title: How can I access the DOM of another HTML page, to test DOM manipulation functions from QUnit
body: <p>I am writing test cases in QUNIT for a JavaScript project. I have already tested functions which return a value.</p>
  
  <p>But there are functions in the codebase which access the DOM and do stuff with it. I want to access the DOM of the HTML pages that are changed by these functions, so that I can check they're working.</p>
  
  <p>I tried <code>document.url</code> as well as <code>window.open</code> but when I try to to do <code>document.getElementByTagName("script")</code> on that page It gives me <code>null</code>. Which means I am not able to access the other page's DOM.</p>