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Imagine it's 1999. Development and QA teams are relieved that the HTML browser is the client of choice for computing. While there have been fast network pipes to deploy and numerous browser compatibility issues to sort out, UI development and deployment have become easer than during the client-server era. End users are used to clicking on links and waiting for pages to download.
Although the birth of Ajax and RIA has not really changed the basic problems of client-side performance, the nature and amount of change in presentation architectures is beginning to tax the skills of testers.
There are several reasons why Ajax challenges established test plans. By moving more work to the client, it begins more to resemble the pre-HTML user interface. Ajax applications in and of themselves are more complex. Because Ajax works asynchronously, test programs are not able to assume state. How Ajax developers parse out their server calls affects performance and test strategies.
While some Ajax client test issues hearken back to the client-server era, others recall the early days of HTML when applications had to be tested against multiple browsers. Today, different browsers treat Ajax differently, and testers must calibrate for that.
Besides different browsers, testers must work with different flavors of Ajax. Many different Ajax frameworks, each with a different twist, have emerged. Since browsers were not originally built to support Ajax, different frameworks have different workarounds for browser shortcomings. Testers must adjust for such workarounds, which, in turn, may change with the next round of browser updates.
From a broad standpoint, said Matt Brayley-Berger, domain specialist for Borland's Silk Performer and Silk Test offerings, Ajax is not necessarily new. "It's new in that it has become very popular," he said. "And it changes testing on the performance side and the functional side."
But it is a moving target. "Ajax is more of a technique than a standard. There is no standard implementation," said Brayley-Berger, noting that he sees JSON-flavored Ajax becoming more popular than XML-flavored varieties.
Variety led to creativity, but since Ajax frameworks largely originated as open-source Web community projects from many sources, maintaining Ajax applications can be uniquely problematic.
"Before Ajax, we could ignore client processing. That is not true anymore," Brayley-Berger said. Testers must now look at how much work gets distributed to the client and how much to the server.
Meanwhile, the rush to Ajax has led to some "under-specified" application development. Brayley-Berger said a good question a tester may ask about an Ajax application is "Was it specified before it was built?"
The past few years have witnessed a swing toward Ajax clients, but there may be reasons for development managers to move toward RIA systems with stricter program boundaries. RIA is seen, for example, in Adobe Flash and Microsoft Silverlight.
"We are seeing a lot of challenges with security and with consistency," said Brayley-Berger. "In my opinion, Flex is the next wave when we get past Ajax itself."
In fact, while the latest Borland Silk test suite tool additions are ultimately aimed at better Ajax testing, the first support out of the box comes for RIA test scripting capabilities.
Ajax test problems
Ajax blurs the lines between a typical Web interface and a more traditional graphical interface, according to Christopher Merrill, chief engineer at WebPerformance Inc., a testing tools and services company. Ajax presents a special challenge for all types of testing, he said. Merrill contributes to the WebPerformance blog on performance issues.
"Where tools were specific to testing websites, you had the luxury of treating one page sort of as its own entity. Ajax removes that," Merrill said. "This requires the tool to understand more about the page than just sending a request to the server and getting a response back."
And now, when a tool has to simulate an Ajax application, it has to get all the page elements in the right order, where that may not have mattered before, Merrill added.
Hovering above all this is the plain fact that Ajax is a more complicated way of showing Web pages. "From a test and quality standpoint, one of the challenges for developers and testers is that the applications are becoming more sophisticated," Merrill said.
An "extreme Ajax application" is gong to be much more like a classic rich client application, he indicated. For example, with Ajax, the state of the application can persist from one operation to the next, which means all the possible routes to a given state have to be taken into account for each point you want to test. In other words, you can get to a state for an application in many ways.
The state of client-side state
At the Ajax Experience conference last year in Boston, Bob Buffone suggested there are similarities between Ajax performance issues and those found in traditional server-side object-oriented development. To avoid pitfalls, developers have to go back to the basics. Knowing your code, and how it does what it does, continues to be the mantra. The differences between Ajax architecture and more recent HTML application architecture must be reckoned with.
"It's a different environment because, with Ajax, the applications are stateful on the client-side. So it can be harder to capture and replay scripts for test," said Buffone, chief architect at Web client development tool maker Nexaweb Technology.
"Testers have to change the way they utilize their test tools. It's almost a migration back to client-server testing, rather than being forms- or page-based," said Buffone, who regularly covers Ajax performance on his RockStarApps blog.
Among good tools to figure through some problems, he noted, is Yslow, a Firefox plug-in, developed by Yahoo, that gives grades on use of resource requests and other factors in Ajax page creation.
The layers of complexity that Ajax can introduce may lead some development managers to rethink some Ajax plans.
How performance is perceived
"In an Ajax application, you are trying to accomplish the same things you are trying to accomplish in a traditional application. You are trying to improve the perception of it," said Ryan Breen of Gomez Inc., which is focused on hosted tools that help customers design build, deploy and manage Web application performance.
"When you design an Ajax application you need to look at what you expect the user to do. The genius of an app like Google Maps is to anticipate what the next user call will be -- and do that," said Breen, who blogs and serves as Gomez's vice president of technology.
"One of the downsides of Ajax for the first year or two was that people would see an application like Google Maps and say, 'I want to do that.' But it isn't really easy to do. To build a quality Ajax application and meet performance goals, you have to start from the design stage to think about what your users are going to do."
The future of Ajax holds more change. After a lull, browser makers may be ready to roll out updated software. "We are seeing all the major browser players coming out with new versions … and they all have pretty substantial tweaks driven by problems people are having," Breen said.
As an example he cites upcoming Microsoft IE 8 changes. "There are substantial changes to the number of connections you can make. The change [Microsoft] made was to allow you to make six connections per host at a time. Before, for every browser, it was two," he said.
Ajax frameworks, Breen noted, had workarounds allowing more connections. But these workarounds could cause havoc for some webmasters unaware of the increase in connections due.
Tools Breen highlighted for Ajax testing at last fall's Ajax Experience East Conference included IBM Page Detailer and (the oft-cited) Firebug for network visualization. He also mentioned Firebug, Firebug Lite and Dojo.Profile for client-side profiling.
Improving Ajax performance
Ajax unquestionably is a Web phenomenon. That same Web is a font of information on the subject of Ajax best performance practices. Programmers and testers both can benefit from their colleagues' experiences. Google and Yahoo, particularly, offer sage performance advice for Ajax application building. Both sites have been major drivers of Ajax use.