Lightweight Code Reviews A Lightweight Alternative to Inspections

In this article, we explore why almost no one does "proper" inspections and set up the case for lightweight peer code review. Try it. You'll like it!

In this article, we explore why almost no one does "proper" inspections and set up the case for lightweight peer code review.

The story begins

Two years ago I was not invited to a meeting with the CTO of a billion-dollar software development shop, but I didn't know that until I walked in the room. I had been asked by the head of Software Process and Metrics to come and talk about a new type of lightweight code review that we had some successes with.

But the CTO made it clear that my presence was Not Appreciated.

"You see," he explained, "we already do code inspections. Michael Fagan invented inspections and his company is teaching us how to do it." His face completed the silent conclusion: "And you sir, are no Michael Fagan."

"Currently 1% of our code is inspected," offered the process/metrics guy. "We believe by the end of the year we can get it up to 7%." Here Mr. Metrics stopped and shot a glace over to Mr. CTO. The latter's face fell. Whatever was coming, they obviously had had this discussion before.

"The problem is we can't inspect more than that. Given the number of hours it takes to complete a Fagan inspection, we don't have the time to inspect more than 7% of the new code we write."

My next question was obvious: "What are you going to do about the other 93%?" Their stares were equally obvious — my role here was to convince the CTO that we had the answer.

This story has a happy ending, but before we get there I have to explain what it means to "inspect" code because this is what most developers, managers, and process engineers think of when they hear "code review." It's the reason this company couldn't review 93% of their code and why developers hate the idea. And changing this notion of what it means to "review code" is what we've been doing at companies like this one for the last four years.

Michael Fagan — father of a legacy If you've ever read anything on peer code review you know that Michael Fagan is credited with the first published, formalized system of code review. His technique, developed at IBM in the mid-1970's, demonstrably removed defects from any kind of document from design specs to OS/370 assembly code. To this day, any technique resembling his carries his moniker of "code inspection."

Take a deep breath...
I'm going to describe a "code inspection" in brief, but brace yourself. This is heavyweight process at its finest, so bear with me. It will all be over soon, I promise. A code inspection consists of seven phases.

In the Planning Phase the author gathers Materials, ensures that they meet the pre-defined Entry Criteria, and determines who will participate in the inspection. There are four participants with four distinct roles: The Author, the Moderator, the Reviewer, and the Reader. Sometimes there is an Observer. All participants need to be invited to the first of several meetings, and this meeting must be scheduled with the various participants.

This first meeting kicks off the Introduction Phase where the Author explains the background, motivation, and goals for the review. All participants get printed copies of the Materials. (This important — it's not a Fagan Inspection unless it's printed out.) The participants schedule the next meeting and leave. This starts the Reading Phase where each person reads the Materials, but each role reads for a different purpose and — this is very important — no one identifies defects.

When the next meeting convenes this starts

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