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A talk given at DANSK-IT's Softwaretest 2010 conference.
From Defect Reporting to Defect Prevention
A Lean Approach to Software Testing
Sune Gynthersen & Lars ThorupBestBrains
Who are we?
Sune GynthersenLean/Agile software consultant
Lars ThorupFounder
Cost of correcting defects
Price
Time
A brilliant solution
No bashing of Waterfall today
"All models are wrong; Some models are useful"- George Box
A quick status...
• Number of currently open defects?o 10?o 50?o 100?o 1000?
A quick status...
• Prioritization of defects?o Priority 1o Priority 2o Priority 3
Is it really that bad?
"Current software projects spend about40 to 50 percent of their effort on avoidable rework"
- Barry Boehm (2001)
A true story (2010)
• 9000 defectso 3 hours per defect (reporting, prioritization, fixing, retest, accept)o 6 effective hours a dayo 220 work days a year
= 20 man-years!
It reminds me of...
How many americans does it take to make a toast?
It reminds me of...
How many americans does it take to make a toast?
Two! One to burn it, one to scrape it
What is the cost of delay?
• A one month delay?• A one year delay?
Greater salary expenses
Lower financial return
Decreasing organisational inertia
Decreasing trust
Short-term prioritization
Vi believe...
• Any undesirable result represents a starting point for generating new learning.
We believe...
Or in plain english...
Every problem is an opportunity
The small details...
• Test versus Quality Assurance?
The small details...
• Testo Verificationo Test-drivingo Something that should
be automated
• Quality Assuranceo Early involvemento Proactivityo Help building the right
system in the right quality
Conventional wisdom
Test/QA should find defects
A new hypothesis
Prevention is far more effective than fault-finding.
Rationale?
Focus
IfPrevention is far more effective than fault-finding
That meansQuality should be built-in from the beginning
Which should produceSignificantly higher profitability
What factors influence the quality?
What can I do?
Do more of this• Strive to create a common understanding
o no later than just before development starts• Exploratory testing
o as soon as possible• Stop feature work
o until defects have been corrected• Find, understand and remove the causes behind defects
Do less of this• Manuel regression testing
4 questions for you...
• What is the most important output from Test/QA?• What is the avg. lead-time for defects? ("found" to "fixed")• How much undiscovered rework does your team have?• How do you reduce the amount of undiscovered rework?
