Testing Glossary - Load Testing

The creation of a simulated "load" on a real computer system by using virtual users who submit work as real users would do at real client workstations and thus "testing" the system's ability to support such a workload. The virtual users are in software running on a "driver machine" or "injector". Testing of critical software during its development and before its deployment has three components:

• Functional testing: Does it conform to the design specifications?
• Performance testing: Does each unit offer acceptable response time?
• Load testing: What hardware and software system configuration will be required to provide acceptable response times and handle the "load" that will be created by the entire community of users when deployed?

Load testing cannot be accomplished before the application software is available. Unlike other modeling methods for estimating future performance, load testing uses real hardware and software. Load testing was historically done with real people at real terminals following a script and recording response times with stop watches.

For systems with hundreds of users, today one can use a load testing tool rather than real people; can capture the activities of real users and then create scripts that "virtual" users submit to the SUT (system under test) and measure the resulting response times.