Difference between revisions of "The Monad.Reader/Issue5/Software Testing With Haskell"
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−  '''This article needs reformatting! Please help tidy it up.'''[[User:WouterSwierstraWouterSwierstra]] 14:27, 9 May 2008 (UTC) 

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−  [[BR]] 

−  ''[[Date(20051002T21:05:41Z)]]'' 

−  '''Abstract.''' 

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−  If you've ever used the 
+  If you've ever used the [http://en.wikipedia.org/wiki/XUnit xUnit] framework in other programming languages, HUnit will feel familiar. The [http://hunit.sourceforge.net/HUnit1.0/Guide.html User's Guide] includes a 'getting started' started section, and there are a thousand introductions to various flavors of the xUnit framework, so we'll mention HUnit only briefly. 
From the user's guide: 
From the user's guide: 

−  "Tests are specified compositionally. [http://hunit.sourceforge.net/HUnit1.0/Guide.html#Assertions Assertions] are combined to make a [http://hunit.sourceforge.net/HUnit1.0/Guide.html#TestCase test case], and test cases are combined into [http://hunit.sourceforge.net/HUnit1.0/Guide.html#Tests tests]." 
+  <blockquote>"Tests are specified compositionally. [http://hunit.sourceforge.net/HUnit1.0/Guide.html#Assertions Assertions] are combined to make a [http://hunit.sourceforge.net/HUnit1.0/Guide.html#TestCase test case], and test cases are combined into [http://hunit.sourceforge.net/HUnit1.0/Guide.html#Tests tests]."</blockquote> 
Here's a short demo: 
Here's a short demo: 

−  +  <haskell> 

module ProtoHunit where 
module ProtoHunit where 

import Test.HUnit 
import Test.HUnit 

−  import Test.HUnit 
+  import Test.HUnit 
testList = TestList  construct a TestList from a list of type TestCase 
testList = TestList  construct a TestList from a list of type TestCase 

−  +  [TestCase $  construct a TestCase from an assertion 

−  +  assertEqual "description" 2 (1 + 1)  construct an assertion from a descriptive string, an expected result, and something to execute 

−  +  ] 

t = runTestTT testList 
t = runTestTT testList 

−  }}} 

+  </haskell> 

−  = 
+  ==QuickCheck== 
QuickCheck was written by Koen Claessan and John Hughes, and is available from Chalmers at http://www.cs.chalmers.se/~rjmh/QuickCheck/ . 
QuickCheck was written by Koen Claessan and John Hughes, and is available from Chalmers at http://www.cs.chalmers.se/~rjmh/QuickCheck/ . 

−  QuickCheck takes a dramatically different approach to software testing. The programmer specifies a property that the code should follow, and the QuickCheck library generates random values and checks to see if the property always holds. 
+  QuickCheck takes a dramatically different approach to software testing. The programmer specifies a property that the code should follow, and the QuickCheck library generates random values and checks to see if the property always holds. 
Some demonstration properties are given below. 
Some demonstration properties are given below. 

−  +  <haskell> 

module ProtoQuickCheck where 
module ProtoQuickCheck where 

import Test.QuickCheck 
import Test.QuickCheck 

 this succeeds in one case of the input. 
 this succeeds in one case of the input. 

−  prop_Fail 
+  prop_Fail :: Int > Bool 
−  prop_Fail x = 
+  prop_Fail x = 
−  +  x == 1 

 this succeeds in three cases of the input. 
 this succeeds in three cases of the input. 

prop_RevUnit :: [Int] > Bool 
prop_RevUnit :: [Int] > Bool 

−  prop_RevUnit x = 
+  prop_RevUnit x = 
−  +  reverse x == x 

 what's wrong with this picture? 
 what's wrong with this picture? 

prop_RevUnitConfusion :: [Int] > Bool 
prop_RevUnitConfusion :: [Int] > Bool 

−  prop_RevUnitConfusion x = 
+  prop_RevUnitConfusion x = 
−  +  reverse [x] == [x] 

 do you see a bug? 
 do you see a bug? 

prop_RevApp :: [Int] > [Int] > Bool 
prop_RevApp :: [Int] > [Int] > Bool 

−  prop_RevApp xs ys = 
+  prop_RevApp xs ys = 
−  +  reverse (xs ++ ys) == reverse xs ++ reverse ys 

prop_RevRev :: [Int] > Bool 
prop_RevRev :: [Int] > Bool 

−  prop_RevRev xs = 
+  prop_RevRev xs = 
−  +  reverse (reverse xs) == xs 

(f === g) x = f x == g x 
(f === g) x = f x == g x 

−  prop_CompAssoc 
+  prop_CompAssoc :: (Int > Int) > (Int > Int) > (Int > Int) > Int > Bool 
prop_CompAssoc f g h = (f . (g . h)) === ((f . g) . h) 
prop_CompAssoc f g h = (f . (g . h)) === ((f . g) . h) 

−  prop_CompCommut 
+  prop_CompCommut :: (Int > Int) > (Int > Int) > Int > Bool 
prop_CompCommut f g = (f . g) === (g . f) 
prop_CompCommut f g = (f . g) === (g . f) 

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 means filter inputs by that condition 
 means filter inputs by that condition 

 below an x and y are only accepted if x is less than or equal to y 
 below an x and y are only accepted if x is less than or equal to y 

−  prop_MaxLe 
+  prop_MaxLe :: Int > Int > Property 
prop_MaxLe x y = x <= y ==> max x y == y 
prop_MaxLe x y = x <= y ==> max x y == y 

instance Show (a > b) where show _ = "<<function>>" 
instance Show (a > b) where show _ = "<<function>>" 

−  }}} 

+  </haskell> 

−  To test one of these properties, load the source into ghci and run 
+  To test one of these properties, load the source into ghci and run <tt>quickCheck prop_Fail</tt>. One possible response is: 
−  +  <haskell> 

Falsifiable, after 0 tests: 
Falsifiable, after 0 tests: 

1 
1 

−  }}} 

+  </haskell> 

−  Since the type signature of prop_Fail is 
+  Since the type signature of prop_Fail is <haskell>Int > Bool</haskell> QuickCheck generated an Int value and checked to see if the property held true. Since the value 1 is not equal to 1, the property is false. 
−  = 
+  ==Everything Else== 
−  The Haskell wiki has information on [ 
+  The Haskell wiki has information on [[haskellmodeone button unit testing]] with the emacs haskellmode. 
Other libraries and applications that deal with software testing in Haskell are mentioned below, but are beyond the scope of this short introduction. 
Other libraries and applications that deal with software testing in Haskell are mentioned below, but are beyond the scope of this short introduction. 

−  +  * [[Hat]] The Haskell Tracer. 

−  +  * [http://www.cs.mu.oz.au/~bjpop/plargleflarp/ Plargeflarp] (declarative debugger formerly known as Buddha) 

−  +  * [http://www.cse.ogi.edu/~hallgren/Programatica/ Programatica] is a collection of tools, that include the ability to specify inline 'certificates'. 'Certificates' are tests, they can be static unit tests, QuickCheck properties, or automated proofs. 

−  +  
−  +  [[Category:Article]] 
Revision as of 02:59, 10 May 2008
Software Testing With Haskell
 by ShaeErisson for The Monad.Reader Issue 5, Date: 20051002T21:05:41Z
The two most commonly used libraries for testing software with Haskell are HUnit and QuickCheck. This article will shortly describe the two different approaches and show some demonstration code.
Both HUnit and QuickCheck are included with GHC 6.4.1 under the module names of Test.HUnit and Test.QuickCheck
HUnit
HUnit was written by Dean Herington and is available on SourceForge at http://hunit.sourceforge.net/ .
If you've ever used the xUnit framework in other programming languages, HUnit will feel familiar. The User's Guide includes a 'getting started' started section, and there are a thousand introductions to various flavors of the xUnit framework, so we'll mention HUnit only briefly.
From the user's guide:
"Tests are specified compositionally. Assertions are combined to make a test case, and test cases are combined into tests."
Here's a short demo:
module ProtoHunit where
import Test.HUnit
import Test.HUnit
testList = TestList  construct a TestList from a list of type TestCase
[TestCase $  construct a TestCase from an assertion
assertEqual "description" 2 (1 + 1)  construct an assertion from a descriptive string, an expected result, and something to execute
]
t = runTestTT testList
QuickCheck
QuickCheck was written by Koen Claessan and John Hughes, and is available from Chalmers at http://www.cs.chalmers.se/~rjmh/QuickCheck/ .
QuickCheck takes a dramatically different approach to software testing. The programmer specifies a property that the code should follow, and the QuickCheck library generates random values and checks to see if the property always holds.
Some demonstration properties are given below.
module ProtoQuickCheck where
import Test.QuickCheck
 this succeeds in one case of the input.
prop_Fail :: Int > Bool
prop_Fail x =
x == 1
 this succeeds in three cases of the input.
prop_RevUnit :: [Int] > Bool
prop_RevUnit x =
reverse x == x
 what's wrong with this picture?
prop_RevUnitConfusion :: [Int] > Bool
prop_RevUnitConfusion x =
reverse [x] == [x]
 do you see a bug?
prop_RevApp :: [Int] > [Int] > Bool
prop_RevApp xs ys =
reverse (xs ++ ys) == reverse xs ++ reverse ys
prop_RevRev :: [Int] > Bool
prop_RevRev xs =
reverse (reverse xs) == xs
(f === g) x = f x == g x
prop_CompAssoc :: (Int > Int) > (Int > Int) > (Int > Int) > Int > Bool
prop_CompAssoc f g h = (f . (g . h)) === ((f . g) . h)
prop_CompCommut :: (Int > Int) > (Int > Int) > Int > Bool
prop_CompCommut f g = (f . g) === (g . f)
 this operator ==>
 means filter inputs by that condition
 below an x and y are only accepted if x is less than or equal to y
prop_MaxLe :: Int > Int > Property
prop_MaxLe x y = x <= y ==> max x y == y
instance Show (a > b) where show _ = "<<function>>"
To test one of these properties, load the source into ghci and run quickCheck prop_Fail. One possible response is:
Falsifiable, after 0 tests:
1
Int > Bool
Everything Else
The Haskell wiki has information on one button unit testing with the emacs haskellmode.
Other libraries and applications that deal with software testing in Haskell are mentioned below, but are beyond the scope of this short introduction.
 Hat The Haskell Tracer.
 Plargeflarp (declarative debugger formerly known as Buddha)
 Programatica is a collection of tools, that include the ability to specify inline 'certificates'. 'Certificates' are tests, they can be static unit tests, QuickCheck properties, or automated proofs.