Comment by nishilpatel

I agree with the core point: the more pure and deterministic a system is, the easier it is to reason about and test. Reducers + property-based testing push correctness into design, not brittle test cases.

One nuance though: property-based testing shines when the domain is already well-modeled. A lot of real QA pain comes where purity breaks down—distributed systems, async flows, partial failures, UI↔backend boundaries. At that point, the hard part isn’t generating tests, it’s reconstructing context.

On LLMs: I don’t think they should be trusted as correctness oracles either. Their real value isn’t guessing answers, but helping surface assumptions, generate counter-examples, and expose gaps in our mental model.

So the future of QA isn’t humans vs LLMs. It’s better system design + explicit invariants + tools that help engineers doubt their own certainty faster. Most serious bugs come from being sure we understood the system when we didn’t.