Agile Development with PHP in Practice

Practising Agile Development for Beginners
30.10.2009

Lars Jankowfsky

CTO swoodoo AG

Freitag, 30. Oktober 2009

About me:

PHP, C++, Developer, Software Architect since 1992

PHP since 1998

Many successful projects from 2 to 20 developers

Running right now three projects using eXtreme
Programming

CTO and (Co-)Founder swoodoo AG

(Co-)Founder OXID eSales AG


lessons learned

COST QUALITY TIME SCOPE

Get Ready
FIRE!
Aim...
Aim...
Aim...

Agile methods are based on

Courage Simplicity

Communication Feedback


http://agilemanifesto.org/

Individuals and interactions over processes and tools

Working software over comprehensive documentation

Customer collaboration over contract negotiation

Responding to change over following a plan


Agile?

Agile? THINK!


popular Agile methods

Adaptive Software Development

Feature Driven Development

DSDM - Dynamic Systems Development Method

Scrum

crystal clear

XP


Scrum

Plan ( product backlog )

Sprint planning session

Sprint ( == Iteration )

Daily meetings

Sprint review

Closure

http://www.controlchaos.com/


eXtreme Programming

for smaller teams ( 2 - 12 )

focuses on automatic testing

a change in the way we program

includes continuous integration

http://www.extremeprogramming.org/


Lessons learned


eXtreme Programming

„Software development is too hard to spend
time on things that don't matter. So, what
really matters? Listening, Testing, Coding,
and Designing.”
Kent Beck, “father” of Extreme Programming


eXtreme Programming

people vs. hardware

automated tests

continuous integration


eXtreme Programming

Planning Designing

Coding Testing


Planning XP

Planning

The Customer Stories

Estimation Release Plan


The Customer Planning

Is always available
Writes User Stories and specifies Functional Tests
Sets priorities, explains stories
May or may not be an end-user
Has authority to decide questions about the stories
Create/Defines acceptance tests


Balancing Power


Customer bill of rights Planning

As the customer, you have the right to:
• An overall plan, to know what can be accomplished, when, and at what cost

• Get the most possible value out of every programming week

• See progress in a running system, proven to work by passing repeatable tests
that you specify

• Change your mind, to substitute functionality, and to change priorities without
paying exorbitant costs

• Be informed of schedule changes, in time to choose how to reduce scope to
restore the original date, even cancel at any time and be left with a useful
working system reﬂecting investment to date.


Programmer bill of rights Planning

As the Developer, you have the right to:
• Know what is needed, with clear declarations of priority;

• Produce quality work at all times;

• Ask for and receive help from peers, superiors, and customers;

• Make and update your own estimates;

• Accept your responsibilities instead of having them assigned to you.


The Stories Planning

A short story about the functionality from the point of view of the
Customer
No technical jargon
One for each major feature in the system
Must be written by the customer
Are used to create time estimates for release planning
Replace a large Requirements Document
The stories are the base for acceptance tests
Only enough detail to make a low risk estimate of how long the story
will take to implement.


Planning XP - the Stories Planning

Use simple technics ( postit )
Find a place where all developer can see the stories


Estimation Planning

Yesterdays Weather
use your experience
ask other teams which may have done similar things
Estimate using „Story Points“ == ideal Person Days


Release Plan Planning

Customer defines the business value of desired
stories ( priority )
Stories which are too large need to be split into
smaller chunks
Higher risks stories should come first
Define release dates - these are fixed, scope not


The Release plan Planning


Never slip a date! Planning

falling behind ? Change the plan!


Iterations Planning

From release backlog the stories with highest priorities are
taken and assigned to the next iteration.

An iteration can be 1-3 weeks usually

Stories for Iteration are broken down into Tasks by Developers

Tasks are estimated by all Developers as a group

Developers “sign up” for Tasks, and estimate the time to
complete


Iterations... Planning

If a task has more than 2-3 Story points, then break it into
smaller parts.

If there are any questions ask the customer, he should attend
Iteration planning meeting

Can only sign up for as many points as were completed in the
last Iteration

Once development begins, Project Velocity measures progress


Iterations... Planning


Stand Up Meeting Planning

Track status in daily Stand-Up Meeting
Ask for Story Points left - not for SP done
Every morning for 5 minutes
STAND UP!
What did you do yesterday ?
What do you plan todo today ?
Any „Showstoppers“ or important issues ? ( e.g. taking half day
off... )
Tell Team what you did, not some „Task number“


During Iteration: Tracking speed Planning


Designing XP

Designing XP

Simplicity Standards

Never Add
Spike Solutions
Functionality Early


(c) spackletoe http://www.ﬂickr.com/photos/spackletoe/90811910/)
(c) aboutpixel.de


Simplicity Designing XP

Keep things as simple as possible as long as possible by never
adding functionality before it is scheduled.

Always do the simplest thing that could possibly work

Beware, keeping a design simple is hard work!


(c) istockphoto


Standards Designing XP

Name classes and methods consistently. (Metaphor)

Choose a system of names for your objects that everyone can
understand easily (Zend?)

Being able to guess at what something might be named if it
already existed and being right is a real time saver

PHP Code Sniffer http://pear.php.net/package/
PHP_CodeSniffer

pre commit hook


Spike Solutions Designing XP

Don‘t guess on difficult questions, try it!

Create simple programs to get answers.

It reduces the risk of a technical problem or increase the
reliability of a user story's estimate.

API? Performance? Database?


Never Add Functionality Early Designing XP

Don‘t implement what you don‘t need now

Only 10% of your guesses will be really used later

Turn a blind eye towards future requirements and extra
flexibility.

Concentrate on what is scheduled for today only.


Coding XP

Coding XP

Code the unit test first. Check in daily.

Collective code ownership. Optimization last.

No overtime. Refactor Mercilessly


Code the unit test first. Coding XP

Upon creation of a function write unit tests

Write many tests for each function

Success case

Error case

Stupid input case


PHPUnit - http://www.phpunit.de/


Proxy for testing protected methods Coding XP

class unittools{
public static function getProxy($superClassName, array $params = null) {
$proxyClassName = "{$superClassName}Proxy";

if (!class_exists($proxyClassName, false)) {

$class = <<<CLASS
class $proxyClassName extends $superClassName {
public function __call($function, $args) {
$function = str_replace('UNIT', '_', $function);

if(method_exists($this,$function)) {
return call_user_func_array(array(&$this, $function), $args);
} else {
throw new Exception("Method ".$function." in class ".get_class($this)." does not exist");
}
}
public function setNonPublicVar($name, $value) {
$this->$name = $value;
}
public function getNonPublicVar($name) {
return $this->$name;
}
}
CLASS;
eval($class);
}
if (!empty($params)) {
// Create an instance using Reflection, because constructor has parameters
$class = new ReflectionClass($proxyClassName);
$instance = $class->newInstanceArgs($params);
}
else {
$instance = new $proxyClassName();
}
return $instance;
}
}


STOP


Enforces layered Architecture


Layer Example Coding XP

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);
}
}


Layer Example Coding XP

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);
}
}


Code the unit test first. Coding XP

OOP, public, private

Globals

Superglobals

Sessions

Cookies


Dependencies ... Coding XP

Separate logic from view

create accessors, add all parameters in calls


Dependency Example Coding XP

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();
}
}


Dependency Example Coding XP

/**
* 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 Coding XP

Make sure that tests don‘t alter fixture

Fixture is FIXture

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

Do never let tests leave altered tests


Fixtures the Ruby way... Coding XP

Ruby uses YAML

www.yaml.org

PHP YAML support done by using Syck

Syck = YAML + fast

http://whytheluckystiff.net/syck/

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


YAML loading Coding XP

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 Coding XP

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 Coding XP

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


Fixtures the other side ... Coding XP

manual fixtures are too much work

use a test database

think about automatic creation of YAML files


Mocking stubs? Coding XP

„...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...“


Mocking stubs? Coding XP

Unittesting is about testing a unit of work, not a complete
workflow

isolates your code from external dependencies

can be done with PHPUnit, but you don‘t need to


Mocking stubs The PHPUnit way Coding XP

/**
* 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));
}
}


Check in daily Coding XP

Forces developer to write small functions

Makes it impossible to create huge frameworks/functions

This is the fundament for having good tests later

Remember: You are not allowed to check in without Tests!


Collective code ownership Coding XP

Collective Code Ownership encourages everyone to contribute
new ideas to all segments of the project. (Don Wells)

Have a look what your collegaues are doing

Any developer can change any line of code to add functionality,
fix bugs, or refactor.


Pair Programming? Coding XP

All code to be included in a production release is created by two
people working together at a single computer... ????

Our experience is different!

Use pair programming on difficult tasks e.g. refactoring,
framework etc.

In small teams it makes no sense to use it always.


Optimize last Coding XP

Make it work, make it right, then make it fast.

Never guess what performance will be - measure it!

Create clear rules for performance and test it. ( „ab“ or „siege“
can be used in unit tests )


No overtime Coding XP

Projects that require overtime to be finished on time will be late
no matter what you do.

Overtime sucks the spirit and motivation out of a team.

Better play a game instead and build castles instead of creating
bugs in the software


Refactor Mercilessly Coding XP

“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


Principle of „Bad smell“

(c) istockphoto

comments „what not why“

long methods
dead code
data classes


Refactor Mercilessly Coding XP

No fear! Your tests will show if you break something.

Keep your code clean!


Testing XP

Testing XP

Create acceptance Use continuous
tests. integration!

Run tests
Publish the results
automatically


Hope vs. Knowledge


ACCEPTANCE TESTS

INTEGRATION TESTS

UNIT TESTS


Acceptance Tests Testing XP

use Selenium

Java solution which enables automatic „click“ tests.

Download Selenium RC

http://www.openqa.org/selenium-rc/download.action

Create Acceptance Tests with Selenium IDE

Use PHPUnit and create Unit Tests

Base Tests on Customer Stories


Integration Tests Testing XP

can be Unit Tests or Selenium

Testing API‘s, whole Modules

Overall picture instead of single functions


continuous integration Testing XP

„Continuous Integration is a software development practice where
members of a team integrate their work frequently, usually each
person integrates at least daily - leading to multiple integrations per
day. Each integration is verified by an automated build (including
test) to detect integration errors as quickly as possible. „

http://www.martinfowler.com/articles/continuousIntegration.html



cruisecontrol - http://cruisecontrol.sourceforge.net/

phpundercontrol - http://phpundercontrol.org

check out http://buildix.thoughtworks.com/


„Questions?“


Resources used:

Extreme Programming: A gentle introduction.

http://www.extremeprogramming.org/

Extreme Programming - Introduction

Mayford Technologies Inc.

Wikipedia

Extreme Programming Explained: Embrace Change - Kent Beck

Refactoring Improving the Design of Existing Code - Martin Fowler


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