content: import Control.Monad     (unless)
  import Test.Hspec        (Spec, describe, expectationFailure, it, shouldBe)
  import Test.Hspec.Runner (configFastFail, defaultConfig, hspecWith)
  
  import Beer (song)
  
  main :: IO ()
  main = hspecWith defaultConfig {configFastFail = True} specs
  
  specs :: Spec
  
  specs = describe "song" $ do
  
            -- First we test the input, line by line, to give more
            -- useful error messages.
  
            it "matches lines" $ sequence_ lineAssertions
  
            -- Finally, because testing lines we are unable
            -- to detect a missing newline at the end of the
            -- lyrics, we test the full song.
  
            it "matches full song" $ song `shouldBe` lyrics
    where
  
      lineAssertions = zipWith checkLine [1 :: Int ..] $ zipMaybe (lines song) (lines lyrics)
  
      checkLine lineno (got, want) =
        unless (got == want) $
          expectationFailure $ "mismatch at line " ++ show lineno ++ "\nexpected: " ++ show want ++ "\n but got: " ++ show got
  
      zipMaybe    []     []  = []
      zipMaybe (x:xs)    []  = (Just x , Nothing) : zipMaybe xs []
      zipMaybe    []  (y:ys) = (Nothing, Just y ) : zipMaybe [] ys
      zipMaybe (x:xs) (y:ys) = (Just x , Just y ) : zipMaybe xs ys
  
  -- Lyrics extracted from `exercism/problem-specifications` on 2016-10-03.
  
  lyrics :: String
  lyrics = "99 bottles of beer on the wall, 99 bottles of beer.\n\
           \Take one down and pass it around, 98 bottles of beer on the wall.\n\
           \\n\
           \98 bottles of beer on the wall, 98 bottles of beer.\n\
           \Take one down and pass it around, 97 bottles of beer on the wall.\n\
           \\n\
           \97 bottles of beer on the wall, 97 bottles of beer.\n\
           \Take one down and pass it around, 96 bottles of beer on the wall.\n\
           \\n\
           \96 bottles of beer on the wall, 96 bottles of beer.\n\
           \Take one down and pass it around, 95 bottles of beer on the wall.\n\
           \\n\
           \95 bottles of beer on the wall, 95 bottles of beer.\n\
           \Take one down and pass it around, 94 bottles of beer on the wall.\n\
           \\n\
           \94 bottles of beer on the wall, 94 bottles of beer.\n\
           \Take one down and pass it around, 93 bottles of beer on the wall.\n\
           \\n\
           \93 bottles of beer on the wall, 93 bottles of beer.\n\
           \Take one down and pass it around, 92 bottles of beer on the wall.\n\
           \\n\
           \92 bottles of beer on the wall, 92 bottles of beer.\n\
           \Take one down and pass it around, 91 bottles of beer on the wall.\n\
           \\n\
           \91 bottles of beer on the wall, 91 bottles of beer.\n\
           \Take one down and pass it around, 90 bottles of beer on the wall.\n\
           \\n\
           \90 bottles of beer on the wall, 90 bottles of beer.\n\
           \Take one down and pass it around, 89 bottles of beer on the wall.\n\
           \\n\
           \89 bottles of beer on the wall, 89 bottles of beer.\n\
           \Take one down and pass it around, 88 bottles of beer on the wall.\n\
           \\n\
           \88 bottles of beer on the wall, 88 bottles of beer.\n\
           \Take one down and pass it around, 87 bottles of beer on the wall.\n\
           \\n\
           \87 bottles of beer on the wall, 87 bottles of beer.\n\
           \Take one down and pass it around, 86 bottles of beer on the wall.\n\
           \\n\
           \86 bottles of beer on the wall, 86 bottles of beer.\n\
           \Take one down and pass it around, 85 bottles of beer on the wall.\n\
           \\n\
           \85 bottles of beer on the wall, 85 bottles of beer.\n\
           \Take one down and pass it around, 84 bottles of beer on the wall.\n\
           \\n\
           \84 bottles of beer on the wall, 84 bottles of beer.\n\
           \Take one down and pass it around, 83 bottles of beer on the wall.\n\
           \\n\
           \83 bottles of beer on the wall, 83 bottles of beer.\n\
           \Take one down and pass it around, 82 bottles of beer on the wall.\n\
           \\n\
           \82 bottles of beer on the wall, 82 bottles of beer.\n\
           \Take one down and pass it around, 81 bottles of beer on the wall.\n\
           \\n\
           \81 bottles of beer on the wall, 81 bottles of beer.\n\
           \Take one down and pass it around, 80 bottles of beer on the wall.\n\
           \\n\
           \80 bottles of beer on the wall, 80 bottles of beer.\n\
           \Take one down and pass it around, 79 bottles of beer on the wall.\n\
           \\n\
           \79 bottles of beer on the wall, 79 bottles of beer.\n\
           \Take one down and pass it around, 78 bottles of beer on the wall.\n\
           \\n\
           \78 bottles of beer on the wall, 78 bottles of beer.\n\
           \Take one down and pass it around, 77 bottles of beer on the wall.\n\
           \\n\
           \77 bottles of beer on the wall, 77 bottles of beer.\n\
           \Take one down and pass it around, 76 bottles of beer on the wall.\n\
           \\n\
           \76 bottles of beer on the wall, 76 bottles of beer.\n\
           \Take one down and pass it around, 75 bottles of beer on the wall.\n\
           \\n\
           \75 bottles of beer on the wall, 75 bottles of beer.\n\
           \Take one down and pass it around, 74 bottles of beer on the wall.\n\
           \\n\
           \74 bottles of beer on the wall, 74 bottles of beer.\n\
           \Take one down and pass it around, 73 bottles of beer on the wall.\n\
           \\n\
           \73 bottles of beer on the wall, 73 bottles of beer.\n\
           \Take one down and pass it around, 72 bottles of beer on the wall.\n\
           \\n\
           \72 bottles of beer on the wall, 72 bottles of beer.\n\
           \Take one down and pass it around, 71 bottles of beer on the wall.\n\
           \\n\
           \71 bottles of beer on the wall, 71 bottles of beer.\n\
           \Take one down and pass it around, 70 bottles of beer on the wall.\n\
           \\n\
           \70 bottles of beer on the wall, 70 bottles of beer.\n\
           \Take one down and pass it around, 69 bottles of beer on the wall.\n\
           \\n\
           \69 bottles of beer on the wall, 69 bottles of beer.\n\
           \Take one down and pass it around, 68 bottles of beer on the wall.\n\
           \\n\
           \68 bottles of beer on the wall, 68 bottles of beer.\n\
           \Take one down and pass it around, 67 bottles of beer on the wall.\n\
           \\n\
           \67 bottles of beer on the wall, 67 bottles of beer.\n\
           \Take one down and pass it around, 66 bottles of beer on the wall.\n\
           \\n\
           \66 bottles of beer on the wall, 66 bottles of beer.\n\
           \Take one down and pass it around, 65 bottles of beer on the wall.\n\
           \\n\
           \65 bottles of beer on the wall, 65 bottles of beer.\n\
           \Take one down and pass it around, 64 bottles of beer on the wall.\n\
           \\n\
           \64 bottles of beer on the wall, 64 bottles of beer.\n\
           \Take one down and pass it around, 63 bottles of beer on the wall.\n\
           \\n\
           \63 bottles of beer on the wall, 63 bottles of beer.\n\
           \Take one down and pass it around, 62 bottles of beer on the wall.\n\
           \\n\
           \62 bottles of beer on the wall, 62 bottles of beer.\n\
           \Take one down and pass it around, 61 bottles of beer on the wall.\n\
           \\n\
           \61 bottles of beer on the wall, 61 bottles of beer.\n\
           \Take one down and pass it around, 60 bottles of beer on the wall.\n\
           \\n\
           \60 bottles of beer on the wall, 60 bottles of beer.\n\
           \Take one down and pass it around, 59 bottles of beer on the wall.\n\
           \\n\
           \59 bottles of beer on the wall, 59 bottles of beer.\n\
           \Take one down and pass it around, 58 bottles of beer on the wall.\n\
           \\n\
           \58 bottles of beer on the wall, 58 bottles of beer.\n\
           \Take one down and pass it around, 57 bottles of beer on the wall.\n\
           \\n\
           \57 bottles of beer on the wall, 57 bottles of beer.\n\
           \Take one down and pass it around, 56 bottles of beer on the wall.\n\
           \\n\
           \56 bottles of beer on the wall, 56 bottles of beer.\n\
           \Take one down and pass it around, 55 bottles of beer on the wall.\n\
           \\n\
           \55 bottles of beer on the wall, 55 bottles of beer.\n\
           \Take one down and pass it around, 54 bottles of beer on the wall.\n\
           \\n\
           \54 bottles of beer on the wall, 54 bottles of beer.\n\
           \Take one down and pass it around, 53 bottles of beer on the wall.\n\
           \\n\
           \53 bottles of beer on the wall, 53 bottles of beer.\n\
           \Take one down and pass it around, 52 bottles of beer on the wall.\n\
           \\n\
           \52 bottles of beer on the wall, 52 bottles of beer.\n\
           \Take one down and pass it around, 51 bottles of beer on the wall.\n\
           \\n\
           \51 bottles of beer on the wall, 51 bottles of beer.\n\
           \Take one down and pass it around, 50 bottles of beer on the wall.\n\
           \\n\
           \50 bottles of beer on the wall, 50 bottles of beer.\n\
           \Take one down and pass it around, 49 bottles of beer on the wall.\n\
           \\n\
           \49 bottles of beer on the wall, 49 bottles of beer.\n\
           \Take one down and pass it around, 48 bottles of beer on the wall.\n\
           \\n\
           \48 bottles of beer on the wall, 48 bottles of beer.\n\
           \Take one down and pass it around, 47 bottles of beer on the wall.\n\
           \\n\
           \47 bottles of beer on the wall, 47 bottles of beer.\n\
           \Take one down and pass it around, 46 bottles of beer on the wall.\n\
           \\n\
           \46 bottles of beer on the wall, 46 bottles of beer.\n\
           \Take one down and pass it around, 45 bottles of beer on the wall.\n\
           \\n\
           \45 bottles of beer on the wall, 45 bottles of beer.\n\
           \Take one down and pass it around, 44 bottles of beer on the wall.\n\
           \\n\
           \44 bottles of beer on the wall, 44 bottles of beer.\n\
           \Take one down and pass it around, 43 bottles of beer on the wall.\n\
           \\n\
           \43 bottles of beer on the wall, 43 bottles of beer.\n\
           \Take one down and pass it around, 42 bottles of beer on the wall.\n\
           \\n\
           \42 bottles of beer on the wall, 42 bottles of beer.\n\
           \Take one down and pass it around, 41 bottles of beer on the wall.\n\
           \\n\
           \41 bottles of beer on the wall, 41 bottles of beer.\n\
           \Take one down and pass it around, 40 bottles of beer on the wall.\n\
           \\n\
           \40 bottles of beer on the wall, 40 bottles of beer.\n\
           \Take one down and pass it around, 39 bottles of beer on the wall.\n\
           \\n\
           \39 bottles of beer on the wall, 39 bottles of beer.\n\
           \Take one down and pass it around, 38 bottles of beer on the wall.\n\
           \\n\
           \38 bottles of beer on the wall, 38 bottles of beer.\n\
           \Take one down and pass it around, 37 bottles of beer on the wall.\n\
           \\n\
           \37 bottles of beer on the wall, 37 bottles of beer.\n\
           \Take one down and pass it around, 36 bottles of beer on the wall.\n\
           \\n\
           \36 bottles of beer on the wall, 36 bottles of beer.\n\
           \Take one down and pass it around, 35 bottles of beer on the wall.\n\
           \\n\
           \35 bottles of beer on the wall, 35 bottles of beer.\n\
           \Take one down and pass it around, 34 bottles of beer on the wall.\n\
           \\n\
           \34 bottles of beer on the wall, 34 bottles of beer.\n\
           \Take one down and pass it around, 33 bottles of beer on the wall.\n\
           \\n\
           \33 bottles of beer on the wall, 33 bottles of beer.\n\
           \Take one down and pass it around, 32 bottles of beer on the wall.\n\
           \\n\
           \32 bottles of beer on the wall, 32 bottles of beer.\n\
           \Take one down and pass it around, 31 bottles of beer on the wall.\n\
           \\n\
           \31 bottles of beer on the wall, 31 bottles of beer.\n\
           \Take one down and pass it around, 30 bottles of beer on the wall.\n\
           \\n\
           \30 bottles of beer on the wall, 30 bottles of beer.\n\
           \Take one down and pass it around, 29 bottles of beer on the wall.\n\
           \\n\
           \29 bottles of beer on the wall, 29 bottles of beer.\n\
           \Take one down and pass it around, 28 bottles of beer on the wall.\n\
           \\n\
           \28 bottles of beer on the wall, 28 bottles of beer.\n\
           \Take one down and pass it around, 27 bottles of beer on the wall.\n\
           \\n\
           \27 bottles of beer on the wall, 27 bottles of beer.\n\
           \Take one down and pass it around, 26 bottles of beer on the wall.\n\
           \\n\
           \26 bottles of beer on the wall, 26 bottles of beer.\n\
           \Take one down and pass it around, 25 bottles of beer on the wall.\n\
           \\n\
           \25 bottles of beer on the wall, 25 bottles of beer.\n\
           \Take one down and pass it around, 24 bottles of beer on the wall.\n\
           \\n\
           \24 bottles of beer on the wall, 24 bottles of beer.\n\
           \Take one down and pass it around, 23 bottles of beer on the wall.\n\
           \\n\
           \23 bottles of beer on the wall, 23 bottles of beer.\n\
           \Take one down and pass it around, 22 bottles of beer on the wall.\n\
           \\n\
           \22 bottles of beer on the wall, 22 bottles of beer.\n\
           \Take one down and pass it around, 21 bottles of beer on the wall.\n\
           \\n\
           \21 bottles of beer on the wall, 21 bottles of beer.\n\
           \Take one down and pass it around, 20 bottles of beer on the wall.\n\
           \\n\
           \20 bottles of beer on the wall, 20 bottles of beer.\n\
           \Take one down and pass it around, 19 bottles of beer on the wall.\n\
           \\n\
           \19 bottles of beer on the wall, 19 bottles of beer.\n\
           \Take one down and pass it around, 18 bottles of beer on the wall.\n\
           \\n\
           \18 bottles of beer on the wall, 18 bottles of beer.\n\
           \Take one down and pass it around, 17 bottles of beer on the wall.\n\
           \\n\
           \17 bottles of beer on the wall, 17 bottles of beer.\n\
           \Take one down and pass it around, 16 bottles of beer on the wall.\n\
           \\n\
           \16 bottles of beer on the wall, 16 bottles of beer.\n\
           \Take one down and pass it around, 15 bottles of beer on the wall.\n\
           \\n\
           \15 bottles of beer on the wall, 15 bottles of beer.\n\
           \Take one down and pass it around, 14 bottles of beer on the wall.\n\
           \\n\
           \14 bottles of beer on the wall, 14 bottles of beer.\n\
           \Take one down and pass it around, 13 bottles of beer on the wall.\n\
           \\n\
           \13 bottles of beer on the wall, 13 bottles of beer.\n\
           \Take one down and pass it around, 12 bottles of beer on the wall.\n\
           \\n\
           \12 bottles of beer on the wall, 12 bottles of beer.\n\
           \Take one down and pass it around, 11 bottles of beer on the wall.\n\
           \\n\
           \11 bottles of beer on the wall, 11 bottles of beer.\n\
           \Take one down and pass it around, 10 bottles of beer on the wall.\n\
           \\n\
           \10 bottles of beer on the wall, 10 bottles of beer.\n\
           \Take one down and pass it around, 9 bottles of beer on the wall.\n\
           \\n\
           \9 bottles of beer on the wall, 9 bottles of beer.\n\
           \Take one down and pass it around, 8 bottles of beer on the wall.\n\
           \\n\
           \8 bottles of beer on the wall, 8 bottles of beer.\n\
           \Take one down and pass it around, 7 bottles of beer on the wall.\n\
           \\n\
           \7 bottles of beer on the wall, 7 bottles of beer.\n\
           \Take one down and pass it around, 6 bottles of beer on the wall.\n\
           \\n\
           \6 bottles of beer on the wall, 6 bottles of beer.\n\
           \Take one down and pass it around, 5 bottles of beer on the wall.\n\
           \\n\
           \5 bottles of beer on the wall, 5 bottles of beer.\n\
           \Take one down and pass it around, 4 bottles of beer on the wall.\n\
           \\n\
           \4 bottles of beer on the wall, 4 bottles of beer.\n\
           \Take one down and pass it around, 3 bottles of beer on the wall.\n\
           \\n\
           \3 bottles of beer on the wall, 3 bottles of beer.\n\
           \Take one down and pass it around, 2 bottles of beer on the wall.\n\
           \\n\
           \2 bottles of beer on the wall, 2 bottles of beer.\n\
           \Take one down and pass it around, 1 bottle of beer on the wall.\n\
           \\n\
           \1 bottle of beer on the wall, 1 bottle of beer.\n\
           \Take it down and pass it around, no more bottles of beer on the wall.\n\
           \\n\
           \No more bottles of beer on the wall, no more bottles of beer.\n\
           \Go to the store and buy some more, 99 bottles of beer on the wall.\n"
  