Sometimes I review code and find some nitpicking issues like trailing white spaces, and missing new lines at the end of files, and they annoy me. I feel this is something that automatic tools should catch, but regardless of whether I should comment that on PR or not, I’d like to elaborate on why it bothers me.

This was a long time ago, circa 2014, I was working on a distributed system. This system was in charge of scanning and monitoring ERP servers, and its architecture was comprised of a main server (a web service), and several sensors which were other agents (in charge of the specific scanning and monitoring). These sensors reported the results back to the main server which contained all the data to display to the users.

It looks like there are a lot of opinions or assumptions about unit tests and code coverage, most of them confusing of biased in several ways. For example, I've heard or read things like "this is fine, it has X% coverage", or "checking for coverage on pull requests doesn't help", or "dropping the coverage level is not an issue", and many more of the like.

This article aims to shed some light on the issue of unit testing with and code coverage. Hopefully by the end of it, we'll get an idea of which of the previous statements are right and which are wrong (spoiler alert: they're all wrong, but for different reasons).