Sinon.JS error Invalid URL, How to fix that

I have attempted try many time but it always not work. I using Mocha unit test. This is my codes unit test:

var expect = require("expect");
var jQuery = require("jquery");
var sinon = require("sinon");

describe("SinonFakeServerWithJasmine", function() {
     var server;

     beforeEach(function() {
          server = sinon.fakeServer.create();
    });

    afterEach(function() {
        server.restore();
    });

    it("should fake a jQuery ajax request", function() {
        server.respondWith("GET", "/something", [200, {
                "Content-Type": "application/json"
            },
            '{ "stuff": "is", "awesome": "in here" }'
        ]);

        jQuery.ajax({
            url: "/something",
            success: function() {
                console.log("success");
            },
            error: function(err) {
                console.log(err);
            }
        });

        server.respond(); // Process all requests so far
    });

});

==> And this is log error Jquery.ajax

{ readyState: 0,
  getResponseHeader: [Function],
  getAllResponseHeaders: [Function],
  setRequestHeader: [Function],
  overrideMimeType: [Function],
  statusCode: [Function],
  abort: [Function],
  state: [Function],
  always: [Function],
  then: [Function],
  promise: [Function],
  pipe: [Function],
  done: [Function],
  fail: [Function],
  progress: [Function],
  complete: [Function],
  success: [Function],
  error: [Function],
  status: 0,
  statusText: 'TypeError: Invalid URL' }

I don't know why it error like that. I not use expect due to it unnecessary in my case, I want to test sinon with mocha Thank everyone have spent time read.