How to test that specific assets (JS/CSS) are available in layouts?

Is it possible -- or even sane -- to verify that specific parts of the asset pipeline are available in specific layouts of a Rails app?

I'm setting up a new Rails 4.2 app with Twitter Bootstrap 4 (incl. its dependencies such as Tether), FontAwesome and DataTables. The scaffold is working fine so far.

As the whole thing is kind of a training on web development, self-control (w.r.t. software development, i.e. actually stick to a balanced mix of TDD and BDD), I want to make sure to test almost everything that could possibly go wrong.
That includes the availability of all the framework stuff mentioned above on all end points where it's required.

Ultimately, I want to write something of the following:

describe 'layouts/application.html.erb', type: :layout, js: true do
  it 'has jQuery' do
    render
    expect(render).to have_js :jquery
  end

  it 'has TWBS v4' do
    render
    expect(render).to have_js :twbs4
    expect(render).to have_css :twbs4
  end
end

Obviously, these .to have_js :jquery and .to have_{js,css} :twbs4 need to have something in the background such as a Javascript evaluation of $.fn.jquery.

Is it even sane to test such things?