Rspec testing association results in failure - ruby-on-rails

Question

I'm trying to create "components" for my project and each component belongs to one of four types (Section, Composition, LearningIntentions, or EssentialQuestion). A section is a component and can contain multiple components, but a section cannot contain a section.
But when I run my spec, I get the error Expected Component to have a has_many association called components (no association called components). But it works when I move the spec from section_spec.rb to component_spec.rb. What is happening here?
component.rb (model):
class Component < ApplicationRecord
# == Constants =============================
TYPES = %w( Section Composition LearningIntentions EssentialQuestion )
# == Associations ==========================
belongs_to :project
belongs_to :section,
class_name: 'Component',
foreign_key: :section_id,
optional: true
# # == Validations ===========================
validates :type,
presence: true,
inclusion: { in: TYPES }
end
section.rb (model):
class Section < Component
# == Associations ==========================
has_many :components,
class_name: 'Component',
foreign_key: :section_id
# == Validations ===========================
validates :section_id, presence: false
end
section_spec.rb:
RSpec.describe Section, type: :model do
subject! { build(:component, :section) }
# == Associations ==========================
it { is_expected.to have_many(:components) }
end

Answer 1

Reason for failed test
But it works when I move the spec from section_spec.rb to component_spec.rb
The location of your rspec is not the cause of failure here, as it looks to me. What you are doing wrong is, assigning a Component instance in your section_spec.rb as the subject and so, it expects the association :components to be present on that Component instance.
Fix for failed test
Change the code to below and see if it works:
RSpec.describe Section, type: :model do
subject { build(:section) }
it { is_expected.to have_many(:components) }
end
Using traits in factory
If you want to build a Section instance with components assigned to it, then define a trait and use it as below:
# Factory
factory :section do
trait :with_components do
after(:build) do |s|
# Modify this to create components of different types if you want to
s.components = [create(:component)]
end
end
end
# Rspec
subject { build(:section, :with_components) }
Couple of more things
This association in your Component model looks fishy:
belongs_to :section,
class_name: 'Component',
foreign_key: :section_id,
optional: true
Are you sure you want to link a Component instance to another Component instance?
And while doing that, you want to use foreign key :section_id instead of conventional component_id?
You already have a model Section in your application. It might cause confusions. See below:
component = Component.first
component.section
=> #<Component id: 10001> # I would expect it to be a `Section` instance looking at the association name