Overview
When testing an application's limits, a load test can help simulate end-user behavior. Apache JMeter is a tool that testers can use to simulate heavy loads on singular or multiple servers, networks, or objects to test a system's strength.
JMeter works by simulating groups of users that send requests to a server or network, then returning statistics back to a user through visual diagrams. Its GUI looks similar to a browser, but it can't render HTML pages or JavaScript as a browser would. Additionally, JMeter supports the use of plug-ins, which can be installed through the Plugin Manager and extend the functionality of JMeter.
Features
JMeter offers unlimited testing capabilities and can work on both local and server-based instances, making it a cross-platform tool. To get started, all you need is Java (JRE) installed on the host.
Being an open-source Java desktop application, JMeter allows you to modify existing plugins or create your own. It's easy to deploy and use - just download and unpack the archive from the official website, install Java (JRE), if you haven’t already, and run jmeter.jar. The interface is intuitive and straightforward, and if you need any help, there is plenty of documentation and use cases available on the official website.
JMeter allows for creating test cases both with manually written code (Java, BSF, JSR223, etc.) and without writing any code at all using a set of ready-made components. You can also execute test cases in the command line, enabling integration with CI tools.
With a wide range of ready components and the ability to create your own, JMeter has everything you need for any kind of testing. It supports regular expressions, clusterability, and allows you to record custom scripts and the sequence of visited pages. The tool supports JQuery selectors and XPath query language for great page structure management.
JMeter provides a convenient way of storing test scripts in repos, making it easy to keep track of and manage all changes. It also offers tools for collecting and displaying results, which can be saved in CSV, XML, HTML, and more.
Lastly, JMeter allows you to load test mail servers and databases, including NoSQL-type databases like MongoDB. It also supports basic Java sampler override (org.apache.jmeter.protocol.java.sampler.JavaSamplerClient) for adding or reducing the number of threads, changing input control, parameters, and data collection.