[RFC] adding test framework #725

Hi all,

Is your feature request related to a problem?

we regurlarly needs to makes python test, regarding PoS. for exemple, https://github.com/OCA/pos/blob/12.0/pos_session_closing_stock_error/tests/test_pos.py by @ivantodorovich, https://github.com/OCA/pos/blob/12.0/pos_multiple_control/tests/test_pos_multiple_control.py#L10 by @quentinDupont and Me.
The test are very verbose. It requires lot of lines of code, just to open a session, make a sale, add payment, etc... and it's quite a mess.

Describe the solution you'd like
Add a module pos_test_framework, that could provide test function like def open_session(), def sale(product=False, qty=False), def close_session(), etc... and make new modules, in V15 depends on that module.
We could also provide helper also for js scripts.

Thanks for your point of view.

CC : @OCA/pos-maintainers