Yes, I wanted to say something similar in response to your phrasing that "type systems (including dynamic and static type systems) are another way to carve out the territory". When you say "dynamic type systems", in particular, I think Python and Ruby, and the modularity guarantees there seem much inferior to tests. But Haskell and the more advanced type systems might well disprove my thesis.
You're right: dynamic type systems tend to provide very weak guarantees. But I'll still take those guarantees over silent failures.
In my opinion, static guarantees (including static types) are the best, followed by unit tests, followed by dynamic guarantees (including dynamic types).
