Add bare-bones test suite

We probably want to be more clever and replace the `--test` invocation
with a `detailed-0.9` testsuite. We probably also should integrate the
QuickCheck tests into the testsuite.
That would take a deeper reorganization than I'm willing to commit to
now, though, so I'll leave it for another day.

Closes: ndmitchell#396

Author: hseg

hlint.cabal

@@ -62,7 +62,7 @@ flag hsyaml
   manual: True
   description: Use HsYAML instead of yaml
 
-library
+library hlint-lib
     default-language:   Haskell2010
     build-depends:
         base == 4.*, process, filepath, directory, containers,
@@ -107,14 +107,15 @@ library
 
     hs-source-dirs:     src
     exposed-modules:
+        HLint
+        -- this doesn't seem used anywhere in its own right?
         Language.Haskell.HLint
     other-modules:
         Paths_hlint
         Apply
         CmdLine
         Extension
         Fixity
-        HLint
         HsColour
         Idea
         Report
@@ -174,14 +175,18 @@ library
         Test.Util
     ghc-options: -Wunused-binds -Wunused-imports -Worphans -Wprepositive-qualified-module
 
-
 executable hlint
     default-language:   Haskell2010
-    build-depends:      base, hlint
+    build-depends:      base, hlint-lib
     main-is:            src/Main.hs
 
     -- See https://github.com/ndmitchell/hlint/pull/1169 for benchmarks
     -- that indicate -A32 is a good idea
     ghc-options:        -rtsopts -with-rtsopts=-A32m
     if flag(threaded)
         ghc-options:    -threaded
+
+test-suite test-hlint
+    type:               exitcode-stdio-1.0
+    main-is:            tests/Main.hs
+    build-depends:      base, hlint-lib

misc/HLint_NoDataFiles.hs

@@ -4,7 +4,7 @@
 -- Running this script should report two errors
 
 import Data.List
-import Language.Haskell.HLint
+import HLint
 import Language.Haskell.TH.Syntax
 import Network.HTTP
 

src/Main.hs

@@ -1,7 +1,7 @@
 
 module Main(main) where
 
-import Language.Haskell.HLint
+import HLint
 import Control.Monad
 import System.Environment
 import System.Exit

tests/Main.hs

@@ -0,0 +1,5 @@
+module Main where
+
+import HLint (hlint)
+
+main = hlint ["--test"]