def test_with_None_from_parseline(self):
        script = textwrap.dedent("""
            import cmd
            class CustomCmd(cmd.Cmd):
                def parseline(self, line):
                    if line.startswith('exit'):
                        return 'exit', '', line
                    return None, None, line

                def completedefault(self, *args):
                    return ['via_completedefault']

                def do_exit(self, args):
                    return True

            CustomCmd().cmdloop()
        """)

        input = b"foo bar\t\nexit\n"

        output = run_pty(script, input)

        self.assertIn(b'via_completedefault', output)