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Summary
AJAX (Asynchronous JavaScript and XML) is a web application implementation method that disconnects some page updating activities from the normal browser display in favor of having the "housekeeping" done by a background interaction between the browser and the server, moderated in some cases by special XML and JavaScript supplied operations.

A major difficulty in testing an AJAX application is the very nature of the implementation: it may involve asynchronous operations. In practice this shows up as a script "typing ahead" of the browser, and this kind of behavior almost always leads to loss of state information and failure of the test.

eValid has natural (automatic) and several manually augmented ways to assure synchronized playback for AJAX applications. Our experience is that one or more of these methods allows a script to play back reliably and still support full validation capabilities within the subject pages. In many cases, the built-in "natural synchronization" is sufficient.

Synchronization Method Summary
Here is a summary of available script playback synchronization methods.

• Natural Synchronization
  Synchronization is build into eValid and works most of the time, automatically, and without additional synchronization steps. eValid uses a number of internal signals to determine if it is OK to continue playback (i.e. if the playback is fully synchronized):
  • The page has reached the Interactive state (this is a DOM internal signal).
  • The page has reached the DocumentComplete (this is a DOM internal signal).
  • eValid has determined that all threaded download activity has been completed (this is an eValid internal method).
  • eValid has determined that the rendering of the page has reached an internal state stable enough for continuation of automated playback (this is an eValid internal method).
  • eValid has determined, by examination of next commanded action in the script file, that that command has sufficient object availability for the command to be successful (this is an eValid internal method).

• Using SyncOnURL
  This method takes advantage of the fact that you can learn the complete set of pages that eValid downloads when rendering a page, in the order of completion of download, by studying the detailed eValid EventLog data. Synchronization is obtained by having a set of SyncOnURL commands that mention several of the pages that are known to arrive last in a download sequence.

  Here is a page that describes Applying the SyncOnURL Command for playback synchronization.

• Using SyncOnText
  Here, eValid uses the SyncOnText command to wait for the appearance of the required string in the internal DOM for the page. If the page is being populated asynchronously this command will wait until it sees the required text, then will continue. You may wish to run several such commands, or choose a phrase that is found at the bottom of the page (because that is the part that will be completed loaded last).

  Here is a description of Testing the Google Gmail Application that illustrates how this works.

• Using SyncOnScreenRect
  This method requires use of the Windows desktop and while it may appear to be a crude approach when it is used correctly it is very, very reliable.

  This method requires that you record a SyncOnScreenRect command that records a checksum of the pixel values in a particular part of a screen which eValid records from. At playback time eValid rechecks the value of the current checksum, and waits until the checksum matches before continuing playback.

Cautionary Notes
The eValid playback engine is a complex multi-threaded activity and multiple confirmations of achieving synchronization may be required in difficult cases. It is easy to be deceived by some browser and/or Windows messages. For example: "Done" is not necessarily done; "In focus" may not necessarily mean that a window is actually in focus.

In addition, autonomous actions by the browser may defeat the best natural [built in] synchronizations. Finally, you may need to pay special attention to a particular web applications' initial state.