UnitTests --------- Portage has some tests that use the unittest framework that ships with python (2.3-2.4ish) Tests have a specific naming convention. in tests/ there is a runTest script that invokes tests/__init__.py This init looks at a hardcoded list of test dirs to search for tests. If you add a new dir and don't see your new tests, make sure that the dir is in this list. On the subject of adding more directories; the layout is basically 1 directory per portage file at this point (we have few files, and even fewer large files). Inside of the dir you should have files of the form test_${function}.py. So if I was to write a vercmp test, and vercmp is in portage_versions. tests/portage_versions/test_vercmp.py would be the filename. The __init__.py file now does recursive tests, but you need to tell it so. For example, if you had cache tests the dir format would be something like... tests/cache/flat_hash/test_foo.py and you would put "cache/flat_hash" into the testDirs variable in __init__.py.