Subject says it all.

There are also no tests of .pkg files.

New changeset 48cb6b67d306 by Eric V. Smith in branch '3.2':
Issue #14817: Add rudimentary tests for pkgutil.extend_path.
http://hg.python.org/cpython/rev/48cb6b67d306

I'm going to leave this open until better tests are added. The one I did add it very simple, but it's good enough for the changes I'm about to make.

This code does not clean up correctly. It needs to remove the added modules in sys.modules. I'll eventually clean it up, once issue 14715 is addressed.

This has broken all 3.x buildbots.

@Eric will you pick this up again?

I would like to work on this and make a PR.

My base idea would be some unittests for the function like:

class ExtendPathBaseTests(unittest.TestCase):
    def test_input_string(self):
        path = 'path'
        name = 'foo'
        self.assertEqual('path', pkgutil.extend_path(path, name))

    def test_parent_package_raise_key_error(self):
        path = ['path']
        # sys.modules['foo'] raise KeyError
        name = 'foo.bar'
        self.assertEqual(['path'], pkgutil.extend_path(path, name))

    def test_parent_package_raise_attr_error(self):
        path = ['path']
        # datetime module don't have __path__ attr
        name = 'datetime.date'
        self.assertEqual(['path'], pkgutil.extend_path(path, name))

I would move forward if we agreed.

@Windson please open a PR for review with your code.

I added some tests in the PR. Actually, there are some tests for extend_path already (see https://github.com/python/cpython/blob/master/Lib/test/test_pkgutil.py#L235). However, I didn't test every line of the code in the extend_path function.