Although Extreme Programming has been around for over twenty years now, the methodologies and concepts explained would be considered radical to many organizations. In Extreme Programming Explained - Embrace Change, Kent Beck explains how a set of aligned values, combined with a human-centric approach to software development, and focus on shortening feedback cycles, dramatically changes the programming landscape.
XP is about social change
Turn the dials to 10 - Extreme
Values:
- communication
- simplicity
- feedback
- courage
- respect
Find starting place, get started, and improve from there
No one stumbles into excellence
Principles:
- humanity
- economics
- mutual benefit
- self-similarity
- improvement
- diversity
- reflection
- flow
- opportunity
- redundancy
- failure
- quality
- baby steps
- accepted responsibility
Software Development is a game of insight that comes to prepared, rested, and relaxed minds
Practices:
- sit together
- energized work
- pair programming
- stories
- weekly cycle
- quarterly cycle
- slack
- ten-minute build
- continuous-integration
- test-first programming
- incremental design
Write all production programs with two people sitting at one machine. Beck's experience: "Pairs are more than twice as effective" - more value
Longer wait to integrate - more costs and more unpredictable
If it's hard to write a test,
it's a signal that you have a design problem,
not a testing problem
Incremental design suggests the most effective time to design is in light of experience
Change begins with awareness
Corollary Practices:
- real customer involvement
- incremental deployment
- team continuity
- shrinking teams
- root-cause analysis
- shared code
- code and tests
- single code base
- daily deployment
- negotiated scope contract
- pay-per-use
XP Health Metrics:
- defect count
- flow (idea to revenue)
Incentivize team performance over individual performance,
social over cowboys
Theory of Constraints:
Maximize production capacity of the system, need to maximize throughput at bottleneck - avoid the local maximum trap
- value stream map
- implement pull system, not push
If bottleneck exists outside of development,
then answer must come from outside
Planning:
Planning XP is an activity, not a phase
Continuous planning to determine how much can get done each iteration
Iron Triangle, only scope negotiable
More time at the desk does not equal increased productivity for creative work
Plan based upon "yesterday's weather",
past iteration done to plan next capacity
Quality
Reduce the occurrence of defects to a level where trust can reasonably grow on the team
Sooner find a defect, cheaper to fix
Continuous design
Test first decouples interface from implementation
When confronted with a ball of mud,
begin lighting lamps where you walk - campsite rule
If you eliminate enough waste, soon you go faster than the people who are just trying to go fast
Community
First change myself,
then offer fruits of that change to others
Expecting others to do what you're not willing to try yourself is disrespectful and ineffective
"If you're looking for a world in which you can be comfortable, living in balance and do good business; XP is a way of thinking about and acting on your ideals."
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