JSON-P doesn’t use `XHR requests, which is what the fake server is concerned with. A JSON-P request creates a script element and inserts it into the document.
There is no sufficiently unobtrusive way to fake this automatically. The best option is to simply stub jQuery in this case:
sinon.stub(jQuery, "ajax"); sinon.assert.calledOnce(jQuery.ajax);
We could potentially have had the fake server detect
jQuery and fake any calls to `jQuery.ajax when JSON-P is used, but that felt like a compromise in the focus of the Sinon project compared to simply documenting the above practice.