Migrate from AssertJ to AssertK

[Goooler]

AssertK is a fluent assertion library for Kotlin, which is designed with Kotlin idioms. It would be nice to migrate to that.

https://github.com/willowtreeapps/assertk

[paul-dingemans]

Currently I see no benefits of migrating ktlint from Assertj to Assertk. Most of the tests are based on ktlint's internal dsl for validating lint/format issues. That dsl is quite complex and might be simplified when using Assertk. I will mark the issue as parked, but if someone else would like to pick it up I am okay with that.

[Goooler]

That dsl is quite complex and might be simplified when using Assertk.

I see it too. Will take a look when I'm free of time.

[fnunezkanut]

imho kotest is more population in kotlin world and has more features of assertK

[Goooler]

AssertK's APIs are more familiar to users who are using AssertJ, Junit, Truth, and so on.

[paul-dingemans]

imho kotest is more population in kotlin world and has more features of assertK

This might really depend on your context. I have never seen it used in any Kotlin project that I have worked on. But as I mentioned in #2586 (comment) I see little value in rewriting it. I guess that 3000 out of 3100 test do not use assertThat directly. They are all wrapped inside Ktlint wrapper that facilitates unit testing of the rules.

Migrating to another assertion library only affects developers who are writing Ktlint rules. And to my knowledge there a no more than a couple of tens of users who have ever written/changed a ktlint rule.