Tag: technology

Use Test Plans to become a more effective Software Developer

Shipping high-quality software is the responsibility of each software developer. Not only are the days when handing untested code to the QA team for validation a common practice long gone, but many companies have also moved away from QA-based testing, making developers fully own the quality of the product. This creates a problem: how can you ensure developers do their due diligence and validate their changes? At Meta (a.k.a. Facebook), we use “test plans.”

What are test plans?

Test plans describe how authors tested their changes. They are an integral part of Meta’s code review process: the code review tool does not allow submitting code for review if the test plan is empty.

While it is common for test plans to say: “unit tests,” many are much more interesting and often include:

  • screenshots showing the UI before and after the change
  • videos showing the change in action
  • API requests and corresponding responses (e.g., JSON payloads)
  • dashboard snapshots from canary runs
  • terminal printouts
  • Funny memes – especially if the testing was not comprehensive or applicable (e.g., auto-generated code, changes to unit tests only, etc.)

Benefits of requiring Test Plans in commits

The most obvious benefit of requiring test plans is forcing developers to think about validating their changes. While not all test plans are comprehensive, most are decent.

Occasionally, test plans reveal that the code change does not work as the author intended. I once proudly included a graph hovering a little below 100% as my test plan, only for a reviewer to point out that my graph represented not the success rate, as I claimed, but the error rate.

However, one often overlooked benefit of requiring test plans is that they can be lifesavers when working with unfamiliar code.

Imagine you are tasked with building a new feature in a mobile app. While working on the feature, you discover that the API powering your app doesn’t return all the necessary information. You can ask the API team to add it, but they may not be able to accommodate your request on short notice. Perhaps it would be faster if you implemented this change yourself. The only problem is that you are not familiar with the backend code. You don’t know how to test it to ensure you didn’t break anything. In these situations, test plans can come in extremely handy. You can check the commit history of the code you want to change and see how developers who regularly contribute to it test it. In addition, checking past test plans may help you discover edge cases you need to consider. I successfully used this strategy multiple times to change an unfamiliar codebase I would otherwise be afraid to touch.

“My unit test coverage is 100%”

Test plans should not be considered a replacement for unit tests. As great as unit testing is, it is not always sufficient. Additional end-to-end validation helps confirm that the changes worked as intended outside of the isolation provided by unit tests and that they didn’t introduce unwanted behavior. I have seen (and caused) situations where my application wouldn’t start even though all unit tests were passing.

Call To Action

Including test plans in pull requests is not a common practice, let alone a requirement, in most companies or teams. Despite that, I encourage you to follow this practice. Your team members will notice it and may start doing the same if they find it useful. And even if they don’t, you will still benefit from this habit. Going the extra mile can help you find issues before they impact users. With time, it will get easier because you can reuse past test plans to validate some of your current changes. You may need to tweak them a little, but you won’t have to start from scratch each time.

Code is tax – have a good reason to write it

I once told software engineers on my team: “We’re not here to write code”. They were flabbergasted. But I strongly believe that our job is not to write code but to solve problems. It just so happens that for many problems, code is the best, if not the only solution.

We often get this backwards. We identify as software developers, we love writing code so we will write code whether it is needed or not.

Years of experience taught me to think about a problem before writing a single line of code. I usually try to answer two questions:

  • does this problem need to be solved now or, even at all?
  • can this problem be solved without writing code?

Surprisingly often, this exercise allows me to discover alternative ways of solving a problem that are more effective than writing code.

Not all problems need to be solved

Sometimes, assessing the importance of a problem is difficult, especially when done in isolation. The issue might seem significant, prompting us to solve it with code, only to realize after the fact (or maybe even not) that this work didn’t yield any noticeable improvement.

Consider a service making blocking I/O calls. Such a service won’t scale well. However, if it receives only a few requests per minute rewriting it to improve its throughput won’t have significant impact and is not necessary.

While many such problems will never require further attention, some might need to be revisited. If the service mentioned above needs to be integrated with a system generating many requests per second, fixing the blocking I/O calls could be a top priority. So, it is important to stay on guard and address issues that were initially punted if they resurface again.

Not all problems need to be solved with code

Many problems can be solved without writing any code.

There is an entire class of problems that can be mitigated by changing the configuration of the software. For example, if your streaming service occasionally crashes due to the Out-Of-Memory exception when processing spikes of data, reducing the maximum allowed batch the service fetches for processing could be a perfectly valid solution. Processing the spikes may take a little longer, but the overall processing time may not be affected in a noticeable way and the issue is fixed without changing the code.

Often, you can solve problems making careful design choices. Take user accounts on a website, for example. When deciding how users log in, there are two common options: using their email or letting them create a unique username. Coming up with unique user names can be challenging for applications with millions of users, so many of them suggest an available user name. Using an email as the user name is an elegant way of solving the problem of unique user names without writing any code. It also simplifies the account verification and password recovery flows.

What’s the problem with writing code anyway?

In my perspective, code should be treated like a tax. Just as taxes, once code is added, it is rarely removed. Every person on the team pays this tax day in and day out because each line of code needs maintenance and is a potential source of alerts, bugs or performance issues. This is why I believe that, as software engineers, we should opt for no-code solutions when possible, and write code only when absolutely necessary.