[英]How can I constrain a QuickCheck parameter to a list of non-empty Strings?
I have a property that takes a list of Strings: 我有一个属性,其中包含一个字符串列表:
myProp :: [String] -> Bool
I need to constrain the inputs that QuickCheck generates so that only non-empty strings are in the list. 我需要约束QuickCheck生成的输入,以便列表中只有非空字符串。
How can I do this? 我怎样才能做到这一点?
You use forAll
together with listOf
(which generates lists) and listOf1
(which generates non-empty lists). 您可以使用
forAll
连同listOf
(生成列表)和listOf1
(生成非空列表)。
quickCheck $ forAll (listOf $ listOf1 arbitrary) $ myProp
-- more verbose alternative to make things clear
nonEmptyString :: Gen String
nonEmptyString = listOf1 arbitrary
quickCheck $ forAll (listOf nonEmptyString) $ myProp
import Test.QuickCheck.Modifiers (NonEmptyList (..))
myProp :: [NonEmptyList Char] -> Bool
myProp xs0 =
let xs = map getNonEmpty xs0
in ...
Or, from first principles (no library functions): 或者,从第一原则(没有库函数):
quickCheck $ \ h t -> let {s :: String ; s = h : t } in length s > 0
here s
runs through all non-empty values. 这里
s
遍历所有非空值。
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