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Grant Watson
Grant Watson

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Why are code reviews important?

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Define what a code review is:

Code review is a software quality assurance activity in which one or several people check a program mainly by viewing and reading parts of its source code, and they do so after implementation or as an interruption of implementation.

Git Push & Merge Conflicts Galore

Ideas of why it is a good idea to perform code reviews:

  • Sharing of knowledge and new techniques
  • Maintainability
  • Compliance in quality and requirements
  • Committers are motivated to write clean code, minimizing mistakes
  • Sharing of knowledge and new techniques

Every project has a host of unwritten rules and tacit understandings. This "institutional knowledge" must be transmitted to all new arrivals on a project. By definition it is impossible (and perhaps not even cost effective) to write down this information or to convey it all in one sitting. The inductee must acquire this information in the first months on the project, usually elicited from experienced developers when he does something wrong.

Code review can facilitate the communication of institutional knowledge as it relates to code written by the newbie. Experienced team members have the opportunity to impart their wisdom and advice.

At the heart of all agile teams is unbeatable flexibility: an ability to take work off the backlog and begin execution by all team members. As a result, teams are better able to swarm around new work because no one is the "critical path." Full stack engineers can tackle front-end work as well as server-side work.

Ensuring maintainability

The expense of developing software is not just in its initial creation but in the ability of developers to use and modify existing code in the future. Software is notoriously difficult and expensive to maintain. This is especially true when a developer leaves a project and a new developer arrives, but it is even true with a single developer looking back on code he wrote six months ago.

Maintainability is generally achieved by code organization and adequate comments. A person uninvolved in the project should be able to read a portion of code and understand what it does, see the constraints and preconditions of its use and contextual information (e.g. the author used a peculiar technique because of a bug in the OS). In addition, software organizations often have coding guidelines ranging from whitespace conventions to the maximum size of a function. A reviewer can provide the ignorance and objectivity necessary to ensure these goals.

Shell Research saved an average of 30 hours of maintenance work for every hour invested in inspections.

— Software Practice and Experience, 22(2):173-182, Feb. 1992.

It dramatically improves code quality

Let’s make something clear: this is not about standards and code linting (at least not exclusively). It’s about making code more efficient. In a team where everybody has their own background and strong suits, asking for improvements (because that’s what it’s about) is always a good idea. Someone could suggest a smarter solution, a more appropriate design pattern, a way to reduce complexity or to improve performance.

Minimizing your mistakes and their impact

This might seem like the most obvious advantage to the code peer review process, but it’s also one of the most important. When you’re working with the real pressures of time and budget, it’s easy to skip this step. Sure, you’re confident in your work, but even the best coders can go crossed-eyed from looking at their own work too long. Code review helps give a fresh set of eyes to identify bugs and simple coding errors before your product gets to the next step, making the process for getting the software to the customer more efficient.

Simply reviewing someone’s code and identifying errors is great. However, when it comes to the code peer review process there also needs to be a level of follow-up and accountability. Make sure there is process in place for checking back in to confirm code discrepancies have been addressed before moving into production.

Ensuring project quality and meeting requirements

The scope of any given software project and its requirements might run through the hands of several developers. The code review process can serve as a check and balance against different interpretations of that scope and requirements compared to the code that ends up being delivered. The second set of eyes can ensure you don’t fall into the “pit” you created based on your own understanding of what is being asked and that something important hasn’t been overlooked. Having code scrutinized by your peers can save a lot of time “confronting” QA later on.

Improving code performance

Due to the lack of experience, some younger developers might be unaware of optimization techniques that could be applied on their code. The code review process provides an opportunity for these developers to acquire skills and boost the performance of their code. Additionally, it gives these younger developers a chance to hone their skills and become experts in their craft.

While realizing the required functionalities, many developers also try to pursue optimized code for conciseness and performance efficiency. However, this will result in more code complexity and less readability. (Note: Code conciseness doesn’t mean its logic is simple to understand.) Moreover, the data model that the code is built on might change in later development phases. Thus, such premature optimization will eventually increase the cost of maintenance.

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