Remember to ensure that your build strategy is set on all associations if you want this to work, e.g.

  FactoryGirl.define do
    factory :user do
      association :account, :strategy => :build
    end
  end

Otherwise when you build a user, the account association will still get persisted to the database.

Even if you do this, though, you're still spinning up a whole network of real objects in what is supposed to be a unit test.

I'll go one recommendation further. Just don't couple user and account. When making a factory named after a model, only set model attributes and never set relations.

    factory :user    # sets only user fields, no relations
    factory :account # sets only account fields, no relations
    
    factory :user_account {creates both}

When you have a large # of tests/factories, it's nearly impossible to keep track over time what the :user factory creates. Today it's one relation. Years from now, it could be 10 other tables relations. Someone later on decides they want to reuse the :user factory, but they don't want the account to be create, so then they do :user_only factory. Yada yada. Shenanigans ensue.

If you stick to the above strategy, things are much faster, but more importantly, there are less unintended surprises, like associations doing a create instead of a build, etc.

My preference is to have the base factories set everything that is needed for the generated record to be valid, and nothing more. If your User model validates the presence of the account, then the account association should be set - if not, it shouldn't. Otherwise, FactoryGirl.create(:user) is going to provide you with an unsaved, invalid record, which would certainly be surprising to me if I were using that factory for the first time. If all you want is a consistent set of initial attributes, then define a constant USER_ATTRIBUTES somewhere with a hash of values, and pass that to #new - using factories for this purpose is a bit sledgehammer/walnut.

I agree that excessive association building can get out of hand (and the latest version of FG even allows you to subscribe to factory events just so you can work out what the hell your test suite is building - a sure sign that you've lost the ability to reason about your tests if ever there was one), but completely abstaining from building associations seems to remove more or less all of the attraction of using factories as a fixture replacement in the first place.

All of the above applies only to integration/acceptance tests, though, where factories-as-fixture-replacements are at least arguably justifiable; my recommendation for unit tests is "don't use factories at all."

That sounds like pretty good advice. I do not have a very large base of factories and tests yet but I can see how unwieldy it could get without really sane naming conventions.