I feel like that’s where property based testing comes in. Quickcheck style libraries.

I only recently started looking into Quickcheck style libraries in the typescript world, and fast-check is fantastic. Like super high quality. Great support for shrinking in all sorts of cases, very well typed, etc.

Hooking fast-check up to a real database/redis instance has been incredible for finding bugs. Pair it up with some regular ol case by case integration tests for some seriously robust typescript!