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Loadrunner Interview Questions and Answers
How do you debug a LoadRunner script?
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.
How do you write user defined functions in LR? Give me
few functions you wrote in your previous project?
Before we create the User Defined functions we need
to create the external
library (DLL) with the function. We add this library to
VuGen bin directory. Once the library is added then we
assign user defined function as a parameter. The
function should have the following format: __declspec (dllexport)
char* <function name>(char*, char*)Examples of user
defined functions are as follows:GetVersion,
GetCurrentTime, GetPltform are some of the user defined
functions used in my earlier project.
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 c) Extended 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.
Where do you set Iteration for Vuser testing?
We set Iterations in the Run Time Settings of the
VuGen. The navigation for this is Run time settings,
Pacing tab, set number of iterations.
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.
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’
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, 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.
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 section, 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 the status
"Stopped". For this to take effect, we have to first
uncheck the “Continue on error” option in Run-Time
Settings.
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.
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