Let's say you have a function thats being called to compute a state using hundreds of attributes spread across tens of different objects, and various different levels of nesting.

Now, you could create hundreds of different integration tests for each branch of the computation..., most of which will assert the same final output state, but achieved through different transitions

Or you can make some integration tests which make sure the logic itself is being called, and then only unittest the specific criteria in isolation.

What you're talking about is likely founded in either frontend testing (component tests vs unittest) or backends which have generally pretty trivial logic complexity. In these cases, just doing an integration test gets it done for the most part, but as soon as you got multiple stakeholders giving you sperate requirements and the consumed inputs get bigger and multiply ... Testing via integration tests gets essentially impossible to do in practice

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!