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Not too long ago I ordered the free book Best Kept Secrets of Peer Code Review by Jason Cohen. Jason is the man behind the CodeCollaborator code review tool – Go figure. The book has it’s obvious marketing points, but that doesn’t detract from the excellent content.

Cover for best kept secrets of peer code review

In the book Jason writes about the benefits of Code Review – common practices, pitfalls and benefits. He’s concise, easy to follow and the book is an enjoyable read. I took away a lot from the book. There are a ton of “golden nuggets” many of them worth noting:

Code Review Benefits

  • Code reviews catch bugs before they go out the front door.
  • Team knowledge (like best practices, common errors, or standards) is spread quickly when performing code reviews.
  • Code review is an excellent method for bringing outsiders up to speed on code.

Code Review Principles

  • Defects per line of code is an unreliable metric.
  • Omissions are the hardest defects to find.
  • Hard code has more defects: The more complex the code gets the more defects you should expect to find.
  • The more defects the better: If more defects are found in development and in review, then less defects make it to the customer.

Code Review Management

  • If quantity of defects is used in performance evaluations, developers do not have incentive to open defects.
  • You must have a quantifiable measure of success or else you cannot know if your review process is making a difference.

Review Best Practices

  • The longer you take in review, the more defects you’ll find: this tops out at the hour and a half mark, and one hour is the optimal amount of time.
  • Inspection meetings need not be in person to be effective.
  • Review code in small batches: Anything below 200 lines produces a relatively high rate of defects, often several times the average.
  • A reviewer will be unable to review more than 300-400 lines of code before they experience a performance drop.
  • Large gatherings of multiple developers are no more effective than one-on-one reviews. In fact, in certain circumstances it is far less effective.

Interesting Facts

  • A cost or ROI can be attached to code review.
  • In one case a software company measured the reduced calls to customer support as their code review ROI. Over a few years they reduced their support calls from 50,000 to 20,000 per year even with a 2-fold increase in sales. Their estimated savings was $2.6 million dollars.

If you like what you read here, go order the book it’s free, seriously who doesn’t like a free book? You don’t even have to pay for shipping! Why haven’t you ordered yet?