Posts tagged haskell

Using types to unit-test in Haskell

⦿ haskell, testing

Object-oriented programming languages make unit testing easy by providing obvious boundaries between units of code in the form of classes and interfaces. These boundaries make it easy to stub out parts of a system to test functionality in isolation, which makes it possible to write fast, deterministic test suites that are robust in the face of change. When writing Haskell, it can be unclear how to accomplish the same goals: even inside pure code, it can become difficult to test a particular code path without also testing all its collaborators.

Fortunately, by taking advantage of Haskell’s expressive type system, it’s possible to not only achieve parity with object-oriented testing techniques, but also to provide stronger static guarantees as well. Furthermore, it’s all possible without resorting to extra-linguistic hacks that static object-oriented languages sometimes use for mocking, such as dynamic bytecode generation.

Climbing the infinite ladder of abstraction

I started programming in elementary school.

When I was young, I was fascinated by the idea of automation. I loathed doing the same repetitive task over and over again, and I always yearned for a way to solve the general problem. When I learned about programming, I was immediately hooked: it was so easy to turn repetitive tasks into automated pipelines that would free me from ever having to do the same dull, frustrating exercise ever again.

Of course, one of the first things I found out once I’d started was that nothing is ever quite so simple. Before long, my solutions to eliminate repetition grew repetitive, and it became clear I spent a lot of time typing out the same things, over and over again, creating the very problem I had initially set out to destroy. It was through this that I grew interested in functions, classes, and other repetition-reducing aids, and soon enough, I discovered the wonderful world of abstraction.

Four months with Haskell

At the end of January of this year, I switched to a new job, almost exclusively because I was enticed by the idea of being able to write Haskell. The concept of using such an interesting programming language every day instead of what I’d been doing before (mostly Rails and JavaScript) was very exciting, and I’m pleased to say that the switch seems to have been well worth it.

Haskell was a language I had played with in the past but never really used for anything terribly practical, but lately I think I can confidently say that it really is an incredible programming language. At the same time, it has some significant drawbacks, too, though probably not the ones people expect. I certainly wasn’t prepared for some of the areas where Haskell would blow me away, nor was I capable of realizing which parts would leave me hopelessly frustrated until I actually sat down and started writing lots and lots of code.