Pair Programming Langr Software Solutions Originally presented to the Phoenix XP Users Group, October 2002

The Rules All production software Two programmers jointly developing code Switch pairs frequently Must pair if asked

All production software

Two programmers jointly developing code

Switch pairs frequently

Must pair if asked

Dynamics Two roles in the pair: Strategic Tactical Developers switch roles frequently Rhythm

Two roles in the pair:

Strategic

Tactical

Developers switch roles frequently

Rhythm

Mechanics Comfortable workstations that accommodate two Side by side Switch pairs at least once a day Core pairing hours Take breaks!

Comfortable workstations that accommodate two

Side by side

Switch pairs at least once a day

Core pairing hours

Take breaks!

General Benefits Continual review Coverage Minimized personnel dependencies Improved design Minimized defects Sustainable More rapid solutions

Continual review

Coverage

Minimized personnel dependencies

Improved design

Minimized defects

Sustainable

More rapid solutions

More Benefits Improved communication Consistent pacing Individuals less likely to bog down Team members rise to common level Builds a true

Improved communication

Consistent pacing

Individuals less likely to bog down

Team members rise to common level

Builds a true

Management Benefits Reduced risk Rapid training for new hires Interviewing criteria Problems less hidden Peer pressure Resource fluidity Cross-pollination

Reduced risk

Rapid training for new hires

Interviewing criteria

Problems less hidden

Peer pressure

Resource fluidity

Cross-pollination

Developer Benefits Awareness of other parts of system Resume building Decreased time in meetings Continuous education Ability to move between teams Rapid learning as new hire The little things E.g. Eclipse shortcuts

Awareness of other parts of system

Resume building

Decreased time in meetings

Continuous education

Ability to move between teams

Rapid learning as new hire

The little things

E.g. Eclipse shortcuts

“But it takes twice as long…” What about… Debugging sessions? Increased cost of change due to poorer design? Mull time? Inconsistent team abilities “ Costs and Benefits of Pair Programming” Laurie Williams, Alistair Cockburn

What about…

Debugging sessions?

Increased cost of change due to poorer design?

Mull time?

Inconsistent team abilities

“ Costs and Benefits of Pair Programming”

Laurie Williams, Alistair Cockburn

Potential Issues Pair dynamics Extrovert and Introvert mixes Expert and Novice mixes Not everyone can work this way Most enjoy it Some dislike but appreciate its benefits A small percentage will refuse Fear

Pair dynamics

Extrovert and Introvert mixes

Expert and Novice mixes

Not everyone can work this way

Most enjoy it

Some dislike but appreciate its benefits

A small percentage will refuse

Fear

Other Considerations Odd number of team members Core hours Skiing Team of one or two Distributed developers Context switching

Odd number of team members

Core hours

Skiing

Team of one or two

Distributed developers

Context switching

When Not Pairing Meetings, email, documents, etc. Review existing code Determine areas for potential refactoring Spike solutions Build tools or AT framework If you must work on production code: Come up with ground rules Do post-development inspections

Meetings, email, documents, etc.

Review existing code

Determine areas for potential refactoring

Spike solutions

Build tools or AT framework

If you must work on production code:

Come up with ground rules

Do post-development inspections

Where Do I Start? Discuss it with your development team Determine its value Learn to pair first To learn when not to pair Influence through metrics If necessary, track pairing vs. not Re-assess pairing value regularly Ensure a coach is monitoring interaction issues

Discuss it with your development team

Determine its value

Learn to pair first

To learn when not to pair

Influence through metrics

If necessary, track pairing vs. not

Re-assess pairing value regularly

Ensure a coach is monitoring interaction issues