问题描述
我查找了一个类似的主题,并从这里找到了以下代码片段:https://stackoverflow.com/a/21419654/14386048
引用:
假设我们有模块 SafePrelude.hs
:
module SafePrelude where
safeHead :: [a] -> Maybe a
safeHead [] = nothing
safeHead (x:_) = Just x
我们可以将测试放入 TestSafePrelude.hs
中,如下所示:
module TestSafePrelude where
import Test.HUnit
import SafePrelude
testSafeHeadForEmptyList :: Test
testSafeHeadForEmptyList =
TestCase $ assertEqual "Should return nothing for empty list"
nothing (safeHead ([]::[Int]))
testSafeHeadForNonEmptyList :: Test
testSafeHeadForNonEmptyList =
TestCase $ assertEqual "Should return (Just head) for non empty list" (Just 1)
(safeHead ([1]::[Int]))
main :: IO Counts
main = runTestTT $ TestList [testSafeHeadForEmptyList,testSafeHeadForNonEmptyList]
-- 结束引用--
是否可以在其中包含多个断言,例如 testSafeHeadForEmptyList
?我正在尝试对类似案例的测试样本进行分类,但只是不同的变化。我想避免下面这样的事情(假设每个断言相等都有不同的变化,但都应该什么都不返回,例如):
testSafeHeadForEmptyList :: Test
testSafeHeadForEmptyList =
TestCase $ assertEqual "Should return nothing for empty list"
nothing (safeHead ([]::[Int]))
testSafeHeadForEmptyList2 :: Test
testSafeHeadForEmptyList2 =
TestCase $ assertEqual "Should return nothing for empty list"
nothing (safeHead ([]::[Int]))
...
testSafeHeadForEmptyList99 :: Test
testSafeHeadForEmptyList99 =
TestCase $ assertEqual "Should return nothing for empty list"
nothing (safeHead ([]::[Int]))
这在 Haskell 中可行吗?
解决方法
如果您仔细查看此处:Test
- 您会看到 TestCase
和 TestList
是 Test
类型的数据构造函数 - 所以您应该能够做一些事情像这样:
testSafeHeadForEmptyList :: Test
testSafeHeadForEmptyList = TestList $
[ TestCase $ assertEqual "Should return Nothing for empty list"
Nothing (safeHead ([]::[Int])),TestCase $ assertEqual "Should return Nothing for empty list"
Nothing (safeHead ([]::[Int]))
...,TestCase $ assertEqual "Should return Nothing for empty list"
Nothing (safeHead ([]::[Int]))
]
甚至 fmap
TestCase
-构造函数,如果您愿意:
testSafeHeadForEmptyList :: Test
testSafeHeadForEmptyList = TestList $ fmap TestCase
[ assertEqual "Should return Nothing for empty list"
Nothing (safeHead ([]::[Int])),assertEqual "Should return Nothing for empty list"
Nothing (safeHead ([]::[Int]))
...,assertEqual "Should return Nothing for empty list"
Nothing (safeHead ([]::[Int]))
]
当然 TestLabel
也是一个构造函数,所以你可以在它上面贴一个标签:
testSafeHeadForEmptyList :: Test
testSafeHeadForEmptyList =
TestLabel "safe head for empty list" $ TestList $ fmap TestCase
[ assertEqual "Should return Nothing for empty list"
Nothing (safeHead ([]::[Int])),assertEqual "Should return Nothing for empty list"
Nothing (safeHead ([]::[Int]))
]
(当然你也可以使用 (~:)
)