In generic terms, load testing can be defined as applying pressure/stress on a system and then evaluating its response and speed. It is done under controlled conditions. For instance, a desktop computer can be load tested by opening multiple programs simultaneously. The performance of the CPU can then be determined in terms of speed and an estimate can be found on how many applications a CPU can withstand at a time.

There are two ways in which a system can be tested. In the first method, a constant work load is applied to a system and its performance is measured over a long period of time. In the second one, heavy work load is applied for a short limited period. Load testing allows detecting bugs and bottlenecks in a system. For example, a high-end mobile phone contains a number of applications besides the regular call and message features. The mobile phone can be tested using the load testing tools to gauge its usability and feasibility. Since it’s a small portable user device, it has to be thoroughly tested for its continuance in the real world. Broadly speaking, a load testing tool creates a virtual environment in which the real case scenarios are tested.

Load testing tools are also used to test a website under load. It creates virtual users and gives the response time and errors encountered by them. It also records the behavior of the website under different load conditions. Here, applying load refers to testing the site with different speeds, different browsers and large no of virtual users. A no of load testing tools are available, of which few are mentioned here.

1) Load Runner: This tool was developed by HP. This tool supports many environments, databases and platforms. It is used to test web applications and provides information on the bugs and bottlenecks present in a system.

2) Load Storm: This tool is managed by Amazon Web services. Load tests can be done on web servers by creating thousands of virtual users, each performing different tasks. This tool processes all the information which is generated during load testing.

3) Curl-Loader: This tool has its stack written entirely in ‘C’ language. It is used for simulation of the application load by creating virtual clients. It provides information and statistics about the activities taking place on the TCP/IP stack.

Overall the aim of using these tools is to develop a fast and responsive system.