How do you do a code review?
Look for consistency in style (adherence to a style guide), functionality, and ensure unit tests and end-to-end tests were performed. Keep an eye out for security issues or maintainability issues. Deploying the code should be straightforward or well documented.
Page 307 of Terraform: Up & Running, 2nd Edition by Yevgeniy Brikman (O'Reilly), Copyright 2019, 978-1-492-04690-5 says code reviews should have 1) written documentation (on how to use the code and why it was written that way) 2) example code 3) code documentation.
Be respectful to the coder when requesting changes.
To learn more, see these postings: