A saliva test can only detect extremely recent usage (72 hours). A piss test is harder to pass, but can be beaten by using the 'water-loading' method. Simply drink as much water as you can often as you can for as long as you can before the sample is due to be taken. Don't use your first urine of the morning, wait til late. Adulterants and substitution methods are hard to pull off and/or don't work, don't be fooled. And unless you are willing to sink some $ into o-t-c drug-passing kits sold at head shops, water loading is the only method that works. I'm a daily smoker and passed after a 4-day heads up for an assistant manager position at my store.