> Before working on it, could someone give me idea to run whole test_asyncio
with and without C version Future easily?

asyncio uses loop.create_future() to create sockets.  I'd suggest you to create two base test classes: one that monkeypatches loop.create_future to return pure python Future in its setUp method; an another, that makes create_future to return a C version of the Future.

The derive some unittests from those base classes (which will effectively double the number of tests).

> And, which is master repository of asyncio? github? or hg.python.org?
If github, can I send separated pull request changing test_asyncio after
this patch is merged?

The master repo for asyncio is github, but since the C version won't be a part of asyncio (it will be checked in only in CPython source tree), I think it's fine to continue the work here, on bugs.python.org.