Imagine an organization with the following practices: Commits code on GitHubRuns its CI/CD pipelines with GitHub ActionsRuns its production workload on KubernetesUses Google Cloud A new engineer manager arrives and asks for the following: On every PR, run integration tests in a Kubernetes cluster similar to the production one. It sounds reasonable.

The subject of testing is vast. It may seem simple from outside, but it’s not. For example, one may define testing as checking that the software is fit for its purpose. But it encompasses a lot more: for example, mutation testing verifies that assertions do actually assert. In this post, I’d like to touch some testing flavors, what’s their purpose and how they compare to each other. The need for testing In an ideal world, we wouldn’t need testing.

I have devoted a significant portion of my time thinking about designing and writing tests of all kinds. I believe my perspective can bring something to the table. In the rest of this post, I’ll follow the terminology proposed in the article.

Most of our day-to-day job is learned through mentorship and experience and not based upon scientific research. Once a dogma has permeated a significant minority of practitioners, it becomes very hard to challenge it. Yet, in this post, I’ll attempt to not only challenge that sometimes tests must be ordered but prove that in different use-cases.

Still working on my legacy application, and still trying to improve unit tests. This week, I noticed how much PowerMock was used throughout the tests, to mock either static or private methods. In one specific package, removing it improved tests execution time by one order of magnitude (from around 20 seconds to 2). That’s clearly abuse: I saw three main reasons of using PowerMock.

Maintenance projects are not fun compared to greenfield projects, but they sure provide most of the meat for this blog. This week saw me not checking the production code but the tests. What you see in tests reveals much of how the production code itself is written. And it’s a way to change things for the better, with less risks. At first, I only wanted to remove as much PowerMock uses as possible. Then I found out most Mockito spies were not necessary.

Even if you don’t like it, your job sometimes requires you to maintain legacy applications. It happened to me (fortunately rarely), and the first thing I look for before writing as much as a single character in a legacy codebase is a unit testing harness. Most of the time, I tend to focus on the code coverage of the part of the application I need to change, and try to improve it as much as possible, even in the total lack of unit tests.