eXtreme Programming In Action Radoslav Nemchev Nemetschek OOD

SofiaBulgaria

Summer School

Summer School IST-2001-34488 eXPERT:

Best Practice on e-Project Development http://www.esi.es/Expert

30 June - 2 July 2003

30 June - 2 July 2003

eXtreme programming - principles & practices

eXtreme Programming In Action

Radoslav NemchevNemetschek OOD

SofiaBulgaria

Summer School



30 June - 2 July 2003

30 June - 2 July 2003


XP in action

• Choose the project

• Involve the customer

• Involve the team

• Apply the practices

• Automate

SofiaBulgaria

Summer School



30 June - 2 July 2003

30 June - 2 July 2003


Choose the project

• Not too big

• Not too small

• Not too important

• Not too unimportant

SofiaBulgaria

Summer School



30 June - 2 July 2003

30 June - 2 July 2003


Involve the Customer

SofiaBulgaria

Summer School



30 June - 2 July 2003

30 June - 2 July 2003


Involve the team

• Guarantee them immunity• Give them time• Strictly control the practices application• Let them see the benefits by themselves• Provide communication – stand-up meetings,

open workspace,…• Shared understanding and responsibility for

the system – System Metaphor

SofiaBulgaria

Summer School



30 June - 2 July 2003

30 June - 2 July 2003


Apply the practices

• Introducing all practices at once, or just one practice at a time?

Answer: Adopt one practice at a time.

• What the order should be?Answer: Follow the natural order – from CR

oriented through design to testing and coding.

SofiaBulgaria

Summer School



30 June - 2 July 2003

30 June - 2 July 2003


Customer on-site

• Customer or Developer on-site?• Get the user stories• Make him determine priorities – high

business value first• Get him to give you immediate and

frequent feedback• Involve him into specification of

functional acceptance tests

SofiaBulgaria

Summer School



30 June - 2 July 2003

30 June - 2 July 2003


Planning game

● How to plan?

– Create and prioritize user stories - customer

– Estimate difficulties - developers

– Select stories for next release - customer

– Split stories into tasks - developers

– Plan the tasks for the next iteration - customer/developers

SofiaBulgaria

Summer School



30 June - 2 July 2003

30 June - 2 July 2003


Small Releases

• My program is all or nothing! Wrong! Inside every large program there are lots of little programs trying to get out. Make them into small releases.

• Make as many iterations as possible per release

• Keep good track of progress

• Deliver business value to the customer fast

• Gives sense of accomplishment to the team

• Keep the team focused

SofiaBulgaria

Summer School



30 June - 2 July 2003

30 June - 2 July 2003


Test First

• Test-Driven development– Design a test that will fail– Compile it and check that it fails– Write just enough code to make the test run

• Design evolves from tests• The benefit must be higher than the cost• Testing slows you down?• Apply same quality standards for test and code• Tests ARE documentation• Automate

SofiaBulgaria

Summer School



30 June - 2 July 2003

30 June - 2 July 2003


Isolation Testing

• Collaborators of the unit under test are:– Trustworthy

• Implicit usage• Object Mother Pattern

– Substituted in the test• Stubs• Self-shunt pattern• Mock objects

SofiaBulgaria

Summer School



30 June - 2 July 2003

30 June - 2 July 2003


NUnit

• Unit tests framework• Write tests• Execute tests• Assert results• Show tests failure/success• Keep the bar green• http://nunit.org/default.htm

SofiaBulgaria

Summer School



30 June - 2 July 2003

30 June - 2 July 2003


NUnit test example

SofiaBulgaria

Summer School



30 June - 2 July 2003

30 June - 2 July 2003


Write test that will fail

SofiaBulgaria

Summer School



30 June - 2 July 2003

30 June - 2 July 2003


Write just the code that makes the test pass

SofiaBulgaria

Summer School



30 June - 2 July 2003

30 June - 2 July 2003


Refactoring

• Why refactor?– Nobody does it quite right the first time– To improve design– To simplify code– To ease future changes in the code

• When do we refactor? – Continuously– When code or test smells

• Automation

SofiaBulgaria

Summer School



30 June - 2 July 2003

30 June - 2 July 2003


C# Refactory

• Integrated tool for Visual Studio• Simplifies code refactoring• Performs automatic code metrics

collection• http://www.xtreme-simplicity.net/

SofiaBulgaria

Summer School



30 June - 2 July 2003

30 June - 2 July 2003


Integration into MS Visual Studio

SofiaBulgaria

Summer School



30 June - 2 July 2003

30 June - 2 July 2003


Code metrics collection

SofiaBulgaria

Summer School



30 June - 2 July 2003

30 June - 2 July 2003


Refactoring with C# Refactory

SofiaBulgaria

Summer School



30 June - 2 July 2003

30 June - 2 July 2003


Member reference finder

SofiaBulgaria

Summer School



30 June - 2 July 2003

30 June - 2 July 2003


Simple design

• How to achieve this?– Evolutionary design – design evolves while coding

and refactoring

– If you don’t need it now, you won’t need it ever -develop only functionality that is required

– Satisfy tests in the simplest possible way

– Refactoring as soon as the tests run

• And again – keep it as simple as possible!

SofiaBulgaria

Summer School



30 June - 2 July 2003

30 June - 2 July 2003


System Metaphor

• What?• Everybody is involved, everybody is interested• Everybody understands and is responsible for:

– Base architecture– Whole system

• How?– Don’t separate the team into designers and coders– Change pairs often

SofiaBulgaria

Summer School



30 June - 2 July 2003

30 June - 2 July 2003


Pair programming

• Why?– 2 > 1– Two programmers will understand the code– Keeps programmers focused

• When do it?– XP says always– Is it possible in real life? Is it really necessary all

the time?

SofiaBulgaria

Summer School



30 June - 2 July 2003

30 June - 2 July 2003


Continuous Integration

• You can’t put it off forever. Better do it all the time

• Spare yourself the Big Bang disaster• Keep the tests working 100% during the

integration• Use a dedicated integrated machine• Keep the build time low• Automate through scripts, tools, etc…

SofiaBulgaria

Summer School



30 June - 2 July 2003

30 June - 2 July 2003


Collective Code Ownership

• This is not my object! WRONG!• Use version control system – CVS, VSS, …• You brake it, you fix it

SofiaBulgaria

Summer School



30 June - 2 July 2003

30 June - 2 July 2003


MS Visual Source Safe

• Automates Continuous Integration and Collective Code Ownership

• Provides version tracking• Integrates with MS Visual Studio

SofiaBulgaria

Summer School



30 June - 2 July 2003

30 June - 2 July 2003


Coding Standards

• I can always read my own code. Wait, it’s all my code!

• Let the team setup coding standards prior to coding and agree on them

• Force coding standards application, no exceptions

• Keep it simple

SofiaBulgaria

Summer School



30 June - 2 July 2003

30 June - 2 July 2003


40 hour week

• Tired people make mistakes• Tired people tend to overlook things like

testing, refactoring, etc.• Work at maximum concentration 8 hours per

day• 6 PM – you are tired, go home• Don’t work more than 1 consecutive week of

overtime

eXtreme Programming In Action Radoslav Nemchev Nemetschek OOD

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