How can you perform Validation testing?

For a little clarification --> when you are looking at a form and you click on the close button, the form should close.  If another form opens you failed validation testing.  If you enter data into a field that should only accept numbers, allowing any other character would fail the validation testing.  Also, as mentioned previously here, the accuracy of your data.  Are you getting the exected data results.

Validation ensures that functionality , as defined in requirements, is the intended behaviour of the product; Validation typically involves actual testing and takes place after verification is completed.

QC is called Validation testing. Ex. Validating data before & after deployment.