The concept of pedagogical diagnostics is broader than a test of knowledge, skills and abilities of students. The process of such testing only determines the results, while not explaining them. Diagnosis consists of monitoring, assessment, data collection, analysis and, as a consequence, determines the ways of achieving the best results, identifies patterns and trends of educational process.

By analogy with the three functions of the educational process are the main areas of diagnosis: education, training, and education.
• In the field of education with the diagnosis determined by the level of personal development, mastering it as a stable system of generalized knowledge about the world, about their place in it, i.e. knowledge in the broadest sense of the word.
• In the field of education diagnose the level of mastery of specific knowledge, skills and abilities acquired in an educational institution.
• In the field of education diagnosis reveals the level of formation of emotional, moral qualities of a person or group of students.

The object of pedagogical diagnostics is a pupil or student of educational institutions and their staff. For diagnosis are responsible for the collection of demographic data on the study of the individual and his / her family, physical and mental health of the student, his cognitive abilities, behavior, motivational sphere, etc. educational science offers a large selection of methods of diagnosis: observation, questioning, testing, conversation, analysis of creative works, etc.

The subjects of diagnosis traditionally, educators and teachers-testology who have received additional education in a specialized educational institution.

The most important stage of diagnosis is the control, i.e. monitoring of the process of assimilation of knowledge, formation of abilities and skills. Control allows you to obtain information about the nature of student's activities, the effectiveness of the use possibilities of the pedagogical process for training purposes. Control is of several types: preliminary, current, topical, periodic, and final. It takes a variety of forms: individual, group, front.

Using different control methods (oral, written, machine, test), pedagogical diagnostics contributes to the successful study of the structure of personality and its functions: intellectual and creative abilities, memory capacity, level of development care.