The Aptitude Test is a yearly assessment taken by every 16 year old.
The test is to examine the child's aptitude or the disposition towards one of the five traits of the five factions. It is a good indicator of what faction a child should choose based on his/her predominant characteristic.
The next day at the Choosing Ceremony, test-takers must choose which faction they will enter into. They can either leave their family and choose an entirely new faction or they can stay with them. Their aptitude test result is taken into account, but the final decision is left up to them.
The tests are administered every year to children reaching the age of sixteen which is considered adulthood in Divergent. The test cannot be administered by a member of the child's own faction, so the volunteer test evaluators usually consist of eight Abnegation, for two of the other four factions, and two from the other factions, to test the two Abnegation-born ones, since ten tests are taken simultaneously.
The rooms where the tests are taken, used specifically only for the administration of the aptitude tests, have mirrored walls and are very bright-lit. In the center of the room is a chair that looks like a dentist's chair. Test-takers are instructed to sit there and electrodes are attached to their head. Then they are given a serum to drink, to connect them to a simulation program. This simulation helps decide what faction they are in. Some test results are inconclusive,like Tris's, resulting in Divergence.
In the simulation, Jeanine's voice is used, as she is the designer of the serum. When asked to choose between the knife and the cheese, the Dauntless choose the knife, while the Amity choose the cheese. In Tris Prior's case she refuses to choose either and submits to the dog that occurs, an Erudite response, and when a child appears and the dog runs at her, Tris throws herself at the dog - a Dauntless and Abnegation response. Another simulation scenario is the one on the bus where a burnt (scarred) man reading a newspaper asks you if you know the man feature on the front page, the one responsible for his problem. The taker is meant to feel like he/she knows the culprit but will also have a horrible feeling that if you say you do, something bad will happen. The Candor always tell the truth. When you insist upon lying, this elaborates and the man will further persuade you, saying that it will help him, showing the taker his true face. The Abnegation, being selfless as they are, admit to knowing the culprit to help the man. The Divergent will most likely deny knowing the man.
The way the simulations work is that in the given scenarios, each stage should eliminate at least one or more of the factions, ultimately eliminating at least four factions and leaving out one as the result. If the test in inconclusive, resulting in the elimination of only three or less factions, the taker is a Divergent. In Tris' case, only two were eliminated, with the other three being inconclusive as well because of her contradicting decisions and her refusal to make a choice in the beginning, ending up with an equal aptitude for Erudite, Abnegation and Dauntless. This is said to be a very rare number, even for a Divergent. Most Divergent have three of the five factions eliminated during their aptitude test, and only have aptitude for two factions. Tobias Eaton has been considered Divergent, not as a natural trait but he is able to manipulate tests.