Adopting code reviews for agile software development

Mario Bernhart, Andreas Mauczka, Thomas Grechenig Research Group for Industrial Software (INSO) Vienna University of Technology, Austria www.inso.tuwien.ac.at

Introduction
Code reviews have many benefits, most importantly to find bugs early [1, 2, 3]
It is commonly accepted that code reviews are resource-intensive [4]
Due to the lack of time and resources many (agile) software development teams do not perform traditional code reviews [5]
Code reviews support knowledge sharing [18] and collective code ownership [22]

Code reviews in agile environm.
Formal reviews such as the IEEE1028 [2] tend to be too heavyweight in agile contexts [4, 5]
There is a growing interest in code reviews and review tools in the agile community [24]
An empirical study [25] proposes a combination of pair programming and code reviews
 Q: How to adopt traditional code reviews to support reviews in an agile environment?

Indust. case: context & problem
EHR exchange service for hospitals
Agile software development project, 24 months, Team of 7, sprint length 4 weeks
Planned code reviews for 4 days at the end of each sprint :
1d inspection, 2d rework, 1d re-inspection
 Reviews were mostly challenged or skipped due to time and resource lack especially at the end of the sprint

Adoption strategy
Make the reviews a continuous task
Make each review task smaller
Create review tasks automatically based on individual team rules
Make review asynchronous and support distributed reviewing
Provide a first-class IDE integration for developers
 Continuous Changeset-Based Review CCBR

CCBR description
Setup = List of (author, reviewer, filter)
E.g. (Peter, Mike, *) + (*, Chris, *test*.java) + …
Continuous review workflow:
The developer commits to the SCM
If there is a matching rule: review task is auto-created
The review is executed by using the compare-view to the previous version of the change-set
The review result is consumed by the author
A (negative) review result is followed up and may create a corrective task for the author

CCBR attributes
Process Coherence
Review is done shortly after the development
Rework is done shortly after the original work
 “ It's All about Feedback and Change” [23]
Information Coherence
Changes within one timeframe often correlate [15]
Task size
small, typically <200 LOC per review task

CCBR vs. traditional reviews (TR) Inspection Re-work Re-inspection t t Development effort Development effort Inspection, re-work and re-inspection effort TR CCBR

Limitations of CCBR
TR sees the „whole“ whereas CCBR only refers to a „small piece“
Focus on a stable state (TR) vs. the creation process (CCBR)
The sum of changed lines in TR < CCBR
one line of code may be changed more than once
Pre-commit reviews vs. Post-commit reviews

Review Tool for CCBR
Eclipse integrated easy to use UI
Review scope = one changeset in the SVN
No additional server (XML/SVN based)
Works offline
Works with Subversive and Subclipse
Flexible filtered review assignments
Create Mylyn tasks out of (bad) reviews
Freeware , 10.000+ downloads
www.inso.tuwien.ac.at/projects/reviewclipse/

ReviewClipse Screenshot

Planned Empirical Evaluation
Research Questions
Is CCBR equally effective as TR?
Is CCBR equally efficient as TR?
Is the rework effort of CCBR < TR?
Plan
Prestudy with 3/3 and 6 subjects of A and B
A: In parallel study 30/30 (targets question 1 + 2)
B: In serial study 60 (targets question 3)

Future Work – Mylyn Reviews
Mylyn Reviews is a task-based code review plugin that integrates with Mylyn
Main Features:
Do code reviews based on Mylyn tasks
Incorporate the review tasks in the Mylyn task list
Provide inline-commenting for source code reviews
Framework for other review tool integrations
www.eclipse.org/reviews

References
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IEEE standard for software reviews and audits. IEEE STD 1028-2008, pages 1–52, 8 2008.
R. Baker, “Code reviews enhance software quality,” In Proceedings of the 1997 (19th) International Conference on Software Engineering , pp. 570–571, May 1997.
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B. Meyer. “Design and code reviews in the age of the internet.” Commun. ACM, 51(9):66–71, 2008.
M. Bernhart, C. Mayerhofer, T. Grechenig, “ReviewClipse - Supporting Code-Reviews within the Eclipse IDE”. Talk at EclipseCon 2009
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M. Stein, J. Riedl, S. J. Harner, and V. Mashayekhi, “A case study of distributed, asynchronous software inspection.” in ICSE ’97: Proceedings of the 19th international conference on Software engineering , (New York, NY, USA), pp. 107–117, ACM, 1997.
T. Gilb, D. Graham, and S. Finzi. “Software Inspection.” Addison-Wesley Longman Publishing Co., Inc. Boston, MA, USA, 1993.
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M.Bernhart, C. Mayerhofer, T. Grechenig. „ReviewClipse@Class - Using a Lightweight Continuous Software Reviewing Tool in Undergraduate Software Development Education“ – to appear in Proceedings of the 23rd Annual IEEE-CS Conference on Software Engineering Education and Training
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Adopting code reviews for agile software development

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