david stotts dept. of computer science univ. of north carolina at chapel hill extreme programming
TRANSCRIPT
DAVID STOTTS
DEPT. OF COMPUTER SCIENCEUNIV. OF NORTH CAROLINA AT CHAPEL HILL
Extreme Programming
In Reaction to…
“Big Process”
SEI Capability Maturity Model (CMM)
“Heavy” development practices
Hard to steer, unresponsive
Can we do better for smaller efforts?
Extreme Programming
Kent Beck, late 90’s
One of several “Agile” processes
Small teams (2 to 8 people)
Modest projects
Emphasis on customer as project driver
“Change Happens”
Embrace change as normal
Not an aberration whose cause needs to be found
Process must be lightweight and agile to respond to change
“Steer”able
XP Core Values
CommunicationSimplicityFeedbackCourage (fearlessness)
XP Practices
Pair programmingTest-first developmentSimple design: Add no function
before its timeRe-factoringThe planning gameUser/client on-site
XP Practices
Small releasesContinuous integrationCollective code ownershipCoding standards (and self-
documenting code)No overtimeSystem metaphor
Why Agile Methods?
Why is change inevitable?People…People are noisy and unpredictableProcess involving people needs
small steps, constant measurement to be steerable
eXtreme Programming
Try it …
Further reading: “XP” by J. Highsmith
Test-first development
If a class does not have automatic tests, you must assume it does not work
Regression testing … tests retain value
JUnit (Beck & Gamma): industrial-strength regression testing for the common man
JUnit
Small, easy to learn, easy to use, effective
Java classes
TestCase, Suite, runners
15 other language implementations
http://www.junit.orghttp://www.xprogramming.com/software.htm
JUnit Test Class
One test method per target method
“test anything that can break” …
“don’t test anything that can’t”
Can we give better guidance?
Can we systematically produce consistent and complete test classes?
The Planning Game
Informal brainstorming… few hours to a few days
Customer talks about what he/she wants
Engineers listen, ask questions, make “user stories”
Each story is a card, a few sentences, describes some function of the system
The Planning Game
Engineers “cost” each story
Customer “values” each story
Rank order of cards
Customer selects top 4 or 5 items…
Engineers produce Release One