There are various ways for language teachers to do speaking tests, all of which have their positives and negatives. Here's my brief summary:
1-1 interviews with the teacher. This method is generally thought to have the highest validity, since no weaker student affect the stronger student in a negative way. However, I think there are more negatives than positives:
1. The power dynamic which can come into play
2. The necessity to have students, alone in an office or classroom. This is something that I'll always try to avoid if possible.
3. Exhaustion on the part of a teacher. It just simply takes a lot of time and mental energy.
4. The teacher needs to serve as examiner and conversation partner, which can get tricky at times, especially at the end of a long day of tests.
Conversations/role-plays among students, usually 1-1 while the teacher just listens/observes. The big negative of this one is that a weaker student can affect a stronger student, and although the teacher accounts for this in grading, it can often be seen as "not fair" in the student's eyes. However, there are lost of positives:
1. No power dynamics
2. It can at least partly replicate "real" conversation, where the people are at a similar level of English ability.
3. The teacher can just focus on listening and not have to act as a conversation partner.
4. Students often feel less nervous with at least one other person in the room besides the teacher.
Presentations, alone or in a group. These are perhaps the easiest on the part of the teacher to administer, especially in groups. You can "test" a group of 30 students in as little as a single 1.5 hour class. The negatives are that it doesn't replicate "conversation" at all and this is most often what courses consist of at Korean universities. But, if the teacher actually spends time teaching students how to do presentations, it can be a valuable life-skill that students can take with them throughout their lives.
So what am I doing? 3 of my classes with have presentations and the other one will have a conversation with another student, who will be selected randomly. It's my first time in a long time teaching "conversation" to really high-level students, so it's an experiment of sorts. I'll let you know how it goes. Here's the book I used to help prepare my students for the presentation exam: