✅ haskell: collatz-conjecture

haskell/collatz-conjecture/test/Tests.hs

@@ -0,0 +1,54 @@
+{-# OPTIONS_GHC -fno-warn-type-defaults #-}
+{-# LANGUAGE RecordWildCards #-}
+
+import Data.Foldable     (for_)
+import Test.Hspec        (Spec, describe, it, shouldBe)
+import Test.Hspec.Runner (configFastFail, defaultConfig, hspecWith)
+
+import CollatzConjecture (collatz)
+
+main :: IO ()
+main = hspecWith defaultConfig {configFastFail = True} specs
+
+specs :: Spec
+specs = describe "collatz" $ for_ cases test
+  where
+
+    test Case{..} = it description assertion
+      where
+        assertion = collatz number `shouldBe` expected
+
+
+data Case = Case { description :: String
+                 , number      :: Integer
+                 , expected    :: Maybe Integer
+                 }
+
+cases :: [Case]
+cases = [ Case { description = "zero steps for one"
+               , number      = 1
+               , expected    = Just 0
+               }
+        , Case { description = "divide if even"
+               , number      = 16
+               , expected    = Just 4
+               }
+        , Case { description = "even and odd steps"
+               , number      = 12
+               , expected    = Just 9
+               }
+        , Case { description = "large number of even and odd steps"
+               , number      = 1000000
+               , expected    = Just 152
+               }
+        , Case { description = "zero is an error"
+               , number      = 0
+               , expected    = Nothing
+               }
+        , Case { description = "negative value is an error"
+               , number      = -15
+               , expected    = Nothing
+               }
+        ]
+
+-- 553e2f7a6ce638a6cf622985b9138e6013626eb3