diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 0b3ca67..c842755 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -15,6 +15,8 @@ jobs:
 
       - name: Set up PureScript toolchain
         uses: purescript-contrib/setup-purescript@main
+        with:
+          purescript: "0.14.0-rc3"
 
       - name: Cache PureScript dependencies
         uses: actions/cache@v2
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 3db9d6b..f64c3b2 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -11,6 +11,7 @@ New features:
 Bugfixes:
 
 Other improvements:
+- Changed test library from `spec` to `assert`
 
 ## [v4.0.1](https://github.com/purescript-contrib/purescript-formatters/releases/tag/v4.0.1) - 2019-02-09
 
diff --git a/packages.dhall b/packages.dhall
index b5baf39..9c3ee6f 100644
--- a/packages.dhall
+++ b/packages.dhall
@@ -1,4 +1,4 @@
 let upstream =
-      https://github.com/purescript/package-sets/releases/download/psc-0.13.8-20200922/packages.dhall sha256:5edc9af74593eab8834d7e324e5868a3d258bbab75c5531d2eb770d4324a2900
+      https://raw.githubusercontent.com/purescript/package-sets/prepare-0.14/src/packages.dhall
 
 in  upstream
diff --git a/spago.dhall b/spago.dhall
index 96f0667..00dcc81 100644
--- a/spago.dhall
+++ b/spago.dhall
@@ -1,16 +1,17 @@
 { name = "formatters"
 , dependencies =
   [ "aff"
+  , "assert"
   , "console"
   , "datetime"
   , "effect"
   , "fixed-points"
   , "generics-rep"
   , "lists"
+  , "numbers"
   , "parsing"
   , "prelude"
   , "psci-support"
-  , "spec"
   , "transformers"
   ]
 , packages = ./packages.dhall
diff --git a/src/Data/Formatter/Parser/Interval.purs b/src/Data/Formatter/Parser/Interval.purs
index ccede26..330c9cd 100644
--- a/src/Data/Formatter/Parser/Interval.purs
+++ b/src/Data/Formatter/Parser/Interval.purs
@@ -10,7 +10,7 @@ import Prelude
 
 import Control.Alt ((<|>))
 import Data.DateTime (DateTime)
-import Data.Either (Either(..), fromRight)
+import Data.Either (Either(..), either)
 import Data.Foldable (class Foldable, fold, foldMap, intercalate)
 import Data.Formatter.DateTime (unformatParser, Formatter, parseFormatString)
 import Data.Formatter.Parser.Number (parseNumber, parseMaybeInteger)
@@ -19,7 +19,7 @@ import Data.Interval.Duration.Iso (IsoDuration, mkIsoDuration, prettyError)
 import Data.Maybe (Maybe)
 import Data.Traversable (sequence)
 import Data.Tuple (Tuple(..), snd)
-import Partial.Unsafe (unsafePartial)
+import Partial.Unsafe (unsafeCrashWith)
 import Text.Parsing.Parser as P
 import Text.Parsing.Parser.Combinators as PC
 import Text.Parsing.Parser.String as PS
@@ -77,4 +77,4 @@ parseDateTime = unformatParser extendedDateTimeFormatInUTC
 
 extendedDateTimeFormatInUTC ∷ Formatter
 extendedDateTimeFormatInUTC = parseFormatString "YYYY-MM-DDTHH:mm:ssZ"
-  # unsafePartial fromRight -- the format must be valid ISO date format
+  # either unsafeCrashWith identity -- the format must be valid ISO date format
diff --git a/src/Data/Formatter/Parser/Number.purs b/src/Data/Formatter/Parser/Number.purs
index bbd8867..078a246 100644
--- a/src/Data/Formatter/Parser/Number.purs
+++ b/src/Data/Formatter/Parser/Number.purs
@@ -15,9 +15,9 @@ import Text.Parsing.Parser as P
 import Text.Parsing.Parser.Combinators as PC
 import Data.Formatter.Parser.Utils (oneOfAs)
 import Text.Parsing.Parser.String as PS
-import Data.Maybe (Maybe)
+import Data.Maybe (Maybe(..))
+import Data.Number (fromString)
 import Data.Foldable (foldMap)
-import Global (readFloat)
 
 parseInteger ∷ ∀ s m. Monad m ⇒ PS.StringLike s ⇒ P.ParserT s m Int
 parseInteger = some parseDigit <#> foldDigits
@@ -26,7 +26,11 @@ parseMaybeInteger ∷ ∀ s m. Monad m ⇒ PS.StringLike s ⇒ P.ParserT s m (Ma
 parseMaybeInteger = PC.optionMaybe parseInteger
 
 parseFractional ∷ ∀ s m. Monad m ⇒ PS.StringLike s ⇒ P.ParserT s m Number
-parseFractional = (some parseDigit) <#> (foldMap show >>> ("0." <> _) >>> readFloat)
+parseFractional = do
+  digitStr <- (some parseDigit) <#> (foldMap show >>> ("0." <> _))
+  case fromString digitStr of
+      Just n -> pure n
+      Nothing -> P.fail ("Not a number: " <> digitStr)
 
 parseNumber ∷ ∀ s m. Monad m ⇒ PS.StringLike s ⇒ P.ParserT s m Number
 parseNumber = (+)
diff --git a/test/src/DateTime.purs b/test/src/DateTime.purs
index 7bf81c9..643519a 100644
--- a/test/src/DateTime.purs
+++ b/test/src/DateTime.purs
@@ -2,17 +2,16 @@ module Test.DateTime (datetimeTest) where
 
 import Prelude
 
-import Control.Alternative (class Alternative, empty)
-import Control.MonadZero (guard)
+import Control.Monad.Reader.Class (class MonadReader)
+import Control.Alternative (class Alternative, empty, guard)
 import Data.DateTime (DateTime)
 import Data.Either (Either(..))
 import Data.Formatter.DateTime as FDT
 import Data.List (fromFoldable)
-import Test.Spec (describe, Spec, it)
-import Test.Spec.Assertions (shouldEqual)
-import Test.Utils (forAll, makeDateTime)
+import Effect.Aff.Class (class MonadAff)
+import Test.Utils (forAll, makeDateTime, describe, it, shouldEqual)
 
-datetimeTest ∷ Spec Unit
+datetimeTest ∷ forall m. MonadReader Int m ⇒ MonadAff m ⇒ m Unit
 datetimeTest = describe "Data.Formatter.DateTime" do
   forAll (\a → a.format <> " | " <> a.dateStr)
     "formatDateTime/unformatDateTime should format/unformat dateTime"
diff --git a/test/src/Interval.purs b/test/src/Interval.purs
index efe3c9d..bb2f8f8 100644
--- a/test/src/Interval.purs
+++ b/test/src/Interval.purs
@@ -2,9 +2,11 @@ module Test.Interval (intervalTest) where
 
 import Prelude
 
+import Control.Monad.Reader.Class (class MonadReader)
 import Effect.Aff (Aff)
+import Effect.Aff.Class (class MonadAff)
 import Data.DateTime (DateTime)
-import Data.Either (Either(..), fromRight)
+import Data.Either (Either(..), either)
 import Data.Foldable (class Foldable, fold)
 import Data.Formatter.Interval (unformatInterval, unformatRecurringInterval, formatRecurringInterval)
 import Data.Formatter.Parser.Interval (parseIsoDuration)
@@ -12,15 +14,13 @@ import Data.Formatter.Parser.Utils (runP)
 import Data.Interval as I
 import Data.Interval.Duration.Iso (IsoDuration, mkIsoDuration)
 import Data.Maybe (Maybe(..))
-import Partial.Unsafe (unsafePartial)
-import Test.Spec (describe, Spec)
-import Test.Spec.Assertions (shouldEqual)
-import Test.Utils (forAll, makeDateTime)
+import Partial.Unsafe (unsafeCrashWith)
+import Test.Utils (forAll, makeDateTime, describe, shouldEqual)
 
-prop ∷ ∀ e f. Foldable f ⇒ String → f {str ∷ String | e} → ({str ∷ String | e} → Aff Unit) → Spec Unit
+prop ∷ ∀ m e f. MonadReader Int m ⇒ MonadAff m ⇒ Foldable f ⇒ String → f {str ∷ String | e} → ({str ∷ String | e} → Aff Unit) → m Unit
 prop = forAll (show <<< _.str)
 
-intervalTest ∷ Spec Unit
+intervalTest ∷ forall m. MonadReader Int m ⇒ MonadAff m ⇒ m Unit
 intervalTest = describe "Data.Formatter.Interval" do
   prop "shouldn't unformat invalid Interval" invalidIntervals \({str, err}) → do
     (unformatInterval str) `shouldEqual` (Left $ err)
@@ -40,7 +40,8 @@ intervalTest = describe "Data.Formatter.Interval" do
 
 unsafeMkToIsoDuration ∷ I.Duration → IsoDuration
 unsafeMkToIsoDuration d = mkIsoDuration d
-  # unsafePartial fromRight -- the duration must be valid ISO duration
+  -- the duration must be valid ISO duration
+  # either (\_ -> unsafeCrashWith "unsafeMkToIsoDuration failed") identity
 
 durations ∷ Array { str∷ String, formatedStr∷ String, dur ∷ IsoDuration }
 durations =
diff --git a/test/src/Main.purs b/test/src/Main.purs
index ef5affb..c21fea9 100644
--- a/test/src/Main.purs
+++ b/test/src/Main.purs
@@ -2,16 +2,15 @@ module Test.Main where
 
 import Prelude
 
+import Control.Monad.Reader.Trans (runReaderT)
 import Effect (Effect)
 import Effect.Aff (launchAff_)
 import Test.DateTime (datetimeTest)
 import Test.Interval (intervalTest)
 import Test.Number (numberTest)
-import Test.Spec.Reporter.Console (consoleReporter)
-import Test.Spec.Runner (runSpec)
 
 main ∷ Effect Unit
-main = launchAff_ $ runSpec [consoleReporter] do
+main = launchAff_ $ flip runReaderT 0 do
   intervalTest
   datetimeTest
   numberTest
diff --git a/test/src/Number.purs b/test/src/Number.purs
index 1a0bac9..00f4b0a 100644
--- a/test/src/Number.purs
+++ b/test/src/Number.purs
@@ -2,14 +2,14 @@ module Test.Number (numberTest) where
 
 import Prelude
 
+import Control.Monad.Reader.Class (class MonadReader)
 import Data.Formatter.Number (Formatter(..), printFormatter, parseFormatString, format, unformat)
 import Data.Either (Either(..))
+import Effect.Aff.Class (class MonadAff)
 
-import Test.Spec (describe, Spec)
-import Test.Spec.Assertions (shouldEqual)
-import Test.Utils (forAll)
+import Test.Utils (forAll, describe, shouldEqual)
 
-numberTest ∷ Spec Unit
+numberTest ∷ forall m. MonadReader Int m ⇒ MonadAff m ⇒ m Unit
 numberTest = describe "Data.Formatter.Number" do
   forAll _.str
     "should print formatter"
diff --git a/test/src/Utils.purs b/test/src/Utils.purs
index e25a7c0..6331d9b 100644
--- a/test/src/Utils.purs
+++ b/test/src/Utils.purs
@@ -2,21 +2,44 @@ module Test.Utils where
 
 import Prelude
 
-
-import Test.Spec (describe, it, Spec)
 import Effect.Aff (Aff)
 
+import Control.Monad.Reader.Class (class MonadReader, ask, local)
 import Data.Foldable (class Foldable, for_)
 import Data.Enum (toEnum)
 import Data.Maybe (fromMaybe)
+import Data.Monoid (power, guard)
 import Data.DateTime (DateTime(..))
 import Data.Date (canonicalDate)
 import Data.Time (Time(..))
+import Effect.Console (log)
+import Effect.Class (liftEffect)
+import Effect.Aff.Class (class MonadAff, liftAff)
+import Test.Assert (assertEqual)
+
+-----------------------------------------------------------------
+
+-- Provide similar API to purescript-spec to reduce code changes
+
+describe :: forall m. MonadReader Int m ⇒ MonadAff m ⇒ String -> m Unit -> m Unit
+describe msg runTest = do
+  indentation <- ask
+  let spacing = guard (indentation > 0) " "
+  liftEffect $ log $ (power ">>" indentation) <> spacing <> msg
+  local (_ + 1) runTest
+
+it :: forall m. MonadReader Int m ⇒ MonadAff m ⇒ String -> m Unit -> m Unit
+it = describe
+
+shouldEqual :: forall m a. MonadAff m ⇒ Eq a ⇒ Show a ⇒ a -> a -> m Unit
+shouldEqual actual expected =
+  liftEffect $ assertEqual { actual, expected }
 
+-----------------------------------------------------------------
 
-forAll ∷ ∀ a f. Foldable f ⇒ (a → String) → String → f a → (a → Aff Unit) → Spec Unit
+forAll ∷ ∀ m a f. MonadReader Int m ⇒ MonadAff m ⇒ Foldable f ⇒ (a → String) → String → f a → (a → Aff Unit) → m Unit
 forAll itTitle title arb f = describe title do
-  for_ arb \a → it (itTitle a) (f a)
+  for_ arb \a → it (itTitle a) (liftAff $ f a)
 
 makeDateTime ∷ Int → Int → Int → Int → Int → Int → Int → DateTime
 makeDateTime year month day hour minute second millisecond =