[kortex]

> A large portion of the kind of code I've written is impractical or impossible to actually "unit test" e.g. Unity3D components or frontend JS that interacts with a million things.

Opinion: This is actually a symptom of what is (imho) a pervasive problem lodged deep in the collective consciousness of software dev: OOP with fine-grained objects. I blame (early) Java in large part for exacerbating this mentality. Encapsulation of state with mutator methods in particular. It sprays state all over the application, encourages mutation in place over immutability, coupling, validating-not-parsing, and makes it nigh-well impossible to write good tests.

It's really hard to write objects that enforce all invariants under every mutation. And when you have state strewn everywhere, it's impossible to test every nook and cranny. The combinatorial space explodes.

Objects are helpful for encapsulating state when they are course-grained, mutations are atomic, coupling occurs in one place, state changes are auditable, and the entire state can be replayed/set at once, to enable mock tests and subsystem integration tests. AKA, things like databases, reactors, and persistent data structures.