Performance Testing vs. Load Testing vs. Stress Testing

If you’re a developer or QA engineer or if you work in DevOps, you know you need to conduct different performance testing types in order to make sure each code change or feature addition (a) doesn’t break the system and (b) works.

But which performance testing types should you conduct, what’s the difference between load testing and stress testing, and which test is suitable for which situation? In this blog post, we’ll cover the answers to these questions and more.

Performance Testing vs. Load Testing vs. Stress Testing

There are multiple types of tests that fall under the performance testing umbrella. For instance, load testing and stress testing are both performance testing types that check how your application performs when many people use it at once. 

While there are those who compare all three types of testing, the more popular comparisons that testers make include: 

• Performance testing vs. load testing.
• Load testing vs. stress testing.

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Let us take a closer look at the above comparisons.

Performance Test vs. Load Test

In general, comparing performance testing vs load testing does not make sense, since performance testing is an “umbrella” term for all activities including (but not limited to):

• Load Testing.
• Stress Testing.
• Soak Testing (sometimes called Endurance Testing).
• Spike Testing.
• And more.

Therefore, load testing is only a part of performance testing.  

Load testing is the process of checking the behavior of the system under test under the anticipated load. For example, the piece of software under test is designed to serve X users (because it is an internal product of an enterprise and there are no more employees), so it does not make sense to conduct testing under a higher load. Therefore, it is sufficient to check if the performance is good enough and matches non-functional requirements or service level agreements. 

So, load testing in a nutshell consists of:

1. Conducting the anticipated load in terms of virtual users or requests per second.
2. Comparing actual metrics (response time, throughput, percentage of errors, resource usage, etc.) with the expected metrics.
3. Deciding whether the current build is ready to go or not. 
    

Load Test vs. Stress Test

While load testing simulates real-life application load, the goal of software stress testing is to identify the saturation point and the first bottleneck of the application under test. 

An ideal application behaves in the following manner:

• Throughput (the number of served requests per second) increases as the load increases.
• Response time stays the same, no matter how much load is applied or even decreases as a result of caching and just-in-time optimizations.

The above points are true to a certain extent. However, at some point you will see that while you are adding more and more virtual users, the number of requests per second remains the same or even goes down due to increased response time. Bottlenecks can happen during this stage with errors and even stop serving incoming requests entirely.  

Therefore, the main way to differentiate between these two types of testing is by focusing on their end goal.

To summarize, load testing and stress testing are two popular performance testing types that each focus on different application behaviors, such as a system’s general behavior under load or the upper limits of a system’s load capacity.

With the comparisons out of the way, let us explore each type of testing on its own.  

What is Performance Testing?

Performance testing is a testing method that evaluates how the system behaves and performs. Software performance testing examines responsiveness, stability, scalability, reliability, speed, and resource usage of your software and infrastructure.

Different types of performance testing provides you with different data, as we will further detail.

Before performance testing, it is important to determine your system’s business goals, so you can tell if your system behaves satisfactorily or not according to your customers’ needs.

After running performance tests, you can analyze different KPIs, such as the number of virtual users, hits per second, errors per second, response time, latency, and bytes per second (throughput), as well as the correlations between them. Through different test reports, you can identify bottlenecks, bugs, and errors, then decide what needs to be done.

When to Use Performance Testing

Run performance tests when you want to check your website and app performance, which may extend to testing servers, databases, networks, etc. If you follow the waterfall methodology, test at least once before you release a new version of your application. If you’re shifting left and going agile, you should test continuously.

The following figure shows an example of a performance testing report on BlazeMeter. This is a good test, given the growing number of users does not affect the response time, the error rate remains low, and the hits per second are in line with the number of virtual users.

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Other Performance Testing Types

While load testing and stress testing are two of the most popular performance testing types, they are far from the only performance testing options available. 

Let us explore three other types of performance tests: soak tests, spike tests, and scalability tests.

Load Tests

Load testing is a type of performance test that checks how systems function under the projected number of concurrent virtual users performing transactions over a certain period of time

In other words, load testing measures how systems handle expected load volumes. There are a few types of open-source load testing tools, JMeter being the most popular.

When to Use Load Testing

Leverage load testing when you want to determine whether your system can support the anticipated number of concurrent users. You can configure tests to simulate various user scenarios which can focus on different parts of your system (such as a checkout page, for example).

You can determine how the load behaves when coming from different geo-locations or how the load might build up, then level out to a sustained level.

Load testing should be performed all the time in order to ensure your system is always on point, which is why it should be integrated into your continuous integration cycles (utilizing tools such as Jenkins and Taurus.)

Software Stress Tests

A stress test is a type of performance test that checks the upper limits of your system by testing it under extreme loads, a simple task with a tool like BlazeMeter. Stress tests examine how the system behaves under intense loads and how it recovers when going back to normal usage. Are the KPIs like throughput and response time the same as before spike in load? Stress tests also look for eventual denials of service, slowdowns, security issues, and data corruption.

Stress testing can be conducted through load testing tools by defining a test case with a very high number of concurrent virtual users. 

Just as a stress test is a type of performance test, there are types of load tests as well. If your stress test includes a sudden, high ramp-up in the number of virtual users, it is called a Spike Test. If you stress test for a long period of time to check the system’s sustainability over time with a slow ramp-up, it’s called a Soak Test.

The following example shows how to create a traffic spike using JMeter’s “Ultimate Thread Group” component. We presume the system will be under traffic three minutes into the test. We define more threads to be added within fixed time windows using the “Initial Delay” setting.

When to Use Stress Testing

Run stress tests against your website or app before major events, like Black Friday, ticket selling for a popular concert with high demand, or elections. We recommend stress testing every once in a while so you know your system’s endurance capabilities. This ensures you’re always prepared for unexpected traffic spikes and gives you more time and resources to fix your bottlenecks.

Another possible positive outcome of stress testing is reducing operating costs. When it comes to cloud providers, they tend to charge for CPU and RAM usage or more powerful instances that cost more. For on-premise deployments, resource-intensive applications consume more electricity and produce more heat. So, identifying bottlenecks not only improves perceived user experience but also saves money and trees. 

Soak Tests

Also known as endurance testing, capacity testing, or longevity testing, soak testing tracks how an application performs under a growing number of users or draining tasks happening over an extended period. 

Soak tests are especially known for their extended duration. Once you go through a ramp-up process and reach the target load that you want to test, soak tests maintain this load for a longer timeframe, ranging from a few hours to a few days. The main goal of soak testing is to detect memory leaks.

Spike Tests

Spike testing assesses performance by quickly increasing the number of requests up to stress levels and decreasing it again soon after. A spike test will then continue to run with additional ramp-up and ramp-down sequences in either random or constant intervals to ensure continued performance.

Spike tests are great to use for scenarios like auto-scaling, failure recovery, and peak events like Black Friday.

Scalability Tests

Scalability tests measure how an application can scale certain performance test attributes up or down. When running a scalability test based on a factor like the number of user requests, testers can determine the performance of an application when the user requests scale up or down.

The main metric is whether the scaling out is proportional to the applied load. If not, this is an indication of a performance problem, since the scalability factor should be as close to the load multiplier as possible.

How to Do Performance Testing

Running your performance tests is an important part of the development process. Here are the different steps you should take for performance testing your application:

Determine Test Metrics

Decide on the metrics you want to test. For example, determine your acceptable response time or non-acceptable error rate. These KPIs should be derived based on product requirements and business needs. If you're running these tests continuously, you can use baseline tests to enforce these SLAs.

Decide on the Testing Scenarios

Detail which scenarios you will be testing. For example, if you have an e-commerce site, you might test the checkout flow.

Choose a Testing Platform

There are many excellent open source solutions out there, like JMeter, Taurus, and Gatling. You can also use BlazeMeter to get additional capabilities like more geolocations, test data, and advanced reporting.

Configure the Test Script

Build the script in the performance testing tool. Simulate the expected load, the capabilities you are testing, test frequency, ramp-up, and any other part of the scenario. To simplify the process, you can record the scenarios and then edit them for accuracy. If you need test data, add it to the script.

Run the Test

Execute the tests. This is the simple part. Usually you click “run."

Monitor Results

Analyze the test results to identify any bottlenecks, performance issues, or other problems. You can use the dashboards provided by the performance testing tool or you can look at solutions like APMs for more information.

Optimize and Retest

Fix the performance issues and retest the application until it meets the performance requirements.

What is the Difference between Performance Testing vs. Performance Engineering?

Performance testing and performance engineering are related concepts but they mean different things. 

Performance testing evaluates the stability, responsiveness, reliability, speed, and scalability of a system or application under varying workloads. The performance of the system or application is tested and analyzed to ensure that it meets the performance requirements.

Performance engineering, on the other hand, is a proactive approach to software development that identifies and mitigates performance issues early in the development cycle, from the design. By addressing issues earlier, engineering organizations prevent issues and accelerate time-to-market. 

Performance testing is one of the steps taken when performing performance engineering.

Performance Testing Tools & How BlazeMeter Can Help

Performance testing tools are platforms that evaluate and analyze the speed, scalability, robustness and stability of the system under tests. These solutions help ensure that applications and websites can handle the expected level of user traffic and function reliably under different loads. As a result, they are an important component of the software development lifecycle. Many such platforms can integrate with CI/CD tools, so that performance tests are run automatically as part of the integration and deployment pipelines.

One such leading performance testing tool is BlazeMeter. BlazeMeter is a continuous testing platform that enables developers and testers to test the performance of their web and mobile applications under different user loads. It provides a comprehensive range of testing capabilities, including load testing, stress testing, and endurance testing that is open-source compatible. BlazeMeter also supports functional testing and API testing, and provides capabilities like mocking and test data.

Bottom Line

Utilize each of the performance testing types detailed in this blog to ensure you are always aware of any issues and can have a plan for dealing with them.

With BlazeMeter, teams can run their performance testing at a massive scale against all your apps, including web and mobile apps, microservices, and APIs. With advanced analytics, teams using BlazeMeter can validate their app performance at every software delivery stage.

BlazeMeter lets you simulate over two million virtual users from 56 locations across the globe (Asia Pacific, Europe, North, and South America) to execute performance tests continuously from development to production. 

See for yourself how you can easily build, scale, analyze, and automate performance tests.

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