pascals-triangle: Rewrite tests to use hspec with fail-fast.

exercises/pascals-triangle/package.yaml

@@ -16,4 +16,4 @@ tests:
     source-dirs: test
     dependencies:
       - pascals-triangle
-      - HUnit
+      - hspec

exercises/pascals-triangle/src/Example.hs

@@ -1,12 +1,7 @@
-module Triangle (triangle, row) where
+module Triangle (rows) where
 
-triangle :: Integral a => [[a]]
-triangle = map row [1..]
+rows :: Integral a => Int -> [[a]]
+rows = flip take triangle
 
-row :: (Integral a) => a -> [a]
-row n = reflect [] $ scanl choices 1 [1 .. pred n `div` 2]
-  where
-    reflect acc [] | odd n     = tail acc
-                   | otherwise = acc
-    reflect acc (x:xs) = x : reflect (x:acc) xs
-    choices z i = z * (n - i) `div` i
+triangle :: Integral a => [[a]]
+triangle = iterate (\x -> zipWith (+) (0 : x) (x ++ [0])) [1]

exercises/pascals-triangle/src/Triangle.hs

@@ -1,7 +1,4 @@
-module Triangle (triangle, row) where
+module Triangle (rows) where
 
-triangle :: Integral a => [[a]]
-triangle = undefined
-
-row :: Integral a => a -> [a]
-row = undefined
+rows :: Int -> [[Integer]]
+rows = undefined

exercises/pascals-triangle/test/Tests.hs

@@ -1,36 +1,28 @@
 {-# OPTIONS_GHC -fno-warn-type-defaults #-}
 
-import Test.HUnit (Assertion, (@=?), runTestTT, Test(..), Counts(..))
-import System.Exit (ExitCode(..), exitWith)
-import Triangle (row, triangle)
+import Data.Foldable     (for_)
+import Test.Hspec        (Spec, describe, it, shouldBe)
+import Test.Hspec.Runner (configFastFail, defaultConfig, hspecWith)
 
-exitProperly :: IO Counts -> IO ()
-exitProperly m = do
-  counts <- m
-  exitWith $ if failures counts /= 0 || errors counts /= 0 then ExitFailure 1 else ExitSuccess
-
-testCase :: String -> Assertion -> Test
-testCase label assertion = TestLabel label (TestCase assertion)
+import Triangle (rows)
 
 main :: IO ()
-main = exitProperly $ runTestTT $ TestList
-       [ TestList triangleTests ]
+main = hspecWith defaultConfig {configFastFail = True} specs
+
+specs :: Spec
+specs = describe "pascals-triangle" $ do
+          describe "rows" $ for_ rowsCases rowsTest
+  where
+
+    rowsTest (description, n, expected) = it description assertion
+      where
+        assertion = rows n `shouldBe` expected
+
+    -- Test cases adapted from `exercism/x-common` on 2016-09-14.
 
-triangleTests :: [Test]
-triangleTests =
-  [ testCase "1 row" $
-    [[1]] @=? take 1 (triangle :: [[Int]])
-  , testCase "2 rows" $
-    [[1], [1, 1]] @=? take 2 (triangle :: [[Int]])
-  , testCase "3 rows" $
-    [[1], [1, 1], [1, 2, 1]] @=? take 3 (triangle :: [[Int]])
-  , testCase "4 rows" $
-    [[1], [1, 1], [1, 2, 1], [1, 3, 3, 1]] @=? take 4 (triangle :: [[Int]])
-  , testCase "5th row" $
-    [1, 4, 6, 4, 1] @=? (row 5 :: [Int])
-  , testCase "20th row" $
-    [(1 :: Int), 19, 171, 969, 3876, 11628, 27132, 50388, 75582, 92378
-    , 92378, 75582, 50388, 27132, 11628, 3876, 969, 171, 19, 1] @=? row 20
-  , testCase "201st row maximum" $
-    (product [101..200] `div` product [1..100] :: Integer) @=? row 201 !! 100
-  ]
+    rowsCases = [ ("no rows"      , 0, [                                    ])
+                , ("single row"   , 1, [[1]                                 ])
+                , ("two rows"     , 2, [[1], [1, 1]                         ])
+                , ("three rows"   , 3, [[1], [1, 1], [1, 2, 1]              ])
+                , ("four rows"    , 4, [[1], [1, 1], [1, 2, 1], [1, 3, 3, 1]])
+                , ("negative rows",-1, [                                    ]) ]