Hey, Buddy!

Thanks to github and their easy-to-use pull request UI, pre-commit code reviews have become much more common in the industry. For me, lightweight peer reviews are a requirement in any well-run development shop. Github certainly did not invent this style of review, but they have certainly help popularize the practice. Thanks, Github!

I have helped establish code reviewing throughout my career ever since seeing its positive effect at my first job, working on formal verification tools at Chrysalis Symbolic Design.

We did a few full formal code reviews at Chrysalis. They ended up being far too heavy and time-consuming. Mostly, we used lighter-weight techniques; handing around branches, textual diffs, and over-the-shoulder inspection. The tooling was primitive, but the value of these reviews was immeasurable. We were working on a product where the original developer was no longer part of the company; we were all learning a foreign code base with each change.

As we explored the code, we gradually learned how the parts fit. The buddy reviews helped validate our findings, but more importantly, helped spread that knowledge around the group.

The teaching aspect of code reviews proved far more valuable than critique. Yes, there is a chance that an expert will catch a fundamental flaw, but more important is the opportunity for non-experts to ask, “Why?” Buddy reviews help educate a team and let everyone become less reliant on “experts”.

I left Chrysalis having seen the power of buddy reviews and have helped promote adoption ever since.

If you aren’t yet using peer reviews, don’t fret. Just ask someone else to look at your code. Easy, right? Code review doesn’t always start with adoption by an entire organization. At Brightcove, I started with just one other developer. We started sharing code and it spread from there, organically at first and then finally was adopted by the entire group.

What follows are some simple guidelines that I brought to Brightcove; we used a similar philosophy at Carbon Design Systems and iPhrase.

Buddy Reviews

All checkins must be reviewed and approved by a peer prior to commit. The intent is to educate each other on different parts of our system and improve the quality of our code.

WHO can be a buddy?

Anyone who is able to understand and critique your changes. This usually means another engineer. Vary your reviewer from commit to commit – try and broaden the number of people understanding any one subsystem.

WHEN to buddy?

Before the commit. Every time, every change. A good time for review is while tests are running, although if there are failures, you will have to have your changes re-reviewed.

There is no excuse to skip the buddy review. If you are alone in the office or working remotely, you still need someone to review your changes. If you are working against a tight deadline, your changes still need review.

Buddy reviews do not always need to be face-to-face (though preferred). Email diffs or pointers to changed source files and discuss your modifications over the phone, IM, etc. Of course, if your commit can wait until the next day (most can), wait for a face-to-face review.

WHAT should a buddy ask?

  1. Do I understand the problem this change is solving?
  2. Is this the best/an appropriate solution?
  3. What cases are not handled?
  4. What impact could this change have on customers, other subsystems, optimizations, etc.
  5. Will this code behave differently with other OS, compiler, etc?
  6. What is the potential performance (compile/runtime) impact?
  7. Is the code clearly written/readable?
  8. Is it appropriately commented/documented?
  9. How has this change been tested?
  10. Has there been sufficient testing?
  11. Are there unit tests?

Some other thoughts on buddy reviews to get you started: