Code Review


Teaching: 5 min
Exercises: 10 min
  • How can I tell when software is ready to be integrated?

  • How can I share knowledge within my team?

  • How can I be more productive when I’m actually writing code?

  • Describe three benefits of code reviews.

  • Explain the difference between pre-commit and post-commit review.

  • Explain what pair programming is and why it improves productivity.

  • Explain when pair programming is best used.


Pair up with someone who is comfortable in the language you are using in your project. Give them a page of code that you are currently working on to read, and read carefully through a page of the code that they are working on.

  1. What can you not understand about their software without more context?
  2. What can you understand, and how useful is feedback on that?
  3. Did they use any features of the language that you haven’t seen before or don’t use?

Pair Programming

Solve the two programming challenges below using pair programming. Switch roles for the two exercises.

Non-Decreasing Sub-Lists
Given a list of numbers, return a list of the sums of each non-decreasing sub-list. For example, if the input is [1, 2, 3, 3, 1, 5, 6, 3, 1, 2, 3], the output should be [9, 12, 3, 6].
Rectangle Overlay
Given two rectangles, each defined by the four values [x0, y0, x1, y1], return the rectangle representing their overlap. Assume all coordinates are integer. For example, if the inputs are [0, 0, 2, 2] and [1, 1, 5, 3], the output should be [1, 1, 2, 2].

Key Points

  • Code review is the most cost-effective way to find bugs known.

  • Use pre-commit review.

  • Review code after all mechanical checks have passed.

  • Keep changes short enough to be reviewed in less than an hour.

  • Use code review to share knowledge within the team.

  • Pair programming is the practice of having two people share one computer while writing code.

  • One person is the driver (typing) while the other is the navigator (watching and commenting).

  • Pairs should switch roles periodically.

  • Pair programming helps spread knowledge.

  • Pair programming is particularly useful for onboarding and difficult tasks.