If we were nothing more than animals' bread would be enough. Instinct drives the beast. The senses serve the animal kingdom well but the inhabitants of the kingdom of God need more. The trinity of Man, spirit, soul and body, requires heavenly food. So, the Christian that seeks the strength to walk out this journey without stumbling repeatedly will need to partake of the food that fuels faith.
Life provides many opportunities that test our faith.
It's not that God desires to see what we're made of, but rather, He desires to show us what we're made of. So, he allows us to be tried. Living in a fallen world becomes for us a school of sorts, where we learn of our severe need of God. That knowledge alone is not enough unless we're responsive and hurriedly run to Him, acknowledging our utter dependence. Discipline is not punishment.