My software runs on Windows, Linux and MacOS. The same Python testing code runs on all three platforms. I mostly dislike Python but I can't think of anything better for this use case.

You might consider Deno with Typescript... it's a single exe runtime, with a self-update mechanism (deno upgrade) and can run typescript/javascript files that directly reference the repository/http/modules that it needs and doesn't require a separate install step for dependency management.

I've been using it for most of my local and environment scripting since relatively early on.

I don't touch Windows so I would not know.

> The same Python testing code runs on all three platforms.

I have no objections to Python being used for testing, I use it myself for the end to end tests in my projects. I just don't think Python as a build script/task runner is a good idea, see below where I got Claude to convert one of my open source projects for an example.