We’ve looked at testing various “depths” in the tiers of the web application, from DNS all the way back to the application server and database. Single-object HTTP requests still leave many questions unanswered, though. How long do whole pages take to load? Can users complete multistep transactions? Are page components functioning correctly?
The majority of synthetic tests retrieve a page, then all of its components. A standard web page lists all of the components it contains; the testing system parses this page, then retrieves each component. The number of concurrent connections between the client and the server affects the total time the page takes to load, and the result is a “cascade” of objects that ultimately drive the total page load time, as Figure 9-12 shows.
Figure 9-12. A cascade diagram from Gomez showing watchingwebsites.com and all its component objects being loaded from Beijing, China
Figure 9-13. A complex page retrieval ...