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@neutrinoceros @astrofrog @nstarman - tagging as this is part of my GSoC 2026 proposal. Same approach as #19410 (time) and #19407 (cosmology) - direct pytest-based tests calling the Cython extension interface, no standalone C files.

Note is that this is "competing" with #19470
We could very likely merge both contributions, but the second one to go in might need some additional effort to harmonize the sum.
@dhruv1955, I see you already have a couple PRs merged, so I would lean towards prioritizing #19470 and come back to this one later. Would that be okay with you ?

@neutrinoceros Thanks for the context. That works for me - happy to wait and harmonize once #19470 lands if needed. Let me know if there's anything you'd like me to adjust in this PR in the meantime.