Depends on who's testing you. Here's my experience with a few. First, the legal system... I thoroughly learned the hard way you can't beat them. After attempting seven times, I promise you getting fucked up isn't worth it. If you're probation office is aggressive, and has suspicion you're up to no good, trying to time your drug use doesn't mean shit. Which, despite what anyone may tell you, is remotely your only hope to beating them for a few reasons: They made me strip practically naked, so trying to use anyone else's urine wasn't an option; once the test gets sent off to the lab, they don't just check for drugs in your system, but any the presence of anything else suspicious... high levels of any byproducts associated with both drug use and substances used for dodging detection. Which means they'll still have proof beyond you not blatantly testing positive! You could always get lucky... I did a few times for whatever reason, but it wasn't replicable!

Here's the thing about drug tests for an employer. No one watches you pee, you get a ton of warning (unless it's given to you after a work accident), and it's rare that your test will have the same quality of scientific scrutiny (I want to use a different word than scientific. Toxicological?) as the ones probation gives. Google how long certain substances stay in the body, and gave yourself time. Don't want to? Alright. Whatever. Have someone piss in a condom, tie it tight, tape it to the inside of your upper thigh for body temperature (there's a temp strip on every and any cup you'll dump pee in!), and you know... Feel gross about it like the weirdo you are for doing that.

Side note now that all this has been brought up: if probation is really that effective at catching drug users, why can't other entities make people sign a waiver to be under the same thumb of control? I'm no lawyer, but regardless of whether or not there's a right to, it's super fucking expensive! Terms of probation make the offender pay for it. There's more to extrapolate there, but imagine the resources you'd need to randomly show up at doorsteps with an already expensive test. Even if you make them come to you, it's still a ton of money.