I've done these ticket selling assessments for some other TOCs (not EMT.)
Basically, if you are suitable for the job, you won't fail the test. In my experience, TOCs always set the pass mark as such a level that anyone with sufficient arithmetic ability can pass. I find it's usually near impossible to complete in the time given.
The test itself often involves having to flicker between pages, such as a rail map, fares grid and percentage discount grid. Using scrap paper is necessary unless you are very good arithmetically. In the real tests, there are always questions where multiple passengers are travelling. They can involve adults with various railcards and children, with some travelling one way and the rest wanting a return. Often with some dodgy time given where some railcards give a discount and others don't.
They often tell you that you don't need to have had any railway experience to do the test as all information within is fictional, which is true, but I find previous cash handling experience and understanding tickets in real life does give you an advantage.
As for the interview, I'm not really in a position to give out advice as I don't know what's on their checklist but wish you the best of luck!