A student pursuing a doctoral degree must complete a comprehensive examination before being admitted to candidacy. Consult with your faculty advisory and supervisory committee as to the requirements for your comprehensive examination.
Graduate studies provides general direction regarding the comprehensive examination: https://catalog.unl.edu/graduate-professional/policies/academic-program-requirements/#candidacy.
When a student has substantially completed studies in the doctoral program, typically two years into the graduate program (e.g., start of the third year), the student must pass a written comprehensive examination in the major and minor fields of study. At the discretion of the supervisory committee, an oral comprehensive examination may also be required.