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?
• Was a framework, API, library, service used that should not be used?
• Was a framework, API, library, service not used that could improve the solution?
• Is the code at the right abstraction level?
• Is the code modular enough?
• Would you have solved the problem in a different way that is substantially better in terms of the code’s maintainability, readability, performance, security?
• Does similar functionality already exist in the codebase? If so, why isn’t this functionality reused?
• Are there any best practices, design patterns or language-specific patterns that could substantially improve this code?
• Does this code follow Object-Oriented Analysis and Design Principles, like the Single Responsibility Principle, Open-Close Principle, Liskov Substitution Principle, Interface Segregation, 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

• If this change requires updates outside of the code, like updating the documentation, configuration, readme files, was this done?
• Might this change have any ramifications for other parts of the system, or backward compatibility?

Security and Data Privacy

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

Performance

• Do you think this code change will impact system performance in a negative way?
• Do you see any potential to improve the performance of the code?

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?
• Does it have enough automated tests (unit/integration/system tests)?
• Do the existing tests reasonably cover the code change?
• Are there some test cases, input or edge cases that should be tested in addition?

Readability

• Was 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 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 committed?
• Will this code change impact different teams?
• Should they have a say on the change as well?

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