diff --git a/Makefile b/Makefile
new file mode 100644
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,8 @@
+run-test:	update-test
+	runhaskell Setup configure --user --enable-tests
+	runhaskell Setup build
+	runhaskell Setup haddock
+	runhaskell Setup test apportionment-test --show-details=streaming
+
+update-test:
+	doctest-extract-0.1 -i src/ -o test/ --import-tested --executable-main=Main.hs Math.Apportionment
diff --git a/apportionment.cabal b/apportionment.cabal
--- a/apportionment.cabal
+++ b/apportionment.cabal
@@ -1,12 +1,12 @@
 Name:                apportionment
-Version:             0.0.0.3
+Version:             0.0.0.4
 Synopsis:            Round a set of numbers while maintaining its sum
 Description:
   Round a set of numbers while maintaining its sum.
   According procedures are used to assign seats to parties in a parliament.
   You may also use it to round percentages that sum up to 100%.
   <https://en.wikipedia.org/wiki/Apportionment_(politics)>
-Homepage:            http://hub.darcs.net/thielema/apportionment
+Homepage:            https://hub.darcs.net/thielema/apportionment
 License:             BSD3
 License-File:        LICENSE
 Author:              Henning Thielemann
@@ -14,15 +14,17 @@
 Category:            Math
 Build-Type:          Simple
 Cabal-Version:       >=1.10
+Extra-Source-Files:
+  Makefile
 
 Source-Repository this
-  Tag:         0.0.0.3
+  Tag:         0.0.0.4
   Type:        darcs
-  Location:    http://hub.darcs.net/thielema/apportionment
+  Location:    https://hub.darcs.net/thielema/apportionment
 
 Source-Repository head
   Type:        darcs
-  Location:    http://hub.darcs.net/thielema/apportionment
+  Location:    https://hub.darcs.net/thielema/apportionment
 
 Library
   Exposed-Modules:     Math.Apportionment
@@ -33,3 +35,17 @@
   Hs-Source-Dirs:      src
   Default-Language:    Haskell2010
   GHC-Options:         -Wall
+
+Test-Suite apportionment-test
+  Type:             exitcode-stdio-1.0
+  Default-Language: Haskell2010
+  GHC-Options:      -Wall
+  Hs-source-dirs:   test
+  Main-Is:          Main.hs
+  Other-Modules:    Test.Math.Apportionment
+  Build-Depends:
+    apportionment,
+    doctest-exitcode-stdio >=0.0 && <0.1,
+    doctest-lib >=0.1 && <0.2,
+    QuickCheck >=2 && <3,
+    base
diff --git a/src/Math/Apportionment.hs b/src/Math/Apportionment.hs
--- a/src/Math/Apportionment.hs
+++ b/src/Math/Apportionment.hs
@@ -18,6 +18,16 @@
 import Data.Ord.HT (comparing, )
 
 
+{- $setup
+>>> import Control.Applicative ((<$>))
+>>> import qualified Test.QuickCheck as QC
+>>>
+>>> forAllNonNegatives ::
+>>>    (Num a, Ord a, Show a, QC.Arbitrary a) => ([a] -> Bool) -> QC.Property
+>>> forAllNonNegatives = QC.forAll $
+>>>    (map QC.getNonNegative <$> QC.arbitrary) `QC.suchThat` (\xs -> sum xs > 0)
+-}
+
 {- |
 Like 'largestRemainder' but result values
 are sorted with respect to descending fractional parts of the inputs.
@@ -33,6 +43,12 @@
           List.sortBy (comparing (negate.snd)) intFracs
    in  map (1+) intUps ++ intDowns
 
+-- ToDo: generalize to Traversable
+
+-- ToDo: require NonEmpty
+
+-- ToDo: It would be safer to use Integer
+
 {- |
 This function rounds values
 such that the sum of the rounded values
@@ -42,6 +58,14 @@
 <https://en.wikipedia.org/wiki/Largest_remainder_method>
 
 Input values must be non-negative, otherwise 'properFraction' bites us.
+
+>>> largestRemainder [1,2,3::Rational]
+[1,2,3]
+>>> largestRemainder [1.1,2.2,3.3,4.4::Rational]
+[1,2,3,5]
+
+prop> \xs -> xs == largestRemainder (map fromIntegral xs :: [Rational])
+prop> forAllNonNegatives $ \xs -> round (sum xs) == sum (largestRemainder (xs :: [Rational]))
 -}
 largestRemainder :: (RealFrac a) => [a] -> [Int]
 largestRemainder = largestRemainderCore . fractions
@@ -50,8 +74,16 @@
 @largestRemainderScaled s xs@
 scales and rounds the values in @xs@ such that their sum becomes @s@.
 
-E.g. @largestRemainderScaled 100 [1,2,3]@
-returns integral percentages proportional to 1:2:3.
+>>> largestRemainderScaled 100 [1,2,3::Rational]
+[17,33,50]
+
+That is, it returns integral percentages almost proportional to 1:2:3.
+
+>>> largestRemainderScaled 100 [1,10,100::Rational]
+[1,9,90]
+
+prop> forAllNonNegatives $ \xs -> xs == largestRemainderScaled (sum xs) (map fromIntegral xs :: [Rational])
+prop> \(QC.Positive s) -> forAllNonNegatives $ \xs -> s == sum (largestRemainderScaled s (xs :: [Rational]))
 -}
 largestRemainderScaled :: (RealFrac a) => Int -> [a] -> [Int]
 largestRemainderScaled s = largestRemainderCore . fractionsScaled s
@@ -89,6 +121,22 @@
 In @highestAveragesScaled divs s xs@,
 @divs@ must be an infinite list of strictly increasing positive numbers.
 E.g. @highestAveragesScaled dHondtDivisors s xs@ runs the d'Hondt method.
+
+>>> highestAveragesScaled dHondtDivisors 100 [1,2,3::Rational]
+[17,33,50]
+>>> highestAveragesScaled dHondtDivisors 100 [1,10,100::Rational]
+[0,9,91]
+
+>>> highestAveragesScaled sainteLagueDivisors 100 [1,2,3::Rational]
+[17,33,50]
+>>> highestAveragesScaled sainteLagueDivisors 100 [1,10,100::Rational]
+[1,9,90]
+
+prop> forAllNonNegatives $ \xs -> xs == highestAveragesScaled dHondtDivisors (sum xs) (map fromIntegral xs :: [Rational])
+prop> forAllNonNegatives $ \xs -> xs == highestAveragesScaled sainteLagueDivisors (sum xs) (map fromIntegral xs :: [Rational])
+
+prop> \(QC.Positive s) -> forAllNonNegatives $ \xs -> s == sum (highestAveragesScaled dHondtDivisors s (xs :: [Rational]))
+prop> \(QC.Positive s) -> forAllNonNegatives $ \xs -> s == sum (highestAveragesScaled sainteLagueDivisors s (xs :: [Rational]))
 -}
 highestAveragesScaled :: (RealFrac a) => [a] -> Int -> [a] -> [Int]
 highestAveragesScaled divs s xs =
@@ -98,6 +146,7 @@
        take s $ Fold.foldl (ListHT.mergeBy (compose2 (>=) snd)) [] $
        Map.mapWithKey (map . (,)) $ outerProduct (/) m divs
 
+-- ToDo: use Stream
 dHondtDivisors :: Num a => [a]
 dHondtDivisors = iterate (1+) 1
 
diff --git a/test/Main.hs b/test/Main.hs
new file mode 100644
--- /dev/null
+++ b/test/Main.hs
@@ -0,0 +1,11 @@
+-- Do not edit! Automatically created with doctest-extract.
+module Main where
+
+import qualified Test.Math.Apportionment
+import qualified Test.QuickCheck as QC
+
+import qualified Test.DocTest.Driver as DocTest
+
+main :: IO ()
+main = DocTest.runWith QC.stdArgs{QC.maxSuccess=3000} $ do
+    Test.Math.Apportionment.test
diff --git a/test/Test/Math/Apportionment.hs b/test/Test/Math/Apportionment.hs
new file mode 100644
--- /dev/null
+++ b/test/Test/Math/Apportionment.hs
@@ -0,0 +1,108 @@
+-- Do not edit! Automatically created with doctest-extract from src/Math/Apportionment.hs
+{-# LINE 21 "src/Math/Apportionment.hs" #-}
+
+module Test.Math.Apportionment where
+
+import Math.Apportionment
+import Test.DocTest.Base
+import qualified Test.DocTest.Driver as DocTest
+
+{-# LINE 22 "src/Math/Apportionment.hs" #-}
+import     Control.Applicative ((<$>))
+import     qualified Test.QuickCheck as QC
+
+forAllNonNegatives     ::
+       (Num a, Ord a, Show a, QC.Arbitrary a) => ([a] -> Bool) -> QC.Property
+forAllNonNegatives     = QC.forAll $
+       (map QC.getNonNegative <$> QC.arbitrary) `QC.suchThat` (\xs -> sum xs > 0)
+
+test :: DocTest.T ()
+test = do
+ DocTest.printPrefix "Math.Apportionment:67: "
+{-# LINE 67 "src/Math/Apportionment.hs" #-}
+ DocTest.property
+{-# LINE 67 "src/Math/Apportionment.hs" #-}
+     (\xs -> xs == largestRemainder (map fromIntegral xs :: [Rational]))
+ DocTest.printPrefix "Math.Apportionment:68: "
+{-# LINE 68 "src/Math/Apportionment.hs" #-}
+ DocTest.property
+{-# LINE 68 "src/Math/Apportionment.hs" #-}
+     (forAllNonNegatives $ \xs -> round (sum xs) == sum (largestRemainder (xs :: [Rational])))
+ DocTest.printPrefix "Math.Apportionment:62: "
+{-# LINE 62 "src/Math/Apportionment.hs" #-}
+ DocTest.example
+{-# LINE 62 "src/Math/Apportionment.hs" #-}
+   (largestRemainder [1,2,3::Rational])
+  [ExpectedLine [LineChunk "[1,2,3]"]]
+ DocTest.printPrefix "Math.Apportionment:64: "
+{-# LINE 64 "src/Math/Apportionment.hs" #-}
+ DocTest.example
+{-# LINE 64 "src/Math/Apportionment.hs" #-}
+   (largestRemainder [1.1,2.2,3.3,4.4::Rational])
+  [ExpectedLine [LineChunk "[1,2,3,5]"]]
+ DocTest.printPrefix "Math.Apportionment:85: "
+{-# LINE 85 "src/Math/Apportionment.hs" #-}
+ DocTest.property
+{-# LINE 85 "src/Math/Apportionment.hs" #-}
+     (forAllNonNegatives $ \xs -> xs == largestRemainderScaled (sum xs) (map fromIntegral xs :: [Rational]))
+ DocTest.printPrefix "Math.Apportionment:86: "
+{-# LINE 86 "src/Math/Apportionment.hs" #-}
+ DocTest.property
+{-# LINE 86 "src/Math/Apportionment.hs" #-}
+     (\(QC.Positive s) -> forAllNonNegatives $ \xs -> s == sum (largestRemainderScaled s (xs :: [Rational])))
+ DocTest.printPrefix "Math.Apportionment:77: "
+{-# LINE 77 "src/Math/Apportionment.hs" #-}
+ DocTest.example
+{-# LINE 77 "src/Math/Apportionment.hs" #-}
+   (largestRemainderScaled 100 [1,2,3::Rational])
+  [ExpectedLine [LineChunk "[17,33,50]"]]
+ DocTest.printPrefix "Math.Apportionment:82: "
+{-# LINE 82 "src/Math/Apportionment.hs" #-}
+ DocTest.example
+{-# LINE 82 "src/Math/Apportionment.hs" #-}
+   (largestRemainderScaled 100 [1,10,100::Rational])
+  [ExpectedLine [LineChunk "[1,9,90]"]]
+ DocTest.printPrefix "Math.Apportionment:135: "
+{-# LINE 135 "src/Math/Apportionment.hs" #-}
+ DocTest.property
+{-# LINE 135 "src/Math/Apportionment.hs" #-}
+     (forAllNonNegatives $ \xs -> xs == highestAveragesScaled dHondtDivisors (sum xs) (map fromIntegral xs :: [Rational]))
+ DocTest.printPrefix "Math.Apportionment:136: "
+{-# LINE 136 "src/Math/Apportionment.hs" #-}
+ DocTest.property
+{-# LINE 136 "src/Math/Apportionment.hs" #-}
+     (forAllNonNegatives $ \xs -> xs == highestAveragesScaled sainteLagueDivisors (sum xs) (map fromIntegral xs :: [Rational]))
+ DocTest.printPrefix "Math.Apportionment:138: "
+{-# LINE 138 "src/Math/Apportionment.hs" #-}
+ DocTest.property
+{-# LINE 138 "src/Math/Apportionment.hs" #-}
+     (\(QC.Positive s) -> forAllNonNegatives $ \xs -> s == sum (highestAveragesScaled dHondtDivisors s (xs :: [Rational])))
+ DocTest.printPrefix "Math.Apportionment:139: "
+{-# LINE 139 "src/Math/Apportionment.hs" #-}
+ DocTest.property
+{-# LINE 139 "src/Math/Apportionment.hs" #-}
+     (\(QC.Positive s) -> forAllNonNegatives $ \xs -> s == sum (highestAveragesScaled sainteLagueDivisors s (xs :: [Rational])))
+ DocTest.printPrefix "Math.Apportionment:125: "
+{-# LINE 125 "src/Math/Apportionment.hs" #-}
+ DocTest.example
+{-# LINE 125 "src/Math/Apportionment.hs" #-}
+   (highestAveragesScaled dHondtDivisors 100 [1,2,3::Rational])
+  [ExpectedLine [LineChunk "[17,33,50]"]]
+ DocTest.printPrefix "Math.Apportionment:127: "
+{-# LINE 127 "src/Math/Apportionment.hs" #-}
+ DocTest.example
+{-# LINE 127 "src/Math/Apportionment.hs" #-}
+   (highestAveragesScaled dHondtDivisors 100 [1,10,100::Rational])
+  [ExpectedLine [LineChunk "[0,9,91]"]]
+ DocTest.printPrefix "Math.Apportionment:130: "
+{-# LINE 130 "src/Math/Apportionment.hs" #-}
+ DocTest.example
+{-# LINE 130 "src/Math/Apportionment.hs" #-}
+   (highestAveragesScaled sainteLagueDivisors 100 [1,2,3::Rational])
+  [ExpectedLine [LineChunk "[17,33,50]"]]
+ DocTest.printPrefix "Math.Apportionment:132: "
+{-# LINE 132 "src/Math/Apportionment.hs" #-}
+ DocTest.example
+{-# LINE 132 "src/Math/Apportionment.hs" #-}
+   (highestAveragesScaled sainteLagueDivisors 100 [1,10,100::Rational])
+  [ExpectedLine [LineChunk "[1,9,90]"]]