Extreme Programming (XP)

   Extreme Programming (XP) is the most widely used Agile Process model. XP uses an object oriented approach as its development paradigm. XP encompasses a set of rules and practices that occur within the context of four framework activities : planning, design , coding and testing.

Planning

• Begins with a set of stories (scenarios).
• Each story written by the customer is assigned a value depending on its priority.
• The members of the XP team assess each story and assigned a cost measured in development weeks.
• If a story has more that three weeks to develop the customer is asked to split it.
• New stories can add any time.
• Customers and XP team work together to decide how to group stories for next increment.
• AS development work proceeds, the customers can add stories, split stories and eliminate them.
• The XP team then reconsiders all remaining releases and modify its plan accordingly.

Design

• A simple design is preferred.
• Design only consider the given stories.
• Extra functionality discouraged.
• Identify the object oriented classes that are relavant to the current system.
• The output of the design process is a set of CRC ( Class Responsibility Collaborator) cards.

Coding

• XP recommends developing a series of unit tests for each of the story.
• Once the code is complete, units should be unit tested.
• Pair programming – two people work together at one computer.

Testing

• The unit tests that has been created in the coding stage should be implemented using a framework that can be implemented.
• This enables regression testing.
• Integration and validation can occur on a daily basis.
• This provides the XP team with a continual indication of the progress and also raise flags early if things are going wrong.
• Acceptance tests are derived from user stories that have been implemented as parts of the software release.