Making Code Walkthroughs Actually Work: A Practical Review Checklist

Why Bother with Code Walkthroughs?

Code walkthroughs sound great in theory, but they're often the first thing to slip when deadlines loom. Yet the numbers are compelling: a well-run walkthrough can catch anywhere from 30% to 70% of the deep logic and design errors that unit tests miss. That's a lot of bugs that never make it to production.

But the benefits go beyond fewer defects. When a developer explains their code to a small group, they often spot their own mistakes mid-sentence. The reviewer gets exposed to new techniques or algorithms. The team builds a shared understanding of the codebase, which pays off when someone else has to modify that code six months later.

I've seen teams treat walkthroughs as a formality—a quick skim before hitting approve. That's a wasted opportunity. The real value comes from being systematic and thoughtful about what you're looking for.

Set the Ground Rules Early

The best walkthroughs start before the code is even written. If you're doing a significant design, open a merge request as soon as you have a branch, even if it's just a skeleton. That way, the review doubles as a design review. You can get feedback on the approach before you've invested days in implementation.

Keep the review window tight. Aim to give feedback within three working days. After that, the context fades and the developer has moved on to something else. A quick turnaround also signals that you respect the reviewer's time.

What Makes a Good Review Session?

• Keep each MR focused on a single task or tightly related changes. Don't bundle a refactor with a feature unless they're inseparable.
• Limit the size. Reviews of 200–400 lines are manageable. Anything larger is a slog and you'll miss things.
• Require tests. If the code doesn't have tests, the review is incomplete. The reviewer shouldn't have to guess whether the edge cases are handled.
• Use a WIP prefix for unfinished work so reviewers know not to spend time on it yet.

If your CI is failing, don't bother reviewing. Fix the build first. Reviewing broken code is like proofreading a draft with missing paragraphs—you'll waste effort on things that will change.

What to Look For: Test Coverage

Tests are the safety net for every change. When reviewing, ask yourself: Is this code actually testable? Are there hidden dependencies that make it impossible to instantiate in a test harness? If the code is a mess to test, that's a red flag.

Check that the tests cover the happy path and the unhappy path—exceptions, boundary conditions, invalid inputs. Is the test coverage staying level or dropping? Are the tests meaningful, or are they just exercising the code without asserting anything useful?

One specific thing I always look for: array index out-of-bounds errors. It's a classic bug that unit tests often miss, especially in languages without built-in bounds checking.

What to Look For: General Code Quality

Beyond tests, the review should focus on whether the code is clean, modular, and maintainable. Some questions to keep in mind:

• Does the code do what it's supposed to? Is the logic correct?
• Is it as modular as it could be? Could you break that big function into smaller pieces?
• Are there global variables that could be scoped differently?
• Are there commented-out blocks that should just be deleted?
• Are loops properly bounded? Is the termination condition clear?
• Could any of this be replaced by a library function that's already battle-tested?
• Are there leftover debug logs or print statements that should be removed?

These are the bread-and-butter issues. They don't require deep architectural insight, but they add up. A codebase full of small sins becomes a nightmare to maintain.

Security: Don't Forget the Obvious

Security reviews often get treated as a separate discipline, but for a lot of teams, the code review is the only security check before production. So look for the basics:

• Are all inputs validated? Type, length, format, range—any of these can be exploited if unchecked.
• Are third-party calls handling errors properly? A caught exception is better than a crash, but swallowing an error is just as bad.
• Are outputs encoded? This is especially important for web apps—XSS is still a top vulnerability.
• What happens with invalid parameters? Does the code handle nulls, empty strings, or out-of-range numbers gracefully?

You don't need to be a security expert to spot these. A simple checklist goes a long way.

Documentation: The Unsung Hero

Good code is self-documenting, but that's not always enough. Check that every function has a comment explaining what it does and why—not just what the code does line by line. The 'why' is the valuable part.

• Are unusual behaviors or edge cases documented?
• Is the use of third-party libraries documented? Which version, what for, any known quirks?
• Are there any unfinished sections? If so, are they marked with TODO or similar, or should they be removed?

If a reviewer can't figure out what a function is supposed to do, that's a problem. If they can't figure out why it exists, that's a bigger problem.

Readability and Maintainability: The Human Factor

Finally, the most subjective but crucial part: is the code easy to read? Naming matters. A variable called 'data' tells you nothing; 'userList' or 'pendingOrders' tells you something.

• Do variable and method names clearly describe their purpose?
• Are comments explaining the intent or business rules, not just restating the syntax?
• Can you quickly grasp what a method does just by reading it?
• Are error messages clear enough that a user or developer knows what went wrong?
• Is there any redundant or duplicated code that could be factored out?

Readability is hard to measure, but it's the difference between a codebase that's a pleasure to work in and one that's a constant source of frustration. A fresh pair of eyes is often better at judging this than the author, who has all the context in their head.

Making the Process Stick

To make walkthroughs a habit, you need more than good intentions. Use merge requests as the vehicle. Automatically assign reviewers based on an OWNER file for each project. Set up notifications so reviewers know when they're needed.

Keep the conversation tied to specific lines of code. That's where the context lives. When the author addresses a comment, they should reply so the reviewer knows it's been handled. The reviewer should be the one to resolve the comment—don't let the author mark their own homework done.

Once all issues are resolved, the reviewer approves the MR and it gets merged. Simple.

Track Your Metrics

You can't improve what you don't measure. Keep an eye on a few key numbers:

• Lines of code changed per MR
• Average time from MR creation to merge
• Number of MRs merged per day
• Review comments per file

These metrics will tell you if your review process is speeding things up or slowing them down. If reviews are taking too long, maybe you're reviewing too much code at once. If you're seeing few comments, maybe reviewers are being too lenient.

Code walkthroughs aren't a silver bullet, but they're one of the cheapest ways to improve quality and spread knowledge across a team. With a little structure, they can become the most valuable part of your development workflow.