Understanding performance, load and stress testing

What are performance, load and stress testing?

Performance testing, load testing and stress testing are three different things done for different purposes. Certainly, in many cases they can be done by the same people with the same tools at virtually the same time as one another, but that does not make them synonymous.

Performance testing is an empirical technical investigation conducted to provide stakeholders with information about the quality of the product or service under test with regard to speed, scalability and/or stability characteristics. It is also the superset of other classes of performance-related testing such as load and stress testing.

A load test is a performance test focused on determining or validating performance characteristics of the product under test when subjected to workload models and load volumes anticipated during production operations.

A stress test is a performance test focused on determining or validating performance characteristics of the product under test when subjected to workload models and load volumes beyond those anticipated during production operations. Stress tests may also include tests focused on determining or validating performance characteristics of the product under test when subjected to workload models and load volumes while the product is subjected to other stressful conditions, such as limited memory, insufficient disk space or server failure.

let's take one example. Imagine your favorite Web site that sells things. Anyone that accepts credit cards and has a shopping cart paradigm will do.

Performance testing would involve things like determining the end user response time under various amounts of traffic and scenarios. For example, you may be interested in finding out what response times a user would encounter during an hour where there were 2000 searches for items, 500 items added to carts and 50 purchases were made. Or you may be interested in finding out what response times a user would encounter during a different hour where there were only 500 searches for items, 400 items were added to carts and 250 purchases were made.

Load testing the same site might involve determining how many searches can be conducted in a given hour before the response time slows to 5 seconds. Stress testing could involve determining how many searches can be conducted in a given hour before the users stop receiving results.