The Apprentice Gauntlet in Ars Magica is the last event and potentially the biggest which a starting Ars Magica Magus character will have before gameplay begins. For some Houses this is just a formality and for others it is an arduous or horrible test. In some sagas the character background is not complete until the player has detailed the gauntlet, and that’s an approach I strongly encourage. The members of House Tremere use the magical competition called Certamen as this test of skill and capability.
The Houses of Hermes book for House Tremere describes a Certamen event between the Master and Apprentice which the Apprentice can lose and usually will. It is ceremonial in nature, and as in many other aspects of a Magi’s life are more complex, I’m imagining that often there is more to the process than a single round of Certamen.