There are no sample tests written for you, only an example on how to do it, you have to write them yourself and it's like that in several languages in this kata.

Test doesn't appear to be working in Elixir

Approved. Thanks ;-)

This wording of the mechanics of this algorithm is deeply confusing. "return the number of people who sit strictly behind you and in your column or to the left, assuming all seats are occupied.". The "or" indicates that I'm returning one number or the other, but with no clear indication of which it is.

EDIT: Finally solved this, the diagram was definitely necessary and helpful. I would suggest rephrasing the question to request the "total number of people that would have their view momentarily obstructed as you leave the theater".