> The kind of "architecture" that you are talking about that was often postulated under the banners of "Single Responsibility Principle" (a poor rule of thumb in fact) and "design for testability", that results in one-method classes, or classes that do not have any state and pass everything in via method parameters is in fact contradicting basic tenets of OOP like encapsulation and having a reusable domain model - I find it, like DHH, a horrible abomination, even if tests are faster because of it.

Both the kinds of design features you describe are generally bad [1] ways of implementing either SRP or design for testability, and don't seem to be the architectural choices the grandparent post was actually suggesting. Things like, however, taking external dependencies as constructor parameters and coding to their required API rather than baking the specific concrete implementation to use into class design and coding the class to that is more what I think the GP is talking about. This doesn't require limiting the internal state of the object, it just pulls decisions that belong to the calling environment out of the object and back to the calling environment, which makes the code more reusable (including being "reusable" in a unit-testing environment where the external requirements are mocks whose behavior is defined by test parameters rather than adaptors to real external resources.)

[1] There are very narrow specific cases where they might be the right thing