This document discusses testing untestable code. It begins with an introduction and agenda. It then discusses what constitutes untestable code and some techniques for making code more testable, including dependency injection, manipulating include paths, namespaces, and mocking filesystems. It also discusses strategies for testing procedural code and internal functions. Finally, it introduces the concept of generative programming and generating test code from configurations.

1. 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

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

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

4. No excuse for bad code!

5. Warning! Use at own risk...

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

7. Theory
What is „untestable code“?

8. Theory
What is „untestable code“?

9. Theory
What is „untestable code“?

10. 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

11. Theory
Required
class
Class to
Unittest
Test
Required
class

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

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

14. Theory
How to achieve „testable“ code?

15. Theory
How to achieve „testable“ code?
Refactoring

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

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

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

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

20. 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

21. 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();

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

23. 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

24. 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();

25. 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

26. 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');
?>

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

28. 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

29. 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);
}
}

30. 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/

31. 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');

32. 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

33. 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);
}

34. 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

35. 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', '....');
}

36. 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

37. 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

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

39. Testing „untestable“ PHP Code

40. Generating testable code
Generative Programming

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

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

43. 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

44. 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()
}
}

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

46. 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', '....');
}
?>

47. Conclusion
How much effort to take?

48. 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

49. http://joind.in/1545