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How to verify and filter out invalid user accounts?

    When performing load tests by simulating users that have to fill out a HTML login form the user accounts and their passwords are normally extracted from an input file and assigned to the HTML form parameters in such a way that each simulated user uses an own username and password. However, such an input file contains often also a couple of invalid user accounts, and when measuring an error during a load test it might be hard to distinguish if the error did occur because the Web application was overloaded or did occur because the user account was invalid. Therefore, we recommend that you make first a small test run to filter out all invalid user accounts before you execute the real load test. For this purpose you can use the pre-installed Plug-In named “Generic Output File (V1.0)” and proceed as follows:
  1. Add the Plug-In “Generic Output File (V1.0)” to your load test and configure its execution to be at the end of each loop. Use as first output value the user name and as second output value the password extracted from the input file containing the user accounts.
  2. Run now a load test by simulating exactly as many users as the input file contains different user names and passwords. Limit the number of “Max. Loops per User” to one, set a really large “Load Test Duration” (for example 2 hours) and set a large “Startup Delay per User” (for example 5 seconds: 5,000 ms) in order that the Web application is not overloaded during this verification run.
  3. After the verification-test has been completed you can acquire the log file of the Plug-In (which has the same file name as the load test program, but has the file extension *.log). The log file will contain only valid user accounts.
  4. As next step you can delete the original input file containing the user accounts and then rename the log file of the Plug-In to the name of the deleted file. After that you should also remove the Plug-In form your load test program.
  5. Finally, generate the load test program once again and start your real load test with the verified and valid user accounts.

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