Code Review: Best Practices for Quality Assurance

Software bugs are errors, or flaws, that cause an application to fail or behave unexpectedly. The further a bug progresses in the software development life cycle (SDLC), the greater the expense of fixing it. Bugs can also delay product launches or service updates, obstructing potential business revenue.

Code review, also known as peer review, helps mitigate these risks by providing an opportunity to catch issues before they escalate. A vital aspect of quality assurance, code reviews can be manual or automated. Learn more about code review, including its various types, advantages, potential challenges, and best practices for effective implementation.

What is code review?

Code review involves carefully evaluating code changes prior to their integration into the main codebase. The review process is iterative, with feedback cycles continuing until the code meets the necessary criteria for integration or deployment. Note that while code reviews help identify certain bugs, they do not eliminate the need for comprehensive software testing. A code review complements testing as part of a broader approach to maintaining software quality.

Who conducts a code review?

Programmers or developers who did not author the code being examined perform code reviews. Common checkpoints in the review process include:

• Does the new code fulfill its intended purpose?

• Is the code clear and easy to read?

• Does the code adhere to the organization's coding conventions?

• Are all possible edge cases accounted for in the code?

• Is the code fully compliant with relevant legal regulations?

Types of code review  

If you’re just starting as a programmer or developer, familiarizing yourself with the various code review methods, such as pair programming and over-the-shoulder, can help you navigate the software development life cycle more effectively. Below are some common types of code reviews you'll encounter as you advance in your career.

Pair programming

In pair programming, you collaborate with another developer in real time. One of you is the “driver,” while the other is the “navigator.” The driver focuses on coding, and the navigator helps spot issues and suggest improvements.

Over-the-shoulder 

In an over-the-shoulder code review, you walk the reviewer through your code changes, either in person or through screen sharing. The reviewer engages by asking questions and offering feedback. This method is faster than pair programming, allowing you to address small issues on the spot while reserving larger changes for later.

Pull requests

A pull request review involves submitting your code changes to a version control system, such as GitHub, for evaluation. Your team then examines the changes and offers feedback. Once the changes are approved, they are merged into the main codebase. The method works without the need for synchronous communication between team members.

Benefits of code review

Code reviews, regardless of the method used, are an integral part of software development that also provide benefits such as sharing knowledge and establishing coding standards. The following are some key benefits of performing code reviews:

Encourages knowledge transfer

Regular code reviews cultivate a learning environment within the team, where insights, best practices, and new techniques are shared freely. The ongoing exchange of information enhances teams’ collective knowledge. 

Enforces coding standards

Code reviews play a key role in upholding coding standards and ensuring uniformity within a team. This is particularly important in large-scale or open-source projects, where numerous contributors actively shape the codebase. 

Facilitates security scans

Code reviews are an important supplement to automated tests, providing an extra layer of defense against security vulnerabilities. Essentially, code reviews facilitate more streamlined and effective quality assurance testing. 

Popular tools for code review

Code review tools allow for asynchronous and remote collaboration, while also offering detailed analytics to optimize workflows. Below are some common code review tools in use today: 

GitHub

On GitHub, pull requests serve as the foundation for conducting and improving code reviews. The GitHub Copilot feature further streamlines development by suggesting code completions and converting natural language prompts into code suggestions that fit your project’s guidelines.

GitLab

GitLab lets you modify the code, run tests, and then push to create a merge request for review. GitLab also allows assigning “maintainers” (experts in code review) based on their area of expertise. For example, the GitLab codebase has dedicated maintainers for the database, frontend, and backend parts of code.

Bitbucket

Bitbucket, like GitHub, includes pull requests for code review. Additionally, it supports defining a checklist for reviewers to follow during code evaluation. Integrated test and security scan results within the pull request view help identify potential bugs before merging.

Challenges in code review 

While code reviews offer several benefits, they also present challenges, such as time consumption and faulty feedback, that can impact the overall success of code reviews. Below are a few pointers to consider:

Hard to scale 

As teams grow and projects scale, conducting effective code reviews can become increasingly difficult. The larger the volume of code changes, the more challenging it is to maintain accuracy and consistency across all projects.

Subjective feedback

Code reviews are inherently subjective, as different reviewers may bring their preferences and approaches to coding, resulting in contrasting opinions. These differences in judgment can create confusion, especially if the feedback is not clear or lacks solid reasoning.

Time constraints 

Code reviews can be time-intensive with large codebases. This can cause delays or hinder focus on other essential tasks. Lengthy code reviews may also stall the development process, creating a bottleneck and affecting a project’s timeline.

Best practices for performing code review

When done correctly, code reviews can help identify issues early, while keeping software development on track. The following are some best practices for enhancing the outcomes of a code review.

Build a supportive code review environment.

It helps to keep feedback constructive and solution-oriented. With this approach, you can foster an environment where everyone feels supported and encouraged to improve their skills.

Maintain a review checklist. 

Checklists help reduce recurring mistakes and missed issues by setting clear review expectations. They also assist in the tracking of reporting and process improvements.

Merge pull requests promptly.

Keeping a pull request open for too long increases the chances of it becoming out of sync with the rest of the codebase. By merging pull requests swiftly, you can prevent your code from becoming outdated. 

Use metrics to gauge effectiveness.

Tracking relevant metrics enables you to assess the effectiveness of code reviews. For instance, monitoring the time spent on each review allows you to determine if the process is efficient or needs changes. You can also track the amount of issues and bugs that occur.

Learn more about code review on Coursera

Code reviews help developers track and inspect code changes as part of quality assurance. You can gain practical experience with the popular code review tool GitHub in the Introduction to Git and GitHub course offered by Google on Coursera. A beginner-friendly course, it offers guidance on installing and running Git on your local machine and using GitHub for version control.

To deepen your understanding of software development, pair the aforementioned course with the University of Minnesota’s Software Development Lifecycle Specialization, which covers software development practices.