentIO monad. I considered writing an
instance for Assertable, but I think that's a red-herring and the answer lies elsewhere. I need to reconcile the 
fact that assert wants an IO Bool, but accumB wants a MomentIO. Maybe I do need to write an instance for Assertable.

Here's the link to the project:
https://github.com/mlitchard/emporos/tree/banana-1.0.0/src