Testing Interview Questions

1.How do you perform functional testing under load?
Functionality under load can be tested by running several Vusers concurrently. By increasing the amount of Vusers, we can determine how much load the server can sustain.

2. What is Ramp-up? How do you set this?
This option is used to gradually increase the amount of Vusers/load on the server. An initial value is set and a vlaue to wait between intervals can be specified. To set Ramp-up, go to “Scenario Scheduling Options”.

3. What is the advantage of running the Vuser as thread?
VuGen provides the facility to use multithreading this enables more Vusers to be run per generator. If the Vuser is run as a process, The same driver program is loaded into memory for each Vuser, Thus taking up a large amount of memory. This limits the number of Vusers that can be run on a single generator. If the Vuser is run as a thread, the only one instance of driver program is loaded into memory for the given number of Vusers (Say 100). each thread shares the memory of the parent driver program thus enabling more Vusers to be run per generator.

4. If you want to stop the execution of your script on error? How do you do that?
The lr_abort function aborts the execution of a Vuser script. It instructs the Vuser to stop executing the actions sections, execute the Vuser_end section and end the execution. This function is useful when you need to manually abort a script execution as a result of a specific error condition. When you end a script using this function, the Vuser is assigned a status “stopped”. For this to take effect we have to first uncheck the “continue on error” option in runtime setting.

5. What is the relation between response time and throughput?
The throughput graph shows the amount of data in bites that the Vusers received from the server in a second. When we compare this with the transaction response time we will notice that as throughput decreased, the response time also decreased. Similarly the peak throughput and highest response time would occur approximately at the same time.

6. Explain the configuration of your system?
The configuration of your system refers to that of the client machines on which we run the Vusers. The configuration of any client machine includes its hardware settings, memory, operating system, software applications, development tools. this system component configuration should match with the overall system configuration that would include the network infrastructure, the web server, the database server, and any other components that go with this larger system so as to achieve the low testing objectives.

7. How do you identify the performance bottlenecks?
Performance bottleneck can be detected by using monitors. these monitors might me application server monitors, web server monitors, database server monitors and network monitor . They help in finding out the troubled area in our scenario, which causes increased response time. The measurements made are usually performance response time, throughput, hits /second, network delay graphs etc..

8. If web server, database and network are all fine where could be the problem?
The problem could be in the system itself or in the application server or in the code written for the application.

9. how do you find web server related issues?
Using web resource monitors we can find the performance of web servers. Using these monitors we can analyze throughput on the web server, number of hits /second that occurred during scenario, the number of hit responses per second the number of download pages per sec.

10. how did you find the database related issues?
By running database monitor and help of data resource graph we can find database related issues. Example, you can specify the resource you want to measure on before running the controller and then you can see database related issues.

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