baptism by fire
Definition from Wiktionary, the free dictionary
From the Bible, Matthew 3:11, John the Baptist said... "and He shall baptize you in the Holy Spirit and in fire."
- (idiomatic) A rite of passage through the survival or success of a crisis or ordeal.
- The new folks really get put through a baptism by fire, to start doing a stressful job with so little training.
rite of passage