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

8.
How does Agile help us with
code?

9.
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

10.
Scrum

11.
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

12.
Pair Programming

13.
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

14.
Tag Teaming
Driver / Navigator

15.
Syntax
PercentageofSyntaxrelatedcomments%

16.
Levels Syntax Vars Methods Domain Phys Other

17.
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

18.
But doesn’t it cost More?
TIME +15% QUALITY +20%

19.
Lines of Code
LINES -10%

20.
Working Space

21.
X

22.
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

23.
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

24.
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

25.
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”

26.
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

27.
XP – making the world safe for developers
and vice versa

28.
Q+A
Lorraine Steyn
@lor_krs @KRSSoftware
Agile Software Development and Coaching
www.krs.co.za