In a post-apocalyptic world the survivors are eeking out a living in the remains of Chicago. For over 100 years they have done so by having a very stratified society in which upon reaching about 16 years old the members must choose which group they will join after taking a Test which "determines" which group will be best for them (strictly speaking there are no rules which require that people choose that selected group, it is understood that nearly everyone does so). I forget the groups' titles, but the 5 factions are the intellectuals, the service providers, the farmers, the lawyers and the police/military. By agreement the leaders are selected from the service providers. There is also a sixth group--the Factionless--which people are forced into should they wash out of the group they chose for whatever reasons, and is undesirable because the Factionless barely live in the margins of this resource-poor society.
(As is the fashion nowadays) the heroine--Beatrice Prior (played by Shailene Woodley
)--is up for her time of testing. She assumes that--like most people--she will choose to join her parents who are in the service provider faction as will her twin(?) brother, but she is uncomfortable with the idea because she can see that her brother is a natural at doing the service providers jobs while she is not. The Test involves the testee being placed into a simulated reality in which she must overcome whatever challenges are brought to her while being monitored by a test-giver. At the end of Beatrice's Test the test-giver quickly whispers to her that she must NOT tell anyone what happened to her during her Test, including her parents. When Beatrice demands that she be told which Faction would be best for her, her test-giver tells her that it doesn't matter. Confused, Beatrice leaves. Having expressed earlier her admiration of the apparent free-going lifestyle that the military seem to have, when she chooses the military at the annual Choosing ceremony during the following week. Over time Tris--the name she adopts upon joining the military--eventually learns that her problem that arose during her Test was that she is a Divergent (hence the book/movie title), meaning that she cannot properly fit into any of the factions and thus is a danger to this strictly regulated society.
I have not read the book so I do not know if this was a failing by the author or by the scriptwriters, but it would have been helpful to have included someone else's Test in which that person got his "expected" results. The viewer has nothing with which to compare Beatrice's Test and we are only told afterwards that her Test was somehow different.
Anyway, a diverting 2.5 hours of mostly mindless entertainment, but not interesting enough to go out of your way to catch.
I see from Woodley's IMDB entry that "Insurgent"--the sequel to "Divergent"--is already in post-production for release later this year, and that she is likely to appear in "Allegiant" which (again as is the fashion nowadays) will be split into two parts for 2016 and 2017.