rspec matcher for build in new action

How/with which matcher can I test if @product.industry_products.build and the rest are defined in my action?

products_controller

def new
  @product = Product.new
  authorize @product
  @product.industry_products.build
  @product.product_features.build
  @product.product_usecases.build
  @product.product_competitions.build
end    

products_controller_spec.rb

context "GET new" do
  let!(:profile) { create(:profile, user: @user) }
  before(:each) do
    get :new
  end

  it "assigns product" do
    expect(assigns(:product)).to be_a_new(Product)
  end

  it { is_expected.to respond_with 200 }
  it { is_expected.to render_template :new }
end