Project Lead at MEKOS, Bremen –Code Review supported by tools in all projects •Co-Organizer JUG Bremen 24.10.2016 Codemotion Berlin / Code Reviews (Rabea Gransberger @rgransberger)
Tools are available? •Tips for Developers and Reviewers •Which social problems can occur? •Time for Questions 24.10.2016 Codemotion Berlin / Code Reviews (Rabea Gransberger @rgransberger)
•Have requirements been met? •Check if code works by testing •Inspect code line by line •Identify issues, write comment and give priority •Difficult: Identify missing parts •Go slowly: 1 liners, at least 5min review 24.10.2016 Codemotion Berlin / Code Reviews (Rabea Gransberger @rgransberger)
be readable. Prefer refactoring to comment • Check coverage of new constants in if/switch • if without else • Correctness of exception handling • Prefer immutable objects • Spell check messages shown to users • synchronized/transactions for atomic operations • Watch out for Strings/Magic Numbers. Prefer value objects Book (Java): T. Gee: What to Look for in a Code Review (2016) 24.10.2016 Codemotion Berlin / Code Reviews (Rabea Gransberger @rgransberger)
language. 2. Documentation: Describe what happens with corner-case input. 3. Documentation: Complex algorithms are explained and justified. 4. Documentation: Code that depends on non-obvious behavior in external libraries is documented with reference to external documentation. 5. Documentation: Units of measurement are documented for numeric values. 6. Documentation: Incomplete code is indicated with appropriate distinctive markers (e.g. “TODO” or “FIXME”). 7. Documentation: User-facing documentation is updated (online help, contextual help, tool-tips, version history). 8. Testing: Unit tests are added for new code paths or behaviors. 9. Testing: Unit tests cover errors and invalid parameter cases. 10. Testing: Unit tests demonstrate the algorithm is performing as documented. 11. Testing: Possible null pointers always checked before use. 12. Testing: Array indexes checked to avoid out-of-bound errors. 13. Testing: Don’t write new code that is already implemented in an existing, tested API. 14. Testing: New code fixes/implements the issue in question. 24.10.2016 Codemotion Berlin / Code Reviews (Rabea Gransberger @rgransberger) 15. Error Handling: Invalid parameter values are handled properly early in the subroutine. 16. Error Handling: Error values of null pointers from subroutine invocations are checked. 17. Error Handling: Error handlers clean up state and resources no matter where an error occurs. 18. Error Handling: Memory is released, resources are closed, and reference counters are managed under both error and nonerror conditions. 19. Thread Safety: Global variables are protected by locks or locking subroutines. 20. Thread Safety: Objects accessed by multiple threads are accessed only through a lock. 21. Thread Safety: Locks must be acquired and released in the right order to prevent deadlocks, even in error-handling code. 22. Performance: Objects are duplicated only when necessary. 23. Performance: No busy-wait loops instead of proper thread synchronization methods. 24. Performance: Memory usage is acceptable even with large inputs. 25. Performance: Optimization that makes code harder to read should only be implemented if a profiler or other tool has indicated that the routine stands to gain from optimization. [10]
risk changes: –Change in important calculations –Safety critical code, e.g. authentication –Code without test coverage –Code of new team members –Change sets with high number of files touched 24.10.2016 Codemotion Berlin / Code Reviews (Rabea Gransberger @rgransberger)
ReviewCodeExample.getFactor() passes double value to BigDecimal Constructor –This method calls the BigDecimal constructor that takes a double, and passes a literal double constant value. Since the use of BigDecimal is to get better precision than double, by passing a double, you only get the precision of double number space. To take advantage of the BigDecimal space, pass the number as a string. 24.10.2016 Codemotion Berlin / Code Reviews (Rabea Gransberger @rgransberger)
and formatting –Wrong API usage (BigDecimal example) • Run before manual review –Developer before commit –Build-System/Continuous Integration • Important: Handling of False-Positives –FindBugs @SuppressFBWarnings 24.10.2016 Codemotion Berlin / Code Reviews (Rabea Gransberger @rgransberger)
• Adding new changes to existing review • Pre-/Post-Commit Review Support • Patch/Live-Code • Where are comments saved? Embedded in code, separate XML/Database? • Overview with all pending reviews • Tracking which code still needs review • Comments and priorities and possibility to mark comment as closed • Webpage / IDE Integration • Notifications by mail • Review by task / whole code base supported • Statistics to check effects of review / improve process 24.10.2016 Codemotion Berlin / Code Reviews (Rabea Gransberger @rgransberger)
BigDecimal(0.1); public Collection<String> getCarNames() { List<Car> cars = getCarsFromDatabase(); List<String> carNames = new ArrayList<>(); for (Car car : cars) { //FIXME 4738 Use set instead of List if (!carNames.contains(car)) carNames.add(car.getName()); } return carNames; } 24.10.2016 Codemotion Berlin / Code Reviews (Rabea Gransberger @rgransberger)
Remove task tag comments • Commit with comment „Rework Review“ • Work-Item to Verification state • Invite reviewer for next review 24.10.2016 Codemotion Berlin / Code Reviews (Rabea Gransberger @rgransberger) Reviewer • All task tags removed • Re-Review code: • Changes between “Review” and “Rework” changesets
review Examples: •Issues by classification •Found issues •% reviewed code compared to full code base 24.10.2016 Codemotion Berlin / Code Reviews (Rabea Gransberger @rgransberger)
@rgransberger) Unit of work (IV-C1) Release Story/ Requirement Task Push/Pull/Comb. commit Singular commit Trigger (IV-C2) Tool Conventions Publicness (IV-C3) Pre-commit Post-commit Unreviewed Release Prevention (IV-C4) Organizational Pre commit review Release branch Swift completion (IV-C5) Priority WIP limit Time slot Author’s responsibility Blocking of process (IV-C6) Full Follow-up Wait for Review No Blocking [20]
is essential for developers •Reviews don’t replace questions. Talk! •Refactoring in separate change set •Checklist review own changes before commit •Remind reviewer of important reviews •Reviewer isn’t necessarily right. Discuss 24.10.2016 Codemotion Berlin / Code Reviews (Rabea Gransberger @rgransberger)
if too many requests •Take time, don’t rush and accept •Don’t postpone reviews with many files •If you can’t test it, ask for walkthrough 24.10.2016 Codemotion Berlin / Code Reviews (Rabea Gransberger @rgransberger)
better •Question don’t critize. Don’t get personal! •Don’t fix code while reviewing (Bad fixes) •Praise good code and personal advances •Learn from team mates code 24.10.2016 Codemotion Berlin / Code Reviews (Rabea Gransberger @rgransberger)
is boring •Author and reviewer get into conflict •Team members block process / approve fast 24.10.2016 Codemotion Berlin / Code Reviews (Rabea Gransberger @rgransberger)
as a crime scene •Continuous Integration Server •Continuous Testing •Mutation testing •Random testing 24.10.2016 Codemotion Berlin / Code Reviews (Rabea Gransberger @rgransberger)
use them •Configure tools for automated reviews •Create relaxed atmosphere •Reward: Less support calls / happy customers •Lowers overall project cost •Adjust process as you go 24.10.2016 Codemotion Berlin / Code Reviews (Rabea Gransberger @rgransberger)
Parameters and Statistical Models, and Underlying Behaviours and Mechanisms, Rigby, Dissertation, 2011 2. Convergent Contemporary Software Peer Review Practices, Rigby, 2013 3. Software Quality in 2002: A survey of the state of the art, Capers Jones, 2002 4. IEEE Standard for Software Reviews and Audits, IEEE Std 1028™-2008 5. Modernizing The Peer Code Review Process, KLOCWORK, White Paper, 2010 6. Code Reviews should be the universal rule of serious Software Development, Chhabra, Blog, 2012 7. How to hold a more effective code review, Stellman & Green, Blog, 2008 8. Code Review in Four Steps, Hayes, Blog, 2014 9. 11 proven practices for more effective, efficient peer code review, Cohen, 2011 10. Best Kept Secrets of Peer Code Review, Cohen, Smart Bear Inc., 2006 11. Don’t waste time on Code Reviews, Bird, Blog, 2014 12. Code Review Defects, Mäntylä & Lassenius, 2007 13. The Ten Commandments of Egoless Programming, Atwood, Blog, 2006 14. Improve Quality and Morale: Tips for Managing the Social Effects of Code Review, Smartbear, 2011 15. Code Reviews Resourcen von Tobias Baum 16. What to Look for in a Code Review, Gee, 2016 17. 20 Best Code Review Tools for Developers, Blog, 2015 18. Effektiver Einsatz von Code Review, OIO, 2015 19. Technische Schulden in Architekturen erkennen und beseitigen, Dr. C. Lilienthal, 2016 20. A Faceted Classification Scheme for Change-Based Industrial Code Review Processes, T. Baum, 2016 24.10.2016 Codemotion Berlin / Code Reviews (Rabea Gransberger @rgransberger)
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