I think that thinking in military terms is useful. A soldier MUST obey the orders of his superior UNLESS the orders are clearly illegal, or if the officer is acting beyond his authority., See the CAINE MUTINY or CRIMSON TIDE ffor movies that explore this idea. How this translates to me is that the Master may demand blind obediance by emphasising that he is fully aware of the situation. Assuming Master is sober, slave must assume that Master has his reasons. Of course should and will are two different things. In America slavery is voluntary and tests can be failed. Example: Master may order slave to break into a certain house. Slave feels that is going to far, she may end up in jail. She refuses. Master then tells her that this was the house of a friend and there had been a surprise party arranged for her. Master is angry.
Who is right? I believe that Master has the right to test his slave. I believe that Master has the obligation to insure the safety and well being of his slave. If Slave does not believe that Master knows what he is doing, and values her, than she should find another Master. Obviously this trust is not developed overnight. My other Paradigm is a biblical paradigm, where God semands Abraham sacrifice his son. Abraham is willing to obey as a true slave of God. God stops him at the last minute, telling him that it was a test. I don't know any slave that would pass that test, but I don't think any Master would test quite that far.
In short a sober Master can test and a slave, with enough trust should obey, and not question.