thoughtbot--factory_bot/spec/acceptance/definition_without_block_spec.rb

describe "an instance generated by a factory" do
  before do
    define_model("User")

    FactoryBot.define do
      factory :user
    end
  end

  it "registers the user factory" do
    expect(FactoryBot.factory_by_name(:user)).to be_a(FactoryBot::Factory)
  end
end