Improving software delivery in every organisation

Code reviews using the pull request workflow

As developers we always appreciate a second pair of eyes and an extra brain. The eyes are really helpful for catching that extra whitespace you might have missed. The additional brain power might help you solve a problem in your code with 5 fewer lines. All of this results in better code and more collaboration.

A way of formalising code reviews within your organisation can be the pull request workflow, which aims to encourage regular code reviews with minimal disruption to your productivity, while gaining tremendous value.

Why code review?

**Knowledge Share**

If you're new to an existing project, what better way to get valuable insight to the workings of it than getting someone familiar to have a look over your changes. It's really difficult to sit and read through the many lines of existing code to fully understand what is available for you to use. They'll have used existing functions a lot more than you, and will help to reduce code duplication, between you there might be a more efficient combination.

The code review encourages the start of conversations that lead to improvement of the overall codebase, sharing of best practices and experience from both the reviewee and reviewer.

It's important that reviews are treated as a positive tool. While it's easy to be defensive of your work there's probably a reason a reviewer is suggesting an alternative. However the reviewee should feel comfortable to start a discussion about suggestions provided, it's a good chance to learn.

Developers shouldn't fear having their code picked over as comments provided should be constructive and it allows to them to gain real insight from their peers. Likewise, a reviewer should always feel comfortable providing constructive criticism if they feel it will lead to improvements.

**Visibility**

You may not just be a new developer joining an existing project, but in fact a new starter to the organisation. Having frequent code reviews is a great onboarding mechanism to get new starters involved in the process early on, helping them become familiar with alien codebases.

More often than not, they'll also have new ideas, or other experiences that you can benefit from. Making the code review process as transparent and as open as possible will only encourage this. It also doesn't restrict the conversation to single teams, but the wider organisation can always input too.

**Standards**

Code standards aid in readability and maintainability of code. Sometimes standards can come in written form—a large set of rules to follow—but other times they can be unwritten rules that you'll only really learn the more you develop within an organisation.

This is where that extra set of eyes come in handy. Ensuring that standards are followed doesn't require much brain power, but they are often easy to miss, especially if you're unfamiliar with them.

Catching these violations early on save time in the long run and allows everyone to be on the same page, ensuring good readability. Also the opportunity to open conversations around the standards themselves. Whitespace vs tabs…ducks

**Testing**

While a reviewer is normally checking over implementation code, a review offers the opportunity to ensure good practices have been followed while developing code, for example Test Driven Development (TDD). It's important to make sure tests are present as part of a review if this is a practice your organisation adheres to.

Tests, hopefully, allow the reviewer to follow the design of the implementation while also opening up another area for improvement. Reviews are a great way to ensure that the test provided are valuable and efficient. An important question to ask here; do the tests cover all the changes?

**Catching bugs**

Having another developer look over your work also provides an opportunity to catch any bugs you may not have noticed. While you might have a wonderful green test suite, a peer might be aware of another edge-case within the project that would otherwise has slipped by.

**Readability of code (comments not required…)**

At Made, we feel that if code isn't understandable without comments then this represents a smell. While it's common to see this crop up as a suggestion, is it really required if your functions and variables are clearly and consistently named throughout and have obvious and sensible data returned. Comments can provide value in some cases but they should never be a hard requirement for a code review for us.

**Checklists not required?**

While some of the above may look like a checklist it's not. We're trying more to present some best practices for code reviews, not rules that you have to follow.

We'll dive deeper into this idea as we expand on the value we derive from having adopted a Pull Request Workflow. Some of the things we've covered above can be easily automated to make code reviewing more valuable as a result of this.

Pull request workflow

Pull Requests (PRs) allow for a standard and efficient way of doing code reviews within an organisation. Most popular tools these days, such as Github or Bitbucket offer features that allow for easy adoption of the pull request workflow.

Adopting the flow

PRs revolve around the idea of using dedicated branches for small feature sets. The branches of work are then submitted to your source control tool (we'll use Github from here on in our examples), and are opened up for review amongst your team. Only when the majority of people involved are happy with the work, will it then be merged into your master branch.

Branches
Working in isolated branches reduces the risk of conflicting with other developer's work. By not working in master, you can remain focused on your goal rather than constantly having to pull in others code.

Single Responsibility Pull Requests
The core idea behind this area is that the less code there is to review the more valuable the review will most likely be. Small features covering only a single area allow for a hyper-focused review and clear understanding of what's trying to be achieved.

A reviewer can easily tell if the tests are present, valuable and covering these small chunks. Working in this style makes it easier for the reviewee themselves to write the tests and feature.

Short lifespans
A great way to avoid merge conflicts with other features and stale code is to impose a completely artificial lifespan on a PR. Whether it's a day or just 15 minutes making sure these don't hang around in limbo is an efficient way to maintain momentum on a project.

If more work arrises out of a review don't just stop the conversation, move it out to an issue or multiple issues and assuming everything has been signed off merge the PR. This allows for more time to be spent on the conversation and potentially more opinions to be provided and more thought around the area.

Sign off
While it can be tempting to review your own work if others are busy… don't. This would render the whole process pointless, as remember that it's the extra eyes and brain power you were after in the first place. It would be equivalent to working directly on the master branch.

Try and encourage a culture within the organisation where people are available to comment on PRs as they're submitted, even if they're working on a different project. This encourages having all repositories on Github, and their PRs open to the organisation.

Tooling the flow

We've talked about code standards and tests as part of your review process. These usually follow codified rules that can easily be automated with modern tools and services.

Using your platform fully
Knowing how to leverage your platform for the easiest adoption of this work style is a lot simpler than it may seem at first.

Minor things such as having a clear and brief title and an accompanying description explaining the feature can make it much easier for the reviewer to quickly grasp the purpose of the PR. This can allow them to assess if they have relevant input or want to involve others and also that the feature matches the description provided.

Keeping the conversations around reviews and PRs within the PR itself is the best way to ensure you don't lose any knowledge that surfaces. While it can be easy to take the conversation offline, to email or to Slack anyone who comes along after will be missing potentially vital context.

Tests and code standards
Github, Bitbucket and other platforms allow integration with 3rd party services or your own Continuous Integration server.

These can be used for automatically running your test suite whenever a pull request is created and updated. This gives constant feedback to the reviewers of a PR, helping them know tests are passing, meaning they don't need to pull down your code and run the tests themselves.

The same can be done for code standards. Linting services are available that can be integrated directly into Github.

All of these integrations mean the reviewers can focus on the feature being developed and best practices around the implementation of that code, which is difficult, or impossible to automate.

Notifications
Github has notifications built into their PR functionality. In its simplest form it sends emails for when a PR is created and also when comments are made.

Integration with chat applications, such as Slack, can be added to your Github organisation to give even faster notifications when PRs are ready for review. This can help you have short lived PRs. When PRs are merged in notifications are sent too.

Optional extras
Github allows protecting branches meaning you can lock down master to avoid anyone pushing to it accidentally. More usefully however, it also allows for PRs to only be merged if the tests and/or linting is in a passing state.

While not essential, adopting these extras can help with keeping master safe and secure from accidental commits.

Visibility

Having the ability to look back and see who introduced a feature and the conversation surrounding reviewing it is a valuable way to foster knowledge sharing. If someone is looking to develop a new similar feature or improve upon the original, they can see from the description and conversation why the feature was implemented in this fashion.

We believe using code reviews and pull requests in tandem gives you the most value in terms of time, knowledge shared and potential cost to clients.

The buy-in to adopt this workflow is far less these days because the tools make it far more accessible to the majority. It can be rolled out across a team, a project or the entire organisation.

About the Author
David Winter
Reliability Engineer at Made Tech. Code, coffee, cake and gin. In no particular order.
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About Made Tech

Our mission is to improve software delivery in every organisation. We work with our customers to deliver modern applications and help them move to a faster, leaner, and more agile software delivery model.