1. You can do with unittest2 and save it under tests folder [1]. Or you can do the yaml test and save it under test folder [2].
2. Argumen init or update needed if you want to update xml data or change field data (database scheme). Any changes in python script will be loaded everytime the server start.

[1] https://doc.odoo.com/trunk/server/05_test_framework/

[2] https://doc.odoo.com/6.1/developer/11_upgrade_and_migration/#yaml-data-serialization