A diagnostic test is a form of pre-assessment that allows a teacher to learn about a student’s strengths, weaknesses, knowledge, and skills before they start studying. It is mostly used to determine what is wrong with children and to create lessons and curricula. Diagnostic test benefit both the instructor and the students. The diagnostic test allows teachers to build meaningful and efficient lesson plans, for starters. When a teacher knows exactly what students know and don’t know about a subject, she may customize lessons to the areas where students need to learn more, rather than what they already know. This decreases unhappiness and boredom among students. Second, it provides information that can be utilized to personalize training. It could signal to a teacher that a small group of students needs further instruction on a certain area of a unit or course. Similarly, if a teacher detects that a group of students has mastered a major portion of a unit of study, he can design activities that allow that group to move beyond the usual curriculum for that topic by engaging in solo or small-group study. Finally, it creates a standard by which future learning can be judged. It shows the teacher and the pupils what they already know before they start learning. As a result, a baseline on a subject is established. As the class progresses, students will be able to see what they are learning and not learning, and the teacher will be able to provide remediation or enrichment as needed.