Debugging 2013- Lars pedersen

Debugging 2013- Lars pedersen

• 1.
  Quality Up Front Howto spend less time debugging Lars Jarnbo Pedersen Co-founder Switch-Gears ApS
• 2.
  About me Partner atSwitch-Gears ApS ● Transitioning companies from old development tools to modern Open Source ones Been working for Nokia 2001-2012 ● Release manager for S40 software for many years ● Part of a small team that introduced Git, Gerrit and Jenkins to S40 development resulting in BIG productivity gains
• 3.
  Pain in SWDevelopment 50% COST OF BUGS of developer time is spent finding and fixing bugs* *http://www.businessweekly.co.uk/hi-tech/14898-software-bugs-cost-more-than-double-eurozone-bailout
• 4.
  Why? Programming is hard… ●you have to map the problem domain to the programming language in use ● its usually a collaborative effort ● time pressure ● best practises are not shared Bugs are discovered late… ● context is lost ● often it is not the programmer who introduced the bug, who is fixing it
• 5.
  Luckily 90% COST OF BUGS ofthe bugs can be caught during development* *http://www.codinghorror.com/blog/2006/01/code-reviews-just-do-it.html
• 6.
  Because Average defect detectionrate is 25 percent for unit testing, 35 percent for function testing, and 45 percent for integration testing. [McConnell93] Furthermore, the average effectiveness of design and code inspections are 55 and 60 percent. [McConnell93]
• 7.
  How?
• 8.
  Peer Code Review ●Beneficial for “quality of review” if the author pre-reviews and leaves comments for subsequent reviewers [Cohen2006] ● The longer a reviewer spends on the initial read-through, the more defects will ultimately be found [Uwano2006] ● Defect detection drops dramatically after ~60 minutes, to zero after ~90 minutes [Dunsmore2000]
• 9.
  Peer Code Review ●Long methods and loops are very time consuming to understand [Uwano2006] ● Review 100 to 300 LOC at a time, in 30-60 minutes chunks, with a break between each sitting [Cohen2006] ● Spend at least 5 minutes reviewing a single line of code [Cohen2006] ● Limit reviewing to 1 hour per day [Ganssle2009]
• 10.
  Mental Model Platform Knowledge + DevelopmentProcess = Platform Quality
• 11.
  Increase Platform Knowledge WriteReadable Code!!! ● You spend much more time reading code than writing it - so make it nice to read! ● Refactor if necessary ● Include test-code Commit changes in logical units ● Always commit working code ● Never mix error-fixes and feature implementations Write descriptive commit messages ● Make sure the reason for the change is clearly explained
• 12.
  Optimize Development Process Makeit simple on the developers, ● allow multiple workflows at the developers desk ● don’t let the release/integration process stop the development flow ● minimize manual process steps while keeping a strict process ● automatically build and test all commits ● require code-review of all commits
• 13.
  This is NOTrocket science! So why don’t we do it already? ● Waterfall development ● Code Reviews are perceived expensive ● Last generation of tools do not support this easily What is enabling it now? ● Agile development ● New breed of Open Source tools
• 14.
  Git / Gerrit/ Jenkins
• 15.
  Git (DVCS) changeseverything! Git is NOT subversion++ ● all operations except for push/pull are local => well suited for continuous integration ● allows for multiple workflows ○ development ○ integration / releasing ● is a first class citizen during development AND debugging! ○ gitk for code analysis ○ git bisect for debugging
• 16.
  Gerrit A developer codes- and asks for feedback
• 17.
  Peer Code Review Anotherdeveloper reviews and comments
• 18.
  Continuous Integration Actually yousaw it in action already! Good tools help you without getting in the way
• 19.
  Our experiences -Low Gain Example [Anonymized and obscured]
• 20.
  Our experiences -High Gain Example [Anonymized and obscured]
• 21.
  References Books ● ● Code Complete: APractical Handbook of Software Construction, Second Edition by Steve McConnell (Jun 16, 2004) Clean Code: A Handbook of Agile Software Craftsmanship by Robert C. Martin (Aug 11, 2008) Articles ● ● ● ● ● SCM Ranking (Switch-Gears) CI Ranking (Switch-Gears) Best Kept Secrets of Peer Code Review (Smartbear) The Cost of Software Bugs (Business Weekly) Code Review - Just Do It (Coding Horror) Videos ● ● Linus Torvalds on Git (Google TechTalk) Development at the Speed and Scale of Google (InfoQ)