diff --git a/CHANGES.md b/CHANGES.md
new file mode 100644
--- /dev/null
+++ b/CHANGES.md
@@ -0,0 +1,7 @@
+Bencodex changelog
+==================
+
+Version 1.0.0
+-------------
+
+Released on November 6, 2018.
diff --git a/LICENSE b/LICENSE
new file mode 100644
--- /dev/null
+++ b/LICENSE
@@ -0,0 +1,674 @@
+                    GNU GENERAL PUBLIC LICENSE
+                       Version 3, 29 June 2007
+
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+IS WITH YOU.  SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF
+ALL NECESSARY SERVICING, REPAIR OR CORRECTION.
+
+  16. Limitation of Liability.
+
+  IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
+WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MODIFIES AND/OR CONVEYS
+THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY
+GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE
+USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF
+DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD
+PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS),
+EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF
+SUCH DAMAGES.
+
+  17. Interpretation of Sections 15 and 16.
+
+  If the disclaimer of warranty and limitation of liability provided
+above cannot be given local legal effect according to their terms,
+reviewing courts shall apply local law that most closely approximates
+an absolute waiver of all civil liability in connection with the
+Program, unless a warranty or assumption of liability accompanies a
+copy of the Program in return for a fee.
+
+                     END OF TERMS AND CONDITIONS
+
+            How to Apply These Terms to Your New Programs
+
+  If you develop a new program, and you want it to be of the greatest
+possible use to the public, the best way to achieve this is to make it
+free software which everyone can redistribute and change under these terms.
+
+  To do so, attach the following notices to the program.  It is safest
+to attach them to the start of each source file to most effectively
+state the exclusion of warranty; and each file should have at least
+the "copyright" line and a pointer to where the full notice is found.
+
+    <one line to give the program's name and a brief idea of what it does.>
+    Copyright (C) <year>  <name of author>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+Also add information on how to contact you by electronic and paper mail.
+
+  If the program does terminal interaction, make it output a short
+notice like this when it starts in an interactive mode:
+
+    <program>  Copyright (C) <year>  <name of author>
+    This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
+    This is free software, and you are welcome to redistribute it
+    under certain conditions; type `show c' for details.
+
+The hypothetical commands `show w' and `show c' should show the appropriate
+parts of the General Public License.  Of course, your program's commands
+might be different; for a GUI interface, you would use an "about box".
+
+  You should also get your employer (if you work as a programmer) or school,
+if any, to sign a "copyright disclaimer" for the program, if necessary.
+For more information on this, and how to apply and follow the GNU GPL, see
+<https://www.gnu.org/licenses/>.
+
+  The GNU General Public License does not permit incorporating your program
+into proprietary programs.  If your program is a subroutine library, you
+may consider it more useful to permit linking proprietary applications with
+the library.  If this is what you want to do, use the GNU Lesser General
+Public License instead of this License.  But first, please read
+<https://www.gnu.org/licenses/why-not-lgpl.html>.
diff --git a/README.md b/README.md
new file mode 100644
--- /dev/null
+++ b/README.md
@@ -0,0 +1,31 @@
+Bencodex reader/writer for Haskell
+==================================
+
+[![Build Status][ci-badge]][ci]
+
+This package implements [Bencodex] serialization format which extends
+[Bencoding].
+
+~~~~ haskell
+> :set -XOverloadedStrings
+> import Data.Bencodex
+> let Right bVal = decodeStrict "lntfi123eu7:Unicodeu4:blobe"
+> bVal
+BList [BNull,BBool True,BBool False,BInteger 123,BText "Unicode",BText "blob"]
+> encodeStrict bVal
+"lntfi123eu7:Unicodeu4:blobe"
+~~~~
+
+[ci-badge]: https://travis-ci.com/dahlia/bencodex-haskell.svg?branch=master
+[ci]: https://travis-ci.com/dahlia/bencodex-haskell
+[Bencodex]: https://github.com/planetarium/bencodex
+[Bencoding]: http://www.bittorrent.org/beps/bep_0003.html#bencoding
+
+
+Author and license
+------------------
+
+Written by [Hong Minhee], and distributed under [GPLv3] or later.
+
+[Hong Minhee]: https://hongminhee.org/
+[GPLv3]: https://www.gnu.org/licenses/gpl-3.0.html
diff --git a/Setup.hs b/Setup.hs
new file mode 100644
--- /dev/null
+++ b/Setup.hs
@@ -0,0 +1,3 @@
+import Distribution.Simple
+
+main = defaultMain
diff --git a/bencodex.cabal b/bencodex.cabal
new file mode 100644
--- /dev/null
+++ b/bencodex.cabal
@@ -0,0 +1,91 @@
+cabal-version: 2.2
+
+-- This file has been generated from package.yaml by hpack version 0.31.0.
+--
+-- see: https://github.com/sol/hpack
+--
+-- hash: 5ea3c026ada5f6413af4826d953a916f384258b271ce203663930eba00c2742c
+
+name:           bencodex
+version:        1.0.0
+synopsis:       Bencodex reader/writer for Haskell
+description:    Please see the README on GitHub at <https://github.com/dahlia/bencodex-haskell#readme>.
+category:       Serialization
+homepage:       https://github.com/dahlia/bencodex-haskell#readme
+bug-reports:    https://github.com/dahlia/bencodex-haskell/issues
+author:         Hong Minhee <hong.minhee@gmail.com>
+maintainer:     Hong Minhee <hong.minhee@gmail.com>
+copyright:      © 2018 Hong Minhee
+license:        GPL-3.0-or-later
+license-file:   LICENSE
+build-type:     Simple
+extra-source-files:
+    README.md
+    CHANGES.md
+
+source-repository head
+  type: git
+  location: https://github.com/dahlia/bencodex-haskell
+
+library
+  exposed-modules:
+      Data.Bencodex
+      Data.Bencodex.Reader
+      Data.Bencodex.Types
+      Data.Bencodex.Writer
+  other-modules:
+      Paths_bencodex
+  autogen-modules:
+      Paths_bencodex
+  hs-source-dirs:
+      src
+  ghc-options: -Wwarn -Wall -fwarn-incomplete-uni-patterns -fprint-explicit-kinds
+  build-depends:
+      attoparsec >=0.12 && <1
+    , base >=4.7 && <5
+    , bytestring
+    , hashable
+    , text
+    , unordered-containers
+  default-language: Haskell2010
+
+test-suite hlint
+  type: exitcode-stdio-1.0
+  main-is: hlint.hs
+  hs-source-dirs:
+      test
+  ghc-options: -Wwarn -Wall -fwarn-incomplete-uni-patterns -fprint-explicit-kinds -threaded
+  build-depends:
+      base >=4.7 && <5
+    , bytestring
+    , hlint >=2.1.7 && <2.2
+    , text
+    , unordered-containers
+  default-language: Haskell2010
+
+test-suite spec
+  type: exitcode-stdio-1.0
+  main-is: Spec.hs
+  other-modules:
+      Data.Bencodex.ReaderSpec
+      Data.Bencodex.SpecDiscovery
+      Data.Bencodex.WriterSpec
+      Paths_bencodex
+  hs-source-dirs:
+      test
+  ghc-options: -Wwarn -Wall -fwarn-incomplete-uni-patterns -fprint-explicit-kinds -Wno-incomplete-uni-patterns -threaded -rtsopts -with-rtsopts=-N
+  build-depends:
+      HsYAML ==0.1.1.2
+    , base >=4.7 && <5
+    , base64-bytestring
+    , bencodex
+    , bytestring
+    , containers
+    , file-embed
+    , filepath
+    , hspec >=2.4.8 && <3
+    , hspec-attoparsec >=0.1.0.2 && <0.2
+    , hspec-discover >=2.4.8 && <3
+    , text
+    , unordered-containers
+  default-language: Haskell2010
diff --git a/src/Data/Bencodex.hs b/src/Data/Bencodex.hs
new file mode 100644
--- /dev/null
+++ b/src/Data/Bencodex.hs
@@ -0,0 +1,13 @@
+module Data.Bencodex
+    ( BKey (..)
+    , BValue (..)
+    , Result (..)
+    , decodeLazy
+    , decodeStrict
+    , encodeLazy
+    , encodeStrict
+    ) where
+
+import Data.Bencodex.Reader
+import Data.Bencodex.Types
+import Data.Bencodex.Writer
diff --git a/src/Data/Bencodex/Reader.hs b/src/Data/Bencodex/Reader.hs
new file mode 100644
--- /dev/null
+++ b/src/Data/Bencodex/Reader.hs
@@ -0,0 +1,119 @@
+module Data.Bencodex.Reader
+    ( Result (..)
+    , bValue
+    , byteString
+    , decodeLazy
+    , decodeStrict
+    , false
+    , integer
+    , list
+    , map'
+    , null'
+    , text
+    , true
+    ) where
+
+import Control.Monad
+import Data.Functor
+import Data.Word
+
+import Data.Attoparsec.ByteString hiding (Result)
+import Data.Attoparsec.ByteString.Lazy as LP
+import Data.ByteString
+import qualified Data.ByteString.Lazy as LB
+import Data.HashMap.Strict
+import Data.Text
+import Data.Text.Encoding
+import Data.Text.Encoding.Error
+
+import Data.Bencodex.Types
+
+decodeLazy :: LB.ByteString -> Result BValue
+decodeLazy = LP.parse bValue
+
+decodeStrict :: ByteString -> Either String BValue
+decodeStrict = parseOnly bValue
+
+bValue :: Parser BValue
+bValue = choice
+    [ (null' $> BNull) <?> "null"
+    , (BBool <$> true) <?> "true"
+    , (BBool <$> false) <?> "false"
+    , (BInteger <$> integer) <?> "integer"
+    , (BByteString <$> byteString) <?> "byte string"
+    , (BText <$> text) <?> "unicode text"
+    , (BList <$> list) <?> "list"
+    , (BMap <$> map') <?> "dictionary"
+    ]
+
+skipWord8 :: Word8 -> Parser ()
+skipWord8 = void . word8
+
+null' :: Parser ()
+null' = skipWord8 0x6e  -- 'n'
+
+true :: Parser Bool
+true = do
+    skipWord8 0x74  -- 't'
+    return True
+
+false :: Parser Bool
+false = do
+    skipWord8 0x66  -- 'f'
+    return False
+
+digits :: Num a => Parser a
+digits = do
+    digits' <- takeWhile1 (\ w -> 0x30 <= w && w <= 0x39) -- '0' - '9'
+    return $ Data.ByteString.foldl'
+        (\ i b -> i * 10 + fromIntegral (b - 0x30))
+        0
+        digits'
+
+integer :: Parser Integer
+integer = do
+    skipWord8 0x69  -- 'i'
+    sign <- option 1 (word8 0x2d $> -1)  -- 0x2d: '-'
+    digits' <- digits
+    skipWord8 0x65  -- 'e'
+    return $ sign * digits'
+
+byteString :: Parser ByteString
+byteString = do
+    size' <- digits
+    skipWord8 0x3a  -- ':'
+    Data.Attoparsec.ByteString.take size'
+
+text :: Parser Text
+text = do
+    skipWord8 0x75  -- 'u'
+    size' <- digits
+    skipWord8 0x3a  -- ':'
+    bytes <- Data.Attoparsec.ByteString.take size'
+    case decodeUtf8' bytes of
+        Right decoded -> return decoded
+        Left (DecodeError msg _) -> fail msg
+        Left e -> fail ("unexpected error: " ++ show e)
+
+list :: Parser [BValue]
+list = do
+    skipWord8 0x6c  -- 'l'
+    elements <- many' bValue
+    skipWord8 0x65  -- 'e'
+    return elements
+
+map' :: Parser (HashMap BKey BValue)
+map' = do
+    skipWord8 0x64  -- 'd'
+    pairs <- many' $ do
+        key <- bKey
+        value <- bValue
+        return (key, value)
+    skipWord8 0x65  -- 'e'
+    return $ Data.HashMap.Strict.fromList pairs
+
+bKey :: Parser BKey
+bKey = choice
+    [ BByteStringKey <$> byteString
+    , BTextKey <$> text
+    ]
diff --git a/src/Data/Bencodex/Types.hs b/src/Data/Bencodex/Types.hs
new file mode 100644
--- /dev/null
+++ b/src/Data/Bencodex/Types.hs
@@ -0,0 +1,29 @@
+{-# LANGUAGE DeriveGeneric #-}
+module Data.Bencodex.Types
+    ( BKey (..)
+    , BValue (..)
+    ) where
+
+import GHC.Generics (Generic)
+
+import Data.ByteString
+import Data.Hashable
+import Data.HashMap.Strict
+import Data.Text
+
+data BValue
+    = BNull
+    | BBool Bool
+    | BInteger Integer
+    | BByteString ByteString
+    | BText Text
+    | BList [BValue]
+    | BMap (HashMap BKey BValue)
+    deriving (Eq, Ord, Show)
+
+data BKey
+    = BTextKey Text
+    | BByteStringKey ByteString
+    deriving (Eq, Generic, Ord, Show)
+
+instance Hashable BKey
diff --git a/src/Data/Bencodex/Writer.hs b/src/Data/Bencodex/Writer.hs
new file mode 100644
--- /dev/null
+++ b/src/Data/Bencodex/Writer.hs
@@ -0,0 +1,76 @@
+module Data.Bencodex.Writer
+    ( encodeLazy
+    , encodeStrict
+    ) where
+
+import Data.List (sort)
+
+import Data.ByteString hiding (sort)
+import Data.ByteString.Builder
+import qualified Data.ByteString.Lazy
+import Data.HashMap.Strict
+import Data.Text.Encoding
+
+import Data.Bencodex.Types
+
+encodeLazy :: BValue -> Data.ByteString.Lazy.ByteString
+encodeLazy = toLazyByteString . renderBValue
+
+encodeStrict :: BValue -> ByteString
+encodeStrict = Data.ByteString.Lazy.toStrict . encodeLazy
+
+renderBValue :: BValue -> Builder
+renderBValue BNull = char7 'n'
+renderBValue (BBool True) = char7 't'
+renderBValue (BBool False) = char7 'f'
+renderBValue (BInteger int) = mconcat
+    [ char7 'i'
+    , integerDec int
+    , char7 'e'
+    ]
+renderBValue (BByteString bs) = mconcat
+    [ intDec (Data.ByteString.length bs)
+    , char7 ':'
+    , byteString bs
+    ]
+renderBValue (BText txt) = mconcat
+    [ char7 'u'
+    , intDec (Data.ByteString.length encoded)
+    , char7 ':'
+    , byteString encoded
+    ]
+  where
+    encoded :: ByteString
+    encoded = encodeUtf8 txt
+renderBValue (BList elements) =
+    char7 'l' <> mconcat (renderBValue <$> elements) <> char7 'e'
+renderBValue (BMap hmap) =
+    char7 'd' <> mconcat renderedPairs <> char7 'e'
+  where
+    pairs :: [(KeyType, ByteString, BValue)]
+    pairs = sort
+        [ case k of
+            BTextKey k' -> (UnicodeKey, encodeUtf8 k', v)
+            BByteStringKey k' -> (BytesKey, k', v)
+        | (k, v) <- toList hmap
+        ]
+    renderedPairs :: [Builder]
+    renderedPairs =
+        [ renderKey kt k <> renderBValue v
+        | (kt, k, v) <- pairs
+        ]
+
+data KeyType = BytesKey | UnicodeKey deriving (Eq, Ord, Show)
+
+renderKey :: KeyType -> ByteString -> Builder
+renderKey kt bs =
+    case kt of
+        BytesKey -> common
+        UnicodeKey -> char7 'u' <> common
+  where
+    common :: Builder
+    common = mconcat
+        [ intDec (Data.ByteString.length bs)
+        , char7 ':'
+        , byteString bs
+        ]
diff --git a/test/Data/Bencodex/ReaderSpec.hs b/test/Data/Bencodex/ReaderSpec.hs
new file mode 100644
--- /dev/null
+++ b/test/Data/Bencodex/ReaderSpec.hs
@@ -0,0 +1,116 @@
+{-# LANGUAGE OverloadedLists #-}
+{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE RecordWildCards #-}
+module Data.Bencodex.ReaderSpec (spec) where
+
+import Control.Monad
+
+import qualified Data.ByteString
+import Data.ByteString.Lazy
+import Test.Hspec
+import Test.Hspec.Attoparsec
+
+import Data.Bencodex.Reader
+import Data.Bencodex.SpecDiscovery
+import Data.Bencodex.Types
+
+type BS = Data.ByteString.ByteString
+
+spec :: Spec
+spec = do
+    let Right specs = listSpecs
+
+    specify "specs" $
+        specs `shouldNotSatisfy` Prelude.null
+
+    describe "decodeStrict" $
+        forM_ specs $ \ Spec' {..} ->
+            specify specPath $
+                decodeStrict expectedEncoding `shouldBe` Right expectedValue
+
+    describe "decodeLazy" $
+        forM_ specs $ \ Spec' {..} ->
+            specify specPath $ do
+                let Done remain result = decodeLazy $
+                        fromStrict expectedEncoding
+                remain `shouldSatisfy` Data.ByteString.Lazy.null
+                result `shouldBe` expectedValue
+
+    describe "bValue" $ do
+        forM_ specs $ \ Spec' {..} ->
+            specify specPath $
+                expectedEncoding ~> bValue `shouldParse` expectedValue
+
+        specify "et cetra" $ do
+            ("n" :: BS) ~> bValue `shouldParse` BNull
+            ("i0e" :: BS) ~> bValue `shouldParse` BInteger 0
+            ("i1234e" :: BS) ~> bValue `shouldParse` BInteger 1234
+            ("i-5678e" :: BS) ~> bValue `shouldParse` BInteger (-5678)
+            bValue `shouldFailOn` ("i12.34e" :: BS)
+            ("0:" :: BS) ~> bValue `shouldParse` BByteString ""
+            ("5:hello" :: BS) ~> bValue `shouldParse` BByteString "hello"
+            bValue `shouldFailOn` ("6:hello" :: BS)
+            ("u0:" :: BS) ~> bValue `shouldParse` BText ""
+            ("u5:hello" :: BS) ~> bValue `shouldParse` BText "hello"
+            bValue `shouldFailOn` ("u6:hello" :: BS)
+            ("le:helloe" :: BS) ~> bValue `shouldParse` BList []
+            ("lntfi12eu5:helloe" :: BS) ~> bValue `shouldParse` BList
+                [BNull, BBool True, BBool False, BInteger 12, BText "hello"]
+            bValue `shouldFailOn` ("ltf" :: BS)
+            ("de" :: BS) ~> bValue `shouldParse` BMap []
+            ("d1:k1:ve" :: BS) ~> bValue `shouldParse`
+                BMap [(BByteStringKey "k", BByteString "v")]
+            ("du1:ku1:ve" :: BS) ~> bValue `shouldParse`
+                BMap [(BTextKey "k", BText "v")]
+            bValue `shouldFailOn` ("dnne" :: BS)
+            bValue `shouldFailOn` ("dtne" :: BS)
+            bValue `shouldFailOn` ("dfne" :: BS)
+            bValue `shouldFailOn` ("di123ene" :: BS)
+            bValue `shouldFailOn` ("dlene" :: BS)
+            bValue `shouldFailOn` ("ddene" :: BS)
+
+    specify "null'" $ do
+        null' `shouldSucceedOn` ("n" :: BS)
+        null' `shouldFailOn` ("t" :: BS)
+
+    specify "true" $ do
+        true `shouldSucceedOn` ("t" :: BS)
+        true `shouldFailOn` ("f" :: BS)
+
+    specify "false" $ do
+        false `shouldSucceedOn` ("f" :: BS)
+        false `shouldFailOn` ("t" :: BS)
+
+    specify "integer" $ do
+        ("i0e" :: BS) ~> integer `shouldParse` 0
+        ("i1234e" :: BS) ~> integer `shouldParse` 1234
+        ("i-5678e" :: BS) ~> integer `shouldParse` (-5678)
+        false `shouldFailOn` ("i12.34e" :: BS)
+
+    specify "byteString" $ do
+        ("0:" :: BS) ~> byteString `shouldParse` ""
+        ("5:hello" :: BS) ~> byteString `shouldParse` "hello"
+        byteString `shouldFailOn` ("6:hello" :: BS)
+
+    specify "text" $ do
+        ("u0:" :: BS) ~> text `shouldParse` ""
+        ("u5:hello" :: BS) ~> text `shouldParse` "hello"
+        text `shouldFailOn` ("u6:hello" :: BS)
+
+    specify "list" $ do
+        ("le:helloe" :: BS) ~> list `shouldParse` []
+        ("lntfi12eu5:helloe" :: BS) ~> list `shouldParse`
+            [BNull, BBool True, BBool False, BInteger 12, BText "hello"]
+        list `shouldFailOn` ("ltf" :: BS)
+
+    specify "map'" $ do
+        ("de" :: BS) ~> map' `shouldParse` []
+        ("d1:k1:ve" :: BS) ~> map' `shouldParse`
+            [(BByteStringKey "k", BByteString "v")]
+        ("du1:ku1:ve" :: BS) ~> map' `shouldParse` [(BTextKey "k", BText "v")]
+        map' `shouldFailOn` ("dnne" :: BS)
+        map' `shouldFailOn` ("dtne" :: BS)
+        map' `shouldFailOn` ("dfne" :: BS)
+        map' `shouldFailOn` ("di123ene" :: BS)
+        map' `shouldFailOn` ("dlene" :: BS)
+        map' `shouldFailOn` ("ddene" :: BS)
diff --git a/test/Data/Bencodex/SpecDiscovery.hs b/test/Data/Bencodex/SpecDiscovery.hs
new file mode 100644
--- /dev/null
+++ b/test/Data/Bencodex/SpecDiscovery.hs
@@ -0,0 +1,97 @@
+{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE TemplateHaskell #-}
+module Data.Bencodex.SpecDiscovery
+    ( Spec' (..)
+    , listSpecs
+    ) where
+
+import Data.Char
+
+import Data.Bencodex.Types
+import Data.ByteString hiding (unpack)
+import Data.ByteString.Base64 as Base64
+import Data.ByteString.Lazy (fromStrict)
+import Data.FileEmbed
+import qualified Data.HashMap.Strict as HashMap
+import qualified Data.Map.Strict as Map
+import Data.Text
+import Data.Text.Encoding
+import Data.YAML
+import Data.YAML.Event hiding (Scalar)
+import System.FilePath
+
+data Spec' = Spec'
+    { specPath :: FilePath
+    , dataPath :: FilePath
+    , expectedValue :: BValue
+    , expectedEncoding :: ByteString
+    } deriving (Eq, Ord, Show)
+
+listSpecs :: Either String [Spec']
+listSpecs = sequence
+    [ case fromYaml specContents of
+        Left msg -> Left (specPath' ++ ": " ++ msg)
+        Right expValue -> Right $ Spec' specPath' dataPath' expValue expEnc
+    | (specPath', specContents, dataPath', expEnc) <- files
+    ]
+  where
+    dir :: HashMap.HashMap FilePath ByteString
+    dir = HashMap.fromList
+            $(embedDir $ joinPath ["spec", "testsuite"])
+    files :: [(FilePath, ByteString, FilePath, ByteString)]
+    files =
+        [ (fileName, valueContents, fileName -<.> "dat", dataContents)
+        | (fileName, valueContents) <- HashMap.toList dir
+        , "yaml" `isExtensionOf` fileName || "yml" `isExtensionOf` fileName
+        , Just dataContents <- [HashMap.lookup (fileName -<.> "dat") dir]
+        ]
+
+fromYaml :: ByteString -> Either String BValue
+fromYaml fileContents =
+    case decodeNode (fromStrict fileContents) of
+        Right [Doc node] -> mapNode node
+        Right _ -> Left "A YAML file must have only one document."
+        Left msg -> Left msg
+
+mapNode :: Node -> Either String BValue
+mapNode (Scalar SNull) = Right BNull
+mapNode (Scalar (SBool bool)) = Right $ BBool bool
+mapNode (Scalar (SInt int)) = Right $ BInteger int
+mapNode (Scalar (SUnknown tag base64))
+  | tagToText tag == Just "tag:yaml.org,2002:binary" =
+        case decodeBase64 base64 of
+            Left msg -> Left msg
+            Right bs -> Right $ BByteString bs
+  | otherwise = Left ("Unsupported tag: " ++ show tag)
+mapNode (Scalar (SStr text)) = Right $ BText text
+mapNode (Scalar (SFloat _)) = Left "Float is unsupported."
+mapNode (Sequence _ nodes) = BList <$> mapM mapNode nodes
+mapNode (Mapping _ map') =
+    BMap . HashMap.fromList <$> sequence translatedPairs
+  where
+    pairs :: [(Node, Node)]
+    pairs = Map.toList map'
+    translatedPairs :: [Either String (BKey, BValue)]
+    translatedPairs =
+        [ case (k, mapNode v) of
+            (Scalar (SStr k'), Right v') -> Right (BTextKey k', v')
+            (Scalar (SUnknown tag k64), Right v')
+                | tagToText tag == Just "tag:yaml.org,2002:binary" ->
+                    case decodeBase64 k64 of
+                        Left msg -> Left msg
+                        Right k' -> Right (BByteStringKey k', v')
+                | otherwise -> Left ("Unsupported tag: " ++ show tag)
+            (_, Left msg) -> Left msg
+            _ -> Left "Unsupported key type."
+        | (k, v) <- pairs
+        ]
+mapNode (Anchor _ _) = Left "Anchor is unsupported."
+
+decodeBase64 :: Text -> Either String ByteString
+decodeBase64 base64 =
+    case Base64.decode (encodeUtf8 base64') of
+        Right b -> Right b
+        Left msg -> Left (msg ++ ":\n" ++ unpack base64')
+  where
+    base64' :: Text
+    base64' = Data.Text.filter (not . isSpace) base64
diff --git a/test/Data/Bencodex/WriterSpec.hs b/test/Data/Bencodex/WriterSpec.hs
new file mode 100644
--- /dev/null
+++ b/test/Data/Bencodex/WriterSpec.hs
@@ -0,0 +1,84 @@
+{-# LANGUAGE OverloadedLists #-}
+{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE RecordWildCards #-}
+module Data.Bencodex.WriterSpec (spec) where
+
+import Control.Monad
+import Data.String
+
+import Data.ByteString.Lazy
+import Test.Hspec
+
+import Data.Bencodex.SpecDiscovery
+import Data.Bencodex.Types
+import Data.Bencodex.Writer
+
+spec :: Spec
+spec = do
+    let Right specs = listSpecs
+
+    specify "specs" $
+        specs `shouldNotSatisfy` Prelude.null
+
+    describe "encodeLazy" $ do
+        forM_ specs $ \ Spec' {..} ->
+            specify specPath $
+                encodeLazy expectedValue `shouldBe` fromStrict expectedEncoding 
+
+        testEncoder encodeLazy
+
+    describe "encodeStrict" $ do
+        forM_ specs $ \ Spec' {..} ->
+            specify specPath $
+                encodeStrict expectedValue `shouldBe` expectedEncoding 
+
+        testEncoder encodeStrict
+
+testEncoder :: (Show a, Eq a, IsString a) => (BValue -> a) -> SpecWith ()
+testEncoder e = do
+    specify "BNull" $
+        e BNull `shouldBe` "n"
+
+    specify "BBool" $ do
+        e (BBool True) `shouldBe` "t"
+        e (BBool False) `shouldBe` "f"
+
+    specify "BInteger" $ do
+        e (BInteger 0) `shouldBe` "i0e"
+        e (BInteger 123) `shouldBe` "i123e"
+        e (BInteger (-456)) `shouldBe` "i-456e"
+
+    specify "BByteString" $ do
+        e (BByteString "") `shouldBe` "0:"
+        e (BByteString "hello") `shouldBe` "5:hello"
+
+    specify "BByteString" $ do
+        e (BText "") `shouldBe` "u0:"
+        e (BText "hello") `shouldBe` "u5:hello"
+        e (BText "\xc720\xb2c8\xcf54\xb4dc") `shouldBe`
+            "u12:\xec\x9c\xa0\xeb\x8b\x88\xec\xbd\x94\xeb\x93\x9c"
+
+    specify "BList" $ do
+        e (BList []) `shouldBe` "le"
+        let elems =
+                [ BNull, BBool True, BBool False, BInteger 123
+                , BByteString "hello", BText "world"
+                , BList [], BList [BNull]
+                , BMap [(BByteStringKey "k", BByteString "v")]
+                ]
+        e (BList elems) `shouldBe` "lntfi123e5:hellou5:worldlelned1:k1:vee"
+
+    specify "BMap" $ do
+        e (BMap []) `shouldBe` "de"
+        let pairs = BMap
+                [ (BTextKey "a", BNull)
+                , (BByteStringKey "b", BBool True)
+                , (BTextKey "c", BBool False)
+                , (BByteStringKey "d", BInteger 123)
+                , (BTextKey "e", BByteString "hello")
+                , (BByteStringKey "f", BText "world")
+                , (BTextKey "g", BList [BNull])
+                , (BByteStringKey "h", BMap [])
+                ]
+        e pairs `shouldBe`
+            "d1:bt1:di123e1:fu5:world1:hdeu1:anu1:cfu1:e5:hellou1:glnee"
diff --git a/test/Spec.hs b/test/Spec.hs
new file mode 100644
--- /dev/null
+++ b/test/Spec.hs
@@ -0,0 +1,1 @@
+{-# OPTIONS_GHC -F -pgmF hspec-discover #-}
diff --git a/test/hlint.hs b/test/hlint.hs
new file mode 100644
--- /dev/null
+++ b/test/hlint.hs
@@ -0,0 +1,12 @@
+import Language.Haskell.HLint (hlint)
+import System.Exit (exitFailure, exitSuccess)
+
+arguments :: [String]
+arguments = ["src", "test"]
+
+main :: IO ()
+main = do
+    hlints <- hlint arguments
+    case hlints of
+        [] -> exitSuccess
+        _ -> exitFailure