A belt test or taekwondo grading is an exam. An exam to see whether you are good enough to move up to the next taekwondo belt.
It's a test of your taekwondo skills. And your mental toughness.
The test is set for your level. And your instructor only expects you to be at that level.
So you are not expected to perform like a red belt at a yellow-stripe grading!
who will test you?
Your instructor will probably sit at the front of the dojang behind a table.
Often your school will invite a taekwondo instructor from another club to assist with the grading. Usually this person is a taekwondo Master. That's a 4th Dan black belt or higher. So it's important to show them a lot of respect.
External examiners are important for making sure that standards are high across all taekwondo schools.
And just so you know what to expect.
The general atmosphere is much more formal than in a normal training session. And your instructor won't smile at you. Or encourage you as he or she might normally.
If that worries you maybe try to remember this.
Your instructor will be willing you on inside the whole time. Hoping so much that you show off your best taekwondo. But because it's an exam. He or she just can't show it.