extreme programming in action radoslav nemchev nemetschek ood
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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
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
XP in action
• Choose the project
• Involve the customer
• Involve the team
• Apply the practices
• Automate
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
Choose the project
• Not too big
• Not too small
• Not too important
• Not too unimportant
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
Involve the Customer
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
NUnit test example
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
Write test that will fail
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
Write just the code that makes the test pass
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
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
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
C# Refactory
• Integrated tool for Visual Studio• Simplifies code refactoring• Performs automatic code metrics
collection• http://www.xtreme-simplicity.net/
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
Integration into MS Visual Studio
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
Code metrics collection
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
Refactoring with C# Refactory
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
Member reference finder
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
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
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
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
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
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
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
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
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
Collective Code Ownership
• This is not my object! WRONG!• Use version control system – CVS, VSS, …• You brake it, you fix it
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
MS Visual Source Safe
• Automates Continuous Integration and Collective Code Ownership
• Provides version tracking• Integrates with MS Visual Studio
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
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
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
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
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