http_mock.js

(function(XHR) {
  "use strict";
  var open = XHR.prototype.open;
  var send = XHR.prototype.send;
  var openUrl = null;
  var responses = [];
  XHR.prototype.open = function(method, url) {
    openUrl = url;
    open.apply(this, arguments);
  };
  XHR.prototype.send = function(data) {
    var self = this;
    var oldOnReadyStateChange;
    var url = openUrl;
    function onReadyStateChange() {
      if(self.status === 200 && self.readyState == 4 /* complete */) {
        if (/URL_REGEX/.test(url)) {
            console.log(url);
            responses.push({
              url: url,
              data: self.responseText,
            });
        }
      }
      if(oldOnReadyStateChange) {
        oldOnReadyStateChange();
      }
    }
    if(this.addEventListener) {
      this.addEventListener("readystatechange", onReadyStateChange,
        false);
    } else {
      oldOnReadyStateChange = this.onreadystatechange;
      this.onreadystatechange = onReadyStateChange;
    }
    send.apply(this, arguments);
  }
  window.__RESPONSES = responses;
})(XMLHttpRequest);