Steel Vellum, part 1:

The worst way to build software

Sometimes, I just want to code something – anything. Like many (if not all) developpers, I have a virtual drawer full of half-finished apps, repos left untouched for years whose last commit message is an unhelpful “WIP”, and domain names still parked long after their initial pun stopped making sense. Today, I’d like to pick one of those unfinished projects and revisit it.

Back around 2016, I started a Rails app cryptically named Ankran Nembo; it was supposedly a character creation app for the D&D campaign I had started, but more importantly, it was a toy project to try out the brand new version of Rails at the time – Rails 5.0. I have good memories of working on this application and experimenting with different techniques, but I don’t feel like salvaging any of it (except for one thing). So instead, let’s start over from scratch, but in the same spirit.

However, there is one problem – if we were to build an application, we wouldn’t be able to start coding right now. Doing things properly would mean thinking about user interactions, UI, and probably spend some time in HTML+CSS land first. And I want to code now, not later! So, instead of a full application, let’s focus on coding some kind of character creation engine – a library with which to build a full app later.

A word of warning! In real life, I would strongly advise against such an approach. Building the things you think you’ll need before even knowing what it is you actually want to do is a sure way to fail – or, at best, to build a working but irrelevant piece of software. I guess that there are situations where such a bottom-up approach makes sense, but unless you’re a very large and fragmented company, or work in a very constrained industry, this is the kind of things only Architecture Astronauts do. And please, don’t be an Architecture Astronaut.

Still, let’s pretend that we have very good reasons for going for a library instead of an application. A “library” can be as simple as a require’d Ruby file, but the most common way to package and distribute a librairy is by organizing it into a gem. So let’s do that – let’s build a gem, which will provide a character creation engine for Dungeons & Dragons, 5th edition. It will give us Ruby classes and methods to create a new character, set its game characteristics (such as race, class, attributes, etc.), and maybe even handle game mechanics such as dice rolls or experience points.

As an exercise, we’ll also try to have a radical use of BDD and TDD, in a “London school” way – albeit with little to no mocking, if possible (because I don’t like mocks that much anymore). This is the part from the Ankran Nembo app that I want to cannibalize: a long “integration test” that provided a nice example of the code we wish we had. We can use it as our “outside in” entry point, and let it drive the design of our library’s API.

So let’s get to it! First, we’ll need to set up our workspace: the gem files and directories layout, and the test runner. Then, we’ll start BDD-ing our way to a full-fledged D&D5 character creation library.

Next: Arranging atoms by hand