An Iyengar assessment is a rigorous process. You are not eligible unless you have practiced Iyengar yoga for a number of years and have studied with a mentor for at least one year.
The assessment takes place over an entire weekend. First you are sent a written exam which is done as a take home test. You have 4 weeks to compete the exam.
Nine days before your assessment, you are given three poses with which you have to create a sequence. You may add one or two other poses to make the sequence cohesive and you must include a headstand and shoulder stand variation. During your assessment weekend you will be expected to teach this sequence to a group of students in 45 minutes while being observed. You will be assigned a designated student who will act as if they have a common condition such as low back pain, headache, shoulder pain, etc. Besides teaching, you will be evaluated on how you handle this situation.
There is a group practice where the assessors and the candidates practice together to get to know each other. Then there is a conducted performance where one of the assessors will call out the names of the poses, in Sanskrit, and observe the candidates perform the poses according to the Iyengar method.
During the weekend you will be expected to perform and inversions practice. These poses are considered an important part of Iyengar Yoga and they want to see how you practice this category of asana. I will have to prepare and perform a 35 - 45 minute inversion sequence. Certain variations of Sirsasana and Sarvangasana are required elements. This past weekend I created a sequence and practiced it to see if the poses make sense. If you like, you can watch a video of it here. It's not a class. I'm not teaching. I talk to myself during part of it. And for a lot of it I am not saying anything. I have to hold Sirsasana and Sarvangasana for 3 minutes each before I can do the variations, so, it is not very exciting to watch. I have until September to perfect it. Since inversions are to be practiced a little every day and completely once a week, I will have plenty of time to work on it.