What is load testing?

Load testing is a method for checking the stability of an application by using simulated loads to test its limits. There are numerous free and paid load testing tools available on the market.

What is a load test?

A load test is used to test the load capacity of a system. These tests can be performed on software during the pre-release phase as well as after a system has already been released for commercial use.

The aim of load testing is to find out how much a system can achieve before performance drops significantly enough to affect the functionality of the service. To do this, high-demand loads are simulated, eventually pushing the system to its limits. This can be done by simulating numerous simultaneous access attempts, or through the repetition of certain actions in rapid succession. The system then responds to these challenges in the best possible way. During load tests, if an overload occurs, the system is not damaged.

What is the goal of load testing?

Load tests can be used in various ways. In agile software development, for example, load tests are used as a quality assurance measure. Before a new software is launched, checks are carried out to better understand what requirements the program can handle and determine when it no longer is able to function efficiently. Errors that were previously overlooked can also be pinpointed Checks are also carried out to see how a system handles unexpected additional loads, at what point limitations occur, and how fast the reaction time to errors is.

Existing systems can also be checked using load tests. These tests are commonly used to check the performance of websites. If operators are expecting a large and unscheduled rush, they can simulate the upcoming overload to ensure that their own system can handle the extra load. A larger rush can occur when a new product is launched, a special event is coming up, or advertising campaigns are carried out to generate more website traffic. The goal of load testing is to check the resilience of a system and its response, so that you can improve performance in advance if necessary.

Which load tests are there?

Not all load tests are the same. There are different approaches designed for different purposes. The distinctions are not entirely clear-cut, and the products of some vendors enable different types of load tests. Roughly, however, there are four different groups: performance, capacity, stress and endurance.

The performance test

The performance test is considered the classic load test and is the simplest form of these test options. The demands placed on a system are comparatively low. The results show whether a new or existing system can withstand expected loads, and whether the quality of the performance remains consistent during this time. This type of load test is suitable, for example, for web apps, which must be able to handle a specific volume of simultaneous access requests. The load test simulates these access requests and checks whether the response times meet expectations.

The capacity test

This type of load test goes a step further. Instead of asking “Can my system do what it is supposed to?” the question here is, “What can my system actually do?” Instead of simulating a rush, the load is increased incrementally. To do this, the exact requirements that the system should fulfill must be determined in advance. For example, the expected system response time should be determined before tests are carried out. Once this is established, the load test begins, gradually setting higher requirements. This continues until the system reaches its limits.

The stress test

The next step up is the stress test. This approach picks up where the capacity test left off. While capacity tests assess how far you can scale a system and then stop at the maximum value, stress tests are designed to intentionally exceed the maximum value. It is not about how much the system can do, but rather how it reacts when it is overloaded. In this load test, you present the system with an unsolvable task and then measure response times. You can also see when the system crashes and how it crashes. Running stress tests helps you prepare for such situations should they occur.

The endurance load test

The load tests presented so far are each designed for short periods of time. These procedures do not provide any information on whether the system can withstand high loads over a longer period of time. This is where endurance load tests can be of help. The test is carried out for several hours, or even days, and determines whether the system remains stable when in continuous operation. It also shines a light on which resources are being consumed and whether unexpected errors occur. As most systems are designed to always be available, endurance tests are important for determining the general reliability and response time of a system.

What should be done before a load test?

Load tests are a good way to test a system, assess potential risks in advance, and possibly improve it. However, it’s important to consider a few things before conducting a load test.

Define expectations

The first question you should ask yourself is what you want to achieve with the load test. Consider your goals and the questions that the test should answer. Is it a final test before launching? Do you want to check what your system can actually do? Do you want to overload the program to prepare for the worst-case scenario? Or are you primarily concerned with the system’s performance over a longer period? Depending on your requirements, you will need a different load test.

Once you are clear about your basic goals, you should define them. What response time do you want to achieve? What should your system be able to do? What values are acceptable and at what point do you need to improve performance? What maximum loads can you expect? If you answer these questions before performing the load test, you will be able to generate much more insightful results.

Determine the schedule

Before conducting a load test, you should consider at what point in the development this test makes sense. If you do it too early, the load test may not produce meaningful results. However, if you perform it too late, changes based upon the results may not be able to be incorporated into the system. If you are working with an existing system, you should consider when the load test will have the least negative impact on your business operations. Choosing the right time is important, especially if you are conducting a continuous load test.

Determine effort

Costs differ significantly between different load testing tools. There are open-source solutions, but a load testing software with a pricing plan is a good option if you intend to run load tests on a recurring basis. You should determine how much you want to invest in a load test. When determining effort, it’s also important to know how close the test environment is to the production environment. If you want to use multiple load tests, you need to coordinate them and develop a plan for evaluating the test data in advance.

How is a load test performed?

When carrying out a load test, safety should be a top priority. The system should be protected and supported in the best way possible. The following approaches are recommended for this purpose:

• Safety precautions: Before starting the load test, create a backup of all the system’s data. If problems occur, you can then quickly switch back to the previous state. Also, check which external systems are connected and make sure that they cannot be affected by the load test.
• Proceed step by step: Even if you want to test your system on a large scale, it is better to start small. It is worth determining what your system can do in theory before you start.
• The right software solution: The choice of a suitable software solution also plays a major role. A load test that is tailored to your requirements will provide you with meaningful results, allowing you to gain valuable insights.

What tools are available for load testing?

There are numerous tools that specialize in load testing that can provide you with valuable services when checking your system. The following programs are great options for conducting load tests:

JMeter

JMeter is an open-source solution and scores points with its large and helpful community. With JMeter, you can perform load tests for numerous applications and servers as well as create simple reports. One disadvantage of this solution is its learning curve. However, if you are willing to take the time to learn the program, it is an excellent alternative to costly load testing.

IBM Rational Performance Tester

The IBM Rational Performance Tester is a strong contender for performance and capacity testing. It also lets you write test scripts in Java, generate statistics, and check your cloud. The load test is comparatively easy to perform and does not require extensive training. In addition to the free trial version, there are several pricing plans.

LoadRunner

LoadRunner is a classic in the field of load testing. The program supports numerous technologies and is available as a free community version and a paid version. LoadRunner is easy to use and offers a host of possibilities for performing load tests that can be adapted to your needs.