ScalaCheck VS sbt-crossproject

Regarding numbers 2 and 3, I believe you are describing "property-based testing"[0]. A Scala version of this is ScalaCheck and can be found here[1].

There appears to be at least one Rust library which claims to provide same, but I am not a Rust developer so cannot recommend any for fitness of purpose.

0 - https://hypothesis.works/articles/what-is-property-based-tes...

1 - https://github.com/typelevel/scalacheck/blob/main/doc/UserGu...

And the readmes and tutorials written for the major libraries are some of the best, and most concise out there. Seriously, even the old stuff, like scalacheck's guide is really good. Compare that to hypothesis. The hypothesis uses readthedocs, but other than the window dressing, much better. Try to find similar concise guides for major Java projects outside of spring boot. They're all external to the projects, published on Baeldung.

Write your test as properties that must be held, and let the framework generate random values and apply the function to thus values and compare the output by those properties. Take a look to ScalaCheck for that approach.

SBT. It's not because of the pseudo-scala config language, that looks especially alien next to braceless Scala 3 code. Or the weird symbolic operators. The big problem is correctness; in almost every project I've had to use spray-resolver because I've encountered weird bugs because SBT reuses the same dirty JVM. I really thing Drip would help here. I'll keep using SBT because it has the best Scala ecosystem support and great plugins like sbt-crossproject. It would also be great to be able to write build.sbt files in modern, regular Scala.