Test of Aql
The Test of Aql, also known as the Trials of Aql or originally the Seven Mystic Questions is the Fremen test of reason, beginning with the question "Who is it that thinks?".[1]
In-Game
The Test Aql is a journey the player can experience, "guided by the spice" and learning the ways of the desert.[3]
From released screenshots, the trial is a series of tests, possibly based around the Seven Mystic Questions of the lore