What’s the Difference Between Verification and Validation?

If you’re tasked with preparing a project management plan, one of the elements of that plan is a test plan. Your test plan should include three distinct tests that you’ll need to perform: verification, validation, and acceptance.

Verification testing ensures that the expressed user requirements, gathered in the Project Initiation phase, have been met in the Project Execution phase. One way to do this is to produce a user requirements matrix or checklist and indicate how you would test for each requirement.  For example, if the product is required to weigh no more than 15 kg. (about 33 lbs.), the test could be, ”Weigh the object – does it weigh 15 kg. or less?”, and note “yes” or “no” on the matrix or checklist.

Validation testing ensures that any implied requirement has been met.  It usually occurs in the Project Monitoring and Control phase of project management. Using the above product as an example, you ask the customer, “Why must it be ‘no more than 15 kg.’?” One answer is, “It must be easy to lift by hand.”  You could validate that requirement by having twenty different people lift the object and asking each one, “Was the object easily to lift?” If 90% of them said it was easy, you could conclude that the object meets the requirement.

We call this an implied requirement because the answer to “Why?” was not stated: the ”easy to lift” requirement was not clearly specified or defined. Another way to validate an implied requirement is to produce some test objects, or prototypes, and have the customer evaluate them in the field.

Next comes Acceptance Testing, the official approval of your deliverables by the customer. Your customer may accept your verification and validation test results and accept the object. The customer may also have their own “easy lifting expert” on hand and use them for the acceptance test. Acceptance testing often occurs at the end of the Project Monitoring and Control phase, but it can also take place at the beginning of the Project Review and Close phase.

So what is the difference?  Verification is a test performed to ensure stated requirements have been met, Validation is a test performed to ensure implied requirements have been met, and Acceptance Testing ensures the customer has received what they asked for.