formatted

LogEntry Nothing (Variable (Fresh 0)) []
LogEntry Nothing (Spawn 0) []
LogEntry (Just 0) (Variable (Write 0)) [BlockedOn Nothing 0]
LogEntry (Just 0) (Variable (Read 0)) []
LogEntry (Just 0) Halt [BlockedOn Nothing 0]

output

blocking program
  should not block FAILED [1]

Failures:

  1) blocking program should not block
       predicate failed on: Left [LogEntry Nothing (Variable (Fresh 0)) [],LogEntry Nothing (Spawn 0) [],LogEntry (Just 0) (Variable (Write 0)) [BlockedOn Nothing 0],LogEntry (Just 0) (Variable (Read 0)) [],LogEntry (Just 0) Halt [BlockedOn Nothing 0]] (after 2 tests): 
       nothing

Randomized with seed 161312233

structured_logs.hs

raceCondition :: MVarM s ()
raceCondition = do
  v <- newMVar :: MVarM s (MVar s ())
  fork $ do
    putMVar v ()
    takeMVar v
  takeMVar v


main :: IO ()
main = hspec $ do
  describe "blocking program" $ do
    it "should not block" $ property $ \s -> do
      res <- interpret s raceCondition
      res `shouldSatisfy` (isRight)