The actual HTML generated by this ERb isn’t particularly relevant, but you might be curious, so here’s a peek:

This sets the variable data-remote="true" inside the form tag, which tells Rails to allow the form to be handled by JavaScript. By using a simple HTML property instead of inserting the full JavaScript code (as in previous versions of Rails), Rails 3 follows the philosophy of unobtrusive JavaScript.

       Having updated the form, we now need to arrange for the Relationships controller to respond to Ajax requests. Testing Ajax is quite tricky, and doing it thoroughly is a large subject in its own right, but we can get started with the code in Listing 11.37. This uses the xhr method (for ‘‘XmlHttpRequest’’) to issue an Ajax request; compare to the get, post, put, and delete methods used in previous tests. We then verify that the create and destroy actions do the correct things when hit with an Ajax request. (To write more thorough test suites for Ajax-heavy applications, take a look at Selenium and Watir.)