Agile development

Extreme Programming (XP)

Abder-Rahman AliM.S.Software Engineering

DePaul CTIabder.rahman.ali@gmail.com

Just before we begin…

Agile development is a:

Software development process model.

.

Software development Process

Task (1)

Task (2)

Task (3)

.

.

.

Task (n)

Goal HIGH QUALITY SOFTWARE

Action

In other words…

THE ROADMAP THAT YOU FOLLOW

Software development Process Models

Nature of SoftwareC

hange

Change in what?

• Software being built (i.e. requirements).

• Team members.

• New technology appearing.

Implications…

• Change is the HEART of software.

• Support for changes should be built in everything we do in software

So, what is Agility?

A rapid and effective response to change.

So, what is Agility?

Effective communication among stakeholders.

So, what is Agility?

Drawing the customer into the team.

This yields to…

Rapid & incremental delivery of software.

An Agile team…

A team that is able to appropriately to changes.

Extreme Programming (XP)

PlanningDesign

Test

Coding

Release

The XP Process

The most widely used Agile process, and it is originally proposed by Kent Benck.

Planning

Design

KIS Principle

We just want the design to provide an implementation guidance for the story as it is written---nothing less, nothing more.

Don’t try to design extra functionality because you assume it will be required later.

Design

CRC Cards

ClassResponsibility Collaborator

Design

Spike Solutions

1- A design problem occurs.

2- Create a PROTOTYPE of that portion of the design.

3- Implement and evaluate the prototype.

Intent:

To lower risk when true implementation starts.

Design

Refactoring

Changing a software system in such a way that:

1- The internal structure is improved.

2- The external behavior is not altered (not changed).

Design occurs CONTINUOUSLY as the system is constructed.

Also means:

Testing

TEST FIRST

Testing

Unit tests are written before the code.

Tests are run to ensure that our software fails.

A good test case is one that ensures that the software fails.

Test is rerun until it passes.

Testing

All unit tests are executed daily.

This can raise warning flags early if things are going wrong.

Testing

Acceptance tests (customer tests):

They are specified by the customer.

They focus on the overall system features and functionality that are visible and reviewable by the customer.

They are derived from user stories.

Testing

Fixing small problems every few hours takes less time than fixing huge problems just before the deadline.

Fact:

Coding

Pair P

rogramm

ing

Coding

Two people work together at one computer to create code for a story.

This provides a mechanism for real-time problem solving and real-time quality assurance.

Keeps the developers focused on the problem at hand.

As pair programmers complete their work, the code they develop is integrated with the work of others.

Coding

ROI

Coding

ROI

Release

Project Velocity

The number of stories that we performed in this release.

When to use XP?

Dynamically changing requirements.

Risky projects.

Small development groups (up to 100).

Non-fixed price contract.

XP Rules…

Planning• User Stories• Release Planning• Small Releases• Measure Project Velocity• Divide project to iterations• Iterations Planning• Move People around• Stand up meeting

Designing• Simplicity• CRC cards• Spike solutions• Refactor

XP Rules…

Coding• Customer available• Code standards• Test-Driven• Pair Programming• Sequential change integration• Integrate often• Collective code ownership• Don’t optimize early• No overtime

Testing

• Unit test everything• All tests pass before release• Bug == new test• Acceptance tests

We Must Ask Ourselves…

Do we need Agile or any other

Software Development Process

models in our lab?

Questions?