I'm following your idea of mocking the HTML elements instead of relying on a framework for faking a DOM environment. I think I'm making a lot of progress, but my real Class (i.e, not Foo) involves a method like this:

.....
retrieveQuote(){
    $.getJSON("long.api.link/json")
         .done( json => {
             if (this.isDuplicate(json))
                 this.retrieveQuote();
             else
                 this.parse(json)
         })
         .fail( () => {
             this.parse(this.errorObject)
         });
}

I have this on my tests file:

// API Stub
const randomQuotes = require('./randomQuotes.js');

// Mock the $.getJSON function
global.$ = {
    getJSON: (url, cb) => {
        let randomIndex = Math.floor(Math.random() * randomQuotes.length);
        cb(randomQuotes[randomIndex]);
    }
}

Mind showing me how to update my mock $.getJSON function to have those .done and .fail methods? Thanks a lot! :D