JavaScript test module that is bound to window with the intern

I am new to testing in js.

I would like to unit-test parts of my js and afterwards add some functional tests. The problem is, that I am using the window object and document.

For e.g. I am exposing my module from the closure like this.

window.nestable = definition(window);

and of course there are things like

document.getElementById('id')

How would I go about unit testing this? I did not find the information in the docs, so I hope you might be able to help me.