A couple of my friends promoted to Shodan or Black Belt last weekend. It takes about 6 years to achieve. It takes a lot of hard work and sweat, not to mention pain.
The test usually takes 3 hours, you have to perform all the requirements in front of all the students and instructor. At the end, we do a randori or free sparring. It is usually about 10 minutes and you have to perform techniques to multiple attackers. Although no one is there to hurt you, it is difficult. Your nerves take the best of you. Those 10 minutes feel like hours.