CODE REVIEW AND COOPERATIVE PAIR PROGRAMMING BEST PRACTICE

International Journal of Software Engineering & Applications (IJSEA), Vol.8, No.4, July 2017
DOI: 10.5121/ijsea.2017.8402 13
CODE REVIEW AND COOPERATIVE PAIR
PROGRAMMING BEST PRACTICE
Qiang Fu, Francis Grady, Bjoern Flemming Broberg, Andrew Roberts, Geir Gil
Martens, Kjetil Vatland Johansen, Pieyre Le Loher
Schlumberger Information Solutions AS, Stavanger, Norway
ABSTRACT
We need ways to improve the code quality. Programmers have different level of tenure and experience.
Standard and programming languages change and we are forced to re-use legacy code with minimum
revision. Programmers develop their habits and can be slow to incorporate new technologies to simplify
the code or improve the performance.
We rolled out our customized code review and pair programming process to address these issues. The
paper discusses the about the improvement of mandatory code review and pair programming practiced in
the commercial software development, and also proposes effective approaches to customize the code
review and pair programming to avoid the pitfalls and keep the benefits.
KEYWORDS
Code review, pair programming, customization
1. INTRODUCTION
Several common issues can be noted from the programming practice of working on an existing
big software: 1) outdated routines/patterns are still used, 2) some code does not follow the
industrial standards, 3) changes are not properly documented. The importance of code quality can
never be underestimated even for a deadline-driven world.
Code review, a manual inspection of source code by developers other than the author, is a
common software engineering practice employed in industrial contexts and is recognized as a
valuable tool for reducing defects and improving quality. The policy of 100 percent code review
has been implemented/discussed in many commercial software projects.
Classical pair programming is an agile software development technique in which two
programmers work together at one workstation [1]. Traditionally, one programmer writes code
while the other reviews each line of code as it is typed in. The two programmers switch roles
frequently. Some obvious benefits can be achieved with pair programming: 1) fewer bugs, 2)
lower cost on production maintenance, and 3) knowledge transfer [2, 3]. Another benefit is that
both developers acquire a good understanding of all the written code; they know what the design
choices were and how the code works. From many aspects, this reduces the fragmentation of
knowledge within a team.

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Another agile software development technique, pair programming is also becoming increasingly
popular in the software industry. It is more suitable for centrally-located team than the
geographically-distributed team. It is commonly considered that pair programming can get more
maintainable design with better quality, but in real working environment it often trapped in some
pitfalls [4, 5]:
1) Discourages introversion. The coder must “program aloud” while the reviewer listens.
Some developers will not raise concerns or suggest corner cases, thus turning the pair
programming into “solitary programming” with automatic code review, which wastes
resources.
2) Prevents creativity. Contrary to the value of “group brainstorming”, creative work
sometimes requires independence and autonomy. In pair programming, developers must
be able to convince a partner of the merits of an idea. This requires talking through the
implementation
3) Step by step and risking being judged if the idea fails.
4) Tiring practice. A good pair programming session is intense and mentally demanding.
Programmers have reported significant exhaustion after just a few hours. This is a
common observation, even from the most experienced practitioners and the advocates of
pair programming.
5) Demanding balance maintenance. Pair programming can cost more work-hours than
solitary programming to produce the same feature if the cooperation is not planned
properly. A balance must be maintained carefully between the quality of code and the
increased programming cost.
Mandatory code review and pair programming are being practiced in our team recently. Based on
the actual circumstance of our team, the traditional code review and pair programming are
tailored to get the advantages and avoid the pitfalls mentioned above.
2. CODE REVIEW
Mandatory code review was introduced in our team in July 2016. Although our main motivation
for conducting code reviews was finding bugs, we found that reviews brought several additional
benefits including knowledge transfer, increased team awareness and the creation of more elegant
solutions.
From the outset, we established some principles:
1) Programmer reviewing. Code should be reviewed by active programmers, not the
managers.
2) Rotating reviewer. Many code review guidelines recommend that the original author of a
piece of code perform the review of any subsequent changes; in our case, that is largely
impossible. Team and code ownership changes mean that the original author may work in
a different team by the time the code is reviewed. Instead, we have introduced a simple
rota for performing reviews. Every week, one developer is “on duty” for reviewing
changes from all other developers.
3) Responsibility on reviewer. Reviewer takes the full responsibility for the changes.

15
To help improve review consistency, we have agreed on a checklist for both the reviewers to
reference and programmers could use to recognize and resolve the issues in the code
(Figure 1), and two reviewers are required when new team members join the team. This enables
us to verify that key code goals such as readability, maintainability, and functionality are met.
Figure 1 Customized code review checklist
Since one of the potential issues with code reviews is the lag time that they introduce into the
development cycle, we added informal requirements that the size of the code to be reviewed be
kept small and that reviews are completed in under 1 hour.
Another common issue is the “inherited” code. Since our software contains a huge legacy code
base, we have agreed on 1) when creating a new program base on “inherited” code, programmer
should be responsible for the existing code incorporated, 2) we recognize the time pressure to go
through the legacy code and have a up-to-date version. Proper test should be in place for the
legacy part of the code. The overview of the code reviews can be set up in the Team Foundation
Server (TFS) dashboard (Figure 2).
3. COOPERATIVE PAIR PROGRAMMING
If two is good, is three better? To push the code quality even further, we also performed
cooperative pair programming. The project on which we tried was the creation of a new public
API. The requirements and acceptance criteria were relatively clear, so the implementation,
proper tests, and sample codes were the main work. Two developers worked on the project
together, and both had adequate understanding on the work, which reduced the amount of

16
discussion needed. Therefore, instead of having two people working on the same computer side
by side all day and swapping roles frequently, we tailored our usage as follows:
1. As with classical pair programming, we sit together and agree on the API details such as
the names, parameters, constants, etc.
2. After the API details are decided, the developers work at separate computers. One person
works on the API implementation and the other works on the tests for the designed API.
3. At the end of each day, regardless of whether the implementation or tests were finished,
the developers swap roles. The person who was working on the API implementation
reviews the test code and continues the test implementation, and vice-versa.
4. Steps 2 and 3 are then repeated until the work is complete.
By following this cooperative pair programming model, we gained several advantages:
1. We performed detailed and in-depth code reviews, which led to fewer bugs. Unlike
common code reviews, we developed a stronger understanding of the code and the
frequent communication that was required made it easier to find some of the more
obscure bugs.
2. We observed a clear improvement in the quality of the code, including better readability
and less unnecessary and unused code.
3. By switching the roles, API implementation code and its test code received a more
thorough review.
4. We perceived increased knowledge sharing because it was necessary to understand the
code thoroughly to continue the work. Because the code was fresh in the one developer’s
mind, it was easier to explain the intent to the other developer in the pair.
5. Both developers retained autonomy and the ability to exercise creativity. Both were free
to try an approach before having to convince the other developer.
6. We obtained 100% code coverage on testing. Both developers spent the same amount of
time writing the unit/acceptance tests as writing the API implementation.
Figure 2 Code review in TFS dashboard

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4. EXPECTATIONS AND OUTCOMES
After 4 months of mandatory code review, we have discovered that finding defects is not the only
benefit of code review. Reinforced by a strong team culture around the reviews, we see several
benefits:
Productivity improvements: We were concerned about the productivity in the beginning. But it
actually improved the productivity. More defects discovered in the early stage, the fewer need to
be tested later in the process. Of course, the review of the code takes time, but with modern tools
like TFS the extra workload and level of disruption are kept to the minimal level.
Code quality improvements: A clear improvement on the code quality can be observed because
of the mandatory review. The code review served as a reminder that other people will see and use
the code and helped to uncover the “blind spots” when the programmers did not follow the coding
standards. Improvements include better unit testing, fewer unnecessary changes and improved
readability.
Defect finding: The detailed checklist and improved code quality enable us to discover obvious
bugs such as exception handling, raw pointer misuser, typos and formatting mistakes. There was
a gap between our expectations and reality in terms of the types of defects found. However, we
still derive a benefit from catching the more obvious bugs earlier than in conventional
programming.
Knowledge transfer: The team works on multiple separate projects. Code reviews help facilitate
knowledge transfer between team members, not only helping to expose reviewers to a wider
range of code, but also directing authors to other resources for learning how to solve some
problems. In at least one case the process led to a mentor relationship between programmer and
the reviewer who was helpful after the code review was done.
Team awareness and transparency: By performing mandatory code reviews, we not only keep
the team generally aware of changes in the code, we also prevent anyone from adding low quality
“Band-Aid” fixes to the code in secret.
From our cooperative pair programming experiment, we have discovered some conditions that
effect the success of pair programming:
1) The maturity of the design
2) The comparative skill levels of the developers involved
3) The scale of the work, with the best scale being a task totalling at least two person-
months estimated work.
5. RECOMMENDATIONS
The roll-out of code review and pair programming is promising. The feedback from the
programmers and reviewers are generally positive. From the experience, we can offer several
observations and recommendations:

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Customized checklist: Each team should have tailored checklist according to its programming
environment and team culture, and this checklist should be updated as the team and its projects
change.
Quality assurance: Code reviews rarely result in identifying subtle bugs, so standard QA
practices such as automated unit testing and acceptance tests should be maintained.
Beyond defects: Code reviews provide benefits beyond finding defects. They can be used to help
standardize style, find alternative solutions and increase learning. These goals should guide code
review policies.
Customized pair programming: Cooperative pair programming is just one of many possible
customizations of pair programming. Depending on the circumstances, different variants of pair
programming could be tried to provide an optimal balance between quality and cost.
Pair rotation: In relatively big engineering team, pair rotation could be considered rather than
having assigned pairing partners working all the time. It can aid in introducing and training new
team members.
REFERENCES
[1] Fagan, M.E., (1976) Design and Code inspections to reduce errors in program development, IBM
Systems Journal, Vol. 15, No 3, pp. 182-211
[2] Shore, James, (2007) The art of agile development, O’Reilly Media, Inc.
[3] Cockburn, Alistair, (2002) Agile software development. Vol. 2006. Boston: Addison-Wesley.
[4] http://www.bennorthrop.com/Essays/2013/pair-programming-my-personal-nightmare.php
[5] https://techcrunch.com/2012/03/03/pair-programming-considered-harmful/
[6] Holzmann, G.J., (2006) The Power of Ten: Rules for developing safety critical code, IEEE Computer.
[7] Russell, G. W. (1991) Experience with Inspection in Ultralarge-Scale Developments, IEEE , pp. 25-
31.
[8] Beller, M; Bacchelli, A; Zaidman, A; Juergens, E (2014), Modern code reviews in open-source
projects: which problems do they fix?, Proceedings of the 11th Working Conference on Mining
Software Repositories
[9] Bisant, David B, (1989) A Two-Person Inspection Method to Improve Programming Productivity,
IEEE Transactions on Software Engineering. 15 (10), pp.1294–1304.

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AUTHORS
Qiang Fu was born in China in 1977. He received the Ph.D degree from Imperial College
London in 2010. He joined Schlumberger Information Solution AS in 2011 as senior
software developer in Petrel Geophysics team. His main areas of research interest are
software processing, developing, geophysics and geology.
Francis Grady received his Master’s degree in Computer Science from the University Of
Oxford in 2006. Since then he has been with Schlumberger, where he is currently a Senior
Software Engineer. His interests include machine learning, high performance computing
and code quality.
Bjoern Flemming Broberg joined Schlumberger in 2013 working as a Senior Software
Engineer developing software. He has a master in industrial mathematics from Trondheim
in Norway, and has more than 20 years of experience as an IT professional working as
business analyst, IT architect, developer and IT project manager.
Andrew Roberts has worked for six years at Sclumberger as a Software Engineer, in
development, build and configuration management, and testing roles. Prior to Sclumberger
he was Software Consultant for over a decade in the mobile devices market working with
such companies as Motorola, Nokia, Panasonic, etc.
Geir Gil Martens was born in Bergen, Norway, 1960. After acquiring an undergraduate
degree in computer science at Rogaland Distriktshøgskule, Norway. He joined
Geophysical Company of Norway – GECO AS in 1985 to develop the Charisma II
Seismic Interpretation Station. Over the years he have been involved with most aspects of
software development and a multitude of more or less formalized development processes.
He is currently working at Schlumberger SNTC as a senior software engineer on the
Petrel system.
Kjetil Vatland Johansen has a M.Sc. degree in Technical Cybernetics from Norwegian
University of Science and Technology. He has combined background from cybernetics
with a passion for software development throughout the professional career. He was a
developer in an C++/.Net environment for 15 years and then moved to project
management.

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