Validation phase - System Testing - Performance Testing - Capacity Planning - Stress Testing

Stress testing is another term that is used for performance testing. Though, load and stress testing are used synonymously for performance related efforts, their goal is different.
Unlike load testing, where testing is conducted for specified number of users, stress testing is conducted for the number of concurrent users beyond the specified limit. The objective is to identify the maximum number of users the system can handle before breaking down or degrading drastically. Since the aim is to put more stress on system. Think time of the user is ignored and the system is exposed to excess load.
The goals of stress testing are:
- It is the testing beyond the anticipated user base.
- It identifies the maximum load a system can handle.
- It checks whether the system degrades gracefully or crashes at a shot.

Stress testing also determines the behavior of the system as user base increases. Let us take an example of online shopping application to illustrate the objective of stress testing. It determines the maximum number of concurrent users an online system can service which can be beyond 1000 users. However there is a possibility that the maximum load that can be handled by the system may found to be same as anticipated limit.

The inference drawn from stress testing are:
- Whether the system is available or not?
- If yes, is the available system stable?
- If yes, is it moving towards unstable state?
- When is the system going to break down or degrade drastically?