rescript-test VS rescript-schema

Besides bindings for JavaScript libraries, there is rescript-test - a lightweight test framework written in ReScript for ReScript. I have heard that some people like it, but for me, it lacks coverage output and Wallaby support.

As soon as you need to change the name or something, delete a field, or change a field… you’ve broken the API. This means you first need to change your Lambda(s) that use this new data, and ensure your unit tests (using ReTest) pass, and your integration tests (using Mocha & JavaScript) which invoke your Lambdas directly on a QA server still work.

To do that, we’re using rescript-test, which feels natural to those used to Jest, Mocha, etc. The only main difference is using testAsync vs test for async code, and having to define your own assertions vs. “Jest/Chai has ALL THE THINGS”.

I have seen something like this in real code, and it led to bugs. ReScript won't allow you to do this, you will have to parse the JSON with a library like rescript-schema (it's like Zod).

Hello, I’m Dmitry Zakharov, a Frontend-engineer at Carla and author of rescript-struct. After using ReScript for two years, of which 9 months are in production, I’ve gotten some insights about testing I wanted to share. I use ReScript not only for FE but for different areas, so if you’re a BE engineer or create a CLI tool, this article will also be useful for you.