Introduction to
Pair Programming
You will never work alone now!
Naresh Jain Bhavin Javia
naresh@agilefaqs.com bjavia@thoughtworks.com
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What is Pair Programming ?
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Video of a Sniper team trying to shoot someone down
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What did we see ?
Two guys working on the same task
Both have the same target
Both have different expertise
One executes the task
The other watches, evaluates the situation, corrects him and
validates success after execution
Two guys working as a team
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What is Pair Programming ?
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What is Pair Programming ?
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What is Pair Programming ?
Pairing
Station
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What is Pair Programming ?
Driver
Pairing
Station
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What is Pair Programming ?
Driver
Pairing
Station
Navigator
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What is Pair Programming ?
Next line of code,
syntax, API,
class under dev
Driver
Pairing
Station
Navigator
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What is Pair Programming ?
Next line of code,
syntax, API,
class under dev Is he doing it right?,
requirements, alternatives,
next test case,
Driver impact
Pairing
Station
Navigator
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Isn't it a waste ?
Two devs will do the work of one
Junior guys will slow down seniors
Less work will get done
My cost will double
Why would I put two people on a job that just one can do?
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How does it help ?
Continuous Review
Less Defects / Defects caught early
Design Quality
Problem Solving
Economical
“pair-pressure” ensures timely delivery
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How does it help ?
Learning, Induction of new team members, saves effort on intra-team
documentation
Less distractions / Higher productivity
Satisfaction
Team Building and Communication
Project Management
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Cost of fixing defects
Cost of defect
Time
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Cost of fixing defects
Cost of defect
Time
“IBM reported spending about $250 million repairing
and reinstalling fixes to 30,000 customer-reported
problems. That is over $8,000 for each defect!”
- “A Discipline for Software Engineering”, 1995, Humphrey, W.S.
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Cost and savings
Pairing experiment at University of Utah
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Cost and savings
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Incorporating pair-programming into a
software development process will help yield
software products of better quality in less
time with happier, more confident
programmers
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Points of resistance
Difficult to convince stakeholders to have two people on one task
Everyone settles into their own “Comfort Zone” over time
Strong code ownership
People who don't care
Inconsistent workstation setup
Small work area
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Techniques of Pairing
Ping-Pong Pairing
Keyboard n Mice Pairing
Selective Pairing
Cross functional Pairing
Distributed Pairing
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Tips n Tricks
Pairing Stations
Pair Rotation with Pair Hinging
Promiscuous Pair Programming
Pairing Round
Pair Stairs
Spikes
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Pairing Smells
No pair rotation
Only one person driving / Distracted Pair
Selective pairing closer to a release
Manager decides the pair
Developers not involved in estimation and planning
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When its not necessary
Tasks which involve mundane work
Trivial bug fixes like typos
One of the person is sick
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F.A.Q.s
How do you do estimation? Its 2 people working on one task now.
How do you do performance reviews for individuals?
Can we keep it optional for some people on a team?
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References
The Costs and Benefits of Pair Programming
- Laurie Williams & Alistair Cockburn
Strengthening the Case for Pair-Programming
- Laurie Williams, Robert R. Kessler, Ward Cunningham & Ron
Jeffries
On the Economic Feasibility of Pair Programming
- Hakan Erdogmus & Laurie Williams
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Thank You!
Questions?
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