This has been pushed by the right for years and in the 7 states where it's been implemented its been a money sucking failure showing that less than 1% of recipients in all states, but one, tested positive for drugs while the national average for drug use is 9.4%.
"The national drug use rate is 9.4 percent. In these states, however, the rate of positive drug tests to total welfare applicants ranges from 0.002 percent to 8.3 percent, but all except one have a rate below 1 percent."
What 7 States Discovered After Spending More Than $1 Million Drug Testing Welfare Recipients
That being said, I say give all new recipients, excluding parents, a couple months to be depressed do drugs party whatever, because for most, going on assistance is a huge negative life changing event. After the 2 months start regular drug testing. Parents on assistance should be tested right away, and consistently through.