Thanks. I suspect some of the Windows problems are indeed due to bogus assumptions in my draft tests, but at the same time, folks should be able to invoke subprocesses with Unicode values without needing extensive knowledge of platform specific Unicode handling arcana (whether that's *nix or Windows).

I've added Victor to the nosy list as well, since he'd previously expressed interest in implementing a cross-platform "force UTF-8" mode for 3.6 (akin to the default behaviour on Mac OS X), and I suspect these proposed test cases will be relevant to such a capability.