My parents are giving me a home drug test. (It looks like a cheap one. I can't open it but it looks like it consists of a tab thing that you insert into the urine.)

They caught me smoking weed so they said they are going to test me. I told them it was my first time. I have been clean for a month now, but I was using for three months before that pretty heavily (1 or 2 times a day average, sometimes more). Since they think that I only used it once they will expect me to be clean NOW.

So my question is this: Can I have a friend pee in a bottle, and save it? Since I don't know exaclty when they are going to test me, I will have to keep it for a few days.

When my parents give me the test, can I whip out the bottle, put it under a heating lamp for a few mins, and then give them that? (They wont be watching me or anything.)

Will the home test be able to tell that the urine was not fresh? (It didn't mention anything about it on the label.) Or would I be in the clear? I could get a fresh sample every few days until they test me just to make sure that its not too old, if that matters.