I see the meaning of these terms changing over time, just look at these responses. Clearly they are in Techlish. Definition migration is a natural phenomenon in any living language, but its only a good thing if the definitions become more precise, not more subjective. I prefer the more classic meanings based on the English dictionary.
Verification is “checking” that something is what it should be. Since in the simplest form “test” means to compare an actual result to a standard (expected result) Verify is basically “test” with a positive expectation. If you don’t have a STANDARD to compare to, you can’t actually test or verify.
Validation means “to prove to be wholesome and correctly executed.” – Validation does not automatically provide the “expected result.” Validation requires proof. The proof is accomplished by providing a convincing argument. Hopefully this is an argument, like a lawyer presents in a court of law. Building a convincing case based on facts that support their assertions of proof and validity. – Unfortunately arguments can also be supported by a show of brute force and intimidation.
Verification only requires a script with expected results. An automation tool can do verification. Validation requires depth of knowledge, and a compelling argument to support the testers opinion of validity. A good tester does both verification and validation.–Compare the outcome to the expected result, AND, judge the validity of thing they are examining. V & V is not limited to requirements, or applications, or systems. It’s how we judge everything.
Is something doing what it is supposed to do? (verification) Is what it is doing wholesome and correctly executed? (validation)
Remember, you can’t Verify if there is no expected result.
You can Validate, but you must create a convincing argument to support your opinion. The most convincing arguments are based on facts and measurements; two skills every tester needs to develop. So, for our picture,
Verify: Ok, she is there on a pony in the parade. Pass!
Validate: Is this a real pony? Doesn’t a pony have 4 legs? Is she the real queen? Is she a ‘she’? etc…
Validity is a funny thing, you may know it when you see it, but how will you convince everyone else.