Safe to take before you finish the show
The Stranger Things character test is a short personality quiz with no major spoilers in it. The questions are about everyday situations, and the result pages describe personalities, not plot. If you are a few episodes in, or you have only absorbed the show through other people's costumes, you can take it without learning much you didn't want to know.
It's unofficial, free, and needs no sign-up. You answer twelve questions in about two minutes and get matched with one of six characters from Hawkins.
The six you might get
Those six are Eleven, Mike, Dustin, Lucas, Max, and Steve. Eleven says little, feels a lot, and will do anything for the few people she trusts. Mike is the organizer who decides the group is not giving up. Dustin is delighted by how things work and wants to tell you about it. Lucas wants evidence before he signs on to anything. Max does things her own way and is not easily impressed. Steve has the hair, the charm, and a habit of making sure everyone gets home safely.
Why the questions are about hikes and broken promises
The show puts ordinary people under pressure and watches what they do. The quiz does a much smaller version of the same thing. You get twelve situations where something goes slightly wrong: your group is lost, a friend lets you down, your team is losing badly.
Because no question names a character, you can't aim for a favorite.
What you walk away with
Your result is one character and one emoji, with a description of how you operate, what you are good at, and where you tend to get in your own way. It also names your best match among the other five. The skeptic and the organizer are just as useful to a group as the one with the dramatic entrance.
Then pass it on. Friend groups usually come back lopsided, with several leaders and nobody willing to check the map, which is useful to know before your next trip together.