The positive ones (use cases) are usually pretty straightforward. It's once you get to failures like "how does the whole system recover if one packet, 3 steps i

The positive ones (use cases) are usually pretty straightforward. It's once you get to failures like "how does the whole system recover if one packet, 3 steps into a transaction is corrupted". If the system is complex enough, that warrants a whole internal fault injection framework and can take a really long time to make it reliable and usable. To be fair most projects don't care beyond "rollback the database and maybe display a 5xx error or something". But some do. Anyway, use cases are fine. It's the failures / edge cases that cause pain.