Load Testing Interview Questions and Answers

Load Testing Interview Questions and Answers

Testing Tools Online Training1. What is load testing?

A. Load testing is to test that if the application works fine with the loads that result from large number of simultaneous users, transactions and to determine weather it can handle peak usage periods.

2. Explain the Load testing process?

A. Step 1: Planning the test. Here, we develop a clearly defined test plan to ensure the test scenarios we develop will accomplish load-testing objectives.

Step 2: Creating Vusers. Here, we create Vuser scripts that contain tasks performed by each Vuser, tasks performed by Vusers as a whole, and tasks measured as transactions.

Step 3: Creating the scenario. A scenario describes the events that occur during a testing session. It includes a list of machines, scripts, and Vusers that run during the scenario. We create scenarios using LoadRunner Controller. We can create manual scenarios as well as goal-oriented scenarios. In manual scenarios, we define the number of Vusers, the load generator machines, and percentage of Vusers to be assigned to each script. For web tests, we may create a goal-oriented scenario where we define the goal that our test has to achieve. LoadRunner automatically builds a scenario for us.

Step 4: Running the scenario.
We emulate load on the server by instructing multiple Vusers to perform tasks simultaneously. Before the testing, we set the scenario configuration and scheduling. We can run the entire scenario, Vuser groups, or individual Vusers.

Step 5: Monitoring the scenario.
We monitor scenario execution using the LoadRunner online runtime, transaction, system resource, Web resource, Web server resource, Web application server resource, database server resource, network delay, streaming media resource, firewall server resource, ERP server resource, and Java performance monitors.

Step 6: Analyzing test results. During scenario execution, LoadRunner records the performance of the application under different loads.

3. When do you do load and performance Testing?

A. We perform load testing once we are done with interface (GUI) testing. Modern system architectures are large and complex. Whereas single user testing primarily on functionality and user interface of a system component, application testing focuses on performance and reliability of an entire system.

4. What are the components of LoadRunner?

A. The components of LoadRunner are The Virtual User Generator, Controller, and the Agent process, LoadRunner Analysis and Monitoring, LoadRunner Books Online.

5. Describe how to identify the memory leakage using loadrunner?

A. In Load runner, every application has a processor running in the system. The processor needs to be identified. Using the performance tab we can check the memory consumption of the processor. Continuous tracking needs to be done while load testing. However, if the memory keeps increasing even on stopping the test, a memory may have occurred. Also, if the memory is not released on stopping the test, a memory may have occurred.

6. What are the Vuser components in LoadRunner?

A. Application Components used are client, database or additionally business application server.

Web Server works on and through LAN, WAN, or www connection.

Application Server components are client, business server and database server without use of www.but through Protocols like FTP.

7. How do you debug a LoadRunner script?

A. VuGen contains two options to help debug Vuser scripts-the Run Step by Step command and breakpoints. The Debug settings in the Options dialog box allow us to determine the extent of the trace to be performed during scenario execution. The debug information is written to the Output window. We can manually set the message class within your script using the lr_set_debug_message function. This is useful if we want to receive debug information about a small section of the script only.

8. What Component of LoadRunner would you use to play Back the script in multi user mode?

A. The Controller component is used to playback the script in multi-user mode. This is done during a scenario run where a v user script is executed by a number of v users in a group.

9. How did you plan the Load? What are the Criteria?

A. Load test is planned to decide the number of users, what kind of machines we are going to use and from where they are run. It is based on 2 important documents, Task Distribution Diagram and Transaction profile.

Task Distribution Diagram gives us the information on number of users for a particular transaction and the time of the load. The peak usage and off-usage are decided from this Diagram.

Transaction profile gives us the information about the transactions name and their priority levels with regard to the scenario we are deciding.

10. What is the difference between Load Test and Volume Test?

A. Volume Testing is mainly for the functionality check, whether the system is behaving as same or not in the Expected Safety Load.

Load testing is mainly to check the System stability. Load testing will be carried out above the expected Load. Normally 1.5 times of the acceptable load.

11. What criteria would you use to select Web transactions for load testing?

A. We can select web transactions from task distribution diagram and transaction profile.

From transaction profile we can come to know what are all the major transactions taking place in a particular day, at what time of the day there will be a peak load etc.

From task distribution diagram we can come to know for which transaction there will be more database activity and risk.

Once the transaction is selected from transaction profile and task distribution diagram, we will perform load testing for that particular transaction.

12. What is the difference between Scalability testing and load testing?

A. Scalability can be considered as a part of performance testing which checks if the system is scalable or not. To find if the functionality and the performance of a system will scale up to meet specified requirements.

Load testing is to check if the system can take load or not. To check the expected usage of a software program by simulating multiple users accessing the program’s services concurrently.

13. How you analyze graphics in loadrunner? how do you work bug log?

A. Basically there may be few pages in the Application consists of More than 5 widgets or more than 10 widgets here we look out for an response time of the page based on the requirement specs we try to analyse the time takes to display.

14. What is throughput?

A. If the throughput scales upward as time progresses and the number of Vusers increase, this indicates that the bandwidth is sufficient. If the graph were to remain relatively flat as the number of Vusers increased, it would be reasonable to conclude that the bandwidth is constraining the volume of data delivered.

15. What is the advantage of running the V user as thread?

A. VuGen provides the facility to use multithreading. This enables more Vusers to be run per generator. If the V user is run as a process, the same driver program is loaded into memory for each V user, thus taking up a large amount of memory. This limits the number of Vusers that can be run on a single generator. If the V user is run as a thread, only one instance of the 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.

16. Explain how to use Regular Expression in Load Runner for web functions?

A. A function can be written in Load runner script to check if a pattern matches against a given subject or not. The pattern and subject can be passed as parameters to the function. Regexec () can be used to compare the subject with the pattern. This script can be then executed to see the results.

E.g Pattern is: – b(c(.*))e
Subject: abcdef
Result: 1 (match found)

17. How do you perform functional testing under load?

A. Functionality under load can be tested by running several V users concurrently. By increasing the amount of V users, we can determine how much load the server can sustain.

18. What Component of LoadRunner would you use to play Back the script in multi user mode?

A. The Controller component is used to playback the script in multi-user mode. This is done during a scenario run where a v user script is executed by a number of v users in a group.

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