A test suite is a very useful thing, it would be great to include it in the pypi release tarball. That way people who download and build the release can run the tests to ensure the library is working.
Linux distributions, such as Debian, base their packages of Python modules on the pypi release. This means the test suite can be run when building a Debian package, and so catch mistakes in the packaging or errors introduced into dependencies.
I've written some more on this topic on the Debian Python mailing list: https://lists.debian.org/debian-python/2016/04/msg00074.html
