Stubbing Chains of FactoryBot Associations

Question

I am working on improving my company's RSpec tests (which have gotten a bit slow), and I suspect one of the culprits is a FactoryBot factory we use in almost every test - a factory that results in a bunch of unnecessary associations due to chaining. For example:

FactoryBot.define do
  # we use a bunch of these and most tests don't care about the value of :b, 
  # but ActiveRecord validations require it
  factory :A do
    association :b
    # some other attributes with simple types
  end

  factory :B do
    association :c
  end

  factory :C do
    association :d
  end
end

How can I create an instance of A without also forcing a B , a C , and a D to get created (I am planning on controlling those with traits)? Using a build_stubbed strategy has been my best answer so far (which doesn't solve all my problems, but is pretty good), but I am curious whether there are other tricks I could shove up my sleeves.

Answer 1

The problem is most likely how you create the model, and not because of FactoryBot. Let's say you have factory a with association b, c and d. In order to create the model you need all associations because you have a not null dependency, in the factory file you can add the following:

  FactoryBot.define do
    factory :a do
      b { build :b }
      c { build :c }
      d { build :d }
   end
  end

Build let you persists the association in the memory database instead of the test database, however if you are doing a specific call to that association in the code which requires a database call, for example abupdate:(some_column: value) you need to override it in the test by creating it like so create:a, b: create(:b) .

It's also common for people to create the model every time instead of using let , which only creates the object whenever you need it instead of in a before:each for example.