Testing contributes to the process of education when the tests are created by a teacher and are relevant to what has been studied. It needs to enhance and reinforce rather than to trick. And standardized testing ought to be done on a limited basis and its results taken with a grain of salt.
I believe that continuous testing is necessary for education to succeed. Most studies are built upon previous learning and unless those previous lessons are properly understood then additional ones will seem incomprehensible. Continuous testing allows both the teacher and the student to recognize areas of weakness and correct them while they do not yet represent insurmountable hurdles.