Comparison of Inspection and testing

Inspection and testing both aim at evaluating and improving the quality of the software engineering product before it reaches the customers. The purpose of both is to find and then fix errors, faults and other potential problems.

Inspection and testing can be applied early in software development, although Inspection can be applied earlier than test. Both Inspection and test, applied early, can identify faults, which can then be fixed when it is still much cheaper to do so.

Inspection and testing can be done well or badly. If they are done badly, they will not be effective at finding faults, and this causes problems at later stages, test execution, and operational use.

We need to learn from both Inspection and test experiences. Inspection and testing should both ideally (but all too rarely in practice) produce product-fault metrics and process¬ improvement metrics, which can be used to evaluate the software development process. Data should be kept on faults found in Inspection, faults found in testing, and faults that escaped both Inspection and test, and were only discovered in the field. This data would reflect frequency, document location, security, cost of finding, and cost of fixing.

There is a trade-off between fixing and preventing. The metrics should be used to fine-tune the balance between the investment in the fault detection and fault prevention techniques used. The cost of Inspection, test design, and test running should be compared with the cost of fixing. The faults at the time they were found, in order to arrive at the most cost-effective software development process