Verification and Validation (V&V)

There are two basic functions of software testing: one is verification and the other is validation. Schulmeyer and Mackenzie (2000) define verification and validation (V&V) as follows:

Verification is the assurance that the products of a particular phase in the development process are consistent with the requirements of that phase and the preceding phase.

Validation is the assurance that the final product satisfies the system requirements.

The purpose of validation is to ensure that the system has implemented all requirements, so that each function can be traced back to a particular customer requirement. In other words, validation makes sure that the right product is being built.

Verification is focused more on the activities of a particular phase of the development process. For example, one of the purposes of system testing is to give assurance that the system design is consistent with the requirements that were used as an input to the system design phase. Unit and integration testing can be used to verify that the program design is consistent with the system design. In simple terms, verification makes sure that the product is being built right. We'll see examples of both verification and validation activities as we examine each phase of the development process in later chapters.

I get the above information from Rapid Testing which is written by Chris Brown, Gary Cobb, Robert Culbertson.