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Performance Testing vs. Load Testing: Which One Is More Suitable for You?

Nov 21, 2019
11 min read

Software testing professionals often use the terms ‘load testing’ and ‘performance testing’ interchangeably. However, in reality, there is a significant difference between these two processes as each of them evaluates the performance levels of different aspects of a system.

Understanding the main goals and objectives of load and performance testing is essential for any software testing professional. The quality of any software system depends on how well you identify underlying vulnerabilities with the help of these testing methods.

Therefore, if you don’t know how these processes differ from each other, you won’t be able to apply them effectively in a specific development environment. Below we cover the differences between load testing and performance testing.

Performance Testing Definition and Goals

Performance testing is a broader scope of software testing. It encompasses load testing as well as other forms of software testing and ensures applications keep performing under different scenarios. Therefore, performance testing is not just limited to testing the effects of user load on a given system.

Performance testing helps testers understand how the components of a system are performing in a given situation. You can validate different aspects of the system, such as scalability, resource usage, and reliability. As a result, it’s easier to focus on addressing the performance issues in any given software product.

Using the e-commerce web service example from load testing, we will test the web service on a much broader scope. Instead of creating testing scenarios based on user load, we will set various benchmarks and performance standards for each feature of the application.

For instance
if the user searches for a particular item by inputting it in search, how much time would the application take in displaying results relevant to the search query? The response time will be measured using a benchmark in the range of X milliseconds and Y milliseconds.

These benchmarks will behave as metrics for measuring the performance of a given feature, action or event. If the application completes the action in the given range, then this means the system is performing according to the given benchmark. However, if the application fails to do its job in the given range, then the testers must find out why this delay is happening.

Performance testing is often used to set up the benchmark behavior of a given system. This means that performance testing must define standards of performance for specific features in the application.

Software testers must test every single feature through different industry-defined benchmarks. Nevertheless, the objective of performance testing is not to find defects in the application or evaluate if it has succeeded or failed. Instead, performance testing only determines the performance metrics of the application.

This is why software testers need to set these standards accurately. To understand and evaluate all critical aspects of the application, the testers must set a benchmark for resource usage, response time, stability, throughput, and speed. Since the performance test is a superset of all the testing procedures, it will test all the attributes listed above.

Types of Performance Testing 

There are six different types of performance testing:

Load Testing

As we discussed above, it evaluates a system’s ability to perform under real-world user loads. The objective of this test is to identify performance bottlenecks in the application before deployment.

Endurance Testing

Since it is a subset of load testing, it is also considered a part of performance testing. Here we measure the application’s performance against anticipated user loads over an extended period. The performance is measured against benchmarks set during initial performance testing.

Volume Testing

In volume testing, a massive amount of data is injected in a database suddenly, and testers evaluate its effect on the collective behavior of the software system. Therefore, testers can check how the system behaves under changing database volumes.

Stress Testing

Stress testing is used to measure an application’s performance against extreme workloads, such as high data processing or traffic. The primary objective of this test is to identify the breaking point of the application.

Capacity Testing

Capacity testing helps software testers identify how many users a software system can handle before the performance of the application goes below expectations.

Scalability Testing

Software testers use scalability testing to determine an application’s ability to scale up, depending on the increase in user load. It helps to identify the system’s ability to adapt to increasing user loads.

Spike Testing

Spike testing refers to the process where testers evaluate how a system responds to large spikes in user load.

What Type of Performance Testing Do You Need?
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Advantages of Performance Testing in Software Development 

Performance testing offers a comprehensive overview of the performance issues in a given system. Here are some of the key advantages of performance testing software development.

Validates Fundamental Features

Performance testing helps identify the problems in the critical features of any given application. As a result, you can ensure that the application performs its core functions without any interruption or problem.

Measure Speed, Accuracy and Stability

Since you are measuring the critical components of your system under varying scenarios, you can directly monitor the application’s speed, accuracy, and stability in these situations. This helps developers meet the internal and global standards they have set and ensure that the system performs up to par.

Keep Users Happy

Research shows that nearly half of users want their mobile and web-based applications to load in less than 2 seconds. By testing your applications and addressing its performance issues, you can increase customer satisfaction and keep them happy.

Identify Discrepancies and Resolve Issues before Release

The cost of handling performance issues is the highest after an application is released. Performance testing allows your developers to have a buffer before releasing the final version of the application. As a result, you will be able to root out all performance issues before release and significantly reduce the costs of resolving those issues. 

Improve Optimization and Load Capability 

With the help of performance testing, you can improve the optimization and load capacity of your system. The ability to scale an application is one of the greatest concerns during software development.

It allows you to evaluate your application’s behavior under increasing user loads. As a result, you can change the load capability according to your needs and optimize the performance of the application.

When You Need to Use Performance Testing? 

Performance testing is critical for the testing process of any given system or application. It helps companies give crucial insight to stakeholders about the performance, speed, stability, scalability, and reliability of an application. 

It helps them identify what they need to improve for a given software before it is released into the market. Without performance testing, it is almost impossible to pinpoint issues related to speed, load capacity, reliability of the software. 

Furthermore, the application is likely to run into issues such as slow response times, inconsistent performance on changing platforms, poor usability, and failure to work under increasing user loads. 

According to Dunn & Bradstreet, 59% of Fortune 500 companies lose roughly $46 million per year just because of 96 minutes of downtime each week! Foregoing performance testing can lead to various other performance issues, including enduring downtimes.

Performance testing is vital to the testing process and you cannot hope to make a successful application without performing efficient performance testing.  

Load Testing Definition and Goals 

Load testing is a subpart of performance testing and specializes in simulating real-world workload for any software or site. This particular testing method checks whether or not a site or software is functioning as it should during normal and high usage loads. Testing professionals  typically utilize load testing methods when a project is near its completion. 

However, load testing is not just limited to software systems or apps. IT professionals around the world use the method as a performance metric and apply it to computers, servers, networks, and other devices. Regardless of the use-case, it tests how a specific system performs under the circumstances it is meant to perform in. 

The main objective of load testing is to identify the effects of user load on the performance of a system. Therefore, we’ll test different features of an application while changing the amount of user load exerted on the system.

For instance
Let’s say we have developed an e-commerce web service that 10000 people can use simultaneously. The service allows users to log in and out, browse products, add or remove products from cart, issue orders and purchase items online.

To perform a load test, we will run the web service under specific testing scenarios, based on the number of people using a certain feature. The testing scenarios can be anything like the following:

  • 2500 people browsing products and then logging off from their accounts.
  • 5000 users logging in, issuing orders, purchasing items and logging out in the middle of a sale.
  • 3000 people logged in but are not showing any activity.

In this example, we are using load testing to replicate user load under specific scenarios and testing if the system can be used in the real-world environment. In the midst of this testing, the testers will note down the performance indicators and analyze either the effects on the system as a whole or evaluate the functionality of particular features.

The main objective of load testing is to expose the vulnerabilities of a system with respect to the load exerted from the overall users of the system. With that said, load is slightly different from stress testing. 

Although stress testing is meant to test an application’s performance under user load, it does that in conditions that go beyond the system’s capacity. This is why in stress testing, testers force the application to work under compromised situation or extreme workloads. 

On the other hand, load testing evaluates the maximum amount of work a system can handle in perfect working conditions. With that said, the testing must expose vulnerabilities, such as buffer overflow, memory leaks and inefficient usage of memory. Similarly, load testing has to identify load balancing problems and bandwidth issues in a network while also showing the maximum capacity of the system. 

As a result
It is easier for testers to figure out the upper limit of all major components of applications, such as database, network applications, hardware, etc. At the same time, since testers are able to understand the capacity of the system through load testing, the process helps testers to design the service level agreements for the product.

Types of Load Testing

Usually, software testers measure the performance of a system under user load in two ways. 

The first method is longevity testing, which is also known as endurance testing. As the name suggests, this method evaluates a system’s endurance by running moderate workloads for an extended time. 

On the flipside, the software system is subjected to a large volume of data for a limited time in volume testing. The method is frequently used to evaluate how a database handles a flurry of exceptionally high requests in a short period of time. 

Regardless of which approach you choose to test your system, these methodologies can help you identify critical bottlenecks, component limitations, and bugs. 

For instance, it’s possible for computers to have high RAM but slow processor to support it. With load testing, testers can understand how many processes the machine can run while maintaining optimal performance.

Advantages of Load Testing in Software Development

The advantages of load testing in software development are numerous. Let us take a closer look at the advantages of load testing: 

Reduces the Risk for System Downtime 

Since load testing also evaluates the system’s performance under high loads, it can minimize the likelihood of system downtime when used in the real world. 

Reduces Failure Cost 

Identifying elements that affect software performance at an early stage can decrease the cost of failure. The cost of resolving faults in a system is exponentially greater if they are detected after launch. 

According to Gartner, network downtime can cost around $5,600 per minute, on average. This means that, on average, it can cost companies $300,000/hour. With the help of load testing, we can avoid these costs and ensure that an application is only deployed when it’s ready. 

Enhances Scalability 

If the software isn’t able to handle the desired number of concurrent users, it can cause memory leaks and result in poor utilization of resources. 

Load testing can help software testers identify the limits of the system’s operational capacity. Therefore, it is easier to identify the infrastructure required to scale the system upwards. 

Improves Customer Satisfaction 

By identifying the elements affecting a system’s response time, load testing helps to optimize response times for a system. As a result, customers use optimized software, which translates into greater user satisfaction. 

Identify Poorly Written Code and Queries 

Complexly written codes and un-optimized queries may not utilize system resources efficiently and can directly affect how your system performs. These issues are not detected in normal scenarios, but they start to show when the system is subjected to high user loads. 

With the help of load testing, you might be able to identify poorly written code structures and queries. By simplifying these code structures, you can achieve 2x greater productivity in most cases and up to 10x times more, in extreme ones. 

Discovers Bottlenecks before System Deployment 

A bottleneck is a component of the system, which limits the capacity and performance at a single point, just like the neck of a bottle slows down its general flow. By load testing a system using real-world scenarios, you can identify the bottlenecks in the system. Therefore, a company can address these problems before they affect user experience. 

When You Need to Use Load Testing? 

Load testing is ideal whenever testers want to figure out how much users a system can handle while maintaining its expected performance. Testers can use various scenarios to focus on different features of an application. 

For instance, load testing can be applied to check how a website’s shopping cart works the same after 5000 users are using it simultaneously. Similarly, testers can utilize load testing to gauge how the search bar reacts when thousands of users search for items at the same time. 

In short
You can apply load testing in every scenario where user load can affect the performance of your system.
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Difference Between Performance and Load Testing 

To summarize, load testing is a subset of performance testing and covers performance issues related to varying user loads. On the other hand, performance has a much larger scope, and it helps testers to highlight the overall performance issues of the system by setting benchmarks for each scenario. 

Performance testing allows you to pinpoint fundamental issues within your system and is vital for the success of your product. To make sure your product remains well-protected against downtimes and crashes induced by varying user load, request a team of QA professionals to root out all the underlying vulnerabilities of your product. 

PFLB specializes in providing quality assurance services for software applications across all major industries. They have years of testing experience, backed by expertise in working with dozens of products. For comprehensive performance testing of your product, contact PFLB now. 

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