Exterminators Week 6 - Code Reviews

Reading time ~3 minutes

This week I helped perform many code reviews. I think code reviews are a great way for teams to communicate. This is the best time to ask deep questions about the code and share information throughout the team.

Code reviews have become a standard practice for many teams I work with. While on the Exterminators I have had the privilege to work with others who have different code review style than my own.

For me code reviews are a conversation about the code being changed and the surrounding system. Common code review themes include:

  • Learning and sharing ideas
  • Understanding the affected logic


I think a review has been successful if you have learnt something new.

One team I was on included two people on every review, an expert and a learner. The expert would be intimately familiar with the system being changed and the surrounding code. The learner could be anyone else and typically the learner would be someone new to the codebase. The expert could user their knowledge to guide the changes and avoid issues. The learner would help by being a fresh pair of eyes with a different perspective.

Learning from reviews has helped developers work outside their area of expertise. Over time the learners will better understand the code and can start contributing. It was not long before the learners could contribute alongside the experts for any given project.

Code reviews can be used to align architectural decisions. On a recent project we shared a refactoring with the team using code reviews. The early reviews had more team members to build consensus for the direction we were headed. As the changes progressed every member of the team was able to see the new changes applied. Knowing what was happening helped the team work together toward the common goal.

Reviews can be a great place to learn a new coding technique or library. I learnt some nifty ways you can use Moq lately from a code review and since been sharing them with the rest of the team. The team has also been great at letting me know when I get carried away using a new technique. I have been using NUnit’s features for data driven tests heavily which for some team members is hard to read. This was valuable feedback; I was able to work with the reviewers to update the code so it was easier to understand.


Code reviews are one of the few times you can evaluate code for logical issues. Humans make horrible compilers and computers cannot truly understand how code interacts.

Logical issues are problems with the decisions behind the code.

  • Algorithmic flaws.
  • Using the wrong constant value.
  • Confusing classes.
  • Misleading comments or parameters.

Stopping logical issues is important. Your code can compile and pass all the unit tests, but with logical errors it is still broken. The longer logical errors survive in a codebase the more likely they are to mislead other developers who then accidentally cause defects.

Unlike other development activities, code reviews provide a great opportunity to step back and look at the code to find logical issues. Going through the code one line at a time and looking for connections is a great way to find relationships which do not make sense.

Behind the logic for the code is a whole series of the decisions the other developer has made. Talking about those decisions can help validate them or expose other assumptions. The less I understand the code the more important it is for me to be able to follow the developer’s reasoning.

A Conversation

There are many different code review styles, but my favourite is to treat code reviews like a conversation.

Code reviews are a two way street. Both the author and reviewers should actively participate and ask questions. Together the author and reviewers can learn from one another and better understand the code being changed.

What was the last thing you learnt from a code review? Did you understand how the bugfix you reviewed fixed the problem it was intended to solve?

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