Code Review Checklist

Implementation

• Does this code change accomplish what it is supposed to do?
• Can this solution be simplified?
• Does this change add unwanted compile-time or run-time dependencies?
• Is a framework, API, library, or service used that should not be used?
• Could an additional framework, API, library, or service improve the solution?
• Is the code at the right abstraction level?
• Is the code modular enough?
• Can a better solution be found in terms of maintainability, readability, performance, or security?
• Does similar functionality already exist in the codebase? If yes, why isn’t it reused?
• Are there any best practices, design patterns or language-specific patterns that could substantially improve this code?
• Does this code adhere to Object-Oriented Analysis and Design Principles, like the Single Responsibility Principle, Open-Close Principle, Liskov Substitution Principle, Interface Segregation, or Dependency Injection?

Logic Errors and Bugs

• Can you think of any use case in which the code does not behave as intended?
• Can you think of any inputs or external events that could break the code?

Error Handling and Logging

• Is error handling done the correct way?
• Should any logging or debugging information be added or removed?
• Are error messages user-friendly?
• Are there enough log events and are they written in a way that allows for easy debugging?

Dependencies

• Were updates to documentation, configuration, or readme files made as required by this change?
• Are there any potential impacts on other parts of the system or backward compatibility?

Security and Data Privacy

• Does the code introduce any security vulnerabilities?
• Are authorization and authentication handled correctly?
• Is (user) input validated, sanitized, and escaped to prevent security attacks such as cross-site scripting or SQL injection?
• Is sensitive data like user data or credit card information securely handled and stored?
• Is the right encryption used?
• Does this code change reveal any secret information like keys, passwords, or usernames?
• Is data retrieved from external APIs or libraries checked for security issues?

Performance

• Do you think this code change decreases system performance?
• Do you see any potential to improve the performance of the code significantly?

Usability and Accessibility

• Is the proposed solution well-designed from a usability perspective?
• Is the API well documented?
• Is the proposed solution (UI) accessible?
• Is the API/UI intuitive to use?

Ethics and Morality

• Does this change make use of user data in a way that might raise privacy concerns?
• Does the change exploit behavioral patterns or human weaknesses?
• Might the code, or what it enables, lead to mental and physical harm for (some) users?
• If the code adds or alters ways in which people interact with each other, are appropriate measures in place to prevent/limit/report harassment or abuse?
• Does this change lead to an exclusion of a certain group of people or users?
• Does this code change introduce unjust impact on people, particularly those related to sensitive characteristics such as race, ethnicity, gender, nationality, income, sexual orientation, ability, and political or religious belief?
• Does this code change introduce any algorithm, AI or machine learning bias?

Testing and Testability

• Is the code testable?
• Have automated tests been added, or have related ones been updated to cover the change?
• Do the existing tests reasonably cover the code change (unit/integration/system tests)?
• Are there some test cases, input or edge cases that should be tested in addition?

Readability

• Is the code easy to understand?
• Which parts were confusing to you and why?
• Can the readability of the code be improved by smaller methods?
• Can the readability of the code be improved by different function, method or variable names?
• Is the code located in the right file/folder/package?
• Do you think certain methods should be restructured to have a more intuitive control flow?
• Is the data flow understandable?
• Are there redundant or outdated comments?
• Could some comments convey the message better?
• Would more comments make the code more understandable?
• Could some comments be removed by making the code itself more readable?
• Is there any commented-out code?

Experts' Opinion

• Do you think a specific expert, like a security expert or a usability expert, should look over the code before it can be accepted?
• Will this code change impact different teams, and should they review the change as well?

For more insights into code reviews go to awesomecodereviews.com.