names_for_let_objects 2

names_for_let_object.rb

module NamesForLetObject
  def names_for_let_objects(objects)
    objects.map { |object| name_for_let_object(object) }
  end
  
  def name_for_let_object(object)
    __memoized.instance_variable_get(:@memoized).key(object)
  end
end

results.txt

expected collection contained:  [:user_1]
actual collection contained:    [:user_1, :user_2]
the extra elements were:        [:user_2]

users_spec.rb

describe(User) do
  describe('.old_enough_to_drink') do
    let!(:bob) { create(:user, age: 21) }
    let!(:alice) { create(:user, age: 20) }
    
    def result
      names_for_let_objects(User.all)
    end

    specify do
      expect(result.to eq([:bob])
    end
  end
end

I believe that users_spec.rb line 7 should be described_class.old_enough_to_drink to be at parity with the 'before' example.

Looks good. I am going to be linking to it in my own list of engineering principles and techniques.