top level directory cached on loader instance we are inside test testunittest testmock so the toplevel is three notches up top level directory cached on loader instance we are inside test test_unittest testmock so the top level is three notches up
import os
import unittest


def load_tests(loader, standard_tests, pattern):
    
    this_dir = os.path.dirname(__file__)
    pattern = pattern or "test*.py"
    
    top_level_dir = os.path.dirname(os.path.dirname(os.path.dirname(this_dir)))
    package_tests = loader.discover(start_dir=this_dir, pattern=pattern,
                                    top_level_dir=top_level_dir)
    standard_tests.addTests(package_tests)
    return standard_tests


if __name__ == '__main__':
    unittest.main()