Are Your Code Reviews Effective?
For many people in the software industry the term Code Reviews is automatically interpreted as an activity done internally within a development team. Some see it as an activity done by peers – reviewing each other’s code. Others see it as the job of the development team leader to review his team members’ code.
Is this approach to code reviews the most effective one?
In order to answer this question, we first have to define our goals and expectations from code reviews. Many consider code reviews as a tool for early identification of bugs (and enforcing some sort of technical coding standard). According to this view, the benefit of code reviews is in the low fixing cost of bugs detected early in the development process.
This is, of course, a fine goal. But why settle for that? Consider code reviews as a tool for improving the overall quality of the design and code. Think about using code reviews for making the code more maintainable and extensible. Let code reviews reduce future development costs by making the code simpler, clearer, and easier to work with. And while we are at it, why not use code reviews a tool for mentoring developers, improving their skills and building their experience in a guided manner?
If you agree these are important goals, it is now easier to answer the question above. The fact that most code reviews deal only with functional defects is not accidental. It is derived from the way reviews are conducted. And you can certainly do better…
Imagine…
Imagine reviews as a mentoring platform. Think of reviews being conducted by a professional mentor – an expert software developer who knows how to create good designs and write good code, and also has mentoring skills. Think about reviews conducted in small increments throughout the development process, from the first day of the project. Think about reviews as a tool not only for identifying functional defects, but also for improving the quality of design and code in order to increase the future value of the product. Think about reviews guiding the developer towards preventing problems, not merely fixing existing ones. Imagine reviews used as a tool to improve the product while gradually improving the skills of the developer literally at the same time.
I call such reviews: Professional Reviews.
Why Professional Reviews?
Reviewing is a skill – Not everyone can conduct an effective code review. Not even every experienced software developer can conduct an effective review. Reviewing code requires a different set of skills.
Mentoring is a skill – Teaching developers the art of producing good designs and writing good code is a mentoring activity. Mentoring also requires certain skills. To be a mentor, you have to be a professional software developer. But, you must also have a mentoring mindset. Working with people on improving their skills is not a trivial task.
In-depth reviewing – A professional mentor (/reviewer) can analyze the code thoroughly. Peers on your team, and most of the time even the team leader, cannot afford “spending” much time on such a profound analysis. Without an in-depth analysis, chances are that the reviewer will only be able to identify outstanding functional defects. More subtle issues, and especially non-functional issues such as issues concerning the design and structure of the code, will probably evade him. This of course is also related to the issue of reviewing skills.
Less context switching – To be effective, code reviews must be frequent. When done by peers, this requires a high level of context switching: the developer must jump between his code and the reviewed code. This introduces an overhead to the process, and might cause the frequency of the reviews to drop, thus making this activity even less effective. A professional reviewer, on the other hand, frees the team members from the need to switch their work context so frequently.
The Benefit of Professional Reviews
A professional reviewer, walking developers throughout the project from day one, helping them create better code that will last longer, and improving their skills at the same time, is by far more effective then regular peer reviews.
With the same investment you probably make in peer reviews you can make your code better and turn your developers into professionals.
***
You might want to have a look at this sample chapter draft from The Quality Within, and at an overview of The Lucid Quality Approach.
***
[Update: May 2nd, 2006]
A follow-up post discussing the issue of sharing project-knowledge was posted.
April 11th, 2006 at 11:15 am
How does this look in the context of an agile project with pair programming and collective code ownership?
April 12th, 2006 at 5:41 am
It does not contradict it. Pair programming and/or peer reviews are a good tool for collective code ownership. I argue that they are not optimal as a reviewing tool.
Professional reviews conducted in a mentoring atmoshpere are able to reveal a wider variety of code quality problems and teach developers how to avoid them. A professional mentor can do this better than any course or book, because code and design quality is extremely context sensitive.
If you are looking for collective code ownership you can still practice pair programming or informal peer reviews within your team in addition to the professional review/mentoring process. If anything, the code will be simpler and clearer when reviewed professionaly, so collective code owenership could be achieved more easily.
April 30th, 2006 at 1:11 am
[…] Are Your Code Reviews Effective? - Lidor Wyssocky asks the question and gives some advice on how to make them better […]
April 30th, 2006 at 8:11 am
You missed some important points.
1. One of the great benefits of code reviews is that the reviewer learns how the software is designed. If “prefessional reviewers” are the only folks who review code, then they’re the only ones who get that benefit of seeing what developers are doing, and learning how the design is changing. Developers who aren’t allowed to wear the reviewer hat are deprived this learning opportunity.
2. Reviewing code is something that takes practice. You say, “Not even every experienced software developer can conduct an effective review,” and you use that as an argument that most developers should never review one line of code. Nonsense. If you’re not a good reviewer, you’ll get better at it with practice, and by reviewing more code, you’ll learn more about the design so you can make better informed comments during the reivews. And all the while, all that knowledge will strengthen your own development skills.
May 1st, 2006 at 2:58 am
Hi Rufus,
Please see my comment above (second comment in this thread).
Sharing knwoledge about the code and design of the product is a great thing. It is a must. However, it is better to collectively own good code and good design. A professional mentor has the ability to improve both developers’ skills and the design and code of the concrete product. Then, you can choose whatever method you like to create a better collective ownership.
These are two methods for achieving two different things.
Most peer reviews (assuming they are really conducted during the entire development period in minimal intervals) focus on functionality. It is rare to see peers reviewing the quality of the code and the quality of the design. Most reviews stress the functionality aspects of the code. This might leave you with code which is hard to understand and maintain, so although everyone seems to "know" the code, many developers will not be confident in changing and extending it.
As for your second argument, you are right. With practice developers can become better code readers. But this again requires professional mentoring. Merely reading code will not turn you into a professional reviewer.
The focus of what I suggest is on mentoring developers to help them become professionals. Not every developer can be a good mentor. This requires certain skills which are not necessarily part of the developer’s job description. A good reviewer for me is a good mentor. These are two aspects of the same activity. Peer reviews are a great complementary tool. They will probably not create a profound change in the quality of the code, but they will help spread the knowledge…
Lidor
May 2nd, 2006 at 2:49 pm
See a follow-up on the issue of knowledge sharing at:
http://blog.qualityaspect.com/2006/05/02/sharing-project-knowledge-with-your-peers/
Lidor
July 10th, 2006 at 9:10 pm
[…] When I first wrote about professional reviews as a mentoring platform, some people responded with the question: what’s wrong with peer reviews anyway? Why do we need a person specializing in code and design reviews instead of assigning this task to peer developers within the development team? […]
October 8th, 2006 at 5:24 pm
I like the idea. I’m not so sure you need to exclude the other peer reviewers from that process though. But I do like the idea that you put the focus back upon improvement.
A common problem in many reviews is simply that no one reads the documents before some meeting, and that meeting turns into a walkthrough. That problem alone is what prevents most developers from conducting a professional review of their own. I think your idea would fix that, since a dedicated reviewer is going to have a hard time justifying, “I didn’t have time to read it, why don’t you read it to me?”
It’d be nice however if you gave some perspective on what a professional reviewer should be doing.
October 9th, 2006 at 1:59 am
You forgot one important aspect of code reviews. They make more people understand how a system works. Too many times, a component/class is only known by one person, and when that person leaves nobody wants to touch that stuff with a 10-foot stick. Code reviews helps people in understanding other parts of the system. They will not become experts, but they will have a hunch of what some components do and how. A hunch is 100% better than no understanding of a component at all.It helps to build a “collective code ownership”, which is an important part of XP.
I wish we could have more positiv code reviews, but at my current place code reviews trickle down to, this is “bad”, “import variable name”, “ugly” and “do that again”. That is not productive.
October 9th, 2006 at 2:48 am
Hi Ryan,
Thanks for your feedback. The lack of preparation before a review is indeed a common problem. Having a professional reviewer/mentor does help addressing this problem.
As for your question on what a professional reviewer should be doing, my upcoming book [b]The Quality Within[/b] will provide an extensive answer to this question.
In short, a professional reviewer is in fact a professional mentor accompanying the development team from the first day of development, and providing developers with professional guidance and mentoring. This is done in different forms, but professional reviews are a primary platform for this mentoring effort.
Have a look at http://lucidquality.qualityaspect.com/Overview/ for an overview of this approach.
Redsolo,
The issue you brought up (sharing product knowledge among team members) is a valid concern. This is indeed something that should be encouraged. But people often tend to confuse code reviews with a knowledge sharing activity. Each of these activities have a different goal and a different target audience. Trying to merge these activities into a single one is not effective.
Please see http://blog.qualityaspect.com/2006/05/02/sharing-project-knowledge-with-your-peers/ for an elaborated discussion on this issue.
Lidor
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