Improving Code Quality In Medical Software Through Code Reviews - Vincit Teatime 2013
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The document discusses improving code quality in medical software through code reviews. It describes how one project implemented peer code reviews to prevent bugs, share knowledge, and improve discipline. The project evolved its workflow from long review cycles with many changes to immediate reviews of individual commits. Reviews check functionality, style, implementation, and readability. Commit messages are also reviewed to improve the project history. Tools like Git, Gerrit and Buildbot help automate version control, reviews and continuous integration.
Improving Code Quality In Medical Software Through Code Reviews - Vincit Teatime 2013
- 1. Improving Code Quality In Medical Software Through Code Reviews Janne R¨onkk¨o (janne.ronkko@vincit.fi) Vincit Oy April 9, 2013
- 2. Contents 1 About Code Reviews 2 Code Reviewing In One Project 3 Summary
- 3. Outline 1 About Code Reviews 2 Code Reviewing In One Project 3 Summary
- 4. Goals In Code Reviews Preventing bugs from ending up in product Keeping main branch working Quality assurance Design verification Knowledge sharing There is always at least two developers who know the change A way to see how others have solved problems
- 5. Are Code Reviews Useful? The earlier you find issue the cheaper it is to fix the issue Can improve your discipline Forces the developer to reason his/her solution There is no single developer knowing certain implementation
- 6. Are Code Reviews Useful? ”I believe that peer code reviews are the single biggest thing you can do to improve your code” Jeff Atwood of Coding Horror at http://www.codinghorror.com/blog/2006/01/code-reviews-just-do-it.html ”Individual inspections typically catch about 60 percent of defects, which is higher than other techniques except prototyping and high-volume beta testing.” Steve McConnell, Code Complete 2nd Edition, page 485
- 7. Types Of Code Review Formal code review Peer review Pair programming
- 8. The Traditional Code Review A lot of code is reviewed in single session Many participants Preparations beforehand Formal
- 9. The Traditional Code Review Problems Iteration takes time A lot of code Leads discussion easily to minor issues
- 10. Peer Reviews Usually immediately after task has been implemented In most cases all the changes are reviewed as single entity Part of the normal work flow
- 11. Pair Programming Continuous review during development
- 12. Outline 1 About Code Reviews 2 Code Reviewing In One Project About The Project Workflow Reviewing - The Way We Do It Tools 3 Summary
- 14. Overview All changes have to be reviewed by our client before approval Code is delivered to our client’s VCS Changes are delivered biweekly
- 15. About The Developed Software C++ Almost 2 million lines of code Tens of subsystems The development of current version started around 2000 Tens of developers, mainly located in Finland Builds for Windows and Linux
- 16. The Vincit Team Initially two developers The team grew up to about 15 developers during the project Most of the Vincit developers had no prior knowledge about the software
- 17. Challenges For Developers Large code base Hard to remember / find utility classes Finding implementation of certain feature is not trivial The way how things are done has evolved Coding style has evolved Strict rules about which C++ features are allowed
- 18. Workflow
- 19. The Initial Workflow No peer review at Vincit Long delay between implementation and comments Multiple changes were reviewed as single change Single comment list for all reviewed changes Reviewing was split on a subsystem basis
- 20. The Initial Workflow Results From Reviews Mainly comments about coding style A lot of questions why something was changed A lot of requests to fix issues not related to the real change in files
- 21. Changes In Project Vincit team had grown from two (2) developers to five (5) Changes done within one delivery cycle had grown Time getting comments from review had grown
- 22. Changes In Project Vincit team had grown from two (2) developers to five (5) Changes done within one delivery cycle had grown Time getting comments from review had grown Something had to be done to improve the situation
- 23. The Revised Workflow In peer review the developer explained the change to another developer the change was discussed usually it was just agreed that after some changes the task would be ready
- 24. The Revised Workflow Results From Reviews Many issues were corrected before handing the code to the client Many enhancement ideas were discovered Because the developer explained the code to reviewer not all the issues that should have been fixed were fixed
- 25. The Revised Workflow Results From Reviews Many issues were corrected before handing the code to the client Many enhancement ideas were discovered Because the developer explained the code to reviewer not all the issues that should have been fixed were fixed But the main problems in review remained: The long delay between implementation and final comments A lot of questions was asked Comments from client were in a single list
- 26. The Current Workflow Immediate (or almost immediate) comments on change Client reviews also one change instead of all changes in single delivery The workflow has worked well even for team of 15 vincitizens
- 27. The Current Workflow Results From Review Practically no remaining coding style issues in client review Developers have become more disciplined Client can review the change faster and easier than before Client can concentrate on functionality
- 28. The Current Workflow Results From Review Practically no remaining coding style issues in client review Developers have become more disciplined Client can review the change faster and easier than before Client can concentrate on functionality We have started talking that a change is ready to be bashed (”valmis lyt¨att¨av¨aksi” in Finnish)
- 29. Reviewing - The Way We Do It
- 30. Overview Each commit is reviewed separately1 Commit is always reviewed after fixing found issues Reviewed commit is required to be self-containing Review is done first internally; client gets review request after internal review has passed 1 A task may contain more than one commit
- 31. Time Spent Reviewing clearly less than 10% of development time reviews can be easily done, for example, while compiling
- 32. Review Workflow
- 35. Reviewed Items Our Checklist Functionality Coding style Implementation (code structure / architecture)
- 36. Reviewed Items Our Checklist Functionality Coding style Implementation (code structure / architecture) Readability
- 37. Reviewed Items Our Checklist Functionality Coding style Implementation (code structure / architecture) Readability Commits and commit messages
- 38. Commits and commit messages Why It Is Important To Review These? Good commits with good commit messages are easier to review are helpful in the future forces you to think what is reasonable change
- 39. Commits and commit messages Why It Is Important To Review These?
- 40. Commits and commit messages Why It Is Important To Review These? There is surprisingly many tools that leverage good commits. For example: VCS log VCS blame (who changed a line and in which commit) find change introducing a bug
- 41. Reviewing Commit Messages say what was changed explain why the change has been done2 have description of the old incorrect behaviour in case of bugfix3 2 just like good comments 3 or reference to the bug which contains the information
- 42. Reviewing Commit self-containing a good chapter in the story of the software’s history would be reasonable piece to revert
- 43. Fixing Found Issues The commit containing issues is replaced with fixed commit because if the issue is found at code review the story of the software’s history contains less issues / bugs the commits remain self-containing and atomic No commit should be broken
- 45. Continuous Integration Usually C.I. is run for changes already put in main branch to find if bad change has been merged automatically build test versions
- 46. Continuous Integration Usually C.I. is run for changes already put in main branch to find if bad change has been merged automatically build test versions Downsides are that C.I. is only reacting to issues not preventing them C.I. could provide valuable information for reviews
- 47. Continuous Integration Reviews Our Commits! Our C.I. tool reviews all the commits immediately after the commits are available for review by running unittests running smoke test running static code analyzer building the most important builds
- 48. What Else Could Be Done At Review Time Build and publish test version for all platforms Have test engineer, client or end user to verify that the change is valid
- 49. Tools
- 50. About Tools All the tools we use in the review process are open source are quite easy to setup4 require very little maintenance have been scaling without issues 4 first usable installation done less than one day
- 51. Version Control System Git (http://git-scm.com/) Distributed VCS Very efficient at branching Fast and efficient Git allows easy way to ”rewrite history” (rebasing).
- 52. Version Control System Git (http://git-scm.com/) Distributed VCS Very efficient at branching Fast and efficient Git allows easy way to ”rewrite history” (rebasing). Currently only Mercurial supports rebasing in addition to Git. Darcs has rebase support in early phase.
- 53. Code Review Tool Gerrit (https://code.google.com/p/gerrit/) Web based code review tool Integrates with git5 Easy to add comments for changes A Quick Introduction To Gerrit: http://gerrit-documentation.googlecode.com/svn/ Documentation/2.6/intro-quick.html 5 Gerrit implements git repository
- 55. Gerrit Reviewing A Fixed Commit
- 56. Gerrit My Comments The best review tool I have used Very efficient and helpfull; makes reviewing easy Just a tool
- 57. Continuous Integration Buildbot (http://buildbot.net/) Python based CI system Master controls which builds should be built and when Slaves do the actual builds Built-in support for gerrit Can be configured to review changes in gerrit
- 58. Outline 1 About Code Reviews 2 Code Reviewing In One Project 3 Summary
- 59. Summary 1 About Code Reviews 2 Code Reviewing In One Project About The Project Workflow Reviewing - The Way We Do It Tools 3 Summary
- 60. Questions? Improving Code Quality In Medical Software Through Code Reviews Janne R¨onkk¨o janne.ronkko@vincit.fi