I'd suggest you either break a finger or sprain an ankle. Also, rub some poison ivy under your left armpit. Drink some liquid dish soap to simulate a nice intestinal parasite. Finally, dump 16 ounces of water over your head and don't dry off.

That's a "realistic" test!

But seriously -

1. First Aid KIt - even if it's a "simulation" can you handle
a) sprains/breaks
b) burns (liquid and fire burns)
c) insect bites
d) diarreah (corrolary - do you have personal sanitation items?)
2. Water
a) Do you have enough water to use what you carry exclusively for the test?
b) If not, can you make/procure clean water with what you are carrying (I've had pond water cleaned up by a filter - worked great)?
3. Shelter
a) Can you stay warm and dry even if it's raining hard?
b) Can you actually REST in your shelter - maybe not sleep, but not be clinging to a tree branch for fear of falling either.
4. Signaling
a) Can you be seen and heard?
b) Do you have a means of attracting attention if you can see help and they can't see you.

This is the basic requirements, food comes much further down the line, perhaps some granola or crackers, but for the 72 hour scenario, you'll be hungry, but not likely to starve or anything.