16. Difference between Verification and Validation?

The terms ‘Verification‘ and ‘Validation‘ are frequently used in the software testing world but the meaning of those terms are mostly vague and debatable.

• Verification takes place before validation, and not vice versa. 
• Verification evaluates documents, plans, code, requirements, and specifications. Validation, on the other hand, evaluates the product itself. 
• The inputs of verification are checklists, issues lists, walkthroughs and inspection meetings, reviews and meetings. The input of validation, on the other hand, is the actual testing of an actual product. 
• The output of verification is a nearly perfect set of documents, plans, specifications, and requirements document. The output of validation, on the other hand, is a nearly perfect, actual product.

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