I usually use yaml test. You can check the documentation here : https://doc.odoo.com/6.1/developer/11_upgrade_and_migration/#yaml-data-serialization

Almost every addons come with yaml test. You can check folder "test". It very useful because you can use python tag to execute python script.

If you want to use unittest2 you can follow https://doc.odoo.com/trunk/server/05_test_framework/.