If you modify some modules in hwp5 package in the pyhwp/ directory, you can test the modification with the hwp5proc script in the bin/ directory.
You can test the hwp5 package by executing bin/test-core, but it’s just a quick test and not a complete test suite. If you want to run a full-blown test suite, run tox, which tries to test pyhwp in various virtualenv-isolated python platforms, including Python 2.5, 2.6, 2.7, Jython 2.5 and PyPy.
$ bin/buildout
(...)
$ vim pyhwp/hwp5/proc/__init__.py
(HACK HACK HACK)
$ bin/test-core
$ bin/hwp5proc ...
$ bin/tox