Verification and Validation: Definition, Differences, Details:

The terms ‘Verification‘ and ‘Validation‘ are frequently used in the software testing world but the meaning of those terms are mostly vague and debatable. You will encounter (or have encountered) all kinds of usage and interpretations of those terms, and it is my humble attempt here to distinguish between them as clearly as possible.

Criteria	Verification	Validation
Definition	The process of evaluating work-products (not the actual final product) of a development phase to determine whether they meet the specified requirements for that phase.	The process of evaluating software during or at the end of the development process to determine whether it satisfies specified business requirements.
Objective	To ensure that the product is being built according to the requirements and design specifications. In other words, to ensure that work products meet their specified requirements.	To ensure that the product actually meets the user’s needs, and that the specifications were correct in the first place. In other words, to demonstrate that the product fulfills its intended use when placed in its intended environment.
Question	Are we building the product right?	Are we building the right product?
Evaluation Items	Plans, Requirement Specs, Design Specs, Code, Test Cases	The actual product/software.
Activities	Reviews Walkthroughs Inspections	Testing

It is entirely possible that a product passes when verified but fails when validated. This can happen when, say, a product is built as per the specifications but the specifications themselves fail to address the user’s needs.

• Trust but Verify.
• Verify but also Validate.