cli: how test click commands

[ppanero]

This is a much bigger task, but we should manage to standardize CLI testing... The problem with these two approaches:
a) The current function requires an external one and does not call the corresponding click command
b) The update cmd test can only test the exit status, no read or anything (because there are 2 app contexts? 🤔)

see test_cli.py::test_process vs test_cli.py:test_update_cmd