I've been thinking that on the scope of NEP-18 it will become very important for us to have tests running on PRs with CuPy as well. I know this may be problematic due to the need for CUDA-capable GPU(s).

Is there any discussion towards that end already? Given the resources (mostly hardware, I assume), I'd be happy to help set it up and get at least some testing in place so that we can start getting more confident. If I recollect correctly, I think I've seen some of the existing CuPy tests are failing in upstream.