Streaming Data with Ajax and Comet - Test-Driven JavaScript Development - page 299

Whereas we had no choice of where to stub while developing ajax.request
(it only depended on the XMLHttpRequest object via the ajax.create
method),

we now have the opportunity to choose if we want to stub

ajax.request
or ajax.create . We will try a slightly different approach in this chapter by
stubbing “lower.” This makes our tests mini integration tests, as discussed in
Chapter 1, Automated Testing, with the pros and cons that follow. However, as we
have just developed a reasonable test suite for ajax.request , we should be able
to trust it for the cases we covered in Chapter 12, Abstracting Browser Differences:
Ajax.
While developing the poller we will strive to fake as little as possible, but we
need to cut off the actual server requests. To do this we will simply keep using the
fakeXMLHttpRequest object from Chapter 12, Abstracting Browser Differences:
Ajax.

13.1.2.4 The First Request

To specify that the start method should start polling, we need to assert somehow
that a URL made it across to the XMLHttpRequest object. To do this we assert
that its open method was called with the expected URL, as seen in Listing 13.9.

Listing 13.9 Expecting the poller to issue a request

setUp: function () {
this.ajaxCreate = ajax.create;
this.xhr = Object.create(fakeXMLHttpRequest);
ajax.create = stubFn(this.xhr);

},

tearDown: function () {
ajax.create = this.ajaxCreate;

},

/* ... */

"test start should make XHR request with URL": function () {
var poller = Object.create(ajax.poller);
poller.url = "/url";

poller.start();

assert(this.xhr.open.called);
assertEquals(poller.url, this.xhr.open.args[1]);

}