diff --git a/ChangeLog.md b/ChangeLog.md
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -1,5 +1,9 @@
 # Changelog for fp-ieee
 
+## Version 0.1.0.1 (2021-01-02)
+
+Fix some packaging issues.
+
 ## Version 0.1.0 (2020-12-27)
 
 Initial release.
diff --git a/decimal-test/Util.hs b/decimal-test/Util.hs
new file mode 100644
--- /dev/null
+++ b/decimal-test/Util.hs
@@ -0,0 +1,71 @@
+{-# LANGUAGE ScopedTypeVariables #-}
+{-# OPTIONS_GHC -Wno-orphans #-}
+module Util where
+import           Control.Applicative
+import           Data.Ratio
+import           Numeric
+import           Numeric.Decimal
+import           Numeric.Floating.IEEE
+import           System.Random
+import           Test.QuickCheck
+
+-- | Compares two floating point values.
+--
+-- Unlike @(==)@, @+0@ and @-0@ are considered distinct and NaNs are equal.
+--
+-- >>> sameFloat 0 (-0 :: Double)
+-- False
+-- >>> sameFloat (0/0) (0/0 :: Double)
+-- True
+sameFloat :: RealFloat a => a -> a -> Bool
+sameFloat x y | isNaN x && isNaN y = True
+              | x == 0 && y == 0 = isNegativeZero x == isNegativeZero y
+              | otherwise = x == y
+
+sameFloatP :: (RealFloat a, Show a) => a -> a -> Property
+sameFloatP x y = counterexample (shows x . showString (interpret res) . showHFloat y $ "") res
+  where
+    res = sameFloat x y
+    interpret True  = " === "
+    interpret False = " =/= "
+
+infix 4 `sameFloat`, `sameFloatP`
+
+variousFloats :: forall a. (RealFloat a, Arbitrary a, Random a, Show a) => Gen a
+variousFloats = frequency
+  [ (10, arbitrary)
+  , (10, choose (-1, 1))
+  , (10, (* encodeFloat 1 expMin) <$> choose (-1, 1) ) -- subnormal or very small normal
+  , (10, (* encodeFloat 1 (expMax-1)) <$> choose (-2, 2) ) -- infinity or very large normal
+  , (1, pure 0) -- positive zero
+  , (1, pure (-0)) -- negative zero
+  , (1, pure (1/0)) -- positive infinity
+  , (1, pure (-1/0)) -- negative infinity
+  , (1, pure (0/0)) -- NaN
+  , (1, pure maxFinite) -- max finite
+  , (1, pure (-maxFinite)) -- min negative
+  , (1, pure minPositive) -- min positive
+  , (1, pure (-minPositive)) -- max negative
+  ]
+  where (expMin,expMax) = floatRange (undefined :: a)
+
+forAllFloats :: (RealFloat a, Arbitrary a, Random a, Show a, Testable prop) => (a -> prop) -> Property
+forAllFloats = forAllShow variousFloats (\x -> show x)
+
+forAllFloats2 :: (RealFloat a, Arbitrary a, Random a, Show a, Testable prop) => (a -> a -> prop) -> Property
+forAllFloats2 f = forAllFloats $ \x -> forAllFloats $ \y -> f x y
+
+forAllFloats3 :: (RealFloat a, Arbitrary a, Random a, Show a, Testable prop) => (a -> a -> a -> prop) -> Property
+forAllFloats3 f = forAllFloats $ \x -> forAllFloats $ \y -> forAllFloats $ \z -> f x y z
+
+-- orphan instances
+instance (FinitePrecision p, Rounding r) => Arbitrary (Decimal p r) where
+  arbitrary = arbitrarySizedFractional
+  shrink = shrinkDecimal
+
+instance (FinitePrecision p, Rounding r) => Random (Decimal p r) where
+  randomR (lo,hi) g = let (x,g') = random g
+                      in (lo + x * (hi - lo), g') -- TODO: avoid overflow
+  random g = let x :: Int
+                 (x,g') = random g
+             in (fromRational (toInteger x % 1000), g') -- TODO
diff --git a/fp-ieee.cabal b/fp-ieee.cabal
--- a/fp-ieee.cabal
+++ b/fp-ieee.cabal
@@ -4,17 +4,18 @@
 --
 -- see: https://github.com/sol/hpack
 --
--- hash: f0bf89e9df957b5023d91e55d09165cecb06208750fddaf58af69fd7c2b7e35d
+-- hash: 62a346063dd10a9b7bb7de4d7624dd805ceef339ead48206730d6c47e94e17d2
 
 name:           fp-ieee
-version:        0.1.0
+version:        0.1.0.1
+synopsis:       IEEE 754-2019 compliant operations
 description:    Please see the README on GitHub at <https://github.com/minoki/haskell-floating-point/tree/master/fp-ieee#readme>
 category:       Numeric, Math
 homepage:       https://github.com/minoki/haskell-floating-point#readme
 bug-reports:    https://github.com/minoki/haskell-floating-point/issues
 author:         ARATA Mizuki
 maintainer:     minorinoki@gmail.com
-copyright:      2020 ARATA Mizuki
+copyright:      2020-2021 ARATA Mizuki
 license:        BSD3
 license-file:   LICENSE
 build-type:     Simple
@@ -166,6 +167,7 @@
   main-is: Spec.hs
   other-modules:
       NextFloatSpec
+      Util
   hs-source-dirs:
       decimal-test
   ghc-options: -threaded -rtsopts -with-rtsopts=-N -fno-ignore-asserts
@@ -299,9 +301,11 @@
       IntegerInternalsSpec
       MinMaxSpec
       NaNSpec
+      NextFloatSpec
       RoundingSpec
       RoundToIntegralSpec
       TwoSumSpec
+      Util
   hs-source-dirs:
       test
   ghc-options: -threaded -rtsopts -with-rtsopts=-N -fno-ignore-asserts
diff --git a/test/NextFloatSpec.hs b/test/NextFloatSpec.hs
new file mode 100644
--- /dev/null
+++ b/test/NextFloatSpec.hs
@@ -0,0 +1,79 @@
+{-# LANGUAGE CPP #-}
+module NextFloatSpec where
+import           Data.Proxy
+import           Numeric.Floating.IEEE
+import           Test.Hspec
+import           Test.Hspec.QuickCheck (prop)
+import           Test.QuickCheck
+import           Util (forAllFloats, sameFloatP)
+
+#if defined(USE_FFI)
+
+foreign import ccall unsafe "nextafter"
+  c_nextafter_double :: Double -> Double -> Double
+foreign import ccall unsafe "nextafterf"
+  c_nextafter_float :: Float -> Float -> Float
+
+class Fractional a => CFloat a where
+  c_nextafter :: a -> a -> a
+
+instance CFloat Double where
+  c_nextafter = c_nextafter_double
+
+instance CFloat Float where
+  c_nextafter = c_nextafter_float
+
+c_nextUp, c_nextDown, c_nextTowardZero :: (RealFloat a, CFloat a) => a -> a
+c_nextUp x = c_nextafter x (1/0)
+c_nextDown x = c_nextafter x (-1/0)
+c_nextTowardZero x | isNegativeZero x = x
+                   | otherwise = c_nextafter x 0
+
+prop_nextUp_match :: (RealFloat a, CFloat a, Show a) => Proxy a -> a -> Property
+prop_nextUp_match _ x = nextUp x `sameFloatP` c_nextUp x
+
+prop_nextDown_match :: (RealFloat a, CFloat a, Show a) => Proxy a -> a -> Property
+prop_nextDown_match _ x = nextDown x `sameFloatP` c_nextDown x
+
+prop_nextTowardZero_match :: (RealFloat a, CFloat a, Show a) => Proxy a -> a -> Property
+prop_nextTowardZero_match _ x = nextTowardZero x `sameFloatP` c_nextTowardZero x
+
+#endif
+
+isPositiveZero :: RealFloat a => a -> Bool
+isPositiveZero x = x == 0 && not (isNegativeZero x)
+
+prop_nextUp_nextDown :: (RealFloat a, Show a) => Proxy a -> a -> Property
+prop_nextUp_nextDown _ x = x /= (-1/0) ==>
+  let x' = nextUp (nextDown x)
+  in x' `sameFloatP` x .||. (isPositiveZero x .&&. isNegativeZero x')
+
+prop_nextDown_nextUp :: (RealFloat a, Show a) => Proxy a -> a -> Property
+prop_nextDown_nextUp _ x = x /= (1/0) ==>
+  let x' = nextDown (nextUp x)
+  in x' `sameFloatP` x .||. (isNegativeZero x .&&. isPositiveZero x')
+
+{-# NOINLINE spec #-}
+spec :: Spec
+spec = do
+  describe "Double" $ do
+    let proxy :: Proxy Double
+        proxy = Proxy
+#if defined(USE_FFI)
+    prop "nextUp vs C nextafter" $ forAllFloats $ prop_nextUp_match proxy
+    prop "nextDown vs C nextafter" $ forAllFloats $ prop_nextDown_match proxy
+    prop "nextTowardZero vs C nextafter" $ forAllFloats $ prop_nextTowardZero_match proxy
+#endif
+    prop "nextUp . nextDown == id (unless -inf)" $ forAllFloats $ prop_nextUp_nextDown proxy
+    prop "nextDown . nextUp == id (unless inf)" $ forAllFloats $ prop_nextDown_nextUp proxy
+
+  describe "Float" $ do
+    let proxy :: Proxy Float
+        proxy = Proxy
+#if defined(USE_FFI)
+    prop "nextUp vs C nextafter" $ forAllFloats $ prop_nextUp_match proxy
+    prop "nextDown vs C nextafter" $ forAllFloats $ prop_nextDown_match proxy
+    prop "nextTowardZero vs C nextafter" $ forAllFloats $ prop_nextTowardZero_match proxy
+#endif
+    prop "nextUp . nextDown == id (unless -inf)" $ forAllFloats $ prop_nextUp_nextDown proxy
+    prop "nextDown . nextUp == id (unless inf)" $ forAllFloats $ prop_nextDown_nextUp proxy
diff --git a/test/Util.hs b/test/Util.hs
new file mode 100644
--- /dev/null
+++ b/test/Util.hs
@@ -0,0 +1,104 @@
+{-# LANGUAGE GeneralizedNewtypeDeriving #-}
+{-# LANGUAGE ScopedTypeVariables #-}
+{-# OPTIONS_GHC -Wno-orphans -Wno-type-defaults #-}
+module Util
+  ( module Util
+  , mapSpecItem_ -- from Test.Hspec.Core.Spec
+  ) where
+import           Control.Applicative
+import           Data.Ratio
+import           Numeric
+import           Numeric.Floating.IEEE
+import           System.Random
+import           Test.Hspec.Core.Spec
+import           Test.QuickCheck
+
+newtype ShowHexFloat a = ShowHexFloat a deriving (Eq,Ord,Arbitrary)
+
+instance RealFloat a => Show (ShowHexFloat a) where
+  showsPrec _prec (ShowHexFloat x) = showHFloat x
+
+-- | Compares two floating point values.
+--
+-- Unlike @(==)@, @+0@ and @-0@ are considered distinct and NaNs are equal.
+--
+-- >>> sameFloat 0 (-0 :: Double)
+-- False
+-- >>> sameFloat (0/0) (0/0 :: Double)
+-- True
+sameFloat :: RealFloat a => a -> a -> Bool
+sameFloat x y | isNaN x && isNaN y = True
+              | x == 0 && y == 0 = isNegativeZero x == isNegativeZero y
+              | otherwise = x == y
+
+sameFloatP :: (RealFloat a) => a -> a -> Property
+sameFloatP x y = counterexample (showHFloat x . showString (interpret res) . showHFloat y $ "") res
+  where
+    res = sameFloat x y
+    interpret True  = " === "
+    interpret False = " =/= "
+
+sameFloatPairP :: (RealFloat a, Show a) => (a, a) -> (a, a) -> Property
+sameFloatPairP (x,y) (x',y') = counterexample (showPair x y . showString (interpret res) . showPair x' y' $ "") res
+  where
+    showPair s t = showChar '(' . showHFloat s . showChar ',' . showHFloat t . showChar ')'
+    res = x `sameFloat` x' && y `sameFloat` y'
+    interpret True  = " === "
+    interpret False = " =/= "
+
+infix 4 `sameFloat`, `sameFloatP`, `sameFloatPairP`
+
+variousFloats :: forall a. (RealFloat a, Arbitrary a, Random a, Show a) => Gen a
+variousFloats = frequency
+  [ (10, arbitrary)
+  , (10, choose (-1, 1))
+  , (10, (* encodeFloat 1 expMin) <$> choose (-1, 1) ) -- subnormal or very small normal
+  , (10, (* encodeFloat 1 (expMax-1)) <$> choose (-2, 2) ) -- infinity or very large normal
+  , (1, pure 0) -- positive zero
+  , (1, pure (-0)) -- negative zero
+  , (1, pure (1/0)) -- positive infinity
+  , (1, pure (-1/0)) -- negative infinity
+  , (1, pure (0/0)) -- NaN
+  , (1, pure maxFinite) -- max finite
+  , (1, pure (-maxFinite)) -- min negative
+  , (1, pure minPositive) -- min positive
+  , (1, pure (-minPositive)) -- max negative
+  ]
+  where (expMin,expMax) = floatRange (undefined :: a)
+
+variousIntegers :: Gen Integer
+variousIntegers = frequency
+  [ (10, arbitrary)
+  , (10, elements [id,negate] <*> choose (2^52, 2^54))
+  , (10, elements [id,negate] <*> choose (2^62, 2^64))
+  , (10, elements [id,negate] <*> choose (2^100, 2^101))
+  , (10, elements [id,negate] <*> choose (2^1020, 2^1030))
+  , (5, elements [id,negate] <*> choose (2^1070, 2^1075))
+  , (5, elements [id,negate] <*> choose (2^16382, 2^16384))
+  , (3, elements [id,negate] <*> choose (2^16440, 2^16445))
+  ]
+
+variousRationals :: Gen Rational
+variousRationals = liftA2 (%) variousIntegers (variousIntegers `suchThat` (/= 0))
+
+forAllFloats :: (RealFloat a, Arbitrary a, Random a, Show a, Testable prop) => (a -> prop) -> Property
+forAllFloats = forAllShow variousFloats (\x -> showHFloat x "")
+
+forAllFloats2 :: (RealFloat a, Arbitrary a, Random a, Show a, Testable prop) => (a -> a -> prop) -> Property
+forAllFloats2 f = forAllFloats $ \x -> forAllFloats $ \y -> f x y
+
+forAllFloats3 :: (RealFloat a, Arbitrary a, Random a, Show a, Testable prop) => (a -> a -> a -> prop) -> Property
+forAllFloats3 f = forAllFloats $ \x -> forAllFloats $ \y -> forAllFloats $ \z -> f x y z
+
+allowFailure :: String -> Item a -> Item a
+allowFailure message item@(Item { itemExample = origExample }) = item { itemExample = newExample }
+  where
+    newExample params around callback = do
+      result <- origExample params around callback
+      case result of
+        Result { resultStatus = Test.Hspec.Core.Spec.Failure loc reason } -> do
+          let message' = case reason of
+                           NoReason -> message
+                           _        -> message ++ ": " ++ show reason
+          return result { resultStatus = Pending loc (Just message') }
+        _ -> return result