Fake server-side using [Sinon.JS](http://sinonjs.org/). Inspiration from this [presentation](http://emdin.info/r/sinon-talk/).

fake_server.js

var srv = sinon.fakeServer.create();
srv.autoRespond = true;     // server should automatically respond after a timeout
srv.autoRespondAfter = 500; // response timeout in milliseconds
srv.xhr.useFitlers = true;  // tell Sinon that some requests should not be faked

// add a filter that will tell Sinon to allowa all requests to access the server
// except fitlers defined when calling Server#fake.
srv.xhr.addFilter(function(method, url, async, username, password) {
  var fakedRequest = _.find(Server.fakedRequests, function(request) {
    return request.method === method && request.regex.test(url);
  });
  return _.isUndefined(fakedRequest) ? true : false;
});

Server = {
  // keep trak of the faked requests
  fakedRequests = [],
  
  // fake a 'methodToFake' request to a URL that matches 'urlRegex'
  fake: function(urlRegex, methodToFake, callback) {
    this.fakedRequests.push({regex: urlRegex, method: methodToFake});
    
    // handle the faked request
    return srv.respondWith(urlRegex, function(xhr, url) {
      if (xhr.method != methodToFake) {
        return;
      }
      console.log("[Fake] " + methodToFake + " " + xhr.url);
      callback.call(undefined, xhr, url);
    });
  }
};

// example
Server.fake(/widgets$/, 'GET', function(xhr, url) {
  xhr.respond(200, {'Content-Type': 'application/json'}, [{name: 'Uber Widget', price: 10}, {name: 'Midlevel Widget', price: 4}]);
});

// make request
$.getJSON('/widgets');

useFitlers should be useFilters, I assume?