How is it even legal to require welfar recipiants to submit such a test? Isn't there a Constitution or something that mentions self-incrimination forbidding that sort of thing?
There is that, but they are not being charged with a crime.
It's violated the Bill of Rights, 4th Amendent if not mistaken. No different than illegal police sobriety checkpoints requiring drivers to submit DNA evidence against themselves. Without just cause, police may not conduct a sobriety check if doing so requires your turning over physical evidence against yourself. If during "observation" or your person they then are willing to tesitfy they believed you were impaired, then they can. But they can't make you submit to a breathalyzer or give cotton swabs or blood just because. Similarly, without just cause, the state cannot require those not charged with crimes to submit evidence possibly incriminating themselves, or to receive governmental benefits. To make that legal, the drug tests would have to be universally applied, not just to welfare recipiants but Social Security recipiants and the like as well.
Perhaps you will explain how employers get away with drug testing for a job or random drug testing of employees without being charged with violating the 4th Amendment.
I'm waiting!