Testing untestable code - DPC10

Testing untestable Code Stephan Hochdörfer, bitExpert AG "Quality is a function of thought and reflection - precise thought and reflection. That’s the magic." Michael Feathers

Agenda 1. About me 2. Theory 3. How to test untestable code 4. Generating testable code 5. Conclusions 6. Questions

About me  Stephan Hochdörfer, bitExpert AG  Department Manager Research Labs  enjoying PHP since 1999  S.Hochdoerfer@bitExpert.de  @shochdoerfer

No excuse for bad code!

Warning! Use at own risk...

Theory "There is no secret to writing tests, there are only secrets to write testable code!" Miško Hevery

Theory What is „untestable code“?

Theory "...our test strategy requires us to have more control or visibility of the internal behavior of the system under test." Gerard Meszaros, xUnit Test Patterns: Refactoring Test Code

Theory Required class Class to Unittest Test Required class

Theory Database Required class External Class to Unittest resource test Required class Required Required Webservice class class

Theory How to achieve „testable“ code?

Theory How to achieve „testable“ code? Refactoring

Theory "Before you start refactoring, check that you have a solid suite of tests." Martin Fowler, Refactoring

Testing „untestable“ PHP Code Let the work begin...

Testing „untestable“ PHP Code For your safty! Do not change existing code!

Testing „untestable“ PHP Code | __autoload <?php class Car { private $Engine; public function __construct($sEngine) { $this->Engine = Engine::getByType($sEngine); } }

Testing „untestable“ PHP Code | __autoload <?php class Car { private $Engine; public function __construct($sEngine) { $this->Engine = Engine::getByType($sEngine); } } How to inject a dependency?  Use __autoload

Testing „untestable“ PHP Code | __autoload <?php function run_autoload($psClass) { $sFileToInclude = strtolower($psClass).'.php'; if(strtolower($psClass) == 'engine') { $sFileToInclude = '/custom/mocks/'.$sFileToInclude; } include($sFileToInclude); } // Testcase spl_autoload_register('run_autoload'); $oCar = new Car('Diesel'); echo $oCar->run();

Testing „untestable“ PHP Code | include_path <?php include('Engine.php'); class Car { private $Engine; public function __construct($sEngine) { $this->Engine = Engine::getByType($sEngine); } }

Testing „untestable“ PHP Code | include_path <?php include('Engine.php'); class Car { private $Engine; public function __construct($sEngine) { $this->Engine = Engine::getByType($sEngine); } } How to inject a dependency?  Manipulate include_path setting

Testing „untestable“ PHP Code | include_path <?php ini_set('include_path', '/custom/mocks/'.PATH_SEPARATOR. ini_get('include_path')); // Testcase include('car.php'); $oCar = new Car('Diesel'); echo $oCar->run();

Testing „untestable“ PHP Code | include_path alternative <?php class CustomFileStreamWrapper { private $_handler; function stream_open($path, $mode, $options, &$opened_path) { stream_wrapper_restore('file'); // @TODO: modify $path before fopen $this->_handler = fopen($path, $mode); stream_wrapper_unregister('file'); stream_wrapper_register('file', 'CustomFileStreamWrapper'); return true; } function stream_read($count) {} function stream_write($data) {} function stream_tell() {} function stream_eof() {} function stream_seek($offset, $whence) {} } stream_wrapper_unregister('file'); stream_wrapper_register('file', 'CustomFileStreamWrapper'); Source: Alex Netkachov, http://www.alexatnet.com/node/203

Testing „untestable“ PHP Code | include_path alternative <?php class CustomFileStreamWrapper { private $_handler; function stream_open($path, $mode, $options, &$opened_path) { stream_wrapper_restore('file'); $this->_handler = fopen($path, $mode); stream_wrapper_unregister('file'); stream_wrapper_register('file', 'CustomFileStreamWrapper'); return true; } function stream_read($count) { $content = fread($this->_handler, $count); $content = str_replace('Engine::getByType', 'MockedEngine::get', $content); return $content; } } stream_wrapper_unregister('file'); stream_wrapper_register('file', 'CustomFileStreamWrapper'); include('engine.php'); ?>

Testing „untestable“ PHP Code | Namespaces <?php class Car { private $Engine; public function __construct($sEngine) { $this->Engine = CarEngine::getByType($sEngine); } }

Testing „untestable“ PHP Code | Namespaces <?php class Car { private $Engine; public function __construct($sEngine) { $this->Engine = CarEngine::getByType($sEngine); } } How to inject a dependency?  Use __autoload or manipulate the include_path

Testing „untestable“ PHP Code | vfsStream <?php class Car { private $Engine; public function __construct($sEngine, $CacheDir) { $this->Engine = CarEngine::getByType($sEngine); mkdir($CacheDir.'/cache/', 0700, true); } }

Testing „untestable“ PHP Code | vfsStream <?php class Car { private $Engine; public function __construct($sEngine, $CacheDir) { $this->Engine = CarEngine::getByType($sEngine); mkdir($CacheDir.'/cache/', 0700, true); } } How mock a filesystem?  Use vfsStream - http://code.google.com/p/bovigo/

Testing „untestable“ PHP Code | vfsStream <?php // setup vfsStream vfsStreamWrapper::register(); vfsStreamWrapper::setRoot(new vfsStreamDirectory('app')); $oCar = new Car('Diesel', vfsStream::url('app')); echo vfsStreamWrapper::getRoot()->hasChild('cache');

Testing „untestable“ PHP Code „I have no idea how to unit-test procedural code. Unit-testing assumes that I can instantiate a piece of my application in isolation.“ Miško Hevery

Testing „untestable“ PHP Code | Test functions <?php function startsWith($sString, $psPre) { return $psPre == substr($sString, 0, strlen($psPre)); } function contains($sString, $sSearch) { return false !== strpos($sString, $sSearch); }

Testing „untestable“ PHP Code | Test functions <?php function startsWith($sString, $psPre) { return $psPre == substr($sString, 0, strlen($psPre)); } function contains($sString, $sSearch) { return false !== strpos($sString, $sSearch); } How to test  PHPUnit can call functions  PHPUnit can save/restore globale state

Testing „untestable“ PHP Code | overwrite internal functions <?php function buyCar(Car $oCar) { global $oDB; mysql_query("INSERT INTO...", $oDB); mail('order@domain.org', 'New sale', '....'); }

Testing „untestable“ PHP Code | overwrite internal functions <?php function buyCar(Car $oCar) { global $oDB; mysql_query("INSERT INTO...", $oDB); mail('order@domain.org', 'New sale', '....'); } How to test  Do not load mysql extension. Provide own implementation  Unfortunatley mail() is part of the PHP core

Testing „untestable“ PHP Code | overwrite internal functions <?php function buyCar(Car $oCar) { global $oDB; mysql_query("INSERT INTO...", $oDB); mail('order@domain.org', 'New sale', '....'); } How to test  Use classkit extension to overwrite internal functions

Testing „untestable“ PHP Code | overwrite internal functions <?php ini_set('runkit.internal_override', '1'); runkit_function_redefine('mail','','return true;'); ?>

Testing „untestable“ PHP Code

Generating testable code Generative Programming

Generating testable code Generative Programming Configuration 1 ... n Implementation Generator Product components Generator application

Generating testable code Generative Programming Configuration Application Implementation Generator components Testcases Generator application

Generating testable code Course of action Extraction  „Mask“ parts of the code Customizing  Change content of global vars  Pre/Postfixes for own functions, methods, classes Recombine  Re-order parts of the code

Generating testable code FileFrm FILEIndex_php5 { private String Prefix = "test_"; private String MailSlot = "mail('order@domain.org', 'New sale', '....');"; public FILEIndex_php5() { setFilename("index.php5"); setRelativePath("/"); } private void assign() { BEGINCONTENT() <?php function buyCar(Car $oCar) { global $oDB; <!{Prefix}!>mysql_query(„INSERT INTO...“, $oDB); <!{MailSlot}!> } ?> ENDCONTENT() } }

Generating testable code 1. Example Prefix: test_ <?php function buyCar(Car $oCar) { global $oDB; test_mysql_query("INSERT INTO...", $oDB); }

Generating testable code 1. Example Prefix: test_ <?php function buyCar(Car $oCar) { global $oDB; test_mysql_query("INSERT INTO...", $oDB); } 2. Example MailSlot: mail('order@domain.org', 'New sale', '....'); <?php function buyCar(Car $oCar) { global $oDB; mysql_query("INSERT INTO...", $oDB); mail('order@domain.org', 'New sale', '....'); } ?>

Conclusion How much effort to take?

Conclusion Conclusion  Change mindset to write testable code  Dependency Injection  Look for other options to raise the bar  Work around limitations of PHP  PHP is flexible, use it that way

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Testing untestable code - DPC10

by Stephan Hochdörfer on Jun 14, 2010

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