Moe,

Not sure if you noticed, but I was the author of that link :P

It's not just about incremental search, that's just one example. Anything in which there is logic in the client that reads in user-entered data and mutates it in a way in which simulating at the protocol level becomes non-trivial and effectively require duplicating the logic that was first written in JavaScript.

For another example: I'm working with a large online invitation website that is doing a big redesign of their site. The new UI is effectively one "page" and everything is done via AJAX calls to a JSON service layer, including login. Authentication to that service layer is done via a custom HTTP header that is a SHA encoding of the username + password + timestamp (among other things). If you wanted to test with 1000's of user accounts with traditional load testing, you end up needing to do the SHA encoding on the fly in whatever tool you're using (VBScript, LoadRunner's crazy C-like language, etc).

I really just can't think of a UI that would allow you easily record a Google search for one term and then abstract the test out to work with N search terms. Because the AJAX requests become data dependent ("foo" causes 3 requests, "foobar" causes 6), you ultimately end up writing control structures (loops, branches, etc) that are better off written in a programming language. Generally, if the browser isn't doing simple "passthrough" of the user data, I find protocol simulation becomes much more difficult.

For these reasons, I'm not sure it's just a UI design issue, though I'd love to be proven wrong. Unless there was an Iterate-over-characters-of-data-X-and-issue-http-requests-with-pattern-Y command as well as a SHA-encode-data-X-and-data-Y command (which of course is way too domain specific), you'll likely end up writing your tests with a Real Programming Language.

As for your questions about data parameterization/randomization, that was the entire point of my article. I specifically called attention to data randomization as the point where it really gets tough. That's what load testing is all about, and that's why traditional approaches are breaking down.

BrowserMob lets you import a Selenium script that has static data in it (ie: "type q google_search"). The script is converted to a JavaScript, which you can then edit and replace the data (ie: "google_search") with a random/parameterized data. The ensuing AJAX HTTP requests are generated automatically and correctly since the browser owns that.

All of that kind of stuff ultimately still has to get done with some scripting. I don't pretend that BrowserMob load testing is "script free". Far from it - we embrace JavaScript as the way to get things done. But if you're scripting a browser, your scripts end up dealing with user behavior emulation, which is almost always simpler than protocol layer emulation.

Understand: I'm not saying this stuff is impossible today. I'm saying it's harder than it needs to be and can be greatly simplified by just using a real browser.

All that said, I appreciate your frustration with the lack of tools. I hope you'll give our approach a closer look. I'd certainly appreciate hands-on feedback. We do offer more traditional virtual user scripting support as well (at 1/10th the price of our real browser service), so if you're good with JavaScript you can get some pretty affordable on-demand testing!

Patrick