And I'd upvote it to Mars. FactoryGirl is completely an anti-pattern, unless maybe you're doing acceptance testing, but you know even then I wouldn't want FactoryGirl in my codebase, people would be too damn tempted to use it everywhere.

That's where we find ourselves currently: constructing 3-4 levels out due to Law of Demeter violations, and it becomes incredibly brittle when seemingly unrelated classes change.

IMO, DHH (and others) argue too hard against core OO principles (like SRP and LoD) that have the possibility of helping out when the domain model becomes more complex. "Just use Rails" is fine when spinning up, but as the app grows, it becomes increasingly less pleasant. Coupling increases in the name of less code.

Ideas like hexagonal architecture look nice, but I'm left wondering how to implement them when the framework insists on infecting core domain classes (AR::Base).

So can someone recommend a Ruby (edit: ideally Sinatra/Sequel, not Rails) app one could look at with a more principled test suite? I'm coming from a more traditional OO background and jumping into Ruby. It's good to see I'm not alone in finding this militant pragmatism somewhat off-putting, but I don't want to reinvent the wheel.

As an FYI to your last point - in Rails master (which will be Rails 4), you can active-record-ify a class by including ActiveRecord::Model, rather than inheriting from ActiveRecord::Base. In fact, that is all ActiveRecord::Base does itself - https://github.com/rails/rails/blob/master/activerecord/lib/....

But your core domain classes are still coupled to their persistence mechanism in the name of 'pragmatism.'

Who says they have to be? That's a design decision. There is literally nothing (besides maybe inertia?) that enforces that "rule".

If you want to be sure to keep FactoryGirl out of unit tests but still have the benefit of using it in higher-level tests, you can use a different test/spec helper. I tend to do "spec_helper_lite", which sets up the bare minimum for unit tests (no FactoryGirl), and "spec_helper", which includes FactoryGirl for higher-level tests.

I say "higher-level" tests to refer to integration, system, and acceptance tests, because I don't have an opinion of where to draw the line for FactoryGirl. Is there a reason you would consider FactoryGirl for acceptance tests, but not integration or system tests? Just curious, because I might learn something.

Integration tests just mean you are testing the integration of multiple components, say view and controller, model and database, controller and model. Acceptance tests are tests from the end-user's perspective and touch the entire stack like a real user would. Acceptance tests are integration tests. It's alright for these tests to hit the database because part of what you are testing is the integration with the database.