I like this, though I don't like using the platform module here and would prefer sys.platform to be canonical (until there's a need to differentiate - e.g. some tests coming for Windows ARM32 will need to be more specific).

In general, I'd like fewer tests to be platform specific and make more functionality "just work" across platforms, or at least platform families. I feel like more precise skips don't actually help with that - they make it too easy to say "this functionality just doesn't work here" instead of trying to make it work.