promote logger and writer mock objects from pathfinder utils

[bob-carpenter]

Summary:

There are some generally useful testing classes in src/test/unit/services/pathfinder/util.hpp that'd be useful higher up. At that point, they should be renamed to something like mock_writer and mock_logger.

Description:

Also add doc.

Current Version:

v2.32.2

[kaifkh20]

Is this issue still open?

[mitzimorris]

yes it is still open.

it looks like this is your first time contributing to Stan. a few requests

• please read the Stan developer process and guidelines, start here: https://github.com/stan-dev/stan/wiki/Introduction-to-Stan-for-New-Developers
• please ask questions! especially of the Stan devs who worked on Add Pathfinder and Multi Pathfinder #3123 in order to understand what they're looking for here.

[ChehakTrehan]

Hii @bob-carpenter is this issue still open? I would like to work on it

[bob-carpenter]

I don't think anything's been done for this yet. In fact, I'm not entirely sure what I was asking for here. So it'd probably be best to start by clarifying the issue a bit. @andrjohns and @mitzimorris and @SteveBronder---you've been working on a lot of the Stan services layer so will probably have the best take on what to do here.

[mitzimorris]

is this a good first issue?

I'm not sure what this issue is about either, but I do know that writing unit tests for any part of the stan::services layer is quite challenging. a first step would be to review all of the "utils.hpp" files under stan/test/unit as well as tests for stan::services::sample to see what has been mocked up across the unit tests and what is missing.

@SteveBronder just did another refactor of Pathfinder - maybe he can comment.

I'm working on a PR now on the Stan callbacks, and am writing unit tests which would greatly benefit from something like this.

[SteveBronder]

Those classes are a little nasty and made mostly for some simple cases. I think we if we need mock writer / callbacks at some point we can pull them out and clean them up, but for now idt this is an issue.