God is not ignorant

Of course not.  It is in order that a person may find out about himself ... People are not as well known to themselves as they are to their Creator, nor do the sick know themselves as well as the doctor does.  A man is sick; he is suffering, the doctor isn't suffering, and the patient is waiting to hear what he is suffering from from the one who isn't suffering.

That is why a man cries out in a psalm, "From my hidden sins cleanse me, O Lord." (Ps 19: 12). There are things in a person which are hidden from the person in whom they are.  And they won't come out, or be opened up, or discovered, except through tests and trials and temptations.  If God stops testing, it means the master is stopping teaching.

God tempts or tests in order to teach, the devil tests or tempts in order to mislead.  But unless the one being tempted gives him a chance, his temptations can be driven off as unsubstantial and ridiculous.

That is why the Apostle says, "Do not give the devil a chance." (Eph 4: 27).  People give the devil a chance with their lusts and longings.  Now it is true that people cannot see the devil they are fighting with, but they have a very easy remedy for that; let them conquer themselves within, and they will triumph over him without.  Why am I saying this?  Because you do not know yourself unless you learn yourself through trial, temptation and testing.  When you have learned yourself, don't be heedless about yourself.  At least, if you were heedless about yourself when hidden from you, don't be heedless about that self when it has become known to you.