I was also as a sample QA to perform the operation during Load Test. They said they make 1200 threads to the web application in which it is working to perform some screen flow after login.
In Jmeter standalone UI you need to set these "numberOfThread"(u), "rampUpTime"(t), "loopCount"(i) correctly to achieve what you want. E.g. u=5(number of users), t=10 means, 5 users(threads) will be spawn in 10 secs which equates to each request/user in a gap of 2 secs.
If you want to continue this for more time, then set i=2 for twice. That means 10 users/requests will be fired against your server-application every 2 secs gap. You can make 100(or 1000) users in 1 sec gap each just by playing around these values.
If my sampler operation on login and doing some approval or reject process, one operation was OK. As you know that one record has been approved and it cannot be approved again.
Then you need to adjust your request payload such that it never sends the same record again if it has been approved.
-OR- Tune your server application to accept the same payload(in this case you are really testing the load your application can handle, not the login feature, so it's ok)
quote=Then in JMeter 1200 threads, would it create many same login and same approvals?
Answered above, you can adjust the Jmeter input values which your OS can handle where JMeter is running.
Now I tried to download the JMeter and tried to learn. I see the screen of below. But I still do not understand of the question that I ask now.
Is there any one understand and can let me know??
There is no magic. Jmeter has simplified all the things behind the scene and give you an UI to control your parameters.
If I have created the JMeter Test Plan to go to some public website and try to simulated 9999 threads, would it make the public website crash?
If the website crashes, then it's not designed properly to handle the loads. e.g. some great sites handles by using rate-limiting your calls.
That means it bans calls with certain frequencies and allows calls with certain frequencies. Hence you should not afraid of those things in my opinion.
Even if it crashes, the owner of the site will bring up again soon he gets notified.
Alternatively can also use the Open Source library Zerocode(github) for load testing using simple
Junit runner. Simply google it for "zerocode load runner" for more examples.
This can help you to integrate with your CI Build pipeline like a any other usual
maven project and manipulate your payload/request for each
thread.
In fact the testing should be part of your build if you are running the project in agile mode.