增強Test.QuickCheck

Question

我想擴展QuickCheck以在測試失敗時給出更好的消息（而不僅僅是種子）。 例如，我希望能夠創建以下內容：

eqTest :: Eq a => a -> a -> TestResult
eqTest x y = if x == y
             then HappyResult
             else SadResult $ show x <> " /= " <> show y

或（具有Monoid實例在其“停止” SadResult和“繼續”上HappyResult ，類似於一個(&&)操作者TestResult ）

listEqTest :: Eq a => [a] -> [a] -> TestResult
listEqTest [] [] = HappyResult
listEqTest [] ys = SadResult $ "Ran out of xs to compare to " <> show ys
listEqTest xs [] = SadResult $ "Ran out of ys to compare to " <> show xs
listEqTest (x:xs) (y:ys) = eqTest x y <> listEqTest xs ys

如何擴展QuickCheck功能？ 或者，是否有一個更具可擴展性的隨機測試庫？

謝謝！

Answer 1

從閱讀QuickCheck文檔，您要查找的類型是Result ：

data Result
  = MkResult
  { ok          :: Maybe Bool     -- ^ result of the test case; Nothing = discard
  , expect      :: Bool           -- ^ indicates what the expected result of the property is
  , reason      :: String         -- ^ a message indicating what went wrong
  , interrupted :: Bool           -- ^ indicates if the test case was cancelled by pressing ^C
  , abort       :: Bool           -- ^ if True, the test should not be repeated
  , stamp       :: [(String,Int)] -- ^ the collected values for this test case
  , callbacks   :: [Callback]     -- ^ the callbacks for this test case
  }

並且由於instance Testable Result您可以將其用作QuickCheck測試的返回類型：

Prelude Test.QuickCheck Test.QuickCheck.Property> let test xs = if 13 `elem` xs then MkResult (Just False) True "Input contained bad number" False False [] [] else succeeded
Prelude Test.QuickCheck Test.QuickCheck.Property> quickCheck test
*** Failed! Input contained bad number (after 17 tests and 3 shrinks):    
[13]