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I'm testing a large BizTalk system using Visual Studio Load Test. Load Test to pushes messages into MQ, these are picked up by BizTalk and then processed.

Rather than having the test finish (and all performance counters ending) as soon as Visual Studio has finished injecting messages to MQ, I want the test to end if and only if some condition is met (in my case if (SELECT COUNT(*) FROM BizTalkMsgBoxDb.dbo.Spool) == 4).

I can see a bunch of ways to run stuff after the test is complete, but no obvious way to extend the test and continue monitoring unless some user-defined exit condition is met.

Is this possible, or if not, does anyone have an idea for a good work-around/hack to achieve this?

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You'll want to write a custom load test plugin. Details begin at this URL: http://msdn.microsoft.com/en-us/library/ms243153.aspx

The plugin can manipulate the scenario, extending the duration of the test until your condition is met.

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I imagine you want to keep the load test running after queueing up a bunch of requests in order to continue to monitor the performance while the requests are processed. Although we can't control the load test duration, there is a way to achieve this.

  1. Don't limit the test duration: Set the load test duration (or number of iterations) to a very large value -- larger than you anticipate (or know) it will take for the end condition to be satisfied.
  2. Limit the scenario that queues up requests: In the load test scenario properties, in the Options section, set the Maximum Test Iterations so that the user load will drop to zero after sending the desired number of requests. If setting an iteration limit is not possible for some reason, you can instead write a load test plugin that sets the user load to zero in a specified scenario after a certain amount of test time has elapsed.
  3. Check for end condition: Write a web test plugin that checks the database for your end condition. Attach this plugin to a new webtest in a new scenario and set Think Time Between Test Iterations on the scenario so that the test runs only as often as needed (60 seconds?). When the condition is reached, the plugin should write a predetermined value into the user context (the user context is accessible in the web test context as $LoadTestUserContext, and is only available in a load test, not when running a webtest standalone).
  4. Abort the test: Write a load test plugin that looks for the flag value in the user context in the TestFinished event. When the value is found, the plugin calls LoadTest.Abort().

There is one minor disadvantage to this method: the test state is marked as Aborted in the results database.

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At time of writing there is (still) no way to extend the duration of the test using a custom load test plugin, nor by having a virtual user type that refused to exit, nor by locking the close-down period of the test and preventing it from exiting that way.

The only way we managed to do something like this was to directly manipulate the LoadTest database and inject performance counter data in afterwards from log files, but this is neither smart nor recommended.

Oh well..

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