Abstract : Several tools have been designed for automating tests on Web applications. They usually drive browsers the same way people do: they click links, fill in forms, press buttons, and they check results, such as whether an expected text appears on the page. WUnit is such a tool, but goes a step further: it can act inside the server, examine server-side components, and even modify them, which gives more controls to the tests to write. For example, in our tests we can get the user session server-side, store an arbitrary object (that does have sense in our test) in the user session, and get the page that renders it. Cheating like this allows to bypass the normal functioning of a Web application and really perform independent unit tests, which gives more flexibility to test-driven development. In this session, we'll present the Active Tags framework from which is derived WUnit, and experiment how to design simply a test suite for an AJAX-based application: how to get a page, fill a form, upload files, and of course how to act on server-sides components.