Top JMeter Interview Questions And Answers


Top JMeter Interview Questions And Answers



Top JMeter Testing Interview Questions & Answers

Question: What is JMeter?

Answer:
JMeter is one of the Java tools which is used to perform load testing client/server applications. Apache JMeter is open source software, a 100% pure Java desktop application designed to load test functional behavior and measure performance of the application. It was originally designed for testing Web Applications but has since expanded to other test functions.

Ø  Java Based Window Application.
Ø  Support many type of applications like HTTP, Web Service, LDAP, JDBC, Java, FTP etc.
Ø  Support Distributed Testing: So that we can distribute load on multiple machine, so that we can simulate load on server, network or object which are coming from different machine to implement real world scenario.
Ø  Record & Playback - Record the user activity on the browser and simulate them in web application using JMeter.


Question: What are the protocols supported by JMeter?

Answer:
The protocols supported by JMeter are:

Web: HTTP, HTTPS sites 'web 1.0' web 2.0 (ajax, flex and flex-ws-amf)
Web Services: SOAP / XML-RPC
Database via JDBC drivers
Directory: LDAP
Messaging Oriented service via JMS
Service: POP3, IMAP, SMT P
FTP Service

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Question: List some of the features of JMeter?

Answer:
Following are some of the features of JMeter:

Ø  Its an open source software.
Ø  It has simple and intuitive GUI.
Ø  JMeter can load and performance test many different server types:
Ø  Web - HTTP, HTTPS, SOAP,  Database via JDBC, LDAP, JMS, Mail - POP3
Ø  It is platform-independent tool. On Linux/Unix, JMeter can be invoked by clicking on JMeter shell script.
Ø  On Windows it can be invoked by starting the jmeter.bat file.
Ø  It has full Swing and lightweight component support (pre-compiled JAR uses packages javax.swing .* ).
Ø  JMeter store its test plans in XML format. This means you can generate a test plan using a text editor.
Ø  It's full multi-threading framework allows concurrent sampling by many threads and simultaneous sampling of different functions by separate thread groups.
Ø  It is highly extensible.
Ø  Can also be used to perform automated and functional testing of your application.

Question: Explain how JMeter works?

Answer:
JMeter acts like a group of users sending requests to a target server. It collects response from target server and other statistics which show the performance of the application or server via graphs or tables.

Question: What is a Test Plan in JMeter?

Answer:
Test Plan defines and provides a layout of how and what to test. For example the web application as well as the client server application. It can be viewed as a container for running tests. A complete test plan will consist of one or more elements such as thread groups, logic controllers, sample-generating controllers, listeners, timers, assertions, and configuration elements. A test plan must have at least one thread group.

Question: List some of the test plan elements in JMeter?

Answer:
Following is a list of some of the test plan elements:
Ø  ThreadGroup
Ø  Controllers
Ø  Listeners
Ø  Timers
Ø  Assertions
Ø  Configuration Elements
Ø  Pre-Processor Elements
Ø  Post-Processor Elements


Question: What is distributed load testing? How
can it be achieved in JMeter?

Answer:
Distributed load testing is the process using which multiple systems can be used for simulating load of large number of users. The reason of using more than one system for load testing is the limitation of single system to generate large number of threads (users). In JMeter we can do distributed load testing using the master slave configuration.

Question: How can we reduce the resource requirement in JMeter?

Answer:
To make the best out of the available resources and in general as a practice, following practices should be incorporated in the tests-

Ø  Use non-GUI mode: jmeter -n -t test.jmx -l test.jtl
Ø  Use as few Listeners as possible; if using the -l flag as above they can all be deleted or disabled.
Ø  Don't use "View Results Tree" or "View Results in Table" listeners during the load test, use them only during scripting phase to debug your scripts.
Ø  Rather than using lots of similar samplers, use the same sampler in a loop, and use variables (CSV Data Set) to vary the sample. Or perhaps use the Access Log Sampler. [The Include Controller does not help here, as it adds all the test elements in the file to the test plan.]
Ø  Don't use functional mode
Ø  Use CSV output rather than XML
Ø  Only save the data that you need
Ø  Use as few Assertions as possible

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Question: What is Thread Group?

Answer:
Group elements are the beg inning points of your test plan. As the name suggests, the thread group elements control the number of threads JMeter will use during the test.
Thread group elements are the beginning points of any test plan.

Ø  All controllers and samplers must be under a thread group.
Ø  Listeners, may be placed directly under the test plan, in which case.
Ø  they will apply to all the thread groups.
Ø  The controls for a thread group allow you to:
Ø  Set the number of threads
Ø  Set the ramp-up period
Ø Set the number of times to execute the test

Question: What are Controllers and its types?

Answer:
JMeter has two types of Controllers:

Ø  Samplers Controllers: Samplers allow JMeter to send specific types of requests to a server. They simulate a user's request for a page from the target server. For example, you can add a HTTP Request sampler if you need to perform a POST, GET, DELETE on a HTTP service.

Ø  Logical Controllers: Logic Controllers let you control order of processing of Samplers in a Thread. Logic Controllers can change the order of request coming from any of their child elements. Some examples are: For Controller, While Controller, Loop Controller, IF Controller, Run Time Controller, Interleave Controller, Throughput Controller, Run Once Controller.

Question: What is Work bench?

Answer:
The Workbench is simply an area to store test elements while you are in the process of constructing a test. The Workbench is a sandbox for any test or portion of a test that you are working on. When you are ready to test what you have designed in the Workbench, you can copy or move the elements into the Test Plan.

It also contains Non- Test Elements Http mirror sever Http Proxy server {which is not available in the thread group & Test plan }

Question: What is Configuration element?

Answer:
A configuration element works closely with a Sampler Configuration elements can be used to set up defaults and variables for later use by samplers.

Note that these elements are processed at the start of the scope in which they are found, i.e. before any samplers in the same scope.

Its elements:

Ø  CSV Data Set Config: Used to read lines from a file, and split them into variables.

Ø  HTTP Authorization Manager : You can specify one or more user logins for web pages that are restricted using server authentication.

Ø  Java Request Defaults: You can set default values for Java testing

Ø  HTTP Cookie Manager: The Cookie Manager element has two functions:

·         It stores and sends cookies just like a web browser.
·         Second, you can manually add a cookie to the Cookie Manager. However, if you do this, the cookie will be shared by all JMeter threads.

Ø  HTTP Request Defaults: This element lets you set default values that your HTTP Request controllers use.
Ø  HTTP Header Manager: The Header Manager lets you add or override HTTP request headers



Question: What are Listeners?

Answer:
Listeners let you view the results of Samplers in the form of tables, graphs, trees or simple text in some log files. They provide visual access to the data gathered by JMeter about the test cases as a Sampler component of JMeter is executed.

Listeners can be added anywhere in the test, including directly under the test plan. They will collect data only from elements at or below their level.

Some of the JMeter Listeners are
o   Spline Visualizer
o   Aggregate Report
o   View Result Tree
o   View Result in Table
o   Monitor Results
o   Distribution Graph
o   BeanShell Listener
o   Summary Report and so on

Question: What does “contain” and “matches” indicates in the regular expression?

Answer:
In the regular expression, contains indicates that the regular expression matched at least some part of the target. While matches means the regular expression matched the whole target. so alphabet is “matched” by ‘al.*t.

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Question: Explain what is timer in JMeter and what are the type’s timer in JMeter?

Answer:
JMeter thread by default will send requests continuously without any pause. To get a pause between the request, Timers are used.

Some of the Timers used are:
Ø  Constant Timer
Ø  Gaussian Random Timer
Ø  Synchronizing Timer
Ø  Uniform Random Timer and so on.

Question: Explain what is Assertion in JMeter? What are the types of assertion?

Answer:
Assertion helps to verify that your server under test returns the expected results.

Some commonly used Assertion in JMeter are:
• Response Assertion
• Duration Assertion
• Size Assertion
• XML Assertion
• HTML Assertion



Question: Why Performance Testing is performed?

Answer:
Performance Testing is performed to evaluate application performance under some load and stress condition. It is generally measured in terms of response time for the user activity. It is designed to test the whole performance of the system at high load and stress condition.

Example: Customer like to withdraw money from an ATM counter,customer inserts debit or credit card and wait for the response. If system takes more than 5 min. then according to requirements system functioning is fail.

Type of Performance Testing:
Ø  Load: analogous to volume testing and determine how application deal with large amount of data.
Ø  Stress: examine application behavior under peak bursts of activity.
Ø  Capacity: measure overall capacity and determine at what time response time become unacceptable.

Question: What are JMeter Functions?

Answer:
JMeter functions are special values that can populate fields of any Sampler or other element in a test tree. A function call looks like this:

${__functionName(var1,var2,var3)}

Question: Mention the execution order of Test Elements?

Answer:
The test plans elements execution order is:

• Configuration elements
• Pre-processors
• Timers
• Samplers
• Post-processors
• Assertions
• Listeners

Question: Explain how you can capture the script of the authentication window in JMeter?

Answer:
Normally, you can capture script by recording.

o   First you have to Thread group in Test plan and then make HTTPProxyServer in Workbench.

o   After that, set port number in Global Setting box (e.g., 8911) and modify your connection setting in IE as local host in address 8911 as in port.

Then you can start http proxy server in JMeter and run your application for login.

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Author:

My Name is Ankur Jain and I am currently working as Automation Test Architect.I am ISTQB Certified Test Manager,Certified UI Path RPA Developer as well as Certified Scrum Master with total 12 years of working experience with lot of big banking clients around the globe.I love to Design Automation Testing Frameworks with Selenium,Appium,Protractor,Cucumber,Rest-Assured, Katalon Studio and currently exploring lot in Dev-OPS as well. I am currently staying in Mumbai, Maharashtra. Please Connect with me through Contact Us page of this website.

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