rails_helper.rb

# spec/rails_helper.rb
RSpec.configure do |config|
  ...
  config.include TurbolinkNav, type: :system
end

thing_spec.rb

# spec/system/thing_spec.rb
RSpec.describe "test of thing", type: :system do
  it "does a turbolink nav" do
    visit root_path

    turbolinks_nav do
      click_on "TurboLink"
    end

    expect(page).to have_content("new content or whatever")
  end
end

turbolinks_nav.rb

# spec/support/turbolinks_nav.rb
module TurbolinkNav
  def turbolinks_nav(&blk)
    id = SecureRandom.hex

    page.evaluate_script(
      <<~JS
        document.addEventListener('turbolinks:load', function() {
          document.body.insertAdjacentHTML(
            'beforeend',
            '<div id="loaded-#{id}" style="display: none;"></div>'
          )
        }, { once: true })
      JS
    )

    blk.call

    find("#loaded-#{id}", visible: false)
  end
end