April flash sale

JMeter Interview Questions and Answers for 2024

JMeter is a versatile and powerful open-source tool for performance testing, load testing, and stress testing of web applications. It offers a range of features, including thread groups, preprocessors, post-processors, functions, and monitoring capabilities. To prepare for JMeter interview questions, you’ll need a comprehensive Interview Questions and Answers guide. KnowledgeHut offers the best software testing courses that cover various levels and aspects of JMeter along with interview preparation tips for beginner to advanced professionals. Additionally, the course covers the tool's concepts, architecture, and practical application of JMeter. By going through this interview guide, one can become well-equipped to excel in their JMeter interviews and advance in their career.

  • 4.7 Rating
  • 65 Question(s)
  • 35 Mins of Read
  • 7280 Reader(s)

Beginner

JMeter, commonly referred to as "Apache JMeter," is a graphical, open-source application built entirely on the Java Programming Language. It is made to evaluate and assess the functional behavior of web applications and a range of services under load.

JMeter is currently useful in functional testing, JDBC database connections, Web services, generic TCP connections, and OS native processes. It is primarily used for testing Web applications or FTP applications. To obtain precise performance data for your web server, you can carry out a variety of testing activities, such as performance, load, stress, regression, and functional testing.

Stefano Mazzocchi of the Apache Software Foundation is the person who created and first developed JMeter. It was primarily built to evaluate Apache JServ's performance (currently known as the Apache Tomcat project). Apache rebuilt JMeter to improve the GUI, provide more features, and enable functional testing.

JMeter operates at the protocol level rather than being a browser and rendering HTML pages the way a browser should.

A basic question in JMeter interview, don't miss this one.

  • Memory Utilization: JMeter can accommodate unlimited cycles of thread groups and samples, but doing so depletes memory because it requires more computational power to conduct these operations while producing high-quality visualizations and reports. The memory overloading caused by JMeter is one of its main drawbacks. 
  • No usage of JavaScript: JavaScript cannot be used in the application since JMeter is a testing tool and not a browser. 
  • Web Application: JMeter can be used to test web apps, but it cannot be used to test desktop applications.  
  • Limited Test Monitoring: JMeter only offers a little amount of test monitoring capability in comparison to other testing solutions.  
  • Lack of Understanding of Scripting: JMeter's scripting is not well understood. Understanding JMeter components, regular expressions, session handling, etc., requires some experience.

Apache JMeter is a Java open-source tool. To utilize Apache JMeter to run load or performance tests, it is possible to use the GUI without needing to know any programming language. Just follow the JMeter manual, and it is easy to start creating API testing scenarios.

Depending on the tests to be run with JMeter, there are currently several Samplers and jobs available either out of the box or through other plugins that can be quickly added using the JMeter Plugins Manager. However, Groovy, which is Apache JMeter's suggested scripting language, can be used to expand the capability. Groovy is adaptable and simple to use.

Although BeanShell programming scripts can be used to create assertions or samplers, most activities can now be completed using JMeter's built-in capability. Regex expertise may be helpful because it may be necessary when writing assertions for a JMeter script. 

JMeter is an open-source software used to load functional test behavior and compute the performance of the server or client's application. It is a 100% Java desktop application. It was designed to test web applications, but later it was used to test other applications. The users can test the performance of static and dynamic resources like Perl scripts, Java Objects, files, Servlets, Queries, FTP Servers, and Data Bases.

Yes, having extensive experience in JMeter, where I have tested out  Perl scripts, Java Objects, files, Servlets, Queries, and FTP Servers. Have tested using the tool on a group of users delivering requests to a target server. It assembles responses and statistics from the target server and could present the server's or applications' performance through tables or graphs to stakeholders.

I am hereby listing some of the best tools available for Testing:  

  1. Selenium 
  2. TestingWhiz 
  3. HPE Unified Functional Testing (HP – UFT, formerly QTP) 
  4. TestComplete 
  5. Ranorex 
  6. Sahi 
  7. Watir 
  8. Tosca Testsuite etc. 

JMeter, commonly referred to as "Apache JMeter," is a graphical, open-source application built entirely on the Java Programming Language. It is made to evaluate and assess the functional behavior of web applications and a range of services under load. 

JMeter is currently useful in functional testing, JDBC database connections, Web services, generic TCP connections, and OS native processes, it is primarily used for testing Web applications or FTP applications. To obtain precise performance data for your web server, you can carry out a variety of testing activities, such as performance, load, stress, regression, and functional testing.

Stefano Mazzocchi of the Apache Software Foundation is the person who created and first developed JMeter. It was primarily built to evaluate Apache JServ's performance (currently known as the Apache Tomcat project). Apache rebuilt JMeter to improve the GUI, provide more features, and enable functional testing.

JMeter operates at the protocol level rather than being a browser and rendering HTML pages the way a browser should. 

It's no surprise that this one pops up often in JMeter questions. Performance testing is a procedure that allows developers to compare an application's performance to performance metrics. This testing helps determine whether apps are defective or underperforming. The results of the performance testing show where improvements need to be made. Additionally, it shows if apps adhere to the standards established at the start of the application development process. Simply put, this testing determines whether the applications are ready for production. 

Performance testing allows developers to locate any bottlenecks in an application's typical operation and fix them before deploying them into a live environment. These are some of the bottlenecks: 

  • CPU utilization 
  • Disk usage 
  • Memory utilization 
  • Network utilization 
  • Operating system limitations.  

Speed, stability, and scalability are some of the crucial performance criteria that determine how well an application performs. Other performance parameters that can be measured through performance testing include data transfer rates, throughput, network bandwidth, dependability, and workload efficiency. 

Additionally, we may test the performance of various applications and compare the results to determine the variables that affect the performance of the applications. As a result, we may optimize apps and enhance their functionality

Load testing ensures that websites function consistently and quickly even under heavy load, evidently following industry standards, and should not crash. This test will also assist us in determining the maximum number of requests that the software system under test can accommodate. 

This is because, in this testing scenario, there's an attempt to duplicate a setting that replicates how a user might react in the real world. This replication of human behavior is transmitted via various API calls, sometimes in the form of numerous concurrent queries.  

Once this testing process is complete, the bottleneck will finally be revealed, which will cause the performance to deteriorate gradually. The software development team can then begin working on optimizing this after the bottleneck has been located, which will eventually produce the optimal user experience.

Stress Testing, which is a type of software testing, examines how the program behaves in challenging situations. It tests how resilient a system will be, as well as its ability to respond and handle errors in circumstances where its regular operation may be jeopardized. 

The information obtained from carrying out stress tests is quite significant. There is always a chance that an excessive number of requests or other circumstances could cause the system to malfunction. It is important to know what kind of response, whether or not our system will recover, and how long it will keep functioning. Understanding operationality is crucial for comprehending the end-user experience.

  • The protocols supported by JMeter include: 
  • 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 
  • JMS based messaging oriented services  
  • SMPT, POP3, and IMAP services 
  • FTP service
  • It is an open-source testing tool that many developers use all over the world. 
  • Plugins for data analysis and visualization offer good customization and extensibility. 
  • It uses a function to provide dynamic input for testing data manipulation. 
  • It increases the setup time and complexity. 
  • After the process, it offers reports and remains locally. 
  • It incorporates open-source third-party libraries like Maven, Gradle, and Jenkins.

A test plan is the JMeter script for conducting tests. Thread groups, logic controllers, sample-generating controllers, listeners, timers, assertions, and configuration elements are examples of test elements. All of the actions that run the script are included in a test plan. Everything that is part of a test plan is carried out top to bottom or per the sequence specified in the test plan. The directory level of a test plan is depicted in the figure below:

A Test Plan contains at least one Thread Group. In each thread group, there is a combination of one or more of the following elements – Sampler, Configuration Element, Listener, Logic Controller, and Timer. One or more Pre-processor elements may become each Sampler, and these may be followed by Post-processor elements, Assertion elements, or both.

Expect to come across this popular question in interview questions on JMeter. The initial components of the Test Plan are Thread Group elements. The thread group elements, as their name suggests, manage how many threads JMeter will employ throughout the test. The Thread Group allows us to regulate the following as well:  

  1. Deciding how many threads to use. 
  2. Choosing the ramp-up period. 
  3. Deciding how many test iterations to run 

This is how the thread group control panel looks: 

The Thread Group Panel has the following: 

  1. Actions to be taken after a Sampler error: If a Sampler error occurs during test execution, there is a choice to either. 
  2. Continue to the next element in the test. 
  3. Stop Thread to stop the current thread. 
  4. Stop Test Now to examine the mistake before Test resumes running. 
  5. Number of Threads (users): Simulates the number of connections or users for the server application. 
  6. Ramp-up Period (in seconds): Shows how long JMeter will take to start all threads. 
  7. Loop Count: Specifies the number of times the test should be run. 
  8. Scheduler Checkbox: When it is selected, the Scheduler Configuration part of the control panel is displayed at the bottom.  
  9. Scheduler Configuration: Configure the start and end times of the test. 
  10. What are Controllers and its types? 

JMeter offers two different kinds of controllers which are the Samplers and Logic Controllers. 

A. Samplers: JMeter can make individual server queries using the samplers. They imitate a user asking the target server for a page. For instance just add an HTTP Request sampler to execute a POST, GET, or DELETE on an HTTP service. 

Some good samplers include: 

  • FTP Request 
  • HTTP Request 
  • Java Request 
  • JDBC Request  
  • RPC Requests 
  • SOAP/XML Request 

B. Logic Controllers: These let users manage the order in which the samplers are processed in a Thread. The order of a request coming from any of a logic controllers which elements can be changed. Some examples of these child elements are: 

  • ForEach Controller 
  • While Controller 
  • Loop Controller 
  • IF Controller 
  • Run Time Controller 
  • Interleave Controller 

C. Throughput Controller: The following are the Logic Controllers offered by JMeter: 

  • ForEach Controller 
  • If Controller 
  • Include Controller 
  • Interleave Controller 
  • Loop Controller 
  • Module Controller  
  • Once Only Controller 
  • Random Controller 
  • Random Order Controller 
  • Recording Controller 
  • Runtime Controller 
  • Simple Controller 
  • Switch Controller 
  • Throughput Controller 
  • Transaction Controller 
  • While Controller 

Configuration Elements allow users to create defaults and variables that samplers can use. They are utilized to amend or add to Samplers' requests. They are executed before any Samplers that are located in the same scope at the beginning of the scope of which they are a part. A Configuration Element can only be accessed from within the branch where it is located.  

Below are the Configuration Elements offered by JMeter: 

  • Counter 
  • CSV Data Set Config 
  • FTP Request Defaults 
  • HTTP Authorization Manager 
  • HTTP Cache Manager 
  • HTTP Cookie Manager 
  • HTTP Proxy Server 
  • HTTP Request Defaults 
  • HTTP Header Manager 
  • Java Request Defaults 
  • JDBC Connection Configuration 
  • Keystore Configuration 
  • LDAP Request Defaults 
  • LDAP Extended Request Defaults 
  • Login Configuration Element 
  • Random Variable 
  • Simple Config Element 
  • TCP Sampler Config 
  • User Defined Variables

Listeners allow users to display the output of Samplers as tables, graphs, trees, or plain text in some log files. As a JMeter Sampler component is run, they offer visible access to the information about the test cases that JMeter has acquired.  

Anywhere in the test, including just below the test plan, can have listeners added. Only elements that are at or below their level will be used to gather data. Below are the listeners offered by JMeter: 

  1. Aggregate Graph 
  2. Aggregate Report 
  3. Assertion Results 
  4. BeanShell Listener 
  5. Distribution Graph (alpha) 
  6. Graph Results 
  7. Graph Full Results 
  8. Mailer Visualizer 
  9. Monitor Results 
  10. Sample Result Save Configuration 
  11. Simple Data Writer 
  12. Spline Visualizer 
  13. Summary Report 
  14. View Results in Table 
  15. View Results Tree. 

Preprocessor Elements: An element that operates immediately before a sampler does is known as a pre-processor element. They are frequently used to update variables that are not extracted from response text or to change a Sample Request's setting right before it executes. Below are the pre-processor elements offered by JMeter: 

  1. BeanShell PreProcessor 
  2. BSF PreProcessor 
  3. HTML Link Parser 
  4. HTTP URL Re-writing Modifier 
  5. HTTP User Parameter Modifier 
  6. JDBC PreProcessor 
  7. JSR223 PreProcessor 
  8. RegEx User Parameters 
  9. User Parameters 

Post-Processor Elements: After a sampler has finished running, a post-processor is executed. The most frequent application of this component is to process the response data, such as to get a specific value for later use. Below are the post-processor elements offered by JMeter: 

  1. BeanShell PostProcessor 
  2. BSF PostProcessor 
  3. CSS/JQuery Extractor 
  4. Debug PostProcessor 
  5. JDBC PostProcessor 
  6. JSR223 PostProcessor 
  7. Regular Expression Extractor 
  8. Result Status Action Handler 
  9. XPath Extractor

The elements of the test plan are executed in the sequence listed below: 

  1. Configuration elements 
  2. Pre-processors 
  3. Timers 
  4. Sampler 
  5. Post-Processors (unless SampleResult is null) 
  6. Assertions (unless SampleResult is null) 
  7. Listeners (unless SampleResult is null)
  • Use Variables: Hard-coded URLs or parameter values are present in recorded scripts. Hard-coded values do not always result in successful test execution, if at all. Tests ought to be independent of outside information and self-contained. The ability to create variables through the use of a JMeter post-processor will help keep tests self-contained and operational without hiccups. 
  • Parameterize Values: To parameterize the hard-coded parameters and enable several users to run the same test with various sets of data, utilize data sets. Instead of evaluating the same data with the same user each time the test is run, this helps to simulate how the application will actually be used.  
  • Update Thread Group Values: Increase the concurrent users, the ramp-up time for those users, and the number of times each user loops through the script by updating the thread group properties. 
  • Add Timers: JMeter runs each test's steps as quickly as it can by default. By altering the "think time" spent on each page, the addition of random time limitations enables the simulation of how various users will respond to the program. 
  • Rename the Samplers: A poor naming convention may be challenging to identify which test or step in the test may be falling while running multiple tests simultaneously. When trying to fix a problem or identify which component is at fault, changing test names and component names can be quite beneficial.

Test Plans are often saved in their XML format, so there is no relationship to any specific operating system. Any OS that supports JMeter can execute it.

The execution outcome of each test plan should be checked by at least one listener. Monitor Tests is an example of a listener. With the monitor test, it is possible to check the server performance graph and the status of the sample the monitor receives.   

The monitor test plan in JMeter has the following features: 

  • Monitors are used for stress testing and system management. 
  • When coupled with stress testing, the monitor provides additional data on server performance. 
  • The relationship between server performance and client response time can be easily seen thanks to monitors with the help of server/protocol supports like Debug Sampler, HTTP Request, Bolt Request, JDBC Request, FTP Request, SMTP Sampler, and a lot more. 
  • As a tool for system administration, the monitor provides a straightforward approach to monitoring many servers from a single interface. 
  • It is feasible to distribute execution across several threads and/or instances when there are numerous monitoring activities.  

The fields of any sampler or other elements in a test tree can be filled with customized values provided by JMeter functions. Below is a list of some JMeter Functions:

Type of Function
Name
Comment

Information 

threadNum 

Get thread number 

Information 

SamplerName 

Get the sampler name (label) 

Information  

Log 

Log (or display) a message (and return the value). 

Information 

machineName 

Get the local machine name. 

Input 

StringFromFile 

Read a line from a file. 

Input 

FileToString 

Read an entire file. 

Input 

CSVRead 

Read from CSV delimited file. 

Input 

XPath 

Use an XPath expression to read from a file. 

Calculation 

Counter 

Generate an incrementing number 

Calculation 

intSum 

Add int numbers 

Calculation 

longSum 

Add long numbers 

Calculation 

Random 

Generate a random number 

Calculation 

RandomString 

Generate a random string. 

Scripting 

BeanShell 

Run a BeanShell script 

Scripting 

javaScript 

Process JavaScript  

Scripting 

jexl, jexl2 

Evaluate a common jexl expression 

Properties 

Property 

Read a property. 

Variables 

Split 

Split a string into variables 

Variables 

Evaluate a variable name 

Variables 

eval 

Evaluate a variable expression 

String 

regexFunction 

Parse previous response using a regular expression. 

String 

escapeOroRegexpChars 

Quote meta chars used by ORO regular expressions. 

Any field of any test component can be written with functions and variables. An effective test plan should have the following features: 

  1. intSum  
  2. longSum 
  3. machineName 
  4. BeanShell 
  5. javaScript 
  6. jexl  
  7. random 
  8. time 
  9. property functions 
  10. log functions 

Variable names supplied as parameters will not be set up and variable references won't work because JMeter thread variables won't have been fully set up by the time the functions are performed. As a result, the functions for variable evaluation, split, and regex will not operate. The threadNum function will not function and is not necessary in terms of the test plan.

  • Don't use GUI mode. 
  • Use the "view results tree" or "view results in table" listeners only during the scripting phase of a test.  
  • Don't use functional mode. 
  • Use the same sampler repeatedly and a variable to modify the sample rather than many samplers that are similar to one another. 

Intermediate

  • Performance and load test in a wide range of server, protocol, and application types: 
    • Web: HTTP, HTTPS (Java, NodeJS, PHP, ASP.NET, etc) 
    • SOAP and REST Web Services 
    • FTP 
    • Database via JDBC 
    • LDAP 
    • Message-oriented middleware (MOM) via JMS 
    • Mail: SMTP(S), POP3(S) and IMAP(S) 
    • Native commands or shell scripts 
    • TCP 
    • Java Objects 
  • Fast Test Plan recording (from browsers or native applications), building, and debugging are all made possible by a full-featured test IDE. 
  • Any Java-compatible OS (Linux, Windows, Mac OSX, etc.) can run load tests in CLI mode, also known as command line mode (formerly known as non-GUI or headless mode).  
  • A finished, presentable dynamic HTML report. 
  • Ability to extract data from the most popular answer formats, HTML, JSON, XML, or any text format, makes correlation simple.  
  • 100% Java purity and total portability. 
  • The whole multithreading framework enables simultaneous sampling of various functions by various threads as well as by various thread groups.  
  • Testing results caching and offline analysis/replay. 
  • Highly Extensible Core:  
    • Pluggable Samplers provide limitless testing options. 
    • Scriptable Samplers (JSR223-compliant languages like Beanshell and Groovy) 
    • A variety of load statistics with pluggable timers. 
    • Plugins for data analysis and visualization offer excellent extensibility and personalization. 
    • Functions can be used to manipulate data or offer a test with dynamic input. 
    • Simple Continuous Integration using Open Source Libraries from 3rd parties for Maven, Gradle, and Jenkins.

Distributed Testing in JMeter aids in scaling up the program's ability to produce the required number of threads (users) for the load test. The master-slave architecture is used for distributed testing, and JMeter is installed on each machine and they all interact using the Java Remote Machine Invocation (RMI).

All of the machines (master and slave) in the distributed architecture are connected to the same local network. One of them is given the role of a master, controlling the other machines while the test is being run. The slave machine carries out the master machine's instructions before sending the request to the target server by hitting the application under test (AUT). JMeter – Distributed Testing (Master-Slave) Architecture is an example of a distributed testing architecture.

The points below will assist in creating a master-slave configuration also known as a distributed environment for JMeter: 

  1. Find out how many threads one computer can handle. 
  2. Calculate the required number of slaves (with the same hardware and software configuration) based on the number of threads that a single machine can handle. For instance, if the goal load is 600 threads (users) and one computer can manage 100 threads, six (600/100) slave machines will be needed.  
  3. Install the same version of JMeter on the master and all slaves. It is advised that you install JMeter using the exact same configuration across all workstations.  
  4. Make sure that all of the machines' firewalls are off. 
  5. Antivirus should be turned off (not for all cases, only recommended when anti-virus interrupts the RMI communication between master and slaves). 
  6. The slaves and master computers should all be connected to the same network. 
  7. All of the machines should be able to access the target application (server). 
  8. The master-slave configuration is then prepared for test execution once this is completed.

Regular expressions are used to search and exit text based on patterns. By integrating the pattern matching program, JMeter understands regular expressions or patterns used throughout a JMeter test plan.  

As Test Plans are constructed or improved, regular expressions will undoubtedly help save time and attain greater flexibility. When it is impossible or extremely difficult to predict an outcome, regular expressions offer a straightforward way to extract information from websites.  

A typical application example of employing regular expressions is obtaining a session ID from the server response. Users can quickly obtain the unique session key if the server returns one by using expressions in the load script. JMeter's Regular Expression Extractor is needed to use regular expressions in a test plan. Regular expressions can be used in any component of a test plan.  

The difference between contains and matches, as used on the Response Assertion test element, should be emphasized.  

Contains signifies that the regular expression at least partially matches the target, so 'alphabet' contains "phab" because the regular expression matches the substring "phabe."  

Matches denote that the entire target was matched by the regular expression. As a result, 'alphabet' is matched by 'al.*t' 

This is a frequently asked question in JMeter testing interview questions. 

Thread Groups: The fundamental building block of a JMeter Test Plan is a thread group. As implied by the name, a thread group is a collection of threads running the same scenario. This is regarded as the test plan's starting point. Other test components including controllers, samplers, config components, and listeners are stored in thread groups.  

While running the test plan, each thread in the thread group will separately execute every component that falls under the thread group. This is the control panel of the thread group element.  For instance, if 100 threads were chosen, JMeter will generate and simulate 100 user requests for the test server.  

Samplers: Although JMeter enables testing a wide range of protocols, including HTTP, FTP, JDBC, and others; while Thread Group simulates user requests to the server, however, a Thread Group determine the kind of requests ((HTTP, FTP, etc.) it needs to send, and for that it needs Samplers.  

JMeter adds samplers as a child of thread groups. These are used to send the server various kinds of requests. Once the server has completed processing the sampler request, JMeter receives the response, which can then be seen and examined in terms of various performance metrics like response time, hits per second, throughput, etc.  

The samplers in JMeter may be launched by using the path- Right-click on the Thread Group, then select Add, then Sampler, before selecting the necessary Sampler.

There are two types of processors exist: 

  • Pre-process: Before sending a Sampler Request, the Pre-processor takes some action. Here's a simple illustration: Suppose a user wants JMeter to "spider" across a website undergoing a test, parse links (check all the links on the page), and then return the HTL. Before generating an HTTP request, it is required to add an action to the controller, such as an "HTML link parser."

Post-processor: After sending a Sampler Request, the Post-processor takes some action. A simple illustration: JMeter makes an HTTP request to the test web server  (e.g., www.google.com), and it receives a reply. If the server answer contains a mistake, JMeter can be used to terminate the test. To do this:

  • Configuration elements: Some of the potential elements in the configuration elements includes CSV Data Set Config, FTP request Defaults, DNS Cache Manager, HTTP Authorization Manager, HTTP Cache Manager, HTTP Cookie Manager, HTTP Request Defaults, HTTP Header Manager, and others.  
  • Pre-Processors: Some of the potential elements in the Pre Processors include HTML Link Parser, HTTP URL Re-writing Modifier, User Parameters, BeanShell PreProcessor, JSR223 PreProcessor, JDBC PreProcessor, RegEx User Parameters, and Sample Timeout. 
  • Timers: Some of the potential elements in the Timers include Timers, Constant Timer, Gaussian Random Timers, Uniform Random Timer, Constant Throughput Timer, Synchronizing Timer, BeanShell Timers, JSR223 Timer, and Poisson Random Timer.   
  • Sampler: Some of the potential elements in the Samples include FTP Request, HTTP Request, JDBC Request, Java Object Request, JMS Request, JUnit Test Request, LDAP Request, Mail Request, OS Process Request, and TCP Request.  
  • Post-Processors: Some of the potential elements in the Post-Processors include Regular Expression Extractor, CSS Selector Extractor, XPath2 Extractor, XPath Extractor, JSON JMESPath Extractor, Result Status Action Handler, BeanShell PostProcessor, JSR223 PostProcessor, JDBC PostProcessor, JSON Extractor, and Boundary Extractor.  
  • Assertions: Some of the potential elements in the Assertions include Response Assertion, Duration Assertion, Size Assertion, XML Assertion, BeanShell Assertion, MD5Hex Assertion, HTML Assertion, XPath Assertion, and others.  
  • Listeners: Some of the potential elements in the Listeners include Simple Data Writer, BeanShell/JSR223 Listener, Mailer Visualizer, Summary Report, Aggregate Report, Aggregate Graph, and others.  

Configuration Elements can be used to specify variables, allowing Samplers to access data via these variables. Configuration element can only be accessed from the tee node where it was defined. A configuration element will also take priority over a similar configuration element declared in a parent node if it is defined inside a tree node.

The process of adding variables in JMeter that will offer a wide variety of configuration choices for a load-testing script is known as parameterization. For instance: 

  • Variables for logging into a web service with various credentials. 
  • Use distinct environment-specific variables (dev, master, etc.) 
  • E-commerce site search criteria for a list of items 

There are four different data parameterization options: 

  • Making use of external files: Using a CSV file is one of the popular approaches to parameterize performance scripts in JMeter. For instance, supposing there's a login request that functions for a single user, that request may simply be parameterized and tested with various users. In order to parameterize the script, two variables to store the email and password will be needed. To do this, a CSV file containing a list of usernames and passwords for use during login must be delivered. There are some various parameters that must be understood to properly create a CSV file:  
    • Name: Name of the element as it will appear in the JMeter tree. 
    • Filename: The input file's name. The path of the current test plan is used to resolve relative file names.  
    • File Encoding: Input file encoding, if it's different from the platform's default. 
    • Variable Names: A list of separated variable names that will serve as a holding area for values that have been parsed. If the file's first line is empty, the variable names will be regarded as being on that line.  
    • Ignore First Line: If the variable names are placed in the first line of the CSV file, then it is true that line should be ignored.  
    • Delimiter: A delimiter that will be used to divide the values from the input file that has been parsed. 
    • Allow Quoted Data: True in cases where delimiter should be present in the elements if double quotes are to be disregarded. 
    • Recycle on EOF: True if the file test plan requires repeated iterations on the file. It will inform JMeter to start the file from the beginning.  
    • Stop Thread on EOF: False to loop over the CSV file again, and true to halt the thread after reading the entire file. 
  • Sharing Mode: 
    • All threads: The file is shared by every virtual user (default) 
    • Current thread group: Each thread group will receive a single opening of the file.  
    • Current thread: For each of the threads, a separate file will be opened. 
    • Edit: Every thread with a given identifier also uses a given file.  
    • After creating a CSV file, the last test is to parameterize the login request with new variables. To do this, substitute the necessary variables from the "Variable Names" configuration field of the CSV Data Set Config for the starting values.  
  • Utilizing Databases: Utilizing database information is another technique to parameterize the performance scripts. The JMeterscripts will be parameterized using JDBC, an application programming interface that specifies how a client may access a database. 
    • To do this, download the appropriate JDBC driver for the database first, then include the .jar file in the test plan. After that, use the 'JDBC Connection Configuration' element to set up the database connection. The following parameters should be understood when configuring the JDBC connection: 
    • Name: The name of the connection configuration that the thread group tree will display. 
    • Variable Name: The name that will be used to identify the database connection specifically. 
    • Max number of connections: The most connections that can be added to the connection pool. Each thread will receive its own pool with a single connection in it if the value is 0.  
    • Max waits (ms): If the set timeout is exceeded during a database connection, the pool throws an error. 
    • Time between eviction runs (ms): The amount of milliseconds to wait in between thread runs that remove inactive connections from the database pool.  
    • Auto commit: Yes switch on auto-commit for connected databases that are linked. 
    • Test while idle: Before an effective request is seen, check for an idle connection.  
    • Soft min evictable idle time (ms): The time frame before a specific connection in the database pool can be removed while it is idle.  
    • Validation Query: Query that will be used as a health check to see if the database is still responding. 
    • Database URL: Database connection string for JDBC. 
    • JDBC driver class: Appropriate driver class name. For instance, "com.mysql.jdbc.Driver." is appropriate for the MySql database. 
    • Username: Username for the database. 
    • Password: Database login (will be stored unencrypted in the test plan).  
  • Using the "Parameterized Controller" plugin: The "Parameterized Controller" plugin can also be used in cases where they need to carry out a recurring series of the same operation with varied parameters. This controller gives the ability to build up a group of variables that will be utilized in each step that is added to the controller.

Correlation is crucial in JMeter, it is the process of obtaining and passing on to subsequent queries the dynamic answer from the server that was received. It is crucial due to the fact that correlation is needed when writing performance load tests for dynamic sites. The script is worthless if it isn't handled properly.

It is important to distinguish between static and dynamic responses from a testing perspective (the data stays the same for iterating requests). Every HTTP web performance test often includes data correlation. Only when evaluating static content sites, such as certain homepages and contacts, may correlation be disregarded. In other situations, correlation handling must be done at some time throughout the test.

Limits often rely on a variety of variables, and JMeter restrictions are no exception. JMeter limitations vary depending on your machine's and network's capabilities, your performance scripts' complexity, the desired number of simulated users, and other factors.

Correlation is crucial in JMeter, it is the process of obtaining and passing on to subsequent queries the dynamic answer from the server that was received. It is crucial due to the fact that correlation is needed when writing performance load tests for dynamic sites. The script is worthless if it isn't handled properly.  

It is important to distinguish between static and dynamic responses from a testing perspective (the data stays the same for iterating requests). Every HTTP web performance test often includes data correlation. Only when evaluating static content sites, such as certain homepages and contacts, may correlation be disregarded. In other situations, correlation handling must be done at some time throughout the test.

Listeners are used to observe and examine the Sampler request and answer as tables, graphs, trees, etc. Additionally, there's the option of saving results to a file for later reading. When a load/stress test is running, the sampler result can be gotten without having to wait. The following is a list of listeners:  

  1. Aggregate Graph: Aggregate graphs enable us to choose the settings for the graph presentation and make it simple to create bar graphs. The resulting data for the graph and table may be specifically saved as PNG and CSV files.  
  2. Aggregate Report: The aggregate report displays a distinct table row for each test's variously titled sampler request. 
  3. Assertion Results: Sampler's assertions are shown in the Assertion Results section. Note that assertion results should not be used in load or stress tests because they use a lot of CPU and memory resources. It is advised to use it for debugging or functional testing.  
  4. View Results in Table: Every sample/request result is displayed in its own row when using View Results in Table. Note that using View Results in Table during a load or stress test will use quite a lot of memory and CPU. It is advised to use it for debugging or functional testing.  
  5. View Results Tree: View Results Trees display the Sampler responses along with their requests in a tree. The View Results Tree should not be used when doing a load or stress test because it uses a lot of CPU and memory resources. It is advised to use it for debugging or functional testing.  

More listeners include: 

  1. Backend Listener 
  2. BeanShell Listener 
  3. BSF Listener 
  4. Comparison Assertion Visualizer 
  5. Generate Summary Results 
  6. Graph Results 
  7. JSR223 Listener 
  8. Mailer Visualizer 
  9. Monitor Results 
  10. Response Time Graph 
  11. Saves Responses to a file 
  12. Simple Data Writer 
  13. Summary Report  

The WorkBench just provides a location to temporarily store test items. It has nothing to do with the Test Plan, as its components are not preserved with the Test Plan, so it may be used as a practice area or for short-term storage. It can also be used to load test scripts straight after recording them.

All HTTP(s) queries made by the application to the server are recorded using the HTTP(s) Test Script Recorder. JMeter has to be configured in a few different ways for it to function. The actions taken to record HTTPS traffic are listed below: 

  1. Enhance WorkBench with HTTP(s) Test Script Recorder. 
  2. Enter the port that you wish to use to launch your proxy server.  
  3. Select "Workbench" as the only option for the Target, or add a Recording Controller to your test plan and choose it as the Target to store all recordings under. 
  4. Now launch the Proxy server 
  5. Manually set up your browser's proxy settings to point to the same port as the test script recorder.  

Special values known as JMeter functions can be used to fill in fields on any Sampler or other element in a test tree. A function is called like this: 

$[__functionName(var1,var2,var3)}

Make careful to escape any commas that are present in function parameters with "," 

The name of a function is the same: 

_functionNamee. For instance, $__threadNum

Variable names provided as parameters won't be created and variable references won't operate, variables are referenced as  

${VARIABLE} 
  • Web HTTP – for testing bowser-based online applications and websites 
  • Web Services – testing SOAP, REST, and other APIs, including those that allow mobile apps. 
  • Ajax True Client – testing single-page web applications 
  • Citrix – testing applications hosted on a Citrix Desktop 
  • SAP – testing SAP programs (i.e Thick Client) that are not web-based. 
  • JAVA – testing Java desktop applications 
  • Mobility – evaluating mobile-specific protocols for devices like wearables and the Internet of Things.  
  • RDP – testing Remote Desktop Protocol testing. 
  • Oracle Web 11i – testing older Oracle web applications prior to Oracle 12 
  • Siebel Web – testing ancient, non-browser-based Siebel programs

One of the most frequently posed JMeter interview questions, be ready for it. Timers are crucial for maintaining equilibrium while doing JMeter performance testing. JMeter threads typically execute one after the other without pausing, this may be implausible in nature because a typical user will pause between each action to read or consider, which is called a Think Time, and it has to be included in the script to make it more realistic.  

JMeter offers 9 different timer types for use in such activities, and the user may choose the one that best fits the situation:  

  • Constant Timer: This can be used to give time some Think Time in between requests. 

The name provided is shown on the tree, and the thread latency is measured in milliseconds here, as 1000 would be inputted for 1 second.  

  • Uniform Random Timer: A random amount of wait time can be added between user requests using the uniform random timer.  

The name element's purpose is to provide a name for the timer that will be displayed in the tree. As the name implies, the maximum think time should be specified in Random Delay Maximum, while Constant Delay Offset is an extra millisecond-based variable.  

  • BeanShell Timer: This scripting-based timer enables users to create a timer implementation logic. 
  • JSR223 Timer: Similar to the Bean Shell timer, JSR223 Timer is also scripting-based. By using the JSR223 Scripting language, delays can be added between user requests in JSR223 Timer.  

More timers include: 

  • Synchronizing Timer 
  • BSF Timer 
  • Constant Throughput Timer 
  • Poisson Random Timer 
  • Gaussian Random Timer

Aggregate Graph: Aggregate graphs enable us to choose the settings for the graph presentation and make it simple to create bar graphs. The resulting data for the graph and table may be specifically saved as PNG and CSV files.  

Aggregate Report: The aggregate report displays a distinct table row for each test's variously titled sampler request. 

Assertion Results: Sampler's assertions are shown in the Assertion Results section. Note that assertion results should not be used in load or stress tests because they use a lot of CPU and memory resources. It is advised to use it for debugging or functional testing.  

View Results in Table: Every sample/request result is displayed in its own row when using View Results in Table. Note that using View Results in Table during a load or stress test will use quite a lot of memory and CPU. It is advised to use it for debugging or functional testing.  

View Results Tree: View Results Trees displays the Sampler responses along with their requests in a tree. The View Results Tree should not be used when doing a load or stress test because it uses a lot of CPU and memory resources. It is advised to use it for debugging or functional testing.  

More listeners include: 

  1. Backend Listener 
  2. BeanShell Listener 
  3. BSF Listener 
  4. Comparison Assertion Visualizer 
  5. Generate Summary Results 
  6. Graph Results 
  7. JSR223 Listener 
  8. Mailer Visualizer 
  9. Monitor Results 
  10. Response Time Graph 
  11. Saves Responses to a file 
  12. Simple Data Writer 
  13. Summary Report 

Performance testing is a non-functional testing method where the effectiveness of the application is assessed under anticipated or greater demand. To make sure that the program doesn't crash and replies within a reasonable amount of time under actual demand, it is done before it is launched on a production server.  

Some benefits of Performance Testing include: 

  • Server Compatibility: Regardless of the server or protocol, JMeter is a very powerful tool that can handle load and performance testing for many goods. Be it a database, FTP, LDAP, or MOM through NoSQL, HTTP, or HTTPS web services.  
  • Expandable architecture: Due to the fact that JMeter is an open-source project, its users are very engaged in the creation of plugins for it. In reality, JMeter provides all the tools needed to work toward reporting objectives, particularly features for server resources monitoring. Overall, using JMeter is pretty convenient if you need to develop your own Plugins.  
  • No investment required: The fact that JMeter is free is another important advantage. JMeter may be used by any team with a minimal budget to create internal tools or work on any commercial project that requires performance control. 
  • Record & Playback: JMeter's drag-and-drop functionality makes it easy for users to make use of the record and playback capability, which speeds up the creation of test scripts while eliminating any latencies.  
  • Customizations: You may always take use of JMeter's open-source status to change its source code and produce anything that meets your requirements if you're a developer who needs to use some more features.  
  • Distributed Load Testing: Developers and testers can collaborate on a master-slave set using JMeter to provide distributed load testing on many computers. 
  • Community Support: Since JMeter is an open-source tool, you may always ask the community for assistance with your testing projects. Additionally, there are several tutorials that are accessible online that may be used to comprehend its application. Even better, it provides a ton of free plugins that may be used to speed up the writing and analysis of scripts. 

JMeter script generation differs slightly from conventional automated script creation. A script may often be written by recording it or utilizing the JMeter UI.

Most definitely, Selenium scripts can be integrated with JMeter via the application of support web driver plugins in the following steps. 

  • Download plugins 
  • Make a copy of the jars found in the "lib" and "ext" folders 
  • Use the selenium written code stationed in the sampler to invoke the web driver sampler configuration features. These are part of the browsers like chrome etcetera. 
  • Other properties can also be configured in the configuration feature elements. 
  • Include a listener to the test plan that has the web driver sampler to be notified of the time taken by users in task execution processes.  
  • The log displayer should be left turned on to detect and view errors while running the tests

Advanced

A staple advanced JMeter interview question, be prepared to answer this one. There is an increased demand by mobile users for better and more efficient applications which is demonstrated by the 5-star rating on high-performing applications compared to low-performing ones. For this reason, the JMeter application has been developed to incorporate features that permit the recording of actions executed during loading a testing process. There are steps to follow in other to record actions on a mobile device using the JMeter app. 

JMeter records action requests on mobile applications using the HTTP(S) Recording Script and it possesses features to initiate, establish and execute tests script performance on mobile applications, but first, there is the need for JMeter configuration on the mobile device which could either be an iOS or an Android device. 

Configuring JMeter Set-Up: 

  • In Administration mode, launch the JMeter 

METER_HOME/bin, Start jmeter.bat or jmeter.sh 

  • Go to the workbench located under the JMeter test plan and include 

Recorder for test script of HTTP(S) 

  • Still under the HTTP(S) test recorder script, include the 'View Result Tree', if indicated. This permits the display of requests and detailed responses during a recording phase. It is not compulsory to include this feature. 
  • Establish a wifi connection with the mobile device and system. 
  • Determine the 'Any Port Number', then set it up, for example, the number, 2023. then click on the start button. 
  • A certificate - JMeterTemporaryRootCA.crt would next be created under the JMETER_HOME/bin and forwarded the certificate to the user's email address. 

Setting Up JMeter on iOS Devices (iPad, iPhone) 

  1. On iPad mobile device 

Open and Install the certificate file sent - JMeterTemporaryRootCA.crt. This is recommended for use to prevent SSL handshake problems if the iOS application utilizes HTTPS. 

Permit the 'trust certificate' option by going to settings, then to general settings, to them about, and to the certificate trust settings. Here, click on the certificate trust button to turn it on. 

  1. On iPhone mobile device 

Open settings, then, wifi setting, and click on the arrow close to the wifi connection. Locate the HTTP proxy icon, and under it, chose the manual button and input the desktops IP address into the server bar, then enter '2023' in the port field. 

Finally, coordinate the business flow and JMeter and commence recording on the mobile application. 

Setting Up JMeter on Android Devices 

  • Open settings from the menu and select the wifi option 
  • Click and hold down the connected network and select the 'Modify Network' option 
  • The advanced settings bar will be opened to permit modifying the proxy 
  • Convert the proxy to manual 
  • Establish the hostname feature as a system IP address and port value to 8080 for the setup of the JMeter app. 
  • Click save 
  • Start the application on the android device so that every request made will be recorded in the JMeter application.  
  • Ensure the HTTP(S) script is started in JMeter before running the application 
  • Once the use of the application has commenced, the script actions will be stored under the 'Recording controller'.  
  • On completing the actions performed in the applications, end the script recording by pressing the 'stop button' in the script recording screen of the  HTTP(S). 
  • Next, expand the 'JMeter's recording controller' to display all recorded scripts of all actions performed in the applications. 
  • Click on the 'play' button to run the recorded scripts as indicated or established in the thread setup. 
  • Lastly, to see the script results, click on the button, 'View Results In Tree'

Graphic User Interface (GUI) is a kind of user interface that permits the interaction of users with electronic devices via graphical and audio features like primary notation, in place of UIs that are text-based. Their actions are executed through direct graphical element manipulation. 

The JMeter GUI mode works best for the addition, and editing of new configuration features thread collections, and samplers, but, the GUI mode exhausts the available memory and resource materials during the operation of the recorded scripts, therefore, the GUI is not a recommended mode for heavy load testing like the JMeter. 

The recommendation to use a non-GUI mode for running JMeter is probably one of the most essential tips to be aware of when using the JMeter application, as earlier mentioned, this is because the JMeter-GUI is not developed to run heavy loads and it consumes a lot of resource features that could be excessively and severely overwhelming for the server, that results in the delivery of false and incomplete information about the test results. It is noteworthy that, the more resources are being consumed by the server, the less load that will be generated in each test session. 

It is thus pertinent to be familiar with the process of running the non-GUI-JMeter tests properly to ensure the efficiency of performance testing. 

Since the GUI-JMeter mode is used to record, script and debug, it is important to use it before the phase of execution, but the JMeter testing could be smoothly run from scratch in a non-GUI mode.  

Here are useful tips on how to convert a GUI to run non-GUI-JMeter performance tests and boost the efficiency of the execution process. 

  • Disable or delete JMeter listeners 

As much as possible, it is advised to use few listeners while staying away from the display of real-time results such as the 'View Results Tree'. By creating a high-level listener for the test run, all other listeners can be disabled or deleted from the test plan. This can be done by including a test flag, for example '-l flag' while specifying the name of the jtl file on which sample results will be logged. 

For example; jmeter-n-t-my_test.jmx-llog.jtl 

  • Apply Functions in Variables 

When operating a non-GUI test, the script variables may be required to be changed every time a test is started, and this can be very challenging since the script has to be opened on the GUI and the parameters edited and the script saved even before running the test via the command line. Hence, it is better to apply certain functions like _time_ or _random_ in the names of the variables to generate a different name on every test run without the need to manually edit the script.

Functions are specific commands created to permit the user to define variables that will replace static values or generate new values at a test run. Functions can be used in several test run fields if it tallies with the format of the fields, for example, a random field can be added to a field that expects a particular number.

  • Use command lines to override or establish properties 

There may be a need to change and rerun a particular test with various settings when adhering to an appropriate performance testing methodology. This can be done by organizing the script parameters into variables and converting them from the GUI before each test run, but again, this is a very challenging task to execute, if each of these tests is to be run in respective non-GUI modes. To solve this problem, the variables need to be defined in terms of their properties.

  • Monitoring 

A major factor that discourages the use of the non-GUI-JMeter mode is its inability to effectively monitor real-time results on the listeners. However, to solve this challenge, certain options like the one that permits an understanding of the running JMeter simultaneously with the non-GUI mode or the configuration of tests to display live results.

In summary, JMeter non-GUI tests are preferred because it is a powerful tool, that helps minimize the challenges encountered with JMeter. Also, almost every tool that can be used on the GUI-JMeter, can be either used via the command line or the properties file of the non-GUI JMeter. 

In the case where selenium automation scripts are available, with a ready functional flow, it is possible to integrate them with JMetre into load-testing for reuse instead of rewriting new java-selenium scripts. Follow the outlined steps below to perform this task of using JMeter to run selenium scripts. 

  • Setup selenium test projects 
    • Download java user selenium libraries and add them to the JMeter classpath 

For example; selenium-java-$version2023.jar to %JMETER_HOME%/lib/. 

  • Ensure the selenium server is setup and listening: java-jarselenium-server-st 
  • Export the test plan and save it to%JMETER_HOME%/lib/junit/. The test plan should permit JMeter to pick it up by extending the test class as a test case or selenite test case.  
  • Configure JMeter 
    • Add JUnit Request Sampler to the test plan for JMeter 
    • Based on the selenium test plan, set up the chosen class name 
    • Establish the test method for the test that is to be executed 
    • Other parameters should be left on default 
  • Start running selenium scripts on JMeter using the java code for the JUnit Request sampler. 

A must-know for anyone heading into a JMeter interview, this question is frequently asked in JMeter Interview Questions. To effectively handle sessions and cookies in JMeter, develop a basic short script with the cookie manager of JMeter that will show its capabilities through the following steps outlined below. 

  • To the test plan, include a thread group. 

Test plan>Add>Threads>Thread group.

  • Set up the second value '2' to the count field loop. This will be required later on to display the movement of a cookie through an iteration.
  • An HTTP element for the cookie manager should be added 

Thread group>Add>Sampler>HTTP request 

Provide information for the following fields: 

  1. Page name: Login page 
  2. Server IP address or name: dazzledemo.com 
  3. Login path 
  • Add a request order that will open the login platform like the HTTP request 

Thread group>Add>Sampler>HTTP request

The values required for this include: 

  1. Page name: Reset password page 
  2. Server IP address or name: dazzledemo.com 
  3. Path: Reset password
  • Include a reset password page by addition of another HTTP request order page 

Thread group>Add>Listener>View Tree Results

  • Run the script 

For every request order, confirm the cookie data bearing in mind that the initial iteration login page request will have no cookies, but all others do and these cookies are found in the request header meaning that they move from the response to the next request order, and not replaced or lost when a new iteration begins.

Another more advanced way of managing cookies is by applying the HTTP cookie manager configuration element. This allows JMeter to either clear or not clear the cookies from one to another iterations. 

  • Cookies may get cleared when a test user behaves like a new user on each iteration. Acting as a new user, therefore, means that no cookies will be remembered by the website of the user.

This can be set up by selecting the clear cookies in each iteration checkbox option in the cookie manager of HTTP, then clearing the already found results and rerunning the script. Next, perform a verification of the login page and make a second iteration request. With this, the cookie will be cleared out when a different iteration is established.

  • Cookies are preserved and not cleared out when a test user acts like a recurrent and continuous user of the website, and this will mean the user would remember the cookies from the website. 

With JMeter, it is possible to create and update CSV files conveniently and easily, and instead of creating the CSV files separately before uploading them for storage, JMeter helps complete the entire process in a single location. The step listed below demonstrates how to read and write CSV files through JMeter and how to store them.  

  • Add a thread group by right-clicking on test plan>threads>thread group 
  • Include a feature that permits the addition of code in java such as a BeanShell element in form of either a sampler, pre or post-processor based on the requirements of the script. 

Thread group>Sampler>BeanShell sampler. Here, the java code will be included together with all the prerequisites for the CSV file.

The codes are responsible for the execution of the writing with the variables contained in the CSV file. The code writes the established parameters to a CSV file and each time the sampler is executed, an additional line is included in the CSV file.

  • A BeanShell element to read the entire CSV file should be added 
  • Each parameter is then configured to a variable so they can be applied to the script subsequently 
  • Incorporate the configuration into the entire script, and integrate the written CSV file into the final test flow. 
  • Now, read and write data to the CSV file through JMeter. 

JMeter is a very common tool used for load testing that encourages the expansion of its capabilities. JMeter plugins are software features used by JMeter to expand functionalities and input functions. Numerous plugins are existing, which are used to enhance JMeter's functionality, these plugins avail a simpler way of installing and maintaining the execution of JMeter for its clients. 

The top-5 JMeter supported plugins include: 

  1. Customized Simple Object Access Protocol (SOAP) Sampler 

The SOAP is a JMeter custom sampler that functions with or without numerous attachments. The sampler serves as a sender for SOAP requests to web services and allows users to edit, add or delete code attachments. 

  1. Performance Server Monitoring Plugins(PerfMon) 

The PerfMon plugin is used for the extension of JMeter using the listener performance and monitoring servers, permitting the follow-up of CPU, disks, and network I/Os and servers memory. 

  1. JMeter Custom Thread Groups 

These custom plugins are used for adding five other thread groups in JMeter. They include: 

  • Stepping 
  • Concurrency 
  • Arrivals free-form 
  • Arrivals  
  • Ultimate 
  1. Flexible Writing File Plugins 

This plugin is used to expand JMeter with a flexible listening file which is applied in writing test results into a specifically flexible file format through the JMeter GUI. 

  1. Dummy Sampler Plugins 

The dummy sampler plugin is known as the most compliant JMeter sampler used to imitate the request orders and responses without the need to run them. This dummy sampler makes it easy to debug post-processors and file extractors. 

Other common JMeter-supported plugins are: 

  • Interrelated thread communication plugins 
  • JMeter custom functions 
  • Put through timer shaping plugins 
  • Plugins manager 

There are two different sorts of controllers in JMeter; the Samplers and the Logical controllers which are responsible for driving the test processing phase.

The Sampler controllers 

  • Inform JMeter on the need to send server requests such as the inclusion of an HTTP sampler request to JMeter to send a type of HTTP request, or the requests can also be customized by adding some elements for configuration to a sampler. Every sampler possesses various properties that can be set up or customized by the inclusion of certain configuration elements to the test plan while remembering to include a listener for display and/or saving of the results of the request results to the disc. 
  • When sending more than one similar request, such as sending the HTTP requests to a particular server, attempt using a default configuration feature. Every controller has a configuration default element. 
  • The samplers inform JMeter about sending requests and waiting for responses to and from the server, which are then processed in the organized format on which they are displayed in the tree. 
  • Controllers help to regulate the occurrence of repetitions within a sample. 
  • To make the JMeter execute simple and basic validation on request responses, include an assertion to the sampler. These assertions can be created with the aid of JMeter's regular expressions.  

Samplers used in JMeter are: 

  • HTTP request order 
  • FTP request order 
  • JOR request order 
  • JUnit request order 
  • JDBC request order 

The Logical Controllers 

  • These controllers permits the customization of the logic used by JMeter in making decisions about when to place and send a request. For instance, the addition of a controller for interleave logic to be shuffled between both HTTP requests samplers. 
  • They allow for changes to be made to the requested order from their primary elements and have the self-ability to modify requests and make JMeter repeat requests. 
  • A test tree can be used to understand the test plan of logic controllers.  
  • Thread groups in JMeter are basic parent-feature components required for the execution of every test plan. 
  • There are several thread groups in JMeter including the Stepping, Concurrency, Arrivals free-form, Arrivals, and Ultimate thread groups.  
  • The ultimate thread group is part of the outer modules used for planning the test type like a spike test type or a responsibility model.  
  • Using the ultimate thread group will require the application of a contingent burden on the server.   
  • Unlike the others, ultimate thread groups permit the definition of diverse schedule records with separate ramp-up periods, shutting down, and flight mode times up to infinity and generates a graphical load display graph that can help in defining test plans that tally with real-time use cases. 
  • Also, in the ultimate thread groups, there is permission for greater than one row which aids flexibility as it relates to a more advanced ramp-up and/or ramp-down pattern of behavior, this means that, in this instance, the addition of a load pattern multiple times is permitted. 
  •  On the contrary, the other types of thread groups such as the concurrency thread group can be linked to the shaping timer through a feedback feature functionality to permit the control of test execution, like the addition of more threads to the numerous requests placed when there is a deficiency in the amount of the thread groups to attain and regulate the present shaping timer. 

Definition/ Explanation 

  • "Spike" refers to a sudden change in traffic which could be in the direction of an increase or a decrease. 
  • Spike testing is a kind of testing done to determine the performance of a test where a particular application obtains a drastic increase or decrease in load. The aim is to establish the behavioral attributes of a software application when it experiences severe variation in traffic. 
  • The issues addressed by spike testing include the maximum load permitted by an application and recovery time verification for an application between activity spikes.  

How to perform spike testing using JMeter: 

  • Performing a spike test may be daunting, as testers may discover that the application's performance progressively worsens, slows down, or is completely halted. Establishing the exact location for the cause of the failure of the application under spike tests permits developers to be more proactive in tackling unforeseen spikes in a load production environment. For instance, a spike test can be applied to a commercial application in preparation for an open sales day. 
  • It is recommended to utilize a different test environment, not the live one when spiking a test application. It is beneficial to identify the maximum load capacity of spike testers to encourage the placing of more effort on more relevant software failures emanating beyond the confines of the expected capacities.  
  • To monitor the software, the JMeter application is applied which allows the simulation of a system under conditions of sudden increase or decrease of test load, executed by the test performers. This is carried out over a shortened time before returning to a normal load.  
  • The simulation monitoring then provides graphs representing performance operations to be analyzed by spike testers to detect possible breaks in the application under the conditions of peak loads.   

The Gaussian timer is a random timer element used in delaying each request made by users for a random period. Based on the gaussian curve distribution, there is a random deviation premised on the constant offset delay. The gaussian timer halts each thread request for a specified and on time, with the majority of the timeframes happening close to the gaussian distribution times value, the specified value, and the offset value.

An example of this is having a deviation of 500 milliseconds and a constant offset delay of 1000 milliseconds. Here, about 65% of the delays will fall between 500 and 1500 milliseconds. This range is obtained by simply subtracting and adding the values (1000-500 and 1000+500) because the gaussian random timer possesses a random deviation that is dependent on the distribution of the gaussian curve about a constant offset delay.

The total delay is the summation of the distributed value of the gaussian curve with a mean of 0.0 and a standard deviation (SD) of 1.0, multiplied by the specified offset and deviation value.

JMeter assertions are values that provide the basis on which they determine what should be seen as a "pass". Assertions are run against samples and subsamples to confirm if values returned to stay in conformation to expected results. They can as well be added to JMeter variables, and the two major reasons for employing the use of assertions are scope and cost in JMeter.  

Some of the different JMeter assertion types are outlined below.  

  • Assertions of Duration 
  • Assertions of  Response 
  • Assertions of Size 
  • Assertions of compare 
  • Assertions of Beanshell 
  • Assertions of SMIME 
  • Assertions of XML 
  • Assertions of HTML 
  • Assertions of XPath 
  • Assertions of MD5Hex 
  • Assertions of BSF and JSR223

JTL stands for JMeter Text Logs and these are results created for use by JMeter test runs. They are often referred to as JTL files by default extension, however, any other extension may be utilized. If greater than one is run via the same name of an output file, the then work of JMeter would be to automatically append new data at the termination of the file. 

To view the JTL file, the following step should be followed. 

  • JMeter should be opened 
  • Load the particular script 
  • Enter the script monitor logs in the ASM UI that is displaying the error. 
  • Click on analysis on the side menu>logs>monitor 
  • Select the root cause or detailed analysis icon in the log 
  • Wait for the analysis window to open up, scroll through and locate the link for the JTL file 
  • Download the link  
  • Return to the JMeter and ensure there is a View Result Tree in the script, if it is not available, right-click on the button on thread group>Add>Listener>View Results Tree(VRT). 
  • Click the VRT option and select browse 
  • Load and open the downloaded JTL file  
  • View steps in the test view  
  • See the results of tests in the sampler result 

A red notification signifies a failed step, and an explanation for this failure will be included for display by the sampler result. 

Test script recorders like HTTP(S) are used to keep a record of every request made by the HTTP(S) to the server from the home application. Before the test script recorder begins to function, certain configurations will need to be made in the JMeter to make it function effectively. 

Here are the steps showing the flow of the test script recorder like the HTTP (s) which should be followed. 

  • To the benchwork, include an HTTP(S) test script recorder 
  • Enter the port number to be utilized in the commencement of the proxy server. 
  • Select the target which could be as the "workbench" alone or include a recording controller in the test plan and pick the same target to save every recording under it. 
  • Initiate the proxy server 
  • Manually perform a browser configuration with a non-automated proxy setting that directs to the same port number that is used in the test script recorder. 

Recording in JMeter is an initial step to getting started with application performance testing. The recording flow of business speeds up the process of generating test plans, and if this step is neglected, more time will be wasted in an attempt to manually craft requests. Generally, almost every performance GUI-based testing tool provides a method by which the application can record by proxy. 

The actions and requests made on a mobile application can be recorded by JMeter using the HTTP(S) Script Recorder. This script recorder possesses specific features to set it up and run the performance test script. The needed action here is to configure JMeter on the mobile device, which varies between an iOS and an Android device. 

The addition of the non-Test element in JMeter to the plan setup permits the capturing of network traffic. This can be achieved by right-clicking on this access path; 

Test plan>Add>Non-Test Elements>HTTP(S) Script Test Recorder.  

This expands the recording capacity of JMeter. 

Tips for commencing a recording phase are to ensure there is a good understanding of the business flow and to have all necessary data available and ready. It is advised to clear out the cache and cookies from a frequently used browser. 

  • A workbench is referred to as a practice premise or a transient and temporary storage area because the component features on the workbench are often not saved together with the test plan. 
  • The workbench is a valuable component in the HTTPS test script recorder that helps to record scripts in a direct manner which the tester can be offloaded subsequently to measure response time. The information temporarily stored by the workbench can be added to the test plan if need be. 
  • The workbench is unrelated to the test plan and JMeter will not save any contents or components of the workbench automatically, and will only save the components of the test plan branch. 
  • If the workbench components must be saved, it has to be done separately in the form of "test fragments"

During the building of a performance test, the importance of using properties and values cannot be overemphasized to keep static values outside the tests, therefore, ensuring that alterations made to these values are all done in one place instead of having to make changes in several tests.

Oftentimes, although a JMeter suite might have been inherited, or the developer had to rush through a creative process, and may have hard coded the values in the tests, meaning that for every alteration made to an endpoint or server name or a payload sampler, then the changes must be made to the static values within the tests.

The need to update tests may also present, or a developer may have decided to update static values together with properties or variables so that subsequently, changes can be made to the input file of each test. This updating process can be exhausting and time-wasting, but since a JMeter test is a simple XML, updates to the tests can be done in an automated manner by parsing the XML and performing a code update.

The Apache's Xerces XML parer comes with the JMeter application, but a user is at liberty to request and select a different parser from JMeter by incorporating a class for a third-party parser in JMeter's classpath and then updating the properties in the jmeter.properties file together with the name of the full class of the parser implementation.

JMeter is used for testing load functionalities and performance measurement. It executed this task by creating a large-scale number of concurrent users in a heavy-load simulation. The performance testing feature of JMeter is an expanded functionality as it was previously designed for basic processes such as test application activities.

The need to use JMeter for performance testing stems from the reasoning that it is a high-capability resource that can load as well as monitor observable performance for various products, regardless of their protocols or servers, which could be HTTP or HTTPS service webers, databases, Message Oriented Middleware (MOM).

Also, the reason for using JMeter as a chosen application for performance testing results from these factors. 

  1. It is cost-free 
  2. Can aid performance testing for both dynamic and static resources 
  3. Its testing in JMeter encompasses both load and stress testing. 
  4. Its framework permits multithreading 
  5. Graphically enhanced representation of performance testing 
  6. An independent java-based platform

Take, for instance, a brand new API that has been created on the REST principles and configured under the ASP.NET interface. An attempt to save this will require the creation and running of certain stress tests for the API to grasp how rapidly it functions and the amount of load supported by it.

The .NET applications currently can be run against web APIs or applications, and the JMeter application operates the endpoints similar to the different media types since the .NET team stopped their cloud-based operation testing services due to poor community adoption.

JMeter can be used for load testing of .net web applications. This is done to know how fast a site will operate when the number of users on it is doubled or multiplied. Assuming the .net application makes use of a "postback" and has given access to the .net security or validation features, the postback here would submit the page to itself and the server will forward some long variables which are hidden to the user

FeaturesJMeter
LoadRunner

 Easy operability 

 It is an application tool, used for performance testing from an open source. 

JMeter requires a java-supported interface, and once java is downloaded, it can be used to upload and run tests from a JMeter script file 

 This is a costly application used for execution processes that are often complex because, for every user, it generates a thread making the whole task a daunting operation. 

 Generating the load 

  

 Load generation using JMeter is till infinity. It creates the ultimate number of loads based on specific requirements. 

  

 It generates a limited amount of loads for load testing. 

 Analysis 

 Newbies and less experienced testers find the ser of JMeter more straightforward, simple, and easy to understand. 

 The reports generated by the LoadRunner are in the form of raw files and must be analyzed and interpreted by engineers separately. 

 Support 

 The JMeter community is large and offers a wide range of support to its users 

 Due to the limited number of users, LoadRunner has a small support community system. 

 Required skills 

 It does not require so many skills. JMeter can be used by a tester with absolutely no knowledge of the words entailed about its scripting and coding. 

 The is a need for accurate scripting skills and knowledge to operate a performance testing process. 

 Elements addition 

 The feature elements can be altered, added, or removed from JMeter without encountering many difficulties. 

 The enormous difficulty is experienced in an attempt to tweak or alter the features in a LoadRunner due to its advanced complexity. 

Description

Top JMeter Interview Tips and Tricks

Here are a few effective and important tips that will help you crack the JMeter interview questions. The tips and tricks will help you to prepare from basic JMeter interview questions to experience people. 

  1. Below are the tips and tricks for a J2EE interview, consider these tips to improve your preparation and performance:  
  2.  Researching your potential employer before your interview allows you to make a positive impression on them.   
  3. Requesting someone to act like an interviewer and ask questions would allow them to provide feedback on your performance and gives you valuable insight into the effectiveness of your answers.  
  4. Conducting several rounds of rehearsal and practice interviews and making adjustments each time allows you to identify any areas for improvement in your answers.  
  5. Study key points. Using only bullet points or critical facts you want to cover in your notes can help you study more efficiently.    
  6. Good research and study would help to sound natural, which may help to make a positive impression on the hiring manager. 

How to Prepare for a JMeter Interview?

Navigating JMeter interview questions and answers can be tricky, so having a good source during the process is essential.

Different programs on KnowledgeHut include a comprehensive curriculum, unmatched teaching methods, expert instructors & SMEs guidance, and career coaching to help you nail your following tech interview. JMeter interview questions for experience discussed in this article will help you with senior roles and your growing career path.

Quick key focus areas of the training courses for JMeter technical interview questions preparations are: 

  1. Solving coding problems with power patterns - Guided coding practice with experts  
  2. Technical & Behavioral Coaching  
  3. Realistic mock interviews practice, Interviewing with different expert Hiring Managers, would nurture communication skills and will help to have detailed personalized feedback.  
  4. Researching your potential employer before your interview allows you to make a positive impression on them. 

Job Roles

With sufficient knowledge of JMeter, anyone can apply for the following few jobs: 

  • JMeter Automation Test Analyst 
  • JMeter QA Engineer 
  • Automated Web Applications Tester 
  • JMeter QA Developer 
  • JMeter Expert 
  • JMeter Automation Test Engineer 
  • Senior Performance Engineer - JMeter 

Top Companies

  1. Impact QA Services LLC 
  2. PerfectQA Services 
  3. Perfomatix 
  4. Envion Software 
  5. Reenbit 
  6. Nestormind Pvt. Ltd. 
  7. TCM STUNNER IT CONSULTANTS LLP 
  8. Anviam Solutions 
  9. Frugal Testing 
  10. TheMarketConnect 
  11. Precise Testing Solution Pvt. Ltd 
  12. Zeus Testing Solutions 
  13. Cherish DEV 
  14. Qualitica 
  15. ADAPS PTY LTD. 

Computer Programming courses for beginners on KnowledgeHut will help candidates reach the ideal way. There is no denying that learning JMeter opens prospects for professionals in the testing domain. So, if you intend to learn JMeter, pull your socks up and start. 

What to Expect in a JMeter Interview?

Within the interview, there would be a mixture of general and technical questions. Below are the few points penned down to expect within the JMeter interview. Performance testing interview questions JMeter for experienced professionals can include questions on topics like XML parser, Workbench, Text Script recorder, and more. JMeter scenario-based interview questions are also a common occurrence in these interviews. 

General Questions 

Expect the hiring manager to ask a little bit about you.  

  1. Expect a question about why you left your last job and next what you are looking for in a job.  
  2. Few Employers would be curious to know how you hear about this position.  
  3. Preparation and research about the company would leave a positive impact, as expected. How did you know about the company?  
  4. Expect a question about What do you expect from your manager and team and where do you think you'll be in five years?  
  5. Be ready to answer why they should hire you. 

 JMeter Technical Interview Questions 

  1. Employers typically ask interview questions to gauge your fundamental understanding of the JMeter.   
  2.  Some interviewers may ask questions that test your knowledge of specific protocols supported, the execution order of Test Elements, ensure re-usability, Assertion, Spike testing, Pre and Postprocessor supported in JMeter,   
  3. Some interviewers may ask you to list the advantages and disadvantages of using JMeter or compare your knowledge of JMeter to other platforms.

Summary

JMeter load testing of Java web applications is one of the best tools available for this is Apache JMeter. Thanks to its Java nature, it is free, open-source, and cross-platform. It requires technical expertise, and there are a lot of possibilities to explore and perform with this tool. Here's the best Software Testing training course to improve your programming skills. Feel free to check it out. 

JMeter is an easy, portable, powerful, and highly extensible tool. With JMeter, it is possible to test the performance of resources effectively. We can conduct performance within web service or from load testing to volume testing. Metrics are used to know the precise picture of performance testing. On top of all, JMeter provides many plugins to support the testing.

Read More