'this is not compatible with compgen but it is with bash itself:
ls /usr/<TAB>'

@pytest.mark.skipif("sys.platform    in    ('win32',    'darwin')")
def test_remove_dir_prefix(self):

    from _pytest._argcomplete import FastFilesCompleter
    ffc = FastFilesCompleter()
    fc = FilesCompleter()
    for x in '/usr/'.split():
        assert (not equal_with_bash(x, ffc, fc, out=py.std.sys.stdout))
