The commandment to not eat from the tree had a number of difficulties associated with it:
1) It was a negative commandment which often meets with impulses wanting to resist it.
2) It was a commandment in the area of forbidden foods, a particularly difficult area where the יצר הרע tempts a person to sin.
3) It was a commandment that was a חוק. Common sense see no reason for thibehavior.
4) It was a commandment based on oral tradition. God told Adam, but Adam told Eve about it. There is room for doubt when it is rooted in an oral tradition.
As explained earlier in verse 9, the challenge of this test was see if Man would choose God’s will to determine what is good and evil, or his own senses and thought process.
To this day, each of us stands before God, as did Adam, before this very same tree of knowledge. Will we listen to God’s instructions or our own? Will we be drawn after our physical sense, or cast doubt on our obligations if their source is an oral tradition?
Beraishis 2:16-17, Pages 61-62