Add fledgeling test suite

We should really get this to run all of the tests in the tests directory
instead.

.travis.yml

@@ -29,6 +29,7 @@ script:
  - cabal build
  - cabal check
  - cabal sdist
+ - cabal test
 # The following scriptlet checks that the resulting source distribution can be built & installed
  - export SRC_TGZ=$(cabal info . | awk '{print $2 ".tar.gz";exit}') ;
    cd dist/;

directory.cabal

@@ -62,6 +62,15 @@ Library
 
     ghc-options: -Wall
 
+test-suite test
+  default-language: Haskell2010
+  hs-source-dirs: test
+  main-is: main.hs
+  type: exitcode-stdio-1.0
+  build-depends: base
+               , directory
+               , containers
+
 source-repository head
   type:     git
   location: https://github.com/haskell/directory

test/main.hs

@@ -0,0 +1,20 @@
+{-# LANGUAGE NoImplicitPrelude #-}
+-- Simplistic test suite for now. Worthwhile to add a dependency on a
+-- test framework at some point.
+module Main (main) where
+
+import qualified Data.Set         as Set
+import           Prelude          (IO, error, fmap, return, show, (==))
+import           System.Directory (getDirectoryContents)
+
+main :: IO ()
+main = do
+    let expected = Set.fromList
+            [ "."
+            , ".."
+            , "main.hs"
+            ]
+    actual <- fmap Set.fromList (getDirectoryContents "test")
+    if expected == actual
+        then return ()
+        else error (show (expected, actual))