Home Testing Validity vs. Actual Lab Testing

I've never had an actual test before. It came up about 5 years ago, but it turns out the job only had pre-employment random screening, and my name wasn't picked.

I'm an occasional guy...I have some stuff in my house that's ancient just because I buy it and don't use it all that often. Unfortunately, one of those times was about a week ago. Literally out of the blue I had an amazing job opportunity pop up, and lo and behold the interview went great and now I've got the "dreaded test"! *cue music*

Anyway. I've ordered myself two different models of tests from two different online suppliers. If those two different tests both report negative, should I have enough faith in them to go ahead w/ the test "normally"?

From what I read, most of the dipstick style tests test at the 50ng/ml level - is that pretty typical of what is tested in most labs? I know the the GC test will test for lower amounts, but that test isn't standard is it?

Either way, I was just wondering. If for a few days in a row I test clean using the tests I purchased should I have faith?

I've got my mouse button hovering over a Submit Order screen for some supplies from Urea Sample and just wonder if I have to outlay the cash for it. It's not a huge deal - this job is the type of job that money is no object to get it :)