Hamcrest: A Cross-Language Library of Matchers

Welcome! Hamcrest A Cross-Language Library of Matchers Sebastian Bergmann http://sebastian-bergmann.de/ May 28 th 2008

Who I am
Sebastian Bergmann
Involved in the PHP Project since 2000
Developer of PHPUnit
Author, Consultant, Coach, Trainer

Motivation
It probably all started with a blog entry by Joe Walnes
“ Flexible JUnit Assertions with jMock”, May 2005, http://joe.truemesh.com/blog/000511.html

Motivation
jMock contains a library of constraints for specifying precise expectations on mock objects

Motivation
These constraints can be reused to write assertions that are more flexible, better readable, and generate more useful failure messages

Motivation
These constraints can be reused to write assertions that are more flexible, better readable, and generate more useful failure messages
assertThat()
takes a constraint as its argument and evaluates it
could eventually replace all other assert*() methods

Motivation What Joe Walnes did import org . jmock . MockObjectTestCase ; import org . jmock . core . Constraint ; public abstract class MyTestCase extends MockObjectTestCase { protected void assertThat ( Object something , Constraint matches ) { if (! matches . eval ( something )) { StringBuffer message = new StringBuffer ( " Expected: " ); matches . describeTo ( message ); message . append ( " but got : " ). append ( something ). append ( " " ); fail ( message . toString ()); } } }

Motivation What Joe Walnes did import org.jmock.MockObjectTestCase; import org.jmock.core.Constraint; public abstract class MyTestCase extends MockObjectTestCase { protected void assertThat(Object something, Constraint matches ) { if (!matches.eval(something)) { StringBuffer message = new StringBuffer(" Expected: "); matches.describeTo(message); message.append(" but got : ").append(something).append(" "); fail(message.toString()); } } }

Motivation What Joe Walnes did assertThat ( something , eq ( "Hello" )); assertThat ( something , eq ( TRUE )); assertThat ( something , isA ( Color . class )); assertThat ( something , contains ( "World" )); assertThat ( something , same ( Food . CHEESE )); assertThat ( something , NULL ); assertThat ( something , NOT_NULL );

Motivation What Joe Walnes did assertThat(something, eq("Hello")); assertThat(something, eq(TRUE)); assertThat(something, isA(Color.class)); assertThat(something, contains("World")); assertThat(something, same(Food.CHEESE)); assertThat(something, NULL); assertThat(something, NOT_NULL); assertThat ( something , or ( eq ( 50 ), between ( 10 , 20 ));

Motivation What Joe Walnes did assertThat(something, eq("Hello")); assertThat(something, eq(TRUE)); assertThat(something, isA(Color.class)); assertThat(something, contains("World")); assertThat(something, same(Food.CHEESE)); assertThat(something, NULL); assertThat(something, NOT_NULL); assertThat ( something , or ( eq ( 50 ), between ( 10 , 20 )); junit.framework.AssertionFailedError: Expected: (50 or an int between 10 and 20) but got : 42

Hamcrest
Refactoring of jMock's constraint library

Hamcrest
Library of matcher objects
Also known as constraints or predicates

Hamcrest
Allows match rules to be defined declaratively
Domain Specific Language
Literate Programming

Hamcrest
To be used in other frameworks
Testing Frameworks
Mock Objects Libraries

Hamcrest
To be used in other frameworks
Testing Frameworks
Mock Objects Libraries
...
http://code.google.com/p/hamcrest/

Hamcrest
Java
Started in March 2006
Version 1.1 released in June 2007
JUnit 4.4 comes with Hamcrest and assertThat()
Timeline

Hamcrest
Java
PHP
Started in December 2007
PHPUnit 3.0 introduced assertThat() in November 2006
Timeline

Hamcrest
Java
PHP
Python
Started in January 2008
Timeline

Hamcrest
Java
PHP
Python
Started in January 2008
Objective-C
Started in April 2008
Timeline

The Biscuit Example PHP <?php require_once 'Hamcrest.php' ; $theBiscuit = new Biscuit ( 'Ginger' ); $myBiscuit = new Biscuit ( 'Ginger' ); assertThat ( $theBiscuit , equalTo ( $myBiscuit )); ?>

The Biscuit Example PHP <?php require_once 'Hamcrest.php'; $theBiscuit = new Biscuit('Ginger'); $myBiscuit = new Biscuit('Ginger'); assertThat ( $theBiscuit , equalTo ( $myBiscuit )); ?>

The Biscuit Example PHP <?php require_once 'Hamcrest.php'; $theBiscuit = new Biscuit('Ginger'); $myBiscuit = new Biscuit('Ginger'); assertThat ( $theBiscuit , is ( equalTo ( $myBiscuit ))); ?>

The Biscuit Example PHP <?php require_once 'Hamcrest.php'; $theBiscuit = new Biscuit('Ginger'); $myBiscuit = new Biscuit('Ginger'); assertThat ( $theBiscuit , is ( $myBiscuit )); ?>

The Biscuit Example Python: unittest.TestCase and Hamcrest from hamcrest import * import unittest class BiscuitTest ( unittest . TestCase ): def testEquals ( self ): theBiscuit = Biscuit ( 'Ginger' ) myBiscuit = Biscuit ( 'Ginger' ) assert_that ( theBiscuit , equal_to ( myBiscuit )) if __name__ == '__main__' : unittest . main ()

The Biscuit Example Java: JUnit and Hamcrest import static org . hamcrest . MatcherAssert . assertThat ; import static org . hamcrest . Matchers .*; import junit . framework . TestCase ; public class BiscuitTest extends TestCase { public void testEquals () { Biscuit theBiscuit = new Biscuit ( "Ginger" ); Biscuit myBiscuit = new Biscuit ( "Ginger" ); assertThat ( theBiscuit , equalTo ( myBiscuit )); } }

The Biscuit Example Objective-C: SenTestingKit and Hamcrest #import <SenTestingKit/SenTestingKit.h> #define HC_SHORTHAND #import <hamcrest/hamcrest.h> @interface BiscuitTest : SenTestCase @end @implementation BiscuitTest - ( void ) testEquals { Biscuit * theBiscuit = [ Biscuit biscuitNamed : @ "Ginger" ]; Biscuit * myBiscuit = [ Biscuit biscuitNamed : @ "Ginger" ]; assertThat ( theBiscuit , equalTo ( myBiscuit )); } @end

Matchers
assertThat()
is()
not()
anything()
allOf()
anyOf()
describedAs()
Core

Matchers
equalTo()
sameInstance()
nullValue()
notNullValue()
Objects and Variables

Matchers
closeTo()
greaterThan()
greaterThanOrEqualTo()
lessThan()
lessThanOrEqualTo()
Numbers

Matchers
containsString()
equalToIgnoringCase()
equalToIgnoringWhiteSpace()
startsWith()
endsWith()
Strings

The Biscuit Example PHP: PHPUnit 3 <?php require_once 'PHPUnit/Framework.php' ; class BiscuitTest extends PHPUnit_Framework_TestCase { public function testEquals () { $theBiscuit = new Biscuit ( 'Ginger' ); $myBiscuit = new Biscuit ( 'Ginger' ); $this -> assertEquals ( $theBiscuit , $myBiscuit ); } } ?>

The Biscuit Example PHP: Assertions in PHPUnit 3 <?php require_once 'PHPUnit/Framework.php'; class BiscuitTest extends PHPUnit_Framework_TestCase { public function testEquals() { $theBiscuit = new Biscuit('Ginger'); $myBiscuit = new Biscuit('Ginger'); $this -> assertThat ( $theBiscuit , $this -> equalTo ( $myBiscuit ) ); } } ?>

The Biscuit Example PHP: Mock Object Matchers in PHPUnit 3 <?php class ObserverTest extends PHPUnit_Framework_TestCase { public function testUpdateIsCalledOnce() { $observer = $this->getMock('Observer', array('update')); $observer -> expects ( $this -> once ()) -> method ( 'update' ) -> with ( $this -> equalTo ( 'something' )); $subject = new Subject; $subject->attach($observer); $subject->doSomething(); } } ?>

The Biscuit Example PHP: PHPUnit 3 and Hamcrest <?php require_once 'PHPUnit/Framework.php'; require_once 'Hamcrest.php'; class BiscuitTest extends PHPUnit_Framework_TestCase { public function testEquals() { $theBiscuit = new Biscuit('Ginger'); $myBiscuit = new Biscuit('Ginger'); assertThat ( $theBiscuit , is ( equalTo ( $myBiscuit ))); } } ?>

The Biscuit Example PHP: PHPUnit 3 and Hamcrest <?php require_once 'PHPUnit/Framework.php'; require_once 'Hamcrest.php'; class BiscuitSpec extends PHPUnit_Framework_TestCase { /** * @test */ public function equalBiscuitsShouldBeEqual () { $theBiscuit = new Biscuit('Ginger'); $myBiscuit = new Biscuit('Ginger'); assertThat($theBiscuit, is(equalTo($myBiscuit))); } } ?> [email_address] ~ % phpunit --testdox BiscuitSpec PHPUnit 3.3.0 by Sebastian Bergmann. Biscuit - Equal biscuits should be equal

Hamcrest
Requires PHP 5.3 (or higher)
Classes and functions in the Hamcrest namespace
Wrapper functions in the global namespace that can be disabled
assertThat() raises an AssertionError exception when a matcher does not match
AssertionError extends PHPUnit_Framework_AssertionFailedError when PHPUnit is installed
AssertionError extends RuntimeException when PHPUnit is not installed
Will be an integral part of PHPUnit 4
PHP Implementation

The End
Thank you for your interest!
These slides will be available shortly on http://sebastian-bergmann.de/talks/.

License
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Hamcrest: A Cross-Language Library of Matchers

by Sebastian Bergmann on May 28, 2008

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Hamcrest: A Cross-Language Library of Matchers — Presentation Transcript