Kategory VS Kotest

Yeah, it has nice funcional capabilities and libraries (like Arrow[0]).

[0]: https://arrow-kt.io

Last but not least, Scala is currently the language with one of the best effect systems in my opinion (https://zio.dev/). Kotlin for example has copied the approach with https://arrow-kt.io/ which I think is great actually. But when comparing Scala and Kotlin here, Scala wins by a large margin, it is a completely different world. It's like building a highly concurrent system in Erlang vs C.

Of course, if you don't want to learn things like union types, traits/typeclasses and effects (similar to async/await but more powerful) you will be annoyed by Scala. But once you learned them, you can never go back.

In my own code, I started to use explicit error handling. I'm currently experimenting with Result (from https://github.com/michaelbull/kotlin-result) and Raise (from https://arrow-kt.io/).

Are there any more-or-less established functional crates in Rust (similar to Kotlin’s Arrow)?

I wonder how the community sees adding Arrow besides standard Kotlin language features. Is it something that's still considered useful or just redundant and causing more confusion?

You can define a function like context(EitherEffect) suspend fun MyType.bind(path: String)like the ones in https://github.com/arrow-kt/arrow/blob/b608a054a5318fe57d7055c35bb64a5effb053b6/arrow-libs/core/arrow-core/src/commonMain/kotlin/arrow/core/computations/either.kt

If you're using Kotlin, I'd highly recommend looking into the https://arrow-kt.io library. It's quite a bit more sophisticated than the Dart FP libs, and meshes well with Kotlin. They've got a great website, but even better is their engagement on the #arrow channel on the kotlinlang.slack.com Slack.

As you might know, Advent of Code will begin this Friday! If, like me, you want to have a go at solving the puzzles in Kotlin, I would like to share with you a little library I've developed to reduce boilerplate and solve the puzzles in a test-driven approach. It is based on Kotest, a modern and Kotlin-first test framework.

Kotlin testing with Kotest and MockK

As a matter of fact, in the previous examples, we have shifted a bit away from the TDD standards in the meaning that we test not only the operability of our code, but rather check if the code runs according to certain specifications (Given/When/Then). These specifications are our tests, and the syntactic sugar in the form of the possibility to give clear names to the tests using DisplayName and the grouping of the tests by a set of similar attributes helps us clearly formulate these specifications. There is an entire family of frameworks in different languages that allow us to create such specifications: for Java it is Spock, for Ruby—RSpec, and for Kotlin—Spek and Kotest frameworks. Below, I will go into more detail about them.

I've tried so many times. SO MANY. I love the idea of mutation testing. Even chatGPT couldn't help me. It just made up fake mutation testing frameworks to try. To me, pitest is dead. kotest is not mutation testing, but it's property testing is the next best thing I have found to revolutionize your unit tests.

The extensions are not particularly useful in this scenario because the described functionality can be incorporated into the Host class. On the other hand, they flourish in test frameworks like Kotest and enable the rapid development of useful add-ons like custom matchers. Extending third-party libraries with utility functions is another prevalent use case. In the next sections, we'll zero in on this specific aspect.

We're using Kotest for our unit tests and are quite happy with it.

Basic testing in Kotlin with Kotest built for kotlin specificatlly (upcoming)

Here you are: https://github.com/kotest/kotest/issues/189