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LoadRunner Interview Questions

LoadRunner Interview Questions and Answers

 

Load Runner is HP tool used to test the performance of a software application. Even though there are many other tools to find testing performance of an application, Loadrunner got its own share of advantage due to its unique features and ease of the tool navigation easy to understand the tool functionality. So, in the interviews when ever you get questions about performance testing, you need answer more about how you have used the loadrunner using its functionality and what kind of different testing you have done such as load testing, benchmark testing, stress testing, endurance testing etc… And also please compare how you have compared and used existing benchmark test results with previous and new results.

For example, we normally conduct a benchmark test for the application initially and take all the measurements in a excel sheet. Examples of measurements will be like below:

  • Sign-in module with 1000 users at a time – 10 sec execution time.
  • Sales category module time with 10 users : 5 sec

So, after a while you have implemented one more new module, then you need to do benchmark testing again to see if there is any impact on existing module performances. For this we conduct once again the same benchmark test and take measures and compare with the previous results (above). If any existing module taking more time after this new module implementation, we will investigate why??

 

1. What components are available in LoadRunner?

The components available in LoadRunner are the following: Controller, Virtual User Generator (VuGen), Agent processor, Analysis, Monitoring, and books online.

2. Which LoadRunner component is used for recording scripts?

The Virtual User Generator (VuGen) is used for script recording.  It can be used to create Vuser scripts for a broad range of communication protocols and application types.

3. Which LoadRunner component is used for the playback of a script in the multi-user mode?

The Controller can be utilized for script playback in the multi-user mode. Script playback is usually performed during scenario testing where multiple Vuser scripts are executed in a group.

4. How can a LoadRunner script be debugged?

Breakpoints and the Run Step-by-Step features of VuGen can be used for debugging and this information is written in the output window. There are debug settings in the Options area that allow the user to set the specifics about the trace that is performed during the execution of the scenario.

5. How does one write a user defined function in LoadRunner?

When creating a user-defined function, one must first create the external library that contains the function. This library must then be added to the bin directory of VuGen. Next, the user-defined function can be assigned as a parameter.

6. What is the process for load testing?

1. Test Planning – Create a clear test plan in order to be certain that the scenarios that will be developed for testing the application will fulfill the objectives for load testing.

2. Vuser Creation – Create scripts for Vusers that have tasks that will be completed by each individual Vuser, by all Vusers together, and those that will be examined as transactions.

3. Scenario Creation – Scenarios explain the actions that will occur during testing and include lists of scripts, machines, Vusers, etc. that run in that time period. LoadRunner can automatically build scenarios.  The LoadRunner Controller is used for this and it is capable of creating both goal-oriented and manual scenarios. For goal-oriented scenarios, the goal that the test has to achieve is defined.  For manual scenarios, the scripts, load generators, volume of Vusers, and amount of Vusers that are to be appointed to each script has to be defined.

4. Scenario Runs – Before running the test, the configuration and scheduling of the scenario is set. Running the test will involve instructing several Vusers to execute tasks at the same time, which emulates the load on a server.

5. Scenario monitoring – The scenario is monitored using some or all of the many performance monitors offered by LoadRunner.  These monitors include the following: system, ERP, web, web application server resource, streaming media, firewall, and database server resources, transaction, online runtime, network delay, and Java performance.

6. Results Analysis – LoadRunner records data from the test and provides various reports and graphs that can be used to evaluate the performance of the application.

7. Define rendezvous point.

Rendezvous points are places in the test execution that command Vusers to wait for other Vusers so that a task(s) can be performed simultaneously. This is done to simulate heavy user traffic on a server.  For example, the peak load for a bank server can be simulated by inserting a rendezvous point that instructs 1000 Vusers to withdraw cash from accounts simultaneously.

8. Why is it useful to establish parameters?

Parameters can be thought of as script variables and are used to simulate real users and alter input to the server. It allows the tester to use a single script to emulate a variety of system users by allowing multiple sets of data to be sent to the server with each script run.

9. Which function is used to capture dynamic data in the web Vuser script?

Web_reg_save_param is the function that saves dynamic data to a parameter.

10.         What are the changes that can be made to run-time settings?

There are four run-time settings that can be made:

Pacing: This contains iteration count.

Log: This is where logging can be set to standard or disabled.

Extended Think Time:  Capable of setting think time to be ignored or replayed.

General:  Allows the setting of Vusers for processes or multithreading.

11.         How can web server related issues be found?

Web resource monitors can be used to find server related issues.  These monitors are capable of analyzing web server throughput, volume of hits per second during the execution of the scenario, the number of pages downloaded per second, and the volume of responses per second.

12.         How can database related issues be found?

Monitors and the Data Resource Graph can be used to find database related issues. LoadRunner allow the tester to specify the resource that is to be measured before the controller is run.

Some more Loadrunner Interview Questions.

13.         What are the types of options are available for goal-oriented scenarios?

There are five goal options available:

  • Number of Vusers (concurrent)
  • Number of transactions/second
  • Number of hits/second
  • Number of pages/minute
  • Transaction response time

14.       How many types of graphs are available in LoadRunner and what are they?

There are 5 types of graphs:

  • Network delay time graph – displays the time the elapses between request and response
  • Two transaction response time graphs – one for load and one for percentile
  • Hits/second graph – Shows application traffic volume.
  • Pages download/second graph – shows the rate that download processes are performed

15.         How can performance bottlenecks be identified?

LoadRunner has monitors that can be used to detect performance bottlenecks. These include network, web server, application server, and database server monitors. These monitors can be used to locate trouble spots in scenarios that cause increases response time and they track throughput, network delays, performance response time, hits/sec, etc.

16.         When should load and performance testing be performed?

Load testing should be performed when the user interface is completed and tested. User interface testing typically focuses on functionality of a system component, whereas load and performance testing focuses on the whole system. For example, a typical scenario will check reliability when 1000 users are logged in at the same time and will examine system response time, operation on various platforms, whether the system crashes, etc.

17.         How can one tell when correlation can be performed?

There are two ways to do this. One is to use the scan function to search for correlations and select a value from the resulting list. The second is to record a pair of scripts and then compare them to each other.

18.         Where are automatic correlation options set?

The automatic correlation is set in recording options area on the correlation tab. From here, correlation can be enabled for the full script and rules for correlation can be defined.   Automatic correlation can be performed on a database by viewing the output window, scanning for correlation, and selecting the value that will be used.

19.         Where is the number of iterations set for testing with Vuser scripts?

The number of iterations is set in the VuGen pacing tab in the Run-time settings area.

20.         What is ramp up and how can it be set?

Ramp up is gradually increasing the load on a server.  This is simulated by gradually increasing the number of Vusers.  This feature can be found in the Scenario Scheduling Options.  When used, the initial value and the time to wait between periods are specified.

21.         What is the benefit of running a Vuser script as a thread?

The advantage of running a Vuser script as a thread is that it allows more Vusers to be used for one load generator. Running Vuser scripts as processes utilizes a lot of memory because all of the loaded scripts use the same driver.  This limits the number of Vuser scripts that can be run on one generator.

22.         How do you set LoadRunner to stop script execution when an error occurs?

Execution of Vuser scripts can be stopped on error using LoadRunner’s lr_abort function. The “Continue on error” option must not be checked in the Run-Time Setting menu.  It is helpful when it is necessary to abort execution when a certain error condition occurs. This function instructs the Vuser to stop performing what is in the Actions section, and to begin performing the vuser_end functions.  When execution is terminated, the Vuser status is changed to “Stopped”.

23.         How are throughput and response time related?

The graph for throughput displays the quantity of data that the server sent to the Vusers in one second. When throughput is compared to the response time of transaction, it decreased as the response time decreased. In addition to this, the highest throughput and response times occur at approximately the same time.

24.         Define think time and explain how do you change the threshold for it.

Think time is the interval of time that a user must wait between actions. An example of this is the time that a user takes to review data after receiving it from the server before responding to it.  The threshold is the maximum level at which this time will be ignored.  The default threshold value is five seconds but this can be modified in the VuGen Recording options.

25.         Explain the difference between standard and extended log.

The standard log contains a subset of functions and messages, which vary based on the type of Vuser, that are generated during the execution of a script. The extended log creates a more detailed listing of functions and messages.

You must also read Automated Testing Interview Questions.

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