Joseph tests his brothers

Genesis 44:1-34
Joseph tests his brothers by hiding his silver cup in Benjamin's sack. Then Benjamin have to stay in Egypt, how his brother will be!
Judah stood out and said to Joseph that he would like to be a servant in Egypt but his youngest brother Benjamin have to go back to his father for his father will die if Benjamin does not go back.
I fear to see the evil that would find my father.
Why?
Joseph may have used his silver cup for divination(卜筮) (interpreting events by the movement of drops of oil on water), as some versions bring out. Or the steward may imply that it is impossible to escape detection by his wise and powerful master.
Judah took his responsibility among brothers and had ready to bear the life of Benjamin.
How?
Joseph is wise and sensitive to the good and evil one.