Pair Programming
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This talk covers how to Pair Program, what benefits you can expect from adopting this as a 100% committed activity, and what you'll need to overcome.
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Pair Programming
- 1. Testability starts with code Lorraine Steyn @lor_krs @KRSSoftware www.krs.co.za
- 2. Statistics, Averages, Lies Pairing in Context of Agile Pair Programming Described Working Space Benefits Arguments Against Pairing Q&A Agenda
- 3. 70-100 defects per 1000 lines of code 70% removed during development Quality Inspections find 1 (true) defect per man-hour QA’s are 20 x more effective than manual testing Manual testing takes between 4 and 16 hours per defect Stats, Averages,Lies
- 4. References: Experience with Inspection in Ultralarge-scale Development, IEEE, Russell 1991 An Experiment to Assess the Cost-Benefits of Code Inspections IEEE, Porter The Costs and Benefits of Pair Programming, ACM, Cockburn and Williams Promiscuous Pairing and Beginner’s Mind, ACM, Belshee 2005 Pair Programming and the Mysterious Role of the Navigator, ACM, Bryant 2008
- 5. Assume 1000 lines of code, 100 defects, developer finds 70% Assume 50 lines of code per hour = 20 hours to develop the code 30 defects go to QA, rate of 1 defect identified per hour = 30 hours 30 defects go to Testing, assume 10 hours to find 1 defect = 300 hours? If we could halve the defects: QA hours would reduce to 15, Testers would reduce to 150 hours … Maths: Time = money
- 6. Applied Software Measurement, Casper Jones, 1996 X X
- 7. Costs Opportunity cost Cost of rework : time, more people, energy, trust … Safety, life-and-death issues Economic loss
- 9. How does Agile help us with code?
- 10. Customer collaboration over contract negotiation Responding to change over following a plan Working software over comprehensive documentation Individuals and interactions over processes and tools The Agile Manifesto
- 11. Scrum
- 12. XP Communication Simplicity Feedback Courage Respect Sit Together Whole Team Informative Workspace Energized Work Stories Weekly Cycle Quarterly Cycle Slack Ten-Minute Build Continuous Integration Incremental Design
- 13. Pair Programming
- 14. Swap often Swap mouse and keyboard every 10 minutes Prevents “watch the master” dysfunction Swap pairs every 90 minutes to 2 hours Highest velocity, lowest exhaustion
- 15. Tag Teaming Driver / Navigator
- 17. Levels Syntax Vars Methods Domain Phys Other
- 18. Flow – achieved together Constant explaining – to self and partner Constant adjusting of approach Syntax corrections, but hold back Both need time to think Micro design, discussed as you go Very tiring! X In Practice
- 19. But doesn’t it cost More? TIME +15% QUALITY +20%
- 20. Lines of Code LINES -10%
- 21. Working Space
- 22. X
- 24. Code Benefits Quality of 70% bug free (solo) rises to 85% (paired) – gain 20% Constant micro design results in cleaner solutions – less code Less code is better – simplicity, easier to read and support Avoids confirmation bias – more innovation Developers consider more alternatives together – robust code
- 25. People Benefits Share knowledge and skills – silo busting Easier on-boarding of new team members – mentoring Shared problems are easier to tackle – motivation Harder to procrastinate – productivity Heightened communication – collaboration
- 26. Issues, Concerns and Excuses None. Personalities who can really not work together Forcing people causes resentment But it costs double… “I work faster alone” Spending more time training than developing Workspace is not comfortable Personal hygiene
- 27. Handling concerns Ego – Primadonnas are not good in a team, lack of care for team members Imposter syndrome – fear of failure People as Resources attitude – “but it costs double”
- 28. Pair Strategies Senior – Senior Highest skills, good value Senior – Junior Great for mentoring, good to great value Junior – Junior Better than working alone, poor value Senior – Tester Collaborate on Test Cases (TDD), winning
- 29. XP – making the world safe for developers and vice versa
- 30. Q+A Lorraine Steyn @lor_krs @KRSSoftware Agile Software Development and Coaching www.krs.co.za
Editor's Notes
- Ask questions at end
- Other defects from QA’s are style preferences, misunderstanding of code, readability suggestions Only 15-35% of QA feedback must be fixed 2 reviewers were slightly more efficient than 1, no gains after 2
- Association for Computing Machinery
- 50 lines of code per hour – so 20 hours to develop the code. 50% longer to inspect bugs out of it
- 1956
- Satisfaction drops, morale, trust in team members, lowers collaboration
- Energized work – not removing value from the code Dial up sitting together if you have a problem
- 2nd screen, only one laptop/pc
- Swap pairs per sprint, or per week, or daily. No wrong way. Small team, and the frequent swaps kept them all involved in all aspects. Mobbing in pairs
- Driver types, navigator directs the design and helps spot coding errors Stats showing this is not exactly what happens, call it tag team rather. Your turn, my turn, etc. The notepad is a big help – write goals and approach
- 17 missing, 3 the navigator fell asleep, 2 driver just obeyed. Overall it’s balanced.
- Hour bursts, use paper, keep on track. Share the load – getting difficult, hand over to partner.
- Less is very good. Most time spent in support, and more reading takes longer.
- Personal space!
- Mob, relaxed, have space to withdraw and come together. Keyboard and mouse accessible by both.
- Not just new members, mentoring good for all We normally work like toddlers, along-side. Pairing is first real collaboration.
- Not judgemental – personal space, religious or cultural issues male/female, autistic people If a team is not convinced, they’ll find ways to avoid pairing