Synnefo » snf-ganeti

{-# LANGUAGE TemplateHaskell #-}

{-| Unittest helpers for TemplateHaskell components.

-}

{-

Copyright (C) 2011, 2012, 2013 Google Inc.

This program is free software; you can redistribute it and/or modify

it under the terms of the GNU General Public License as published by

the Free Software Foundation; either version 2 of the License, or

(at your option) any later version.

This program is distributed in the hope that it will be useful, but

WITHOUT ANY WARRANTY; without even the implied warranty of

MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

General Public License for more details.

You should have received a copy of the GNU General Public License

along with this program; if not, write to the Free Software

Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA

02110-1301, USA.

-}

module Test.Ganeti.TestHelper

  ( testSuite

  , genArbitrary

  ) where

import Control.Applicative

import Data.List (stripPrefix, isPrefixOf)

import Data.Maybe (fromMaybe)

import Test.Framework

import Test.Framework.Providers.HUnit

import Test.Framework.Providers.QuickCheck2

import Test.HUnit (Assertion)

import Test.QuickCheck

import Language.Haskell.TH

-- | Test property prefix.

propPrefix :: String

propPrefix = "prop_"

-- | Test case prefix.

casePrefix :: String

casePrefix = "case_"

-- | Test case prefix without underscore.

case2Pfx :: String

case2Pfx = "case"

-- | Tries to drop a prefix from a string.

simplifyName :: String -> String -> String

simplifyName pfx string = fromMaybe string (stripPrefix pfx string)

-- | Builds a test from a QuickCheck property.

runProp :: Testable prop => String -> prop -> Test

runProp = testProperty . simplifyName propPrefix

-- | Builds a test for a HUnit test case.

runCase :: String -> Assertion -> Test

runCase = testCase . simplifyName casePrefix

-- | Runs the correct test provider for a given test, based on its

-- name (not very nice, but...).

run :: Name -> Q Exp

run name =

  let str = nameBase name

      nameE = varE name

      strE = litE (StringL str)

  in case () of

       _ | propPrefix `isPrefixOf` str -> [| runProp $strE $nameE |]

         | casePrefix `isPrefixOf` str -> [| runCase $strE $nameE |]

         | case2Pfx `isPrefixOf` str ->

           [| (testCase . simplifyName case2Pfx) $strE $nameE |]

         | otherwise -> fail $ "Unsupported test function name '" ++ str ++ "'"

-- | Convert slashes in a name to underscores.

mapSlashes :: String -> String

mapSlashes = map (\c -> if c == '/' then '_' else c)

-- | Builds a test suite.

testSuite :: String -> [Name] -> Q [Dec]

testSuite tsname tdef = do

  let fullname = mkName $ "test" ++ mapSlashes tsname

  tests <- mapM run tdef

  sigtype <- [t| Test |]

  body <- [| testGroup $(litE $ stringL tsname) $(return $ ListE tests) |]

  return [ SigD fullname sigtype

         , ValD (VarP fullname) (NormalB body) []

         ]

-- | Builds an arbitrary value for a given constructor. This doesn't

-- use the actual types of the fields, since we expect arbitrary

-- instances for all of the types anyway, we only care about the

-- number of fields.

mkConsArbitrary :: (Name, [a]) -> Exp

mkConsArbitrary (name, types) =

  let infix_arb a = InfixE (Just a) (VarE '(<*>)) (Just (VarE 'arbitrary))

      constr = AppE (VarE 'pure) (ConE name)

  in foldl (\a _ -> infix_arb a) constr types

-- | Extracts the name and the types from a constructor.

conInfo :: Con -> (Name, [Type])

conInfo (NormalC name t)     = (name, map snd t)

conInfo (RecC    name t)     = (name, map (\(_, _, x) -> x) t)

conInfo (InfixC t1 name t2)  = (name, [snd t1, snd t2])

conInfo (ForallC _ _ subcon) = conInfo subcon

-- | Builds an arbitrary instance for a regular data type (i.e. not Bounded).

mkRegularArbitrary :: Name -> [Con] -> Q [Dec]

mkRegularArbitrary name cons = do

  expr <- case cons of

            [] -> fail "Can't make Arbitrary instance for an empty data type"

            [x] -> return $ mkConsArbitrary (conInfo x)

            xs -> appE (varE 'oneof) $

                  listE (map (return . mkConsArbitrary . conInfo) xs)

  return [InstanceD [] (AppT (ConT ''Arbitrary) (ConT name))

          [ValD (VarP 'arbitrary) (NormalB expr) []]]

-- | Builds a default Arbitrary instance for a type. This requires

-- that all members are of types that already have Arbitrary

-- instances, and that the arbitrary instances are well behaved

-- (w.r.t. recursive data structures, or similar concerns). In that

-- sense, this is not appropriate for all data types, just those that

-- are simple but very repetitive or have many simple fields.

genArbitrary :: Name -> Q [Dec]

genArbitrary name = do

  r <- reify name

  case r of

    TyConI (DataD _ _ _ cons _) ->

      mkRegularArbitrary name cons

    TyConI (NewtypeD _ _ _ con _) ->

      mkRegularArbitrary name [con]

    TyConI (TySynD _ _ (ConT tn)) -> genArbitrary tn

    _ -> fail $ "Invalid type in call to genArbitrary for " ++ show name

         ++ ", type " ++ show r