Stress testing is testing the software under less than ideal conditions. So subject your software to low memory, low disk space, slow cpus, and slow modems and so on. Look at your software and determine what external resources and dependencies it has. Stress testing is simply limiting them to bare minimum. With stress testing you starve the software.

For e.g. Word processor software running on your computer with all available memory and disk space, it works fine. But if the system runs low on resources you had a greater potential to expect a bug. Setting the values to zero or near zero will make the software execute different path as it attempt to handle the tight constraint. Ideally the software would run without crashing or losing data.

Load testing is testing the software under customer expected load. In order to perform load testing on the software you feed it all that it can handle. Operate the software with largest possible data files. If the software operates on peripherals such as printer, or communication ports, connect as many as you can. If you are testing an internet server that can handle thousands of simultaneous connections, do it. With most software it is important for it to run over long periods. Some software‘s should be able to run forever without being restarted. So Time acts as a important variable.

Stress testing and load testing can be best applied with the help of automation tools.

Stress testing and load testing are the types of performance testing.

The Microsoft stress utility program allows you to individually set the amounts of memory, disk space, files and other resources available to the software running on the machine.

Example: Open many number of browsers in the windows simultaneously. Connect more than the specifies clients to the server. Connect more than one printer to the system.