Software Testing: Top 20 Questions of Load Runner
1. What is load testing?
Load testing is the method to test if the application works fine under certain defined load. Load can be the number of vusers which will performance a certain amount of transaction in a defined unit of time.
2. What is Performance testing?
Performance Testing is the process of determining the performance (speed, effectiveness, reliability, scalability) of the system which involves tests to be executed in a dedicated testing environment having production like infrastructure in place to get the results which can pin-point the issue/bottleneck (if any).
3. What are the components of LoadRunner?
The components of LoadRunner are The Virtual User Generator, Controller, and the Agent process, LoadRunner Analysis and Monitoring, LoadRunner Books Online.
4. What Component of LoadRunner would you use to record a Script?
The Virtual User Generator (VuGen) component is used to record a script. It enables you to develop Vuser scripts for a variety of application types and communication protocols.
5. What is a rendezvous point?
You insert rendezvous points into Vuser scripts to emulate heavy user load on the server. Rendezvous points instruct Vusers to wait during test execution for multiple Vusers to arrive at a certain point, in order that they may simultaneously perform a task. For example, to emulate peak load on the bank server, you can insert a rendezvous point instructing 100 Vusers to deposit cash into their accounts at the same time.
6. What is a scenario?
A scenario defines the events that occur during each testing session. For example, a scenario defines and controls the number of users to emulate, the actions to be performed, and the machines on which the virtual users run their emulations.
7. What is correlation? Explain the difference between automatic correlation and manual correlation?
Correlation is used to obtain data which are unique for each run of the script and which are generated by nested queries. Correlation provides the value to avoid errors arising out of duplicate values and also optimizing the code(to avoid nested queries). Automatic correlation is where we set some rules for correlation. It can be application server specific. Here values are replaced by data which are created by these rules. In manual correlation, the value we want to correlate is scanned and create correlation is used to correlate.
8. When do you disable log in Virtual User Generator, When do you choose standard and extended logs?
Once we debug our script and verify that it is functional, we can enable logging for errors only. When we add a script to a scenario, logging is automatically disabled.
Standard Log Option: When you select Standard log, it creates a standard log of functions and messages sent during script execution to use for debugging. Disable this option for large load testing scenarios. When you copy a script to a scenario, logging is automatically disabled
Extended Log Option: Select extended log to create an extended log, including warnings and other messages. Disable this option for large load testing scenarios. When you copy a script to a scenario, logging is automatically disabled. We can specify which additional information should be added to the extended log using the extended log options.
9. What are the changes you can make in run-time settings?
The Run Time Settings that we make are:
- a) Pacing – It has iteration count.
- b) Log – Under this we have Disable Logging Standard Log and Extended.
- c) Think Time – In think time we have two options like Ignore think time and Replay think time.
- d) General – Under general tab we can set the vusers as process or as multithreading and whether each step as a transaction.
10. 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 value to wait between intervals can be specified. To set Ramp Up, go to ‘Scenario Scheduling Options’
11. What is the relation between Response Time and Throughput?
The Throughput graph shows the amount of data in bytes 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.
12. What does vuser_init action contain?
Vuser_init action contains procedures to login to a server.
13. What does vuser_end action contain?
Vuser_end section contains log off procedures.
14. What are the benefits of multiple Action files within a Vuser?
They allow you to perform different business processes in one Vuser to repsent A real user who does the same thing. They let you build Vusers that emulate real Users defined in the User Community Profile. They also allow you to record the Login and logoff separately from the Action files and thus to avoid iteration.
15. How can you determine which field is data dependent?
Rerecord the same script using different input values, then compare the two Scripts.
16. What is difference between manual scenario and Goal oriented scenario? What Goal Oriented scenarios can be created?
–Main purpose is to learn how many Vusers can run concurrently
– Gives you manual control over how many Vusers run and at what times
Goal oriented scenario:
– Goal may be throughput, response time, or number of concurrent Vusers
– LoadRunner manages Vusers automatically
17. Different Goal Oriented Scenarios are:
- Virtual Users
- Hits per second
- Transaction per second
- Transaction Response time
- Pages per minute
18. Why wouldn’t you want to run virtual users on the same host as the Load-Runner Controller or Database Server?
Running virtual users on the same host as the LoadRunner Controller will skewthe results so that they no longer emulate real life usage. By having both the Controller and the Vusers on the same machine, the tester will not be able to determine the effects of the network traffic.
19. Each time you run the same scenario, the results will be slightly different. Whatare some of the factors that can cause differences in performance measurements?
Different factors can effect the performance measurements including networktraffic, CPU usage and caching.
20. What are some of the reasons to use the Server Resources Monitor?
- To find out how much data is coming from the cache
- To help find out what parts of the system might contain bottlenecks
21. Explain the following:
- Hits per second graph
The Hits per Second graph shows the number of HTTP requests made by Vusers to the Web server during each second of the scenario run. This graph helps you evaluate the amount of load Vusers generate, in terms of the number of hits.
- Pages download per second graph
The Pages Downloaded per Second graph shows the number of Web pages (y-axis) downloaded from the server during each second of the scenario run (x-axis). This graph helps you evaluate the amount of load Vusers generate, in terms of the number of pages downloaded.
- Transaction Response time (under load) graph
The Transaction Response Time (Under Load) graph is a combination of the Running Vusers and Average Transaction Response Time graphs and indicates transaction times relative to the number of Vusers running at any given point during the scenario. This graph helps you view the general impact of Vuser load on performance time and is most useful when analyzing a scenario with a gradual load.
- Transaction Response time (percentile) graph
The Transaction Response Time (Percentile) graph analyzes the percentage of transactions that were performed within a given time range. This graph helps you determine the percentage of transactions that met the performance criteria defined for your system.
- Network delay time graph
The Network Delay Time graph shows the delays for the complete path between the source and destination machines (for example, the database server and Vuser load generator).