Questions about Oral Exams :)

Hello everyone, I'm teaching EFL and would like to ask the experienced English Teachers at the English Forums about the best way to make an oral exam. I would be so grateful if you would kindly answer the following inquiries: how long the test should last(how much time spent with each candidate)? what are the assessment categories of the oral exam? Should the instructor's main focus be directed at fluency alone?



Thanks in advance