rescript-jest VS rescript-stdlib-vendorer

Another popular option is to use bindings for Jest. However, in my opinion, Jest is a monstrous combine that is slow, has a hacky mock system, bad ESM support, and purely tries to mimic DOM API with JSDOM. AVA literally doesn't have any of these. Also, the available Jest bindings don't allow doing multiple assertions per test, which is often useful to me.

In order to write tests in ReScript, and thus test your code directly, you can use bs-jest, which provides ReScript bindings to Jest. If you prefer, you can also use the slightly less mature bs-mocha. You can also test the generated JavaScript or TypeScript files with no extra configuration.

~/rescript-project-template/src/Demo.res:1 Found "Js" module usage. Use the vendored standard library instead. Read more at: https://github.com/DZakh/rescript-stdlib-vendorer

One problem is that it suggests creating A.res, which is publicly available from other application parts. It’s usually fine for FE apps, but for developing BE and CLIs, I prefer to follow the hexagonal architecture by creating the implementation inside the Main.res and passing it to other modules via function arguments. Once again, an example from rescript-stdlib-vendorer: