Haskell语言学习笔记（96）Hspec

hspec 模块

Hspec 是一个测试框架。
hspec 模块需要安装

$ cabal install hspec --lib
Completed    hspec-2.7.1 (lib)

示例 1

-- file Spec.hs
import Test.Hspec
import Test.QuickCheck
import Control.Exception (evaluate)

main :: IO ()
main = hspec $ do
  describe "Prelude.head" $ do
    it "returns the first element of a list" $ do
      head [23 ..] `shouldBe` (23 :: Int)

    it "returns the first element of an *arbitrary* list" $
      property $ x xs -> head (x:xs) == (x :: Int)

    it "throws an exception if used with an empty list" $ do
      evaluate (head []) `shouldThrow` anyException

Prelude> :set -package QuickCheck
package flags have changed, resetting and loading new packages...
Prelude> :l Spec.hs
[1 of 1] Compiling Main             ( Spec.hs, interpreted )
Ok, one module loaded.
*Main> main

Prelude.head
  returns the first element of a list
  returns the first element of an *arbitrary* list
    +++ OK, passed 100 tests.
  throws an exception if used with an empty list

Finished in 0.0012 seconds
3 examples, 0 failures

示例 2

-- file MathSpec.hs
module MathSpec where

import Test.Hspec
import Math

main :: IO ()
main = hspec $ do
  describe "absolute" $ do
    it "returns the original number when given a positive input" $
      absolute 1 `shouldBe` 1

    it "returns a positive number when given a negative input" $
      absolute (-1) `shouldBe` 1

    it "returns zero when given zero" $
      absolute 0 `shouldBe` 0

-- file Math.hs
module Math where

absolute :: Int -> Int
absolute n = if n < 0 then negate n else n

Prelude> :l MathSpec
[1 of 2] Compiling Math             ( Math.hs, interpreted )
[2 of 2] Compiling MathSpec         ( MathSpec.hs, interpreted )
Ok, two modules loaded.
*MathSpec> main

absolute
  returns the original number when given a positive input
  returns a positive number when given a negative input
  returns zero when given zero

Finished in 0.0008 seconds
3 examples, 0 failures