Load Testing vs. Performance Testing vs. Stress Testing

Michiel Mulders Developer Tips, Tricks & Resources

Just conducting one type of testing is generally not enough. For example, let’s say you decide to perform unit testing only. However, unit tests only verify business logic. Many other types of tests exist to verify the integration between components, such as integration tests.

But what if you want to measure the maximum performance of your application? Or what if you want to know how the application behaves under extreme stress?

To answer these questions, you can pursue these types of testing:

  • Load testing
  • Performance testing
  • Stress testing

These types of tests are ideal for answering the above questions. However, the difference between those testing types is subtle. This article will guide you through each of those testing types. You’ll find out about each type of testing and learn about the differences between them.

What Is Performance Testing?

Performance testing is an umbrella term for both load and stress testing. Performance testing refers to all testing related to verifying the system’s performance and monitoring how it behaves under stress. Therefore we can say that performance testing is concerned with the following metrics:

  • Reliability: Determine the error rate and how it changes under higher loads.
  • Stability: You can measure this through memory and CPU usage.
  • Response time: Measure the average response time for requests.
  • Scalability: Determine how the application behaves under different types of loads.

Performance testing is often linked to a customer’s functional requirements. Imagine a client who asks to develop a service that handles ticket sales for events. For example, the client expects the application to be able to handle up to 50,000 requests per minute. This is a functional requirement that performance testing helps to validate.

The goal of performance testing is not to find bugs but to find performance bottlenecks. Why is this important? A single performance bottleneck can have a huge impact on the overall application’s performance. Therefore, it’s crucial to conduct performance testing to detect such issues.

In addition, this type of testing also verifies the performance in different environments to make sure the application works well for different setups and operating systems. To give an example, an application might work fine on a Linux server but have performance issues on a Windows server. Performance testing should help you rule out such problems.

In short, the goal of performance testing is to gather insights into the application’s performance and communicate these performance metrics to the stakeholders.

Benefits of Performance Testing

It’s always a good idea to measure the performance of an application. Delivering an application that hasn’t been performance tested is the same as delivering a bike with brakes that haven’t been tested.

Performance testing helps you with the following aspects:

  • Measure the stability of the software.
  • Assess how your application behaves under a normal load, as this is key information for the client.
  • Find performance bottlenecks early on in the development life cycle.
  • Measuring performance helps you to further improve performance because it helps you tailor configurations for components to make them more streamlined.

Next, let’s get into the details of load testing.

yellow load here signage

What Is Load Testing?

Load testing specifically tries to identify how the application behaves under expected loads. Therefore, you should first know what load you expect for your application. Once you know this, you can start load testing the application.

Often, load testing includes a scenario where 100 extra requests hit the application every 30 seconds. Next, you’ll want to increase the number of requests up to the expected load for the application. Once the expected load has been reached, most testing engineers prefer to continue hitting the application for a couple more minutes to detect possible memory or CPU issues. These kinds of issues might only pop up after hitting the application for a while and are rarely visible from the beginning.

Moreover, the goal is to gather statistics about important metrics, such as response time, reliability, and stability. Here, application monitoring tools such as Stackify’s Retrace tool come in handy. An application monitoring tool gives you insights into memory usage and CPU time. In addition, for Node.js specifically, it can give you insights into the Node.js event loop and how long it’s blocked. An event loop that’s continuously blocked is often a bad sign.

To summarize, load testing is generally concerned with collecting all this data and analyzing it to detect anomalies. The idea of load testing is to create an application that behaves stably under an expected load. You don’t want to see an ever-increasing memory usage, as that might indicate you have a memory leak.

Benefits of Load Testing

Load testing helps you to get a better understanding of the expected load your application can handle. And understanding those limits helps you to reduce the risk of failure.

Let’s say your application can handle 5,000 requests per minute. Because you know this limit, your organization can take precautions to scale the application in case the number of requests per minute gets close to this limit. By taking these precautions, you’re reducing the risk of failure.

In addition, load testing gives you good insights into the memory usage and CPU time of your application. This data is of great value for measuring the stability of your application. Ideally, the memory usage for your application should remain stable when you’re performing load testing.

Last, let’s explore the true meaning of stress testing.

What Is Stress Testing?

Stress testing helps you detect the breaking point of an application. Also, it allows a testing engineer to find the maximum load an application can handle. In order words, it lets you determine the upper limit of the application.

To give an example, let’s say a certain application programming interface can handle 5,000 simultaneous requests, but it will fail if it has to process more requests for the given setup. This limit is important for companies to know because it allows them to scale their application when needed.

In addition, it’s also a common practice to increase “stress” on the application by closing database connections, removing access to files, or closing network ports. The idea here is to evaluate how the application reacts under such extreme conditions. Therefore, this type of testing is extremely useful when you want to evaluate the robustness of your application.

Benefits of Stress Testing

Stress testing provides the following benefits for you and your organization:

  • Find the exact breaking point for your application.
  • Evaluate the robustness of an application.
  • Determine which components are most likely to break first when putting the application under extreme stress and how to handle this type of failure accordingly.

Finally, let’s compare the above three testing types and learn about the differences between performance testing, load testing, and stress testing.

Differences Between Performance, Load, and Stress Testing

To finish off, let’s do a quick recap of performance testing, load testing, and stress testing so that you see how these tests are related.

  • Performance testing is an umbrella term that includes both load testing and stress testing. Performance testing is concerned with evaluating the overall system’s performance and collecting metrics such as availability, response time, and stability.
  • Load testing is a technique that verifies whether the application can handle the expected load. Load testing works well for detecting performance bottlenecks, as they can have a big impact on the overall performance.
  • A testing engineer uses stress testing to find the breaking point of an application. In addition, this type of testing verifies how the application behaves in extreme stress situations, such as losing database connectivity or not being able to access an application programming interface. The goal is to find out how the application behaves in such stress situations to determine its robustness.

To conclude, don’t neglect performance testing. It’s a great tool for increasing customer satisfaction because you can provide your clients with accurate numbers about the performance of the application. In my opinion, it’s a crucial factor as you strive to deliver quality software.

About Michiel Mulders

This post was written by Michiel Mulders. Michiel is a passionate blockchain developer who loves writing technical content. Besides that, he loves learning about marketing, UX psychology, and entrepreneurship. When he's not writing, he's probably enjoying a Belgian beer!