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Load Testing - User Load vs. Iteration

    Question

  • Hi,

    I was reading one of the posts in this forum about some violations. I came across with a reply from Edwer Fang saying:

    "...If you specify the length of load test to be 1 iteration, then there will be one 1 web test run during load test running, even if you set user load to 10, it will not run 1 web test for each user. The total number of web test running is 1..."

    I'm completely confused by this comment. I'm new to to load testing.

    If only 1 web test is run during the load test when the iteration is set to 1, then what is the point to have 10 virtual users? I thought the point of load test is to have to 10 virtual users to run the same/mixed web test(s) concurrently. Then, "... it will not run 1 web test for each user ...", what does this mean?

    Could someone who is good at load testing give some discussions on user load and iteration. Really appreciated.

     

    Wednesday, November 03, 2010 4:53 PM

Answers

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  • Maybe this post will help:

    http://social.msdn.microsoft.com/Forums/en-US/vstswebtest/thread/b384dc59-86d4-42cb-962f-ab61673d7ce1

    Setting use iterations = true and iterations = 1 and user count > 1 doesn't make sense.  I think of iterations as the maximum number of tests that will run and I pretty much never use it when load testing.


    Tim
    • Marked as answer by meshushi Thursday, November 04, 2010 2:08 PM
    Wednesday, November 03, 2010 8:55 PM
  • Hi Tim,

    I read the link you posted above. Something said in that link is interesting:

    "..... The Run Settings -> Test Iterations property (when Use Test Iterations = True) is truly a global counter - that value is the total number of test iterations for all tests and - has nothing to do with number of users as Bill pointed out. Maybe the name of that propety should be Global Test Iterations? .... "

    My understanding is, if Use Test Iterations = True and Test Iterations = 1, then the Load Test is runned just once. If the Test Iterations = 50, Then the same Load Test is run 50 times.

    In each iteration, the Load Test is run according to the settings of the Load Test, i.e., vitural users and test mix etc. 

    I think the word, 'web test', used in Edwer Fang's original comment is a bit confusing. At least, I confused it with web performance test.

    I hope I've now understood iterations and user load correctly. It now sounds simple. I guess it is just too many words said :) 

    I have another question, pardon me if it sounds silly. Let's say, I have a load test with 25 virtual users and just one web performance test in the test mix, Test A 100%. Without thinking time. Warm-up time 20 sec. Run duration is 3 min.

    When I start run the load test, all the 20 virtual users start different threads for making requests for Test A. Test A only takes no more than 1 minute to be finished on average.

    My questions is, during the load test, does each virtual user repeat Test A until the run duration is reached? or does each virtual user just do Test A once, then stop?

    From the virtual user activities chart, it seems the virtual users just keep on repeating Test A until the duration is reached.

    Thanks

    Su 

    Thursday, November 04, 2010 10:55 AM
  • in VS 2008 the test was called a web test, in vs 2010 it has been renamed to web performance test.

     

    Each virtual user will repeat test A until the time runs out


    Tim
    • Marked as answer by meshushi Thursday, November 04, 2010 2:08 PM
    Thursday, November 04, 2010 11:59 AM
  • excellent. many thanks, Tim, have a nice day : )

    Thursday, November 04, 2010 2:08 PM