Test validation is the process of making sure that a test that we give our students really measures what it is supposed to measure.
In making educational assessments, we are typically supposed to be testing whether a student has mastered the content that we have taught over a given unit or course. The student’s grade often depends largely on tests. Therefore, we must make sure the test really covers the things we have taught. If the test does this, we say that it is valid. If it does not, it is invalid.
Test validation, then, is the process of ensuring that the test is valid; that it actually measures the degree to which the student has learned the material from the unit or course the test covers.