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Want Higher Quality Software
from Your Agile Team?
Cross-Functional Peer Review Works
Mark Hammer
When you create or receive
a test plan, who sees it – and how?
Product Mgmt

Development

Testing

User stories

Code

Test Plans
Product Mgmt

Development
User stories
Code
Test Plans

Testing
Cross-Functional Peer Review
Requirements

Discussion

Design

Review

Architecture

Review
Requirements

Discussion

Design

Review

Architecture

Review

Code

N/A
Hapless
Developer

Version
Control

Reviewers
Types of Code Review






Over-the-Shoulder
Email
Pair Programming
Formal Inspection Meetings
Tool
Largest Peer Code Review Study
•

•
•
•
•
•

Objectives:
– lightweight vs. formal inspections
– What constitutes an effect...
Defects Found

60-90 minutes max

Time (minutes)
Go slow: 200-500 LOC/hour
Defect Density vs. Inspection Rate

Defect Density (defects/kLOC)

150
125
100
75
50
25
0
0

200...
Not too much: 200-400 LOC
Defect Density vs. LOC

Defect Density (defects/kLOC)

200

150

100

50

0
0

200

400

600

LO...
Industry Metrics
Measure

Industry
Average

High
Performance
Teams

Net Promoter Score

20%

> 70%

% defects of total injected found by cu...
Measure

Industry
Average

High
Performance
Teams

Net Promoter Score

20%

> 70%

% defects of total injected found by cu...
Case Study:
Large National Insurance Company
• 2011: 350 developers
• 2013: 650 team members
• User stories are shared in ...
Benefits: Cross-Functional Peer
Review
• Every member of the extended development team
knows what’s happening
• Problems w...
Product Mgmt

Development
User stories
Code
Test Plans

Testing
“The simple fact of knowing your work will be
reviewed by others means you’ll do it better.”
Questions?
Comments?

Mark Hammer
Cross functional peer review preso 10-01-2013
Cross functional peer review preso 10-01-2013
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Cross functional peer review preso 10-01-2013

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  • So one of the key findings of the study is that as you do code review, it is effective in discovering defects until about the 60 minutes mark, you see the defects discovered continued to go up along with the time. But after that mark, it starts to plateau, further time spent do not result in more defects discovered.
  • As you can see from this set of data, the defects density, in another word, how many defects discovered per thousand lines of code tends to cluster between 0 and 500 lines of code examined per hour. So if you go way too fast, let’s say you looked at 1200 lines of code per hour, the number of defects that you discovered goes way down. So like I tell my daughter who just started to drive, go slow.
  • This is similar to the last one, don’t pile on thousands and thousands of lines of code for someone to review, they will not be able to focus and detect the errors due to the volume. So do just enough code and have it reviewed, in the 200 to 400 range, which give you the best yield.
  • Transcript of "Cross functional peer review preso 10-01-2013"

    1. 1. Want Higher Quality Software from Your Agile Team? Cross-Functional Peer Review Works Mark Hammer
    2. 2. When you create or receive a test plan, who sees it – and how?
    3. 3. Product Mgmt Development Testing User stories Code Test Plans
    4. 4. Product Mgmt Development User stories Code Test Plans Testing
    5. 5. Cross-Functional Peer Review
    6. 6. Requirements Discussion Design Review Architecture Review
    7. 7. Requirements Discussion Design Review Architecture Review Code N/A
    8. 8. Hapless Developer Version Control Reviewers
    9. 9. Types of Code Review      Over-the-Shoulder Email Pair Programming Formal Inspection Meetings Tool
    10. 10. Largest Peer Code Review Study • • • • • • Objectives: – lightweight vs. formal inspections – What constitutes an effective review? 10-month case study at Cisco Cisco MeetingPlace product, teleconferencing solution 3.2 million lines of code 2500 reviews 50 developers
    11. 11. Defects Found 60-90 minutes max Time (minutes)
    12. 12. Go slow: 200-500 LOC/hour Defect Density vs. Inspection Rate Defect Density (defects/kLOC) 150 125 100 75 50 25 0 0 200 400 600 800 1000 Review Inspection Rate (LOC/hour) 1200 1400
    13. 13. Not too much: 200-400 LOC Defect Density vs. LOC Defect Density (defects/kLOC) 200 150 100 50 0 0 200 400 600 LOC under Review 800 1000
    14. 14. Industry Metrics
    15. 15. Measure Industry Average High Performance Teams Net Promoter Score 20% > 70% % defects of total injected found by customer 15% < 2% % effort spent in finding and fixing defects 50% < 10% % effort for post-release support 30% < 5% Unit test code coverage Varies > 80% Post release defect density 7.5 defects/KLOC < 0.5 defects/KLOC
    16. 16. Measure Industry Average High Performance Teams Net Promoter Score 20% > 70% % defects of total injected found by customer 15% < 2% % effort spent in finding and fixing defects 50% < 10% % effort for post-release support 30% < 5% Unit test code coverage Varies > 80% Post release defect density 7.5 defects/KLOC < 0.5 defects/KLOC  Bugs found in development are 8-12X less expensive to fix than those found in testing phase  And 30-100X less expensive than bugs that reach customers
    17. 17. Case Study: Large National Insurance Company • 2011: 350 developers • 2013: 650 team members • User stories are shared in Word format with entire team • Design documents are shared in Powerpoint with entire team • Code is shared with entire team • Test cases are shared in Excel format with entire team
    18. 18. Benefits: Cross-Functional Peer Review • Every member of the extended development team knows what’s happening • Problems with user stories, code, and test plans are found faster • Developers are forced to write readable code • Optimization methods/tricks/productive programs spread faster • Teams can iterate from story to code to test plan • It's Agile • It’s fun
    19. 19. Product Mgmt Development User stories Code Test Plans Testing
    20. 20. “The simple fact of knowing your work will be reviewed by others means you’ll do it better.”
    21. 21. Questions? Comments? Mark Hammer
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