What is Load Testing: Process, Tools, & Best Practices

Imagine being a developer who created a word changing application that would drastically improve the lives of thousands of people. You decide eventually that this app needs to be shared with the world. Can you imagine people all over the world using your app and your system crashes cause it’s unable to handle the load?

This is the exact scenario software organizations want to avoid when they are building applications that cater to large audiences and need to scale as load increases.

What is Load Testing?

Load testing evaluates a system’s capability to manage a defined workload and user traffic, making it a form of performance testing. It is a valuable tool for gauging the performance and scalability of software applications, websites, and other information systems.

This process is crucial as it offers a multitude of advantages for these systems, ensuring optimal performance and identifying potential bottlenecks. By subjecting the system to varying loads, load testing helps developers and administrators optimize the system for improved user experience and reliability.

Objectives of Load Testing

Load testing has specific objectives centered around ensuring optimal performance under anticipated and peak user loads while adhering to defined performance criteria. Its primary goals include:

• Validate performance: Load testing is a subset of performance testing, focusing on validating the system’s performance under varying user loads. Its primary aim is to assess the system’s response to an increasing number of concurrent users and requests.
• Assess stability: Testing your system is crucial to ensure its ability to handle unexpected loads without crashing, hanging, or encountering excessive errors.
• Analyze response times: Load testing measures system response times for operations and transactions, ensuring they stay within acceptable limits to deliver a satisfactory user experience.
• Analyze scalability: As user loads increase, you need to identify the point at which the system’s performance starts to degrade, and then take informed decisions about horizontal or vertical scaling.
• Optimize resources: Load testing monitors essential resources such as CPU, memory, and network bandwidth utilization. This aids in optimizing resource allocation and ensuring efficient usage.
• Assess compliance and SLA readiness: Load testing may be required to meet compliance or SLA performance thresholds.
• Avoid downtime: Load testing identifies performance issues early, preventing unexpected downtime and ensuring system stability.

Different Types of Load Testing

Load testing can be categorized into several different types, each with its specific focus and objectives. The main types of load testing include:

1. Baseline Load Testing: Used to set a performance baseline for the system under normal or typical load conditions. These baselines can be used to find standards against which the system behavior can be observed. 
2. Stress Testing: Stress testing subjects the system to a load that surpasses its intended capacity, aiming to uncover breaking points and failure conditions. By doing so, it helps determine the system’s maximum load-handling capacity.
3. Soak Testing: Soak testing assesses the system’s performance under continuous usage by applying a consistent load for an extended duration (hours or days). The objective is to identify potential memory leaks, resource exhaustion, or performance degradation over time.
4. Spike Testing: Spike testing tests the system’s capability to handle abrupt and substantial user load surges. It simulates scenarios with sudden spikes in user traffic while monitoring the system’s response to ensure stability.
5. Concurrency Testing: Concurrency testing evaluates how the system performs when multiple users or processes access it simultaneously. It measures how well the system manages concurrent user interactions.
6. Distributed Load Testing: Distributed load testing employs multiple machines or virtual users to simulate a large-scale load on the system. This method facilitates handling much larger loads than a single testing machine could manage.

Apart from the above load testing types, there are several more that might be custom to a system environment and required to test the stability of the system.

Process of Load Testing 

The process of Load Testing can be explained with the following flow diagram:

As part of the process of load testing, complete the following steps:

1. Perform a baseline test to identify your system’s default behavior. Identify what you want to test as part of load testing and gather system usage data.
2. Record your test scripts and add relevant test data and user data to ensure tests run as intended.
3. Based on the goals identified as part of load testing, define test case scenarios. Run the test scenarios and collate results.
4. Use the results and analyze the system behavior against baseline results. Identify bottlenecks.
5. Use the bottleneck data to tweak the tests and change data points. Re-run your tests. 

You can repeat the process till the system is equipped to handle goals that you identified in the first step.

Load Testing Example

The fundamental premise of load testing is to verify your system is ready and equipped to handle any loads that the environment presents. 

Some examples of load testing that you would test for are:

• Users trying to download large number of files
• Server that is running multiple applications
• Printer at a large organization where large queue of prints are simultaneously triggered
• OTT platform where multiple users are accessing the same series or episodes

In any of these scenarios, the high level premise for load testing would be:

1. Set your test environment: Create a dedicated environment that closely replicates your production environment.
2. Define performance criteria: Perform some baseline load testing to identify the metrics around how a stable system behaves.
3. Define load tests: To conduct load tests, we undertake various tasks, including preparing test data for each transaction, estimating the number of users accessing the system, evaluating connection speeds, considering different browsers and operating systems, and configuring servers accordingly.
4. Define your users: Identify tasks that test users will perform.
5. Run and monitor your tests: Define your tests, run them, and monitor for changes in your system behavior.
6. Analyze the results and iterate: Examine the reports to identify performance bottlenecks and propose actionable recommendations for their resolution.

Metrics used in Load Testing

In load testing, various performance metrics are used to evaluate the system’s behavior and performance under different load conditions. These metrics provide insights into how well the system is handling the load and help identify any bottlenecks or areas of improvement. Some of the key metrics used in load testing include:

1. Response Time: Response time is the duration between a user’s request and the system’s response. Shorter response times signify improved system performance and faster user interactions.
2. Peak Response Time: The peak response time in a load test refers to the maximum duration taken by a transaction or request to obtain a response. It serves to identify the worst-case scenario for response times.
3. Throughput: Throughput measures the volume of transactions or requests processed by the system within a specific timeframe (e.g., requests per second or transactions per minute). A higher throughput indicates the system’s capacity to handle a greater number of requests effectively.
4. Concurrent Users: Concurrent users represent the count of virtual users or simultaneous connections accessing the system during the load test.
5. Network Latency: Network latency refers to the time it takes for data to travel between the client and the server. Elevated network latency can adversely affect response times and user experience.
6. Transactions per Second (TPS): Transactions per second (TPS) denotes the count of successful transactions processed by the system in one second. It serves as a metric to measure the overall system load.

Together, these metrics offer a comprehensive overview of the system’s performance, aiding testers and developers in identifying performance bottlenecks, areas for enhancement, and ensuring the system can effectively manage the anticipated user load.

Load Testing Tools

Some of the popular load testing tools are:

• Apache JMeter: This tool supports creation of complex load testing scenarios and offers comprehensive reporting functionalities. It supports multiple protocols, including HTTP, HTTPS, FTP, JDBC, and more.
• LoadRunner: LoadRunner, crafted by Micro Focus, is a load testing tool engineered to test diverse applications, protocols, and environments. It boasts extensive support for various technologies and offers in-depth analysis of test results.
• BlazeMeter: This cloud-based load testing platform enables effortless scalability and supports multiple testing protocols. It provides real-time reporting and seamless integration with various CI/CD tools.
• k6: This developer-centric load testing tool, which is open-source, prioritizes ease of use and script creation. It is suitable for conducting load tests either locally or on cloud platforms.

You must select the load testing tool based on your specific requirements, technology stack, and budget restrictions.

Advantages and Disadvantages of Load Testing

It is recommended that if you expect your application to be scalable and to serve multiple applications, you must consider load testing. 

Some advantages of using load testing are:

• Improves the scalability of the system.
• Minimize risks related to system downtime.
• Improves system reliability
• Improves user experience

Disadvantages of using load testing are:

• Requires niche programming skill set
• Increase resources that are required to set up the test environment
• Limits the test scope and hence it is suggested that load testing is combined with some functional tests.

Performance vs Load Testing

Load testing is part of performance testing and there are subtle differences between them.

Conclusion

Load testing needs to be an integral part of your testing  checklist. With the abundance of testing tools, invest in load testing tools and ensure that you test across devices and operating systems. For load testing, you must simulate real-world conditions and for that using a real device cloud is a great option. Access to multiple devices helps you predict and handle issues before your product reaches production. BrowserStack Automate provides access to an array of web browsers and OS for you to test your applications.

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Load testing evaluates a system’s capability to manage a defined workload and user traffic, making it a form of performance testing. Learn about what is load testing, how to perform load testing, and best practices related to it.