Here's a rough and ready version using os.walk
:
import os
prefix = 'tests/unit'
for dirpath, dirnames, filenames in os.walk(prefix):
trimmedmods = [f[:f.find('.py')] for f in filenames if not f.startswith('__') and f.find('.py') > 0]
for m in trimmedmods:
mod = dirpath.replace('/','.')+'.'+m
print mod
__import__(mod)