Load testing tools

Load testing is one of the elements of complex performance testing aimed at analyzing the speed of the system's response to an external request. The main purpose of this check is to find out whether the application (device) being tested meets the stated requirements. This method is widely used in professional circles during product testing when it is necessary to understand how the program will react to simultaneous operation by a certain number of users.

Load testing is most often used to investigate multi-user resources and various general systems, but other types of software products can also be tested using this method. For example, you can check whether the graphics editor can handle opening a large image. It is also possible to find out the system’s ability to generate a financial report by analyzing the data for several months or even years. A qualitatively created loading test will provide the most reliable results.

The basic idea of load testing is to create a specific load using the same hardware and software to track the product's performance index. This method will be most effective in the early stages of development, because this approach will allow you to obtain optimal results in measuring system performance indicators.

Main principles of the load testing :

1. Uniqueness of the requests. Real statistics, requirements, and expected behavior of the system should be taken into account when creating the scenario.
2. System response time. By managing a certain number of measurements, it is possible to determine to which time interval a particular request will fall.
3. The distribution of the system depends on the response time. The number of nodes affects the spread of the system's response time, each of which increases the amount of delay when scanning requests. This fact should be taken into consideration when drawing up product performance requirements.
4. Correctness of reproduction of loading profiles. The complexity of the software requires a significant investment of time and resources for design, programming and further support. Test development and system functionality coverage should be balanced to obtain the most effective test results in the shortest possible time.

Means of load testing

There is an opinion that the same tools are used for load testing as for automated testing. What is the main difference? This method is performed using tools that work exclusively with system protocols, while automated testing is used at the user interface level.

Let's look through the difference between these techniques in a specific example. There is a browser that does a link jump when a button is clicked. In order to apply automated testing, you need to write a script that sends mouse clicks to the browser. In order to run a load test, it is necessary to transfer a hyperlink from the browser to a certain number of users with a unique name or password.

There are a number of free and paid commercial tools for load testing. Let's have a look in detail at the most used among them.

Apache JMeter. One of the most popular free products in load testing, functionality and even in software development. Support for add-ons from other developers helps to include new features.

Advantages of JMeter:

• the program is absolutely free for all users;
• it runs on different platforms, as it is a Java product;
• installation and start are easy;
• intuitive interface;
• visual display of work results;
• possibility to write own cases;
• supports protocols: HTTP, SOAP, LDAP, JDBC, JMS, and FTP;
• integration with Selenium and Bean Shell for automated testing;
• possibility to record all activities in the browser.

Disadvantages of JMeter:

• absence of the function to record HTTPS communication;
• AJAX traffic is not intercepted;
• no advanced options are provided when generating reports.

An example of using Jmeter. Get request generated on the Google site.

Before starting the program (click on Run =>Start), you need to save the jmx file.

In order to analyze the effectiveness of the test, you need to focus on two parameters: Throughput and Deviation. Bandwidth is the most important parameter. It represents the server's ability to handle a heavy load. The higher the bandwidth, the better the performance of the web server.

The Grinder is another well-known load testing program based on Java. The Jython language (a special implementation of Java in Python) is used for writing scripts. This tool provides a more powerful script engine with script writing functionality.

Advantages of The Grinder:

• the use of platforms is not limited, all are suitable where the Java virtual machine is launched;
• support for most protocols;
• easy and quick development of test scenarios;
• the ability to create your own plugins for the interface;
• simplified setting of parameters;
• flexibility in the implementation of third-party libraries;
• integration with Jira.

Disadvantages:

• periodic malfunctions when downloading large files;
• the console is not able to adjust the load levels;
• there is no possibility of extended analysis;
• The tool requires knowledge of Jython or Clojure.

An example of writing a script in the Grinder program

The Grinder log file

Report in the Grinder

Galting. A powerful tool for performing load tests, using the Scala programming language. There are two files in this program: one is responsible for writing the test scripts, and the second is for their execution.

Advantages of Galting:

• flexibility in interaction with different operating systems and browsers;
• visualization of reports in the form of graphic tables;
• simple interaction with Jenkins and testing through Gradle and Maven (using appropriate plugins);
• simplified debugging of test cases;
• ease of finding flaws at the first stages of development.

Disadvantages:

• a change to the API may lead to problems running test scripts of previous versions;
• no opportunity to distribute the load between devices;
• no horizontal scaling.

Example of use. The easiest way to run a check is to use bundle. It is necessary to place the file in gatling-charts-highcharts-bundle-2.3.0\user-files\simulations\ and start gatling-charts-highcharts-bundle-2.3.0\bin\gatling.bat.

Then an ability to choose a script will appear in the console.

All the brief descriptions described above are of the most popular free load testing tools. The list does not end there. There is a large number of reliable assistants for testing and development specialists. It includes: Locust, Apache Bench, Taurus and many others. Among the commercial variants, one must pay attention to Webload, Loadrunner and Blazemeter. The tool must be chosen taking into consideration all the advantages and disadvantages. However, it depends also on the personal qualities and knowledge of the specialist, as well as the complexity and specificity of the performed inspections or the development process.