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?