How do you deal with legacy code or code without tests in code review?

2 Use tools and standards to automate and simplify the review

Code review can be tedious and time-consuming, especially if you have to deal with legacy code or code without tests. To make your life easier, you can use tools and standards to automate and simplify the review process. For example, you can use code analysis tools to detect syntax errors, code smells, security vulnerabilities, or code style violations. You can also use code formatting tools to ensure consistent and readable code. Additionally, you can follow code review standards or checklists to guide your review and avoid missing important aspects.

3 Write tests or run existing tests to verify the code's behavior

One of the main challenges of reviewing code without tests is that you don't have a reliable way to verify the code's behavior. You can't rely on the author's claims or assumptions, and you can't easily spot bugs or edge cases. Therefore, you should write tests or run existing tests to check the code's functionality, reliability, and robustness. You can use unit tests, integration tests, or end-to-end tests, depending on the level of abstraction and complexity of the code. You can also use test coverage tools to measure how well the code is tested and identify gaps or redundancies.

5 Communicate your feedback clearly and respectfully

The final and most important tip for reviewing legacy code or code without tests is to communicate your feedback clearly and respectfully. Code review is not only about finding errors or flaws, but also about sharing knowledge, learning from each other, and building trust and collaboration. Therefore, you should avoid harsh or vague comments, and instead use positive and constructive language. You should also explain your reasoning, provide evidence, and offer suggestions or alternatives. Moreover, you should acknowledge the author's efforts, appreciate their strengths, and invite their feedback or questions.

6 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?