Add test suite (#42)

dhall.cabal

@@ -69,3 +69,16 @@ Executable dhall
     GHC-Options: -Wall
     Other-Modules:
         Paths_dhall
+
+Test-Suite test
+    Type: exitcode-stdio-1.0
+    Hs-Source-Dirs: tests
+    Main-Is: Tests.hs
+    Other-Modules:
+        Normalization
+    Build-Depends:
+        base             >= 4        && < 5,
+        dhall,
+        tasty            >= 0.11.2   && < 0.12,
+        tasty-hunit      >= 0.9.2    && < 0.10,
+        text             >= 0.11.1.0 && < 1.3

src/Dhall/Core.hs

@@ -84,7 +84,7 @@ import qualified NeatInterpolation
     Note that Dhall does not support functions from terms to types and therefore
     Dhall is not a dependently typed language
 -}
-data Const = Type | Kind deriving (Show, Bounded, Enum)
+data Const = Type | Kind deriving (Show, Eq, Bounded, Enum)
 
 instance Buildable Const where
     build = buildConst
@@ -287,7 +287,7 @@ data Expr s a
     | Note s (Expr s a)
     -- | > Embed path                               ~  path
     | Embed a
-    deriving (Functor, Foldable, Traversable, Show)
+    deriving (Functor, Foldable, Traversable, Show, Eq)
 
 instance Applicative (Expr s) where
     pure = Embed

tests/Normalization.hs

@@ -0,0 +1,18 @@
+{-# LANGUAGE OverloadedStrings #-}
+module Normalization (normalizationTests) where
+
+import           Dhall.Core
+import           Test.Tasty
+import           Test.Tasty.HUnit
+
+normalizationTests :: TestTree
+normalizationTests = testGroup "normalization" [ constantFolding ]
+
+constantFolding :: TestTree
+constantFolding = testGroup "folding of constants" [ naturalPlus ]
+
+naturalPlus :: TestTree
+naturalPlus = testCase "natural plus" $ normalize' (NaturalPlus (NaturalLit 1) (NaturalLit 2)) @?= NaturalLit 3
+
+normalize' :: Expr () () -> Expr () ()
+normalize' = normalize

tests/Tests.hs

@@ -0,0 +1,7 @@
+module Main where
+
+import Normalization (normalizationTests)
+import Test.Tasty
+
+main :: IO ()
+main = defaultMain (testGroup "Dhall Tests" [ normalizationTests ])