System Test - Capacity Testing

Scheduling Capacity Testing
Performance Test and Stress/Load Test occur during System Test or when enough of the application has been delivered. The earlier capacity testing can be applied, the earlier defects can be detected and mediated. It is critical to detect capacity related defects early because these types of defects often require architectural changes to the system. Because these tests usually depend on functional interfaces, it may be wise to delay until function testing has demonstrated some predefined level of reliability. A balance must be struck between testing early and testing when appropriate.

Designing Capacity Tests
Lack of capacity testing requirements and goals is one of the most common errors made during any capacity testing exercise. Test organizations will often go through the process of capacity testing only to discover the testing results do not present the project with any useful information. The solution is to treat Performance and Stress/Load testing the same as any other testing effort. The test organization needs to perform: Test Planning, Partitioning / Functional Decomposition, Requirements Definition / Verification, Test Case Design, Traceability (Traceability Matrix), Test Case Execution, Defect Management, and Coverage Analysis (for more on this see "Requirements based Function Test").

Implementing Capacity Tests
Both Performance and Stress/Load testing require a toolset that can put the system under a known load and measure the performance of the application while under load. Several shops have developed their own in-shop solutions for capacity testing and there are several capacity testing freeware, shareware, and commercial products available to meet this need. It is easy to fall into the .over-engineering. trap when implementing a capacity testing toolset - to avoid this trap ensure the solution meets the test organizations goals and that the toolset does not become a "goal" in itself.