Hi,
@dcwong Welcome to the Cove!
To evaluate internal auditor competency, we are doing following things:
1. An Independent audit for particular department - This can be consider as one type of test also. This is pretty traditional and efficient way to assess technical and theoretical knowledge.
2. Self-assessment questionnaires - We have some per-defined questionnaires that auditor need to fill by himself after the completing the audit and submitting report to the Top Management. It shows their abilities and self-perception. This method should be used in combination with some other, more objective one as it can be too optimistic or too pessimistic.
3. Feedback from the Teammates - Ask teammates to share their feedback on each other's performance (P.S.: Take care sometimes it goes to personal) and see if each of them can do his/her job on a good level.
4. Practical knowledge - The most efficient way to train and assess skills - nothing can be better than practice. If you are sure in high qualification of an auditor, you can put them in real life conditions to challenge them and check their proficiency.
To sum up, It is up to you to choose the best method. Combination of a few of them would be great set. Also, look at
this thread . Experts posted their views on the same subject. It might be helpful for you. Thanks.