It depends on what the dr ordered:
1. Spot test requires just one poop
2. 3 day poop test requires daily diary of food (recommend 100g fat/day)
Both tests measures amount of fat in stool but #2 is more accurate because you will record EXACTLY what your child ate and collect all poop (befire it hits water). Fór number 2, there will be a calculation that tell you how much your child is absorbing based on food intake. I also read that prior to this 3 day fecal fat test one must be a "normal" diet at about 100g fat per day ( good luck if you can manage that) to get accurate reading.
Have you asked for fecal elastase too? That's just a single easy poop sample.
If you think there is malabsorption, suggest asking for fat soluble vitamins levels, A, D, K and E (blood test) which are often low in malabsorption disorders.
Hope that helps,
Julie