Milan one more thing to change in your patch, in all your TCs you're modifying client state, I mean this part:

# lets cheat a bit here:
client.state = 'SELECTED'

It's OK to do that on the mocked server, but this is not acceptable doing on the tested library. It's better to call client.login() to change the state to 'AUTH' properly and only after that, call the actual method under test.