Setup QuickCheck and add Literal Parse/Print test

Currently fails the prop tests: https://github.com/evancz/Elm/issues/420

Also ignore emacs backup files.

.gitignore

@@ -10,3 +10,4 @@ cabal-dev
 data
 */ElmFiles/*
 .DS_Store
+*~

Elm.cabal

@@ -228,12 +228,41 @@ Executable elm-doc
 
 Test-Suite test-elm
   Type:            exitcode-stdio-1.0
-  Hs-Source-Dirs:  tests
+  Hs-Source-Dirs:  tests, compiler
   Main-is:         Main.hs
+  other-modules:   Tests.Compiler
+                   Tests.Property
+                   Tests.Property.Arbitrary
+                   SourceSyntax.Helpers
+                   SourceSyntax.Literal
+                   SourceSyntax.PrettyPrint
   build-depends:   base,
                    directory,
                    Elm,
                    test-framework,
                    test-framework-hunit,
+                   test-framework-quickcheck2,
                    HUnit,
-                   filemanip
+                   pretty,
+                   QuickCheck >= 2 && < 3,
+                   filemanip,
+                   aeson,
+                   base >=4.2 && <5,
+                   binary >= 0.6.4.0,
+                   blaze-html == 0.5.* || == 0.6.*,
+                   blaze-markup == 0.5.1.*,
+                   bytestring,
+                   cmdargs,
+                   containers >= 0.3,
+                   directory,
+                   filepath,
+                   indents,
+                   language-ecmascript >=0.15 && < 1.0,
+                   mtl >= 2,
+                   pandoc >= 1.10,
+                   parsec >= 3.1.1,
+                   pretty,
+                   text,
+                   transformers >= 0.2,
+                   union-find,
+                   unordered-containers

compiler/SourceSyntax/Literal.hs

@@ -8,7 +8,7 @@ data Literal = IntNum Int
              | Chr Char
              | Str String
              | Boolean Bool
-               deriving (Eq, Ord, Show)
+             deriving (Eq, Ord, Show)
 
 instance Pretty Literal where
   pretty literal =

tests/Main.hs

@@ -3,6 +3,9 @@ module Main where
 import Test.Framework
 
 import Tests.Compiler
+import Tests.Property
 
 main :: IO () 
-main = defaultMain [ compilerTests ]
+main = defaultMain [ compilerTests
+                   , propertyTests
+                   ]

tests/Tests/Property.hs

@@ -0,0 +1,22 @@
+module Tests.Property where
+
+import Test.Framework
+import Test.Framework.Providers.QuickCheck2
+import Test.QuickCheck
+
+import SourceSyntax.Literal     (Literal)
+import SourceSyntax.PrettyPrint (pretty)
+import Parse.Helpers            (iParse)
+import Parse.Literal            (literal)
+import Tests.Property.Arbitrary
+
+propertyTests :: Test
+propertyTests =
+  testGroup "Parse/Print Agreement Tests"
+  [
+    testProperty "Literal test" prop_literal_parse_print
+  ]
+
+prop_literal_parse_print :: Literal -> Bool
+prop_literal_parse_print l =
+  either (const False) (== l) . iParse literal . show . pretty $ l

tests/Tests/Property/Arbitrary.hs

@@ -0,0 +1,23 @@
+{-# OPTIONS_GHC -fno-warn-orphans #-}
+module Tests.Property.Arbitrary where
+
+import Control.Applicative       ((<$>))
+import Test.QuickCheck.Arbitrary
+import Test.QuickCheck.Gen
+
+import SourceSyntax.Literal
+
+instance Arbitrary Literal where
+  arbitrary = oneof [ IntNum   <$> arbitrary
+                    , FloatNum <$> arbitrary
+                    , Chr      <$> arbitrary
+                    , Str      <$> arbitrary
+                      -- Booleans aren't actually source syntax 
+                      -- , Boolean  <$> arbitrary
+                    ]
+  shrink l = case l of
+    IntNum n   -> IntNum   <$> shrink n
+    FloatNum f -> FloatNum <$> shrink f
+    Chr c      -> Chr      <$> shrink c
+    Str s      -> Str      <$> shrink s
+    Boolean b  -> Boolean  <$> shrink b