Lin2/STM2: Port Lin and STM to QCheck2

[jmid]

Lin and STM are both based on the battle-tested QCheck module from qcheck-core.

The QCheck2 module however offers integrated shrinking, which should simplify the interface a bit, e.g.,

• by removing the need for a shrink_cmd function and
• by building on only one generator type QCheck2.Gen.t (as opposed to the current QCheck.arbitrary and QCheck.Gen.t mix)

For this reason, we should experiment with porting the libraries to QCheck2.

Note: This may hit and involve improvements to QCheck2's shrinkers, such as c-cube/qcheck#157.

[SitaGanesh]

Can i work on this issue?

[jmid]

You are welcome to give it a stab - this is open source after all! :slightly_smiling_face:

What's your experience with OCaml. the QCheck library, and the Lin and STM libraries? I'm thinking this may be a bit of a mouthful for a first-time contributor, depending on your experience with the above.

[SitaGanesh]

I am a bit familiar with the syntax of OCaml, and I know some concepts related to software testing. The Lin and STM libraries are among the tools I remember

[jmid]

I am a bit familiar with the syntax of OCaml, and I know some concepts related to software testing.

OK. In that case I would suggest

• starting by contributing to QCheck first as Lin and STM build on it - and this porting project requires knowing both QCheck and QCheck2 well -- see https://github.com/c-cube/qcheck/issues
• writing some tests that utilize the Lin and STM libraries first - to get working experience with the interfaces they expose before taking on a project of changing them -- see, e.g., #64

The Lin and STM libraries are among the tools I remember

Oh? I'm curious to learn where you have heard of these two libraries before? :thinking:

[SitaGanesh]

Thanks for the suggestions! I'll begin by contributing to QCheck and learning about the libraries. This will help me understand things better before working on the task.

I came across these libraries while exploring tools for testing, I just read the abbreviation and remembered it as STM for my academic.

[jmid]

Hm. Despite the same acronym, the OCaml qcheck-stm package (STM for short) is a state-machine testing library and has nothing to do with https://en.wikipedia.org/wiki/Software_transactional_memory

There's a description here: https://github.com/ocaml-multicore/multicoretests?tab=readme-ov-file#a-parallel-state-machine-testing-library and a short paper here: https://github.com/ocaml-multicore/multicoretests/blob/main/doc/paper.pdf

[SitaGanesh]

I will definitely refer to them, thankyou for the clarification Sir!

[SitaGanesh]

Sir @jmid, after going through the codebase and resources, I see there’s a lot to explore in this tech stack. It’s really interesting! I’ve started a tutorial on OCaml and the libraries. A small suggestion: could you provide a step-by-step guide for beginners on where to start contributing to this organization? What would that be?

And from the above discussion, I just wanted to clarify that my knowledge of these libraries is mostly theoretical. I’ve never implemented them in practice, so it’s taking me some time to understand these concepts fully.

[jmid]

Thanks! For this repository my recommendation in https://github.com/ocaml-multicore/multicoretests/issues/497#issuecomment-2553910942 still stands. I don't have the resources to provide a step-by-step guide unfortunately. :shrug:

As for the other ocaml-multicore repositories, I recommend asking on the ones that you would like to help out on.