Theory and practice – migrating your legacy code into our modern test driven development world

Theory and practice – migrating your legacy code into our modern test driven development world.

Hartmann, Jankowfsky, Rinne

Jankowfsky, Rinne – Mayflower/swoodoo

Legacy Code?

Wikipedia says „Legacy code is source code that relates to a no-longer supported or manufactured operating system or other computer technology. The term can also mean code inserted into modern software for the purpose of maintaining an older or previously supported feature“


Agenda

- Where are we now, and why?

- Ammunition!

- Refactor!

Bad News? -> Workshop

Who we are

Johann Peter Hartmann:

- CTO and Founder of Mayflower GmbH

- CEO and Founder of SektionEins GmbH


Lars Jankowfsky:

- CTO and (Co)Founder swoodoo.com

- (Co)Founder of OXID eSales. Refactored OXID eShop during 1.5 years with 10 developers.

Thorsten Rinne:

- Senior Developer & Team Lead at Mayflower GmbH

- Founder and main developer of phpMyFAQ

Who are you?

- What‘s your profession?

- Sofware company or agency?

- What‘s your team size?

- Using MVC?

- Who does other languages, too?

- Using agile methods?

- Using continuous integration?

- Using unit tests?


What about your projects?

- What‘s your average project lifetime?

- Is there PHP code more than 5 years old?

- How many lines of code?

- How many change requests per year?

- Has there been a specification?

- Were all features in the first released version implemented like they‘re specified in the specification?


Typical problems?

- Typical legacy applications

- Started some years ago with PHP 4

- written in Spaghetti code

- half procedual, half object-orientated

- „PHP 4“ OOP

- using old, unmaintained libraries like PEAR::DB


PHP, made in 2000

- no coding standards

- no PHPDoc

- no Design Patterns

- few separation of concerns

- has been changed a lot

- no refactoring, because „it worked“

- updated to run with php 4 in 2003

- updated to run with php 5 in 2006


Big ball of mud


http://en.wikipedia.org/wiki/Big_ball_of_mud

A Big Ball of Mud is a haphazardly structured, sprawling, sloppy, duct-tape-and-baling-wire, spaghetti-code jungle.

These systems show unmistakable signs of unregulated growth, and repeated, expedient repair....



Enough Ammunition?


- change requests get more and more expensive

- bug rate is increasing

- clearly a dead-end street!

- team motivation decreases

- hard to bring in new members into the team

- deprecated functions cause problems in future PHP releases

Enough Ammunition?

Ever heard things like this?

„Only X can fix that.“

„It will take ages to fix it.“

„Changing this button will take two weeks.“

„I don‘t want to work for this project.“

„I don‘t want to touch this code.“

„I don‘t know how this bug could reappear.“


Enough Ammunition?

60-80 % of all development effort is maintenance

http://elearning.tvm.tcs.co.in/SMaintenance/SMaintenance/6.htm

http://www.bitpipe.com/detail/RES/1138902960_291.html




What you should never do!

Please don‘t try a complete rewrite!

- Too expensive

- Takes too long

- the old codebase is used, tested & bugfixed

- Developers love to rewrite:new code is more fun, code is easier to write than to read


Remember?


Netscape 6? Rewrite....

dBase for Windows? Rewrite....

Quattro Pro? Rewrite....

Access refatored...

Excel

joel in 2000

„When you throw away code and start from scratch, you are throwing away all that knowledge. All those collected bug fixes. Years of programming work.“

http://www.joelonsoftware.com/articles/fog0000000069.html




Test Driven Adoption

1. Unit tests for existing code with PHPUnit

2. experience of confidence in own code

3. Insight: Tests are easier if written before software

4. Insight: Tests help documenting the code

5. Insight: Tests define the real API


PHP and Unit Testing

- Layout & UI code is hard to unit-test, acceptance-test instead

- test maintenance costs:- unit test work fine with stable APIs- high change rate in PHP results in API changes- tests need to be changed, too

- slows down development, increases initial development costs

- ... but your software survives more than 4 years


Refactoring?

- Modifying code without changing it‘s behaviour

- „cleaning up“


“Refactoring is the process of changing a software system in such a way that it does not alter the external behavior of the code yet improves its internal structure.” (Martin Fowler)

Team?


- experience in Test driven Development?

- „know how vs. understanding“

- In PHP? It‘s different to the Java World!

- Developers are conservative. They do not like any changes. How much use still vi or emacs?

- Courage?- You need to make sure

that everybody understands TDD before you start.

Let‘s start.

- Identify the nastiest, ugliest and...

- probably most important piece of code and let‘s start with this one.

- if you take the easy files you won‘t solve the critical issues and...

- move the risk to the end.



COURAGE

Modifying without... ?????

- if you refactor you need tests to proove that you did not break any functionality

- Have tests first. Then change code.

- legacy code ? There are no tests!!


And now ?

- Write tests first.

- You will need to refactor your application while writing tests.


- Write selenium tests for your application. - no :(

While refactoring ...

- adjust coding style

- add missing documentation

- remove redundant code / copy & paste-code

- remove unused(!) code

- maintain a list of future todos with priorities


Spaghetti Code?


- Very old code, maybe developed in the last PHP 3 century

- a lot of redundant copy-paste code

- missing separation of concerns

- No or just minor separation of code and layout

- No use of libraries like PEAR, Zend Framework or eZ components

- No or outdated documentation

- No tests at all

Spaghetti Code?


function getThema($id, $lang){global $db, $PMF_LANG;

$result = $db->query(sprintf("SELECT thema FROM %sfaqdata WHERE id = %d AND lang = '%s'", SQLPREFIX, $id, $lang));

if ($db->num_rows($result) > 0) { while ($row = $db->fetch_object($result)) { $output = htmlentities($row->thema);

} } else { $output = $PMF_LANG["no_cats"]; } return $output;

}

phpMyFAQ 1.3.x 2002/2003

Spaghetti Code - strategy

- Identify recurring code parts and implement classes

- Use of standard libraries like Zend Framework or eZ components

- Add inline documentation

- Fix your coding styles!

- Add unittests for the new, refactored backend

- Add Selenium tests for the frontend


„Half procedual –halb object-orientated“

- Code with different quality

- Just a few documentation

- Maybe some tests ... maybe ...

- „the typical current PHP 4 project“

- Found everywhere! Really everywhere!


„Half procedual –half object-orientated“ - strategy

- Add inline documentation for all classes and methods

- Improve the re-using of duplicate code

- Add unittests and Selenium tests

- Improve every code part with PHP 5 functions, for example using file_put_contents() instead of fopen(), fwrite(), and fclose().


PHP 4 OOP

- Application was developed using „object-orientated“ PHP 4

- Using of - PHP 4 references - Re-declaration of $this


PHP 4 OOP - strategy

- Maybe you‘re lucky and there are no problems. Maybe.

- If you see problems, they are fatal errors like - Objects are referenced by value - $foo =& new Foo();

- Solution: - Implement unittests - UsestandardAPIs

- Fix the PHP 5 problems


Global Problems

- OOP, Public, Private ?

- Globals ?

- Super Globals...

- Session

- Cookies


Proxy for testing protected methods


public function getProxy($superClassName) { $proxyClassName = "{$superClassName}Proxy";

if (!class_exists($proxyClassName)) {

$class = <<<CLASS class $proxyClassName extends $superClassName { public function __call(\$function, \$args) { \$function = str_replace('protected_', '_', \$function); return call_user_func_array(array(&\$this, \$function), \$args); } }CLASS; eval($class); } return new $proxyClassName(); }

Global ?


class someOtherClass { var $setting;

function calculateSomething($a, $b) { return $a+$b; }}

class myOldNastyClass {

function needToTestThisFunction() {

$class = new someOtherClass();

$z = $_GET['input'];

// ....

return $class->calculateSomething( $class->setting, $z); }}


class someOtherClass { private $setting;

public function calculateSomething($a, $b) { return $a+$b; }

public function setSetting($set) { $this->setting = $set; }

public function getSetting() { return $this->setting; }}

class myInput { public function getParameter($name) { return $_GET[$name]; }}

class myOldNastyClass {

private $input; // set e.g. in constructor

public function needToTestThisFunction(someOtherClass &$class, $z) {

$z = $input->getParameter('input'); // ....

return $class->calculateSomething( $class->getSetting(), $z); }}

Dependencies...

- Separate Logic from View

- Create accessors, add all Parameter in calls


Dependencies...


class displayUserDetails(){ /** * Processes input and sends user first name, last name to display; */ function show() { global $dbLink; global $templateEngine; $itemId = (int) $_REQUEST['user_id']; $firstName = $dbLink->getOne("select first_name from users where id = $itemId"); $lastName = $dbLink->getOne("select last_name from users where id = $itemId"); $templateEngine->addTemplateVar('firstName', $firstName); $templateEngine->addTemplateVar('lastName', $lastName); $templateEngine->display(); }}


/** * A view class responsible for displaying user details. */class userView(){ /** * Loads user object and sends first name, last name to display */ public function show() { $userId = $this->_inputProcessor->getParameter("user_id"); $this->templateEngine->addTemplateVar('user', $this->model->loadUser(userId)); $this->templateEngine->display(); }} /** * And the corresponding model */class userModel(){ public function loadUser($userId) { $user = new User( $userId ); return array( 'firstName' => $user->getFirstName(), 'lastName' => $user->getLastName()); }}

Fixtures

- Make sure that tests do not alter fixture.

- Fixture is FIXture

- if you feel that creating fixtures is too much work - refactor more!

- Do never let tests leave altered data!


Fixtures the ruby way...

- Ruby uses „YAML Ain’t Markup Language“

- http://www.yaml.org/

- PHP YAML support done via Syck

- Syck = YAML + fast.

- http://whytheluckystiff.net/syck/

- http://www.frontalaufprall.com/2008/05/05/


http://www.yaml.org

http://www.yaml.org

http://whytheluckystiff.net/syck/

http://whytheluckystiff.net/syck/

http://www.frontalaufprall.com/2008/05/05/php-unit-database-fixtures-the-ruby-way/

http://www.frontalaufprall.com/2008/05/05/php-unit-database-fixtures-the-ruby-way/

yaml - loading


public static function create($fileName) { $fileName = 'Fixtures'.DIRECTORY_SEPARATOR.$fileName; ob_start(); include $fileName; $fileContents = ob_get_contents(); ob_clean(); $yamlData = syck_load($fileContents); return $yamlData; }

yaml - storing


public static function load($fixtures, $tableName) { if (is_array($fixtures) && count($fixtures)) { foreach ($fixtures as $fixture) { if (is_array($fixture) && is_array(current($fixture))) { Fixtures::load($fixture, $tableName); } $fields = array_keys($fixture); $statement = "INSERT INTO $tableName (" . implode(', ', $fields) . ") VALUES (:" . implode(", :", $fields) . ")"; $stmt = self::$_db->prepare($statement); if (count($fixture)) { foreach ($fixture as $key => $value ) { $stmt->bindValue(':'.$key, $value); } } $stmt->execute(); self::$_usedTables[$tableName] = $tableName; } } }

yaml - cleanup


if (!empty(self::$_usedTables)) { foreach (array_reverse(self::$_usedTables) as $tableName) { self::$_db->execute("TRUNCATE TABLE $tableName"); } }

Fixtures the other side...

- manual fixtures are too much work?

- use a test database

- think about automatic creation of yaml files


Mocking Stubs?


„...may simulate the behavior of existing code (such as a procedure on a remote machine) or be a temporary substitute for yet-to-be-developed code...“

Why do we need this ?

stub: einfache klasse, die so tut, als wäre sie wie das original mock: das gleiche, aber mit introspektion und von aussen konfigurierbar

Stubs

- Unit testing is about testing a unit of work, not a complete workflow

- isolates your code from external dependencies

- can be done with PHPunit, but doesn‘t need to


Stubs

/** * A simple stub providing a simple result directly instead of using the database */class UserModelStub extends UserModel { public getUserCount() { return 10; }}

UserModelStub extends PHPUnit_Framework_Testcase { public function testGetUserCount() { $stub = $this->getMock(‘UserModel‘); $stub->expects($this->any())->method(‘getUserCount‘)->will($this->returnValue(10)); }}


/** * The PHPUnit way */

Mock Objects

- Helpful tool to fake complex objects

- Useful to mock service apis, external software, ...

/** * The PHPUnit way */class UserModelTest extends PHPUnit_Framework_Testcase { public function testGetUserCountIsCalled() { $usermock = $this->getMock(‘UserModel‘); $usermock->expects($this->once())->method(‘getUserCount‘)->with($this->equalTo(ADMIN)); $admin = new AdminModel($usermock); $admin->getNumber(); }}


About Mocking

- a better separation of concerns helps

- writing less mock objects

- writing easier mock objects

- if there is a lot of mock objects, rethink your architecture -> refactor more!


Golden rules

- know your budget: what are your maintenance costs? What are the things you can‘t do now?

- there is no silver bullet. Introducing TDD takes A LOT of time

- TDD wins on the long run, not on the short

- Confident developers are efficient developers

- There is no way around proper coding style and documentation

- You have to rewrite code, some even twice.Jankowfsky, Rinne – Mayflower/swoodoo

Tools?

- CruiseControl for continous integration- PHPUnit- SeleniumRC and SeleniumIDE

- PHP Code Sniffer- PHP CodeBrowser



Questions?


Thank you for your interest!

eMail: [email protected]@mayflower.de

mailto:[email protected]




Technology

Theory and practice – migrating your legacy code into our modern test driven development world