kit.javascripts << "path/to/file" won't load javascript

[profsmallpine]

html = render_to_string(:file => '/static/home', :layout => '/layouts/application')
@kit = IMGKit.new(html, :quality => 50, 'javascript-delay' => 10000)
@kit.stylesheets << "#{Rails.root}/app/assets/stylesheets/shops/#{@shop.subdomain}_preview.css"
@kit.javascripts << "#{Rails.root}/app/assets/javascripts/small_preview.js"

app/assets/javascripts/small_preview.js

someDiv = document.getElementById("desktop-header");
someDiv.innerHTML = "<h1>CATS</h1>";

I am trying to just get a sample working with adding a javascript file to my IMGKit jpg. This should just append CATS to my image, but it will not work. Is there anything special to know about adding javascripts? The stylesheets aren't having any problems. I hopped into the code where javascripts are being added in the IMGKit gem, and everything looked good.