diff --git a/lib/Quox/Parser/FromParser.idr b/lib/Quox/Parser/FromParser.idr
index 6326a5e..afe2ae4 100644
--- a/lib/Quox/Parser/FromParser.idr
+++ b/lib/Quox/Parser/FromParser.idr
@@ -13,7 +13,7 @@ import System.File
 import System.Path
 import Data.IORef
 
-import public Quox.Parser.FromParser.Error
+import public Quox.Parser.FromParser.Error as Quox.Parser.FromParser
 
 %default total
 
diff --git a/tests/Tests/Equal.idr b/tests/Tests/Equal.idr
index bf1472b..54dc143 100644
--- a/tests/Tests/Equal.idr
+++ b/tests/Tests/Equal.idr
@@ -1,12 +1,14 @@
 module Tests.Equal
 
 import Quox.Equal
+import Quox.Typechecker
 import Quox.Syntax.Qty.Three
 import public TypingImpls
 import TAP
+import Quox.EffExtra
 
 0 M : Type -> Type
-M = ReaderT (Definitions Three) (Either (Error Three))
+M = TC Three
 
 defGlobals : Definitions Three
 defGlobals = fromList
@@ -23,10 +25,10 @@ defGlobals = fromList
 parameters (label : String) (act : Lazy (M ()))
            {default defGlobals globals : Definitions Three}
   testEq : Test
-  testEq = test label $ runReaderT globals act
+  testEq = test label $ runTC globals act
 
   testNeq : Test
-  testNeq = testThrows label (const True) $ runReaderT globals act $> "()"
+  testNeq = testThrows label (const True) $ runTC globals act $> "()"
 
 
 parameters (0 d : Nat) (ctx : TyContext Three d n)
diff --git a/tests/Tests/FromPTerm.idr b/tests/Tests/FromPTerm.idr
index 211cf26..05b65fe 100644
--- a/tests/Tests/FromPTerm.idr
+++ b/tests/Tests/FromPTerm.idr
@@ -1,11 +1,12 @@
 module Tests.FromPTerm
 
-import Quox.Parser.Syntax
+import Quox.Parser.FromParser
 import Quox.Parser
 import TermImpls
 import TypingImpls
 import Tests.Parser as TParser
 import TAP
+import Quox.EffExtra
 
 import System.File
 import Derive.Prelude
@@ -16,21 +17,19 @@ import Derive.Prelude
 
 public export
 data Failure =
-    ParseError (Parser.Error)
-  | FromParser FromParserError
+    ParseError Parser.Error
+  | FromParser FromParser.Error
   | WrongResult String
   | ExpectedFail String
 
 %runElab derive "FileError" [Show]
-%runElab derive "Parser.Error" [Show]
-%runElab derive "FromParserError" [Show]
 
 export
 ToInfo Failure where
   toInfo (ParseError err) = toInfo err
   toInfo (FromParser err) =
     [("type", "FromParserError"),
-     ("got", show err)]
+     ("got", show $ prettyError True True err)]
   toInfo (WrongResult got) =
     [("type", "WrongResult"), ("got", got)]
   toInfo (ExpectedFail got) =
@@ -38,7 +37,7 @@ ToInfo Failure where
 
 
 parameters {c : Bool} {auto _ : Show b}
-           (grm : Grammar c a) (fromP : a -> Either FromParserError b)
+           (grm : Grammar c a) (fromP : a -> Either FromParser.Error b)
            (inp : String)
   parameters {default (ltrim inp) label : String}
     parsesWith : (b -> Bool) -> Test
@@ -62,11 +61,14 @@ parameters {c : Bool} {auto _ : Show b}
 
 FromString BName where fromString = Just . fromString
 
+runFromParser : Eff [Except FromParser.Error] a -> Either FromParser.Error a
+runFromParser = extract . runExcept
+
 export
 tests : Test
 tests = "PTerm → Term" :- [
   "dimensions" :-
-  let fromPDim = fromPDimWith [< "𝑖", "𝑗"]
+  let fromPDim = runFromParser . fromPDimWith [< "𝑖", "𝑗"]
   in [
     note "dim ctx: [𝑖, 𝑗]",
     parsesAs dim fromPDim "𝑖" (BV 1),
@@ -77,18 +79,19 @@ tests = "PTerm → Term" :- [
   ],
 
   "terms" :-
-  let fromPTerm' = fromPTermWith [< "𝑖", "𝑗"] [< "A", "x", "y", "z"]
+  let fromPTerm = runFromParser .
+                  fromPTermWith [< "𝑖", "𝑗"] [< "A", "x", "y", "z"]
   in [
     note "dim ctx: [𝑖, 𝑗]; term ctx: [A, x, y, z]",
-    parsesAs term fromPTerm' "x" $ BVT 2,
-    parseFails term fromPTerm' "𝑖",
-    parsesAs term fromPTerm' "f" $ FT "f",
-    parsesAs term fromPTerm' "λ w ⇒ w" $ [< "w"] :\\ BVT 0,
-    parsesAs term fromPTerm' "λ w ⇒ x" $ [< "w"] :\\ BVT 3,
-    parsesAs term fromPTerm' "λ x ⇒ x" $ [< "x"] :\\ BVT 0,
-    parsesAs term fromPTerm' "λ a b ⇒ f a b" $
+    parsesAs term fromPTerm "x" $ BVT 2,
+    parseFails term fromPTerm "𝑖",
+    parsesAs term fromPTerm "f" $ FT "f",
+    parsesAs term fromPTerm "λ w ⇒ w" $ [< "w"] :\\ BVT 0,
+    parsesAs term fromPTerm "λ w ⇒ x" $ [< "w"] :\\ BVT 3,
+    parsesAs term fromPTerm "λ x ⇒ x" $ [< "x"] :\\ BVT 0,
+    parsesAs term fromPTerm "λ a b ⇒ f a b" $
       [< "a", "b"] :\\ E (F "f" :@@ [BVT 1, BVT 0]),
-    parsesAs term fromPTerm' "f @𝑖" $
+    parsesAs term fromPTerm "f @𝑖" $
       E $ F "f" :% BV 1
   ],
 
diff --git a/tests/Tests/Typechecker.idr b/tests/Tests/Typechecker.idr
index 7cdc972..deb04b7 100644
--- a/tests/Tests/Typechecker.idr
+++ b/tests/Tests/Typechecker.idr
@@ -5,6 +5,7 @@ import Quox.Syntax.Qty.Three
 import Quox.Typechecker as Lib
 import public TypingImpls
 import TAP
+import Quox.EffExtra
 
 
 data Error'
@@ -25,13 +26,10 @@ ToInfo Error' where
      ("wanted", prettyStr True bad)]
 
 0 M : Type -> Type
-M = ReaderT (Definitions Three) $ Either Error'
+M = Eff [Except Error', DefsReader Three]
 
-inj : (forall m. CanTC Three m => m a) -> M a
-inj act = do
-  env <- ask
-  let res = runReaderT env act {m = Either (Typing.Error Three)}
-  either (throwError . TCError) pure res
+inj : TC Three a -> M a
+inj = rethrow . mapFst TCError <=< lift . runExcept
 
 
 reflTy : IsQty q => Term q d n
@@ -92,10 +90,12 @@ defGlobals = fromList
 parameters (label : String) (act : Lazy (M ()))
            {default defGlobals globals : Definitions Three}
   testTC : Test
-  testTC = test label $ runReaderT globals act
+  testTC = test label {e = Error', a = ()} $
+    extract $ runExcept $ runReader globals act
 
   testTCFail : Test
-  testTCFail = testThrows label (const True) $ runReaderT globals act $> "()"
+  testTCFail = testThrows label (const True) $
+    (extract $ runExcept $ runReader globals act) $> "()"
 
 
 anys : {n : Nat} -> QContext Three n
@@ -114,12 +114,10 @@ empty01 = eqDim (K Zero) (K One) empty
 
 inferredTypeEq : TyContext Three d n -> (exp, got : Term Three d n) -> M ()
 inferredTypeEq ctx exp got =
-  catchError
-    (inj $ equalType ctx exp got)
-    (\_ : Error' => throwError $ WrongInfer exp got)
+  wrapErr (const $ WrongInfer exp got) $ inj $ equalType ctx exp got
 
 qoutEq : (exp, got : QOutput Three n) -> M ()
-qoutEq qout res = unless (qout == res) $ throwError $ WrongQOut qout res
+qoutEq qout res = unless (qout == res) $ throw $ WrongQOut qout res
 
 inferAs : TyContext Three d n -> (sg : SQty Three) ->
           Elim Three d n -> Term Three d n -> M ()
@@ -395,7 +393,7 @@ tests = "typechecker" :- [
     testTC "0 · ℕ ⇐ ★₇" $ check_ empty szero Nat (TYPE 7),
     testTCFail "1 · ℕ ⇍ ★₀" $ check_ empty sone Nat (TYPE 0),
     testTC "1 · zero ⇐ ℕ" $ check_ empty sone Zero Nat,
-    testTC "1 · zero ⇍ ℕ×ℕ" $ check_ empty sone Zero (Nat `And` Nat),
+    testTCFail "1 · zero ⇍ ℕ×ℕ" $ check_ empty sone Zero (Nat `And` Nat),
     testTC "ω·n : ℕ ⊢ 1 · succ n ⇐ ℕ" $
       check_ (ctx [< ("n", Nat)]) sone (Succ (BVT 0)) Nat,
     testTC "1 · λ n ⇒ succ n ⇐ 1.ℕ → ℕ" $
diff --git a/tests/quox-tests.ipkg b/tests/quox-tests.ipkg
index 62766f0..0f576bb 100644
--- a/tests/quox-tests.ipkg
+++ b/tests/quox-tests.ipkg
@@ -1,6 +1,6 @@
 package quox-tests
 
-depends = base, contrib, elab-util, snocvect, quox-lib, tap
+depends = base, contrib, elab-util, snocvect, quox-lib, tap, eff
 
 executable = quox-tests
 main = Tests