Taming the Untestable Beast

How do you test … booby traps in the Peruvian Jungle that protect a golden idol? object(Cave) object(Boulder) object(IndianaJones) Still photo from ”Raiders of the Lost Ark”, Copyright 1981 Lucasfilm and Paramount Pictures

How do you test … booby traps in the Peruvian Jungle that protect a golden idol? <?php

How do you test … booby traps in the Peruvian Jungle that protect a golden idol? <?php $indy = ActorFactory::getActor('Harrison Ford') ->actAs('Henry Jones Jr.');

How do you test … booby traps in the Peruvian Jungle that protect a golden idol? <?php $indy = ActorFactory::getActor('Harrison Ford') ->actAs('Henry Jones Jr.'); $trap = PropFactory::getProp('Trap') ->armWith(PropFactory::getProp('Boulder'));

How do you test … booby traps in the Peruvian Jungle that protect a golden idol? <?php $indy = ActorFactory::getActor('Harrison Ford') ->actAs('Henry Jones Jr.'); $trap = PropFactory::getProp('Trap') ->armWith(PropFactory::getProp('Boulder')); $cave = StageFactory::getStage('Cave') ->decorateWith($trap);

How do you test … booby traps in the Peruvian Jungle that protect a golden idol? <?php $indy = ActorFactory::getActor('Harrison Ford') ->actAs('Henry Jones Jr.'); $trap = PropFactory::getProp('Trap') ->armWith(PropFactory::getProp('Boulder')); $cave = StageFactory::getStage('Cave') ->decorateWith($trap); $indy->walkInto($cave)->setOff($trap);

How do you test … booby traps in the Peruvian Jungle that protect a golden idol? <?php $indy = ActorFactory::getActor('Harrison Ford') ->actAs('Henry Jones Jr.'); $trap = PropFactory::getProp('Trap') ->armWith(PropFactory::getProp('Boulder')); $cave = StageFactory::getStage('Cave') ->decorateWith($trap); $indy->walkInto($cave)->setOff($trap); // …

How do you test … booby traps in the Peruvian Jungle that protect a golden idol? <?php $indy = ActorFactory::getActor('Harrison Ford') ->actAs('Henry Jones Jr.'); $trap = PropFactory::getProp('Trap') ->armWith(PropFactory::getProp('Boulder')); $cave = StageFactory::getStage('Cave') ->decorateWith($trap); $indy->walkInto($cave)->setOff($trap); // … $indy->walkInto($cave)->setOff($trap); ?>

How do you test … booby traps in the Peruvian Jungle that protect a golden idol? <?php $indy = ActorFactory::getActor('Harrison Ford') ->actAs('Henry Jones Jr.'); $trap = PropFactory::getProp('Trap') ->armWith(PropFactory::getProp('Boulder')); $cave = StageFactory::getStage('Cave') ->decorateWith($trap); $indy->walkInto($cave)->setOff($trap); // … $indy->walkInto($cave)->setOff($trap); ?> Uncaught exception 'MovieException' with message 'Harrison Ford was already run over by a boulder.'

Did we just kill Harrison Ford?

We need a stuntman! Photo by Bud Gray – Copyright MPTV

How do you test … booby traps in the Peruvian Jungle that protect a golden idol? <?php $indy = ActorFactory::getStuntmanFor('Harrison Ford') ->actAs('Henry Jones Jr.'); $trap = PropFactory::getProp('Trap') ->armWith(PropFactory::getProp('Boulder')); $cave = StageFactory::getStage('Cave') ->decorateWith($trap); $indy->walkInto($cave)->setOff($trap); // … $indy = ActorFactory::getStuntmanFor('Harrison Ford') ->actAs('Henry Jones Jr.'); $indy->walkInto($cave)->setOff($trap);

How do you test … booby traps in the Peruvian Jungle that protect a golden idol? <?php class Cave { protected $trap; public function __construct(Trap $trap) { $this->trap = $trap; } public function setOffTrapByPerson(Person $person) { $this->trap->setOff($person); } }

How do you test … booby traps in the Peruvian Jungle that protect a golden idol? <?php class Trap { protected $boulder; public function __construct(Boulder $boulder) { $this->boulder = $boulder; } public function setOffTrapByPerson(Person $person) { $this->boulder->roll(); } }

How do you test … booby traps in the Peruvian Jungle that protect a golden idol? <?php class Boulder { public function roll() { } } class Person { protected $name; public function __construct($name) { $this->name = $name; } }

How do you test … booby traps in the Peruvian Jungle that protect a golden idol? <?php $indy = new Person('Henry Jones Jr.');

How do you test … booby traps in the Peruvian Jungle that protect a golden idol? <?php $indy = new Person('Henry Jones Jr.'); $boulder = new Boulder;

How do you test … booby traps in the Peruvian Jungle that protect a golden idol? <?php $indy = new Person('Henry Jones Jr.'); $boulder = new Boulder; $trap = new Trap($boulder);

How do you test … booby traps in the Peruvian Jungle that protect a golden idol? <?php $indy = new Person('Henry Jones Jr.'); $boulder = new Boulder; $trap = new Trap($boulder); $cave = new Cave($trap);

How do you test … booby traps in the Peruvian Jungle that protect a golden idol? <?php $indy = new Person('Henry Jones Jr.'); $boulder = new Boulder; $trap = new Trap($boulder); $cave = new Cave($trap); $cave->setOffTrapByPerson($indy);

How do you test … booby traps in the Peruvian Jungle that protect a golden idol? <?php class TrapTest extends PHPUnit_Framework_TestCase { public function testSomething() { $indy = $this->getMock('Person'); $boulder = new Boulder; $trap = new Trap($boulder); $cave = new Cave($trap); $indy->expects($this->any()) ->/* … */; $cave->setOffTrap($indy); // … } }

How do you test … booby traps in the Pankot Palace that protect a cult? <?php $ceilingHeight = 100; $trapActive = FALSE; while (TRUE) { // ... if ($trapActive && $ceilingHeight > 0) { $ceilingHeight -= 10; } if ($ceilingHeight <= 0) { // ... } // ... } function trigger_trap() { $GLOBALS['trapActive'] = TRUE; } function disable_trap() { $GLOBALS['trapActive'] = FALSE; }

To Be Continued ...

... without the aliens

Taming the Untestable Beast Sebastian Bergmann & Stefan Priebsch November 1st 2010

Get the help you need from the experts you trust. Consulting | Code Review | Training

Greenfield Project A project that is not constrained by prior work (legacy code).

Brownfield Project A project that is constrained by prior work (legacy code).

Four Reasons to Change Software – Michael Feathers  Adding a feature  Fixing a bug  Improving the design  Optimizing resource usage

The Legacy Code Change Algorithm – Michael Feathers  Identify change points  Find test points  Break dependencies  Write tests  Make changes and refactor

The Legacy Code Dilemma – Michael Feathers When we change code, we should have tests in place. To put tests in place, we often have to change code.

Sample Application: ”The Beast” http://github.com/thePHPcc/zendcon10-theBeast

class UserController { public function resetPasswordAction() {

class UserController { public function resetPasswordAction() { if (!isset($_POST['email'])) { return new ErrorView( 'resetPassword', 'No email specified' ); }

class UserController { public function resetPasswordAction() { if (!isset($_POST['email'])) { return new ErrorView( 'resetPassword', 'No email specified' ); } $db = new PDO(Configuration::get('DSN'));

class UserController { public function resetPasswordAction() { if (!isset($_POST['email'])) { return new ErrorView( 'resetPassword', 'No email specified' ); } $db = new PDO(Configuration::get('DSN')); $statement = $db->prepare( 'SELECT * FROM Users WHERE email=:email;' ); $statement->bindValue( ':email', $_POST['email'], PDO::PARAM_STR ); $statement->execute(); $record = $statement->fetch(PDO::FETCH_ASSOC);

if ($record === FALSE) { return new ErrorView( 'resetPassword', 'No user with email ' . $_POST['email'] ); }

if ($record === FALSE) { return new ErrorView( 'resetPassword', 'No user with email ' . $_POST['email'] ); } $code = CryptHelper::getConfirmationCode();

if ($record === FALSE) { return new ErrorView( 'resetPassword', 'No user with email ' . $_POST['email'] ); } $code = CryptHelper::getConfirmationCode(); $statement = $db->prepare( 'UPDATE Users SET code=:code WHERE email=:email;' ); $statement->bindValue( ':code', $code, PDO::PARAM_STR ); $statement->bindValue( ':email', $_POST['email'], PDO::PARAM_STR ); $statement->execute();

mail( $_POST['email'], 'Password Reset', 'Confirmation code: ' . $code );

mail( $_POST['email'], 'Password Reset', 'Confirmation code: ' . $code ); return new View('passwordResetRequested'); } }

class Configuration { protected static $values = array(); public static function init(array $values) { self::$values = $values; } public static function get($key) { if (!isset(self::$values[$key])) { throw new Exception('No such key'); } return self::$values[$key]; } }

class View { protected $viewScript; public function __construct($viewScript) { $this->viewScript = $viewScript; } }

class View { protected $viewScript; public function __construct($viewScript) { $this->viewScript = $viewScript; } } class ErrorView extends View { protected $errorMessage; public function __construct($viewScript, $errorMessage) { $this->errorMessage = $errorMessage; parent::__construct($viewScript); } }

class CryptHelper { protected static $salt = '...'; public static function getConfirmationCode() { return sha1(uniqid(self::$salt, TRUE)); } }

CREATE TABLE "Users" ( "id" INTEGER PRIMARY KEY AUTO_INCREMENT NOT NULL, "username" VARCHAR UNIQUE NOT NULL, "email" VARCHAR UNIQUE NOT NULL, "code" VARCHAR );

$db = new PDO('sqlite::memory:'); $db->exec(file_get_contents(__DIR__ . '/schema.sql'));

$db = new PDO('sqlite::memory:'); $db->exec(file_get_contents(__DIR__ . '/schema.sql')); $db->exec( "INSERT INTO Users (username, email) VALUES ('John Doe', 'user@example.com');" );

$db = new PDO('sqlite::memory:'); $db->exec(file_get_contents(__DIR__ . '/schema.sql')); $db->exec( "INSERT INTO Users (username, email) VALUES ('John Doe', 'user@example.com');" ); Configuration::init(array('DSN' => 'sqlite::memory:'));

$db = new PDO('sqlite::memory:'); $db->exec(file_get_contents(__DIR__ . '/schema.sql')); $db->exec( "INSERT INTO Users (username, email) VALUES ('John Doe', 'user@example.com');" ); Configuration::init(array('DSN' => 'sqlite::memory:')); $_POST['email'] = 'user@example.com';

$db = new PDO('sqlite::memory:'); $db->exec(file_get_contents(__DIR__ . '/schema.sql')); $db->exec( "INSERT INTO Users (username, email) VALUES ('John Doe', 'user@example.com');" ); Configuration::init(array('DSN' => 'sqlite::memory:')); $_POST['email'] = 'user@example.com'; $controller = new UserController; $view = $controller->resetPasswordAction();

class UserControllerTest extends PHPUnit_Framework_TestCase { protected function setUp() { $this->db = new PDO('sqlite::memory:'); }

class UserControllerTest extends PHPUnit_Framework_TestCase { protected function setUp() { $this->db = new PDO('sqlite::memory:'); $this->db->exec( file_get_contents(__DIR__ . '/schema.sql') ); }

class UserControllerTest extends PHPUnit_Framework_TestCase { protected function setUp() { $this->db = new PDO('sqlite::memory:'); $this->db->exec( file_get_contents(__DIR__ . '/schema.sql') ); $this->db->exec( "INSERT INTO Users (username, email) VALUES ('John Doe', 'user@example.com');" ); }

class UserControllerTest extends PHPUnit_Framework_TestCase { protected function setUp() { $this->db = new PDO('sqlite::memory:'); $this->db->exec( file_get_contents(__DIR__ . '/schema.sql') ); $this->db->exec( "INSERT INTO Users (username, email) VALUES ('John Doe', 'user@example.com');" ); Configuration::init( array('DSN' => 'sqlite::memory:') ); }

class UserControllerTest extends PHPUnit_Framework_TestCase { protected function setUp() { $this->db = new PDO('sqlite::memory:'); $this->db->exec( file_get_contents(__DIR__ . '/schema.sql') ); $this->db->exec( "INSERT INTO Users (username, email) VALUES ('John Doe', 'user@example.com');" ); Configuration::init( array('DSN' => 'sqlite::memory:') ); $this->controller = new UserController; }

public function testDisplaysErrorViewWhenNoEmailAddressGiven() { $_POST['email'] = ''; $view = $this->controller->resetPasswordAction(); $this->assertType('ErrorView', $view); } }

public function testDisplaysErrorViewWhenNoEmailAddressGiven() { $_POST['email'] = ''; $view = $this->controller->resetPasswordAction(); $this->assertType('ErrorView', $view); } public function testDisplaysViewWhenEmailAddressGiven() { $_POST['email'] = 'user@example.com'; $view = $this->controller->resetPasswordAction(); $this->assertType('View', $view); } }

public function testDisplaysErrorViewWhenNoEmailAddressGiven() { $_POST['email'] = ''; $view = $this->controller->resetPasswordAction(); $this->assertType('ErrorView', $view); } public function testDisplaysViewWhenEmailAddressGiven() { $_POST['email'] = 'user@example.com'; $view = $this->controller->resetPasswordAction(); $this->assertType('View', $view); } protected function tearDown() { unset($this->db); unset($this->controller); Configuration::init(array()); $_POST = array(); } }

class UserController { protected $dsn; public function __construct($dsn) { $this->dsn = $dsn; } // ... }

class UserControllerTest extends PHPUnit_Framework_TestCase { protected function setUp() { $this->db = new PDO('sqlite::memory:'); $this->db->exec( file_get_contents(__DIR__ . '/schema.sql') ); $this->db->exec( "INSERT INTO Users (username, email) VALUES ('John Doe', 'user@example.com');" ); $this->controller = new UserController('sqlite::memory:'); } }

class UserControllerTest extends PHPUnit_Framework_TestCase { protected function setUp() { $this->db = new PDO('sqlite::memory:'); $this->db->exec( file_get_contents(__DIR__ . '/schema.sql') ); $this->db->exec( "INSERT INTO Users (username, email) VALUES ('John Doe', 'user@example.com');" ); $this->controller = new UserController('sqlite::memory:'); } protected function tearDown() { unset($this->db); unset($this->controller); $_POST = array(); } }

class UsersTableDataGateway extends TableDataGateway { protected $db; public function __construct(PDO $db) { $this->db = $db; }

class UsersTableDataGateway extends TableDataGateway { protected $db; public function __construct(PDO $db) { $this->db = $db; } public function findUserByEmail($email) { $statement = $this->db->prepare( 'SELECT * FROM Users WHERE email=:email;' ); $statement->bindValue(':email', $email, PDO::PARAM_STR); $statement->execute(); return $statement->fetch(PDO::FETCH_ASSOC); }

public function updateUserWithConfirmationCode($email, $code) { $statement = $this->db->prepare( 'UPDATE Users SET code=:code WHERE email=:email;' ); $statement->bindValue(':code', $code, PDO::PARAM_STR); $statement->bindValue(':email', $email, PDO::PARAM_STR); $statement->execute(); } }

class UserController { protected $gateway; public function __construct(TableDataGateway $gateway) { $this->gateway = $gateway; } }

class UserController { protected $gateway; public function __construct(TableDataGateway $gateway) { $this->gateway = $gateway; } public function resetPasswordAction() { // ... $record = $this->gateway->findUserByEmail( $_POST['email'] ); // ... $this->gateway->updateUserWithConfirmationCode( $_POST['email'], $code ); // ... } }

class MockUsersTableDataGateway extends TableDataGateway { public function findUserByEmail($email) { return FALSE; } }

class UserControllerTest extends PHPUnit_Framework_TestCase { protected function setUp() { $this->gateway = new MockUsersTableDataGateway; $this->controller = new UserController($this->gateway); } }

class UserControllerTest extends PHPUnit_Framework_TestCase { protected function setUp() { $this->gateway = new MockUsersTableDataGateway; $this->controller = new UserController($this->gateway); } public function testDisplaysErrorViewWhenNoUserFound() { $_POST['email'] = 'nonsense'; $result = $this->controller->resetPasswordAction(); $this->assertType('ErrorView', $result); } }

class UserControllerTest extends PHPUnit_Framework_TestCase { protected function setUp() { $this->gateway = new MockUsersTableDataGateway; $this->controller = new UserController($this->gateway); } public function testDisplaysErrorViewWhenNoUserFound() { $_POST['email'] = 'nonsense'; $result = $this->controller->resetPasswordAction(); $this->assertType('ErrorView', $result); } protected function tearDown() { unset($this->controller); unset($this->gateway); $_POST = array(); } }

class UserController { protected $gatewayClass = 'UsersTableDataGateway'; public function setGatewayClass($className) { $this->gatewayClass = $className; } }

class UserController { protected $gatewayClass = 'UsersTableDataGateway'; public function setGatewayClass($className) { $this->gatewayClass = $className; } public function resetPasswordAction() { $gatewayClass = $this->gatewayClass; // ... $record = $gatewayClass::findUserByEmail($_POST['email']); // ... $gatewayClass::updateUserWithConfirmationCode( $_POST['email'], $code ); // ... } }

class UserControllerTest extends PHPUnit_Framework_TestCase { protected function setUp() { $this->controller = new UserController; $this->controller->setGatewayClass( 'MockUsersTableDataGateway' ); } // ... }

class MockUsersTableDataGateway extends TableDataGateway { public function findUserByEmail($email) { return array( 'id' => 42, 'username' => 'John Doe', 'email' => 'user@example.com', 'code' => NULL ); } public function updateUserWithConfirmationCode($email, $code) { throw new PDOException(/* ... */); } }

class UserControllerTest extends PHPUnit_Framework_TestCase { protected $usersGateway; protected function setUp() { $this->usersGateway = $this->getMockBuilder('UsersTableDataGateway') ->disableOriginalConstructor() ->getMock(); // ... } }

class UserControllerTest extends PHPUnit_Framework_TestCase { protected $usersGateway; protected function setUp() { $this->usersGateway = $this->getMockBuilder('UsersTableDataGateway') ->disableOriginalConstructor() ->getMock(); // ... } // ... public function testDisplaysErrorViewWhenNoUserFound() { $this->usersGateway ->expects($this->once()) ->method('findUserByEmail') ->will($this->returnValue(FALSE)); // ... } }

function send_mail() { if (TEST_MODE) { log(/* ... */); } else { mail(/* ... */); } }

function send_mail() { if (TEST_MODE) { log(/* ... */); } mail(/* ... */); }

class Mailer { public function send($recipient, $subject, $content) { return mail($recipient, $subject, $content); } }

class UserController { protected $gateway; protected $mailer; public function __construct(TableDataGateway $gateway, Mailer $mailer) { $this->gateway = $gateway; $this->mailer = $mailer; } }

class UserController { protected $gateway; protected $mailer; public function __construct(TableDataGateway $gateway, Mailer $mailer) { $this->gateway = $gateway; $this->mailer = $mailer; } public function resetPasswordAction() { // ... $this->mailer->send( $_POST['email'], 'Password Reset', 'Confirmation code: ' . $code ); // ... } }

class UserControllerTest extends PHPUnit_Framework_TestCase { protected function setUp() { // ... $this->mailer = $this->getMockBuilder('Mailer') ->disableOriginalConstructor() ->getMock(); $this->controller = new UserController( $this->usersGateway, $this->mailer ); // ... }

public function testSendsEmailToTheUser() { }

public function testSendsEmailToTheUser() { $_POST['email'] = 'user@example.com'; }

public function testSendsEmailToTheUser() { $_POST['email'] = 'user@example.com'; $this->usersGateway ->expects($this->once()) ->method('findUserByEmail') ->with('user@example.com') ->will($this->returnValue( array('id' => 42, 'username' => 'John Doe', 'email' => 'user@example.com', 'code' => NULL))); }

public function testSendsEmailToTheUser() { $_POST['email'] = 'user@example.com'; $this->usersGateway ->expects($this->once()) ->method('findUserByEmail') ->with('user@example.com') ->will($this->returnValue( array('id' => 42, 'username' => 'John Doe', 'email' => 'user@example.com', 'code' => NULL))); $this->mailer ->expects($this->once()) ->method('send') ->with('user@example.com'); }

public function testSendsEmailToTheUser() { $_POST['email'] = 'user@example.com'; $this->usersGateway ->expects($this->once()) ->method('findUserByEmail') ->with('user@example.com') ->will($this->returnValue( array('id' => 42, 'username' => 'John Doe', 'email' => 'user@example.com', 'code' => NULL))); $this->mailer ->expects($this->once()) ->method('send') ->with('user@example.com'); $this->controller->resetPasswordAction(); }

public function testStoresConfirmationCode() { $_POST['email'] = 'user@example.com'; $this->usersGateway ->expects($this->once()) ->method('findUserByEmail') ->with('user@example.com') ->will($this->returnValue( array('id' => 42, 'username' => 'John Doe', 'email' => 'user@example.com', 'code' => NULL))); $this->usersGateway ->expects($this->once()) ->method('updateUserWithConfirmationCode') ->with('user@example.com'); // ... } }

class CryptHelper { protected static $salt = '...'; public static function getConfirmationCode() { return sha1(uniqid(self::$salt, TRUE)); } }

class CryptHelper { protected static $salt = '...'; public static function getConfirmationCode() { return sha1(uniqid(self::$salt, TRUE)); } } class UserController { public function resetPasswordAction() { $code = CryptHelper::getConfirmationCode(); // ... } }

class CryptHelper { protected static $salt = '...'; public function getConfirmationCode() { return sha1(uniqid(self::$salt, TRUE)); } }

class UserControllerTest extends PHPUnit_Framework_TestCase { protected function setUp() { // ... $this->cryptHelper = $this->getMockBuilder('CryptHelper') ->disableOriginalConstructor() ->getMock(); $this->controller = new UserController( $this->usersGateway, $this->mailer, $this->cryptHelper ); // ... } }

class UserControllerTest extends PHPUnit_Framework_TestCase { protected function setUp() { // ... $this->cryptHelper = $this->getMockBuilder('CryptHelper') ->disableOriginalConstructor() ->getMock(); $this->controller = new UserController( $this->usersGateway, $this->mailer, $this->cryptHelper ); // ... } protected function tearDown() { // ... unset($this->cryptHelper); // ... } }

class UserController { protected $gateway; protected $mailer; protected $cryptHelper; public function __construct(TableDataGateway $gateway, Mailer $mailer, CryptHelper $cryptHelper) { $this->gateway = $gateway; $this->mailer = $mailer; $this->cryptHelper = $cryptHelper; } }

class UserController { protected $gateway; protected $mailer; protected $cryptHelper; public function __construct(TableDataGateway $gateway, Mailer $mailer, CryptHelper $cryptHelper) { $this->gateway = $gateway; $this->mailer = $mailer; $this->cryptHelper = $cryptHelper; } public function resetPasswordAction() { // ... $code = $this->cryptHelper->getConfirmationCode(); // ... } }

class MockCryptHelper { protected $index = 0; protected $codes = array('...', '...', '...', /* ... */); public function getConfirmationCode() { return $this->codes[$this->index++]; } }

class Request { protected $post = array(); public function __construct(array $post) { $this->post = $post; } public function getPost($key) { return $this->post[$key]; } public function hasPost($key) { return empty($this->post[$key]); } }

class UserController { public function resetPasswordAction(Request $request) { // ... } }

class UserController { public function resetPasswordAction(Request $request) { // ... } } class UserControllerTest extends PHPUnit_Framework_TestCase { public function testDisplaysErrorViewWhenNoUserFound() { $request = new Request( array('email' => 'user@example.com') ); $result = $controller->resetPasswordAction($request); // ... } }

class Response { public function addError(/* ... */) { } // ... }

Testable Code ”The secret in testing is in writing testable code” Miško Hevery

Avoid the hell that is global state. This includes singletons and static methods.

Separation of Concerns Concerns should be implemented separate from each other.

Separation of Concerns Concerns should be implemented as decoupled components.

Separation of Concerns Design Patterns such as Dependency Injection help decouple components.

A good architecture is the foundation of a flexible, scalable, and testable software system.

The End  Web: http://thePHP.cc/ http://sebastian-bergmann.de/ http://priebsch.de/  Twitter: @s_bergmann @spriebsch  Slides: http://talks.thePHP.cc/

http://it-republik.de	56
http://www.berejeb.com	50
http://www.virtualogos.net	15
http://entwickler.com	13
http://jaxentercom.loc	10
http://phpcoe.mimos.my	9
http://entwickler.de	5
http://development.jaxenter.com	5
http://www.devetdesign.com	4
http://entwickler-magazin.de	1
http://translate.googleusercontent.com	1
http://tools.sandsmedia.com	1
http://dev.sandstools.loc	1

Taming the Untestable Beast

by Sebastian Bergmann on Nov 01, 2010

Accessibility

Categories

Tags

Upload Details

Usage Rights

13 Embeds 171

Statistics

Taming the Untestable Beast — Presentation Transcript