Tilt table testing looks for differences in erect and supine blood pressures. Basically, when you stand up, gravity naturally pulls your blood down to your feet. This means the amount of blood going through the heart drops, and your blood pressure drops. To prevent this from happening, certain reflexes are invoked to maintain the blood flow through your heart and your blood pressure. In some people, this reflex doesn't work properly and they can faint on standing up because of low blood pressure and hence decreased blood flow to the brain. Probably the most common cause is antihypertensives such as beta-blockers and diuretics. I presume you are on neither.
Anyway, the test is painless and I imagine it will show no abnormality.
Hope this helps