Load Testing

Load Testing

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A software product, throughout its development life cycle, undergoes a number of tests. When it is about to launch, one test that determines its readiness is load testing. It is a kind of performance testing helping you validate your software product’s behavior under normal and peak conditions. It is the only way to know whether your product can handle the demands of end users or not. 

If you are creating an application and are unfamiliar with load testing, this article is for you. 

What is Load Testing?

Load testing is one of the types of performance testing that evaluates the performance of an application under the expected real-world load. It determines the application’s behavior when multiple users access or use it simultaneously. 

The primary goal of load testing is to uncover and improve performance bottlenecks. Also, it aims to ensure the application’s stability and smooth functioning before launching it to real users. 



The objective of load testing is to:

  • Maximize the application’s operating capacity.
  • Identify whether the latest infrastructure can run the application.
  • Determine the application’s sustainability with respect to the peak load. 
  • Identify the application’s scalability. 
  • Allow more users to use the application.

How Does Load Testing Work? 

With the use of specialized software, load testing involves simulating the load on an application. This means the software creates a large number of virtual users to simulate the actual users accessing the application simultaneously. The testing software measures various performance bottlenecks and attributes during the test, such as the response time. 

If the application becomes unstable while handling multiple requests or extends its response time, it is likely to reach its peak operating capacity. This indicates that performance bottlenecks exist, and they need to be addressed. 

The testing team can analyze the following parameters of the applications during load testing: 

  • Resource utilization levels
  • Concurrency issues
  • Software design issues
  • The performance of hardware, such as CPU and RAM
  • Load balancer performance
  • The maximum operating capacity 
  • Issues in the application’s functionality when subjected to the load
  • The number of users the application can handle before reaching its operating capacity

Furthermore, load testing helps uncover different issues, such as system lag, slow page load times, and crashes when different levels of traffic (users) access the application. 

How to Perform Load Testing? 

Here are the steps to perform load testing: 

  1. Outline Test Objectives – The first step is to enlist the test objectives. Identify what aspects of the application you want to evaluate. Further, find out performance metrics that align with your testing goals, such as the response time, error rates, transactions per second, CPU and memory utilization, and latency. 

  1. Determine the Workload – To determine the workload, it is essential to consider various factors, such as the number of concurrent users, the frequency of transactions, and the types of actions users carry out. Based on these parameters, estimate the workload patterns and create realistic test scenarios. 

  1. Set up the Test Environment – The next step is to set up the test environment. This means setting up the dedicated hardware, network configurations, and software components. The test environment should closely resemble the production environment. 

  1. Select a Load Testing Tool – The most important element in load testing is choosing the appropriate tool. The chosen tool must generate the desired workload and simulate the behavior of real users. 

    JMeter and LoadRunner are among the prominent tools. These testing tools allow you to write scripts that make different requests to the server, just like real-world users. Along with that, these tools provide various configurations like-
  • Number of threads or virtual users
  • Duration of load test
  • Performance attributes
  • Graphs that we want to analyze, etc.

  1. Configure Test Parameters – Now, it is time to set load parameters, such as the number of virtual users, the period of gradual increase in load, and the test duration. Doing this will help you determine the intensity of the load and the time duration the application can withstand. 

  1. Execute Load Tests – Execute the test scripts, monitor the performance metrics, such as the response time, CPU and memory utilization, throughput, etc., on the execution of load tests, and record the results. 

  1. Analyze the Result – Finally, analyze the load test results and look for any performance bottlenecks, such as high response times, resource constraints, or high error rates. 

  1. Optimize and Retest – If you find any performance bottlenecks, address them by optimizing your application. Again, retest the application to check whether performance bottlenecks have been eliminated or not. 

Load Testing Metrics 

During the execution of load tests, it is essential to look at the following metrics, as they help you know how accurately load testing takes place under different test scenarios. 

  • Average Response Time – It is the average taken by the application to respond to user requests. In other words, it is the application’s speed in responding to user queries or requests. 

  • Error Rate – It is expressed in percentage. An error rate is the number of errors occurred during the user requests to the total number of user requests. A request could be anything, such as requesting images, text, web pages, documents, or any other resources. 

    Errors during requests occur because the application is not capable of handling more requests at a specific time. 

  • Requests Per Second – This metric determines the number of requests the application’s server receives in one second. 

  • Throughput – In load testing, throughput refers to the number of transactions per second, which gauges the number of requests your application receives in a second. 

  • Concurrent Users – This metric determines the count of users using the application at a specific point in time or at any time. It helps you understand the time at which the maximum number of users use your app. 

  • Peak Response Time – The peak response time measures the time required for a request-response cycle. Rather than taking the average, it primarily concentrates on the longest cycle. 

Advantages of Load Testing

The following are the significant benefits of load testing-

  • Identifies performance bottlenecks before deploying applications into the production stage.

  • Helps in configuring the most optimal infrastructure for the setup, reducing infrastructure costs by terminating extra machines. Also, an additional machine can be added in the case of suboptimal infrastructure.

  • Minimizes the risk of downtime by identifying and isolating the requests whose performance needs to be improved.

  • Provides a sense of confidence and reliability in the application’s performance.

  • Reduces the cost of the system failure. 

  • Load testing identifies the application’s maximum capacity. Hence, you can ensure that your app can handle a large number of users or transactions.

  • Detects bottlenecks in the application, such as network congestion, insufficient memory, slow database queries, etc. 

  • Identifies issues that lead to heavy load conditions, such as slow response times and increased error rates. 

  • By addressing issues and performance bottlenecks, you can ensure that your app provides a positive experience to end users. 

Disadvantages of Load Testing

  • Many load testing tools are licensed and charge a good amount of money for the license.

  • Even with free and open-source tools like JMeter, you need to set up a test environment that resembles the production environment. This again leads to additional resources and costs.

  • Load test script creation requires scripting knowledge of the language supported by the tool.

  • Incorrectly configured or scripted load test plans/scripts can lead to false performance issues that take considerable time and resources.

  • Load testing is resource-intensive, requiring hardware and software resources.

  • It primarily focuses on the performance of the application under load and does not discover any other issues. 

  • You may find it challenging to simulate real-world usage.

Performance Testing and Load Testing – Are They Same?

Load testing is actually a type of performance testing that focuses on analyzing the behavior of web applications under a particular load for a predefined amount of time.

On the other hand, performance testing is a broader term that includes checking different aspects of the system like –

  • Application’s state at workload higher than expected – stress testing;
  • Performance of application with a large volume of data – volume testing;
  • The ability of the system to sustain a normal workload for a large duration of time – endurance testing, etc.


Load testing determines the readiness of your application. It validates the system’s behavior under normal and peak conditions. It is a type of performance testing that one must not disregard before releasing the software product into the market. So, missing out on load testing is something you cannot afford.

You can learn about different performance testing concepts and script creation from our Apache JMeter tutorial.

That’s it from my side. If you require any further information, let me know in the comment. Also, check out our software testing tutorial here.

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