I'm just really nervous about both of the techniques. Mostly due to the gravity test, and if the lab can tell that it's fake piss. I heard that if they shake it, and it doesn't foam, they know right away.
Anyone with a background in urology would understand that some human samples can exhibit a no-foam condition. So therefore, it would be erroneous to conclude that a given urine sample is "synthetic" simply because the sample wont foam.

As far as the Specific Gravity tests, an unexpired, untampered synthetic batch that had been stored properly will register a satisfactory S/G. You can run your own S/G test on the synthetic with a validity test strip. These inexpensive kits are found by doing a Google search for "drug adulteration test kits".