Solve 'Duck Duck Goose' kata

Author: borisskert

src/DuckDuckGoose.hs

@@ -0,0 +1,11 @@
+module DuckDuckGoose (duckDuckGoose, Player (..)) where
+
+import Preloaded (Player (name))
+
+-- https://www.codewars.com/kata/582e0e592029ea10530009ce/train/haskell
+
+duckDuckGoose :: [Player] -> Int -> String
+duckDuckGoose players goose = name . (!! index) $ players
+  where
+    count = length players
+    index = (`mod` count) . subtract 1 $ goose

src/Preloaded.hs

@@ -39,3 +39,5 @@ data Circle = Circle
   { center :: Point
   , radius :: Double
   } deriving (Show, Eq)
+
+newtype Player = Player {name :: String} deriving (Show, Eq)

test/DuckDuckGooseSpec.hs

@@ -0,0 +1,29 @@
+module DuckDuckGooseSpec where
+
+import Test.Hspec
+import Test.HUnit
+import DuckDuckGoose (duckDuckGoose)
+import Preloaded
+
+spec :: Spec
+spec = do
+  describe "Fixed Tests" $ do
+    it "should find the correct goose" $ do
+      let players = Player . (:"") <$> "abcdcefghz"
+      runTest players 1 "a"
+      runTest players 3 "c"
+      runTest players 10 "z"
+      runTest players 20 "z"
+      runTest players 30 "z"
+      runTest players 18 "g"
+      runTest players 28 "g"
+      runTest players 12 "b"
+      runTest players 2 "b"
+      runTest players 7 "f"
+      
+runTest :: [Player] -> Int -> String -> Expectation
+runTest players goose expected =
+  assertEqual (showInput players goose) expected $ duckDuckGoose players goose
+  
+showInput :: [Player] -> Int -> String
+showInput players goose = unwords ["duckDuckGoose", show players, show goose]