Ethics and its relation to testing are historically an important question and still are. In this article, we briefly report on how neuropsychology emerged as a specific field, how tests are developed and we particularly focus on the ethical conditions under which a test can be administered. The point of view of the neuropsychologist who develops a new test, of the neuropsychologist who uses this test, of the person requiring a neuropsychological assessment, and finally of the subject, are respectively taken. In each case, different ethical questions are raised. Illustrations and examples are provided. A misunderstanding of what a test really is (a given and precise experimental situation) leads to many difficulties. Furthermore, many fail to know that neuropsychological assessment requires specific skills and clinical practice. A test is not related to truth or to a verdict; it only allows classifying a performance with regard to a given norm.