Central to its practice are psychological assessment and psychotherapy, although clinical psychologists also engage in research, teaching, consultation, forensic testimony, and program development and administration. In many countries, clinical psychology is regulated as a health care profession. Clinical Psychologists are required to study the full spectrum of psychological science, including both research and clinical practice, the primary objective of Clinical Psychology degree programs has historically been training students in conducting research as well as clinical practice; while the primary objective of Psy.D. programs has been preparing students to apply their knowledge in clinical practice. Clinical psychologists provide psychotherapy, psychological testing, and diagnosis of mental illness.