product_spec.rb

require 'rails_helper'

describe Product do

  context "when the product has comments" do
    
    let(:product) { Product.create!(name: "race bike") }
    let(:user) { User.create!(first_name: "John", last_name: "Smith", email: "[email protected]", password: "password123") }
    
    before do
      product.comments.create!(rating: 1, user: user, body: "Awful bike!")
      product.comments.create!(rating: 3, user: user, body: "Ok bike!")
      product.comments.create!(rating: 5, user: user, body: "Great bike!")
    end
    
    it "returns the average rating of all comments" do
      expect((product.comments.rating(1) + product.comments.rating(2) + product.comments.rating(3))/3).to eq 3
    end
  
  end

end