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Summary
Here is an outline of a class of counterexamples that illustrate WHY a stateful user emulation of browser state is necessary in some cases -- and why in those cases the capture of the entire bidirectional HTTP user interaction cannot EVER be fully realistic. This is particularly important in load testing in which HTTP taffic capture is unlikely to be successful because the traffic differs over time.

• General Idea
  Any recording which involves any non-deterministic action will have a HTTP URL sequence that is different each time you make a recording.

  ...or...

  Actions taken by the user employing ONLY the JavaScript code that is running in the browser which do NOT produce any HTTP traffic.

  If you record the HTTP URL sequence today, the non-deterministic behavior in the future will invalidate the recorded URL sequence.

  OR: You can build a program that simulates the action of the eValid browser.

• Dynamic Pages
  In these cases the actual content of the web page changes based on both the actions the user takes (changing the state of the browser) and the actions those cause in the change in state of the server.

  To achieve a realistic test the test agent can act on the structur of the web page autonomously while the pages change. The details of the state need not be preserved for the test to be meaningful so long as the sequence of changes is preserved.

• Non-Deterministic Actions At Client/Browser
  Examples that come to mind include:

  1. Random number generation in JavaScript inside client browser.

  2. Client response time depends on web latency: if the server response is within NNN msecs then the browser does one thing, but if not the it does another. This is non-deterministic but can be simulated.

  3. The pages requested are a function of the time of day, which can be sensed inside the client/browser and make for a very large number of possible URL sequences.

  4. The browser action is based on a TAG sent over by the server which [randomly] will match or not match. If TAG != TAG' the browser does a different action than if it does match, TAG = TAG'.

• Other Possibilities
  Session cookie information is lost on browser restart (batch mode re-start of the browser will restore defaults to the session cookie storage area), but the server will not have been informed (user did not log out), so the server is out of sync with the client/browser.