Like any game, testing is mostly just playing it and making notes whenever you’re not having fun. Especially in the case of a game like this that’s mechanically dense and built for solo play, I don’t think it’s much different from balancing a video game.
That said, testing the creative/social elements of tabletop games is much more reliant on having playtesters. If anyone plays this I’d love to hear about their experience, particularly places where they felt the fiction engine was working for them or leaving them adrift.