Verification vs Validation

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What is Verification?

Verification is testing that your product meets the specifications / requirements you have written. “Did I build what I said I would?”.

What is Validation?

Validation tests how well you addressed the business needs that caused you to write those requirements. It is also sometimes called acceptance or business testing. “Did I build what I need?”

V&V together make sure that your software has delivered on its purpose in an error-free (ideally) way.

Verification vs Validation: Key Difference

Verification	Validation
The verifying process includes checking documents, design, code, and program	It is a dynamic mechanism of testing and validating the actual product
It does not involve executing the code	It always involves executing the code
Verification uses methods like reviews, walkthroughs, inspections, and desk- checking etc.	It uses methods like Black Box Testing, White Box Testing, and non-functional testing
Whether the software conforms to specification is checked	It checks whether the software meets the requirements and expectations of a customer
It finds bugs early in the development cycle	It can find bugs that the verification process can not catch
Target is application and software architecture, specification, complete design, high level, and database design etc.	Target is an actual product
QA team does verification and make sure that the software is as per the requirement in the SRS document.	With the involvement of testing team validation is executed on software code.
It comes before validation	It comes after verification

Verification and validation in waterfall vs agile

In a more traditional Waterfall process, with Specifications and Requirements defined at the start, Validation is often performed at the end of the testing cycle. You spend tons of time defining a product, build it, make sure your software was bug-free, and then do user acceptance testing, or submit it to a client / users, perhaps even a Beta release.

In an Agile development process, ideally both verification and validation activities occur as close to simultaneously as possible. This is because you are always updating and refining your User Stories, necessitating constant small V&V loops to enable this continual feedback.