Code review at Google

Google's code review process is a cornerstone of their software development cycle, ensuring high-quality code and product integrity. Here's an in-depth look at the advice and wisdom Google imparts on the subject, beneficial for developers and teams outside Google.

Code review at Google is not just a formality—it's an integral part of the development process. The main goals are to maintain code quality, facilitate knowledge sharing, and ensure that every new feature or product adheres to the highest standards of coding.

  • Design: Is the code well-designed and appropriate for your system?

  • Functionality: Does the code behave as the author intended and is it good for users?

  • Complexity: Is there a way to simplify the code for better understanding and use in the future?

  • Tests: Are there correct and well-designed automated tests?

  • Naming: Are the variables, classes, methods, etc., named clearly?

  • Comments: Are the comments in the code clear and useful?

  • Style: Does the code adhere to Google's style guides?

  • Documentation: Is the related documentation updated and relevant?

The best reviewer is someone who can provide a thorough and correct review promptly. This might be the owner of the code, but it's essential to include different perspectives. If an ideal reviewer is unavailable, at least keeping them in the loop via CC on the change is recommended.

In-person reviews can be beneficial. If a piece of code was pair-programmed by a qualified reviewer, it's considered reviewed. In-person reviews focus on questioning rather than commentary, allowing the developer to explain their logic only when queried.

  1. Understand the Review: Know what to look for, such as structure, style, logic, performance, test coverage, design, readability, and functionality.

  2. Preparation: Build and test before the review to ensure stability and reduce errors, saving time during the review process.

  3. Time Management: Limit code reviews to no more than 60 minutes at a time to maintain attention to detail.

  4. Scope: Check no more than 400 lines at a time to avoid missing defects.

  5. Constructive Feedback: Give feedback that is helpful, not hurtful. Use questions to guide rather than direct criticism.

  6. Communication: Clearly communicate the goals and expectations of the review process.

  7. Inclusivity: Include all relevant team members in the code review process, regardless of seniority.

  8. Positive Culture: Foster a culture that values code reviews as a growth and learning opportunity, not just a quality gate.

  9. Automation: Use automation where possible to save time and focus human review on areas that require human judgment.

  • Collaboration is paramount, and the process is as much about team-building as it is about product quality.

  • Code reviews should be frequent, focused, and inclusive, considering a variety of aspects from security to maintainability.

  • A positive approach to reviews encourages better code and team morale.

By integrating these principles, any organization can enhance its code review process, benefiting from Google's extensive experience and emphasis on quality and collaboration.