haskell - Monadic QuickCheck 测试不适用于任意 Repa 数组

Question

我正在尝试在 Haskell 中为任意 Repa 数组编写测试。出于某种原因，以下代码段：

import Test.QuickCheck
import Test.QuickCheck.Monadic
import Data.Array.Repa (Array, DIM2)

prop_id :: Array U DIM2 Double -> Property
prop_id array = monadicIO $ array `R.equalsP` array >>= assert

抛出此异常：

*** Failed! (after 1 test): 
Exception:
Test.QuickCheck.resize: negative size
CallStack (from HasCallStack):
    error, called at ./Test/QuickCheck/Gen.hs:82:22 in QuickCheck-2.9.2-Jyj4gc4JxkEIgGFLAsGhs9:Test.QuickCheck.Gen
Exception thrown while printing test case:
Test.QuickCheck.resize: negative size
CallStack (from HasCallStack):
    error, called at ./Test/QuickCheck/Gen.hs:82:22 in QuickCheck-2.9.2-Jyj4gc4JxkEIgGFLAsGhs9:Test.QuickCheck.Gen

我不确定如何解释这些信息。谢谢你的帮助。

Answer 1

这是 repaArbitrary实例中的一个错误。arbitrary在大小为 0 时崩溃。您可以同时修复您的财产使用的生成器：

quickCheck $ forAll (scale (+1) arbitrary) prop_id