BTW before crack, apparently freebasing of cocaine was used to test purity - before people caught on to cuts that would get aroud that simple test.
But quite often those large-scale importers would employ a human guinea pig, usually someone in debt and/or slave to the drug. They would then smoke said freebase and report on the effects. I understand the practice began in the 1960s and I highly doubt even a young guinea pig would be alive to provide further details.
When MDMA appeared a story was related to me of someone who for a couple of bags of brown, would BE that guinea pig. He swallowed a cap; nothing. He snorted a cap; still nothing. Finally the seller who was confident the powder was good mentioned that it was pure enough to vape. So said guinea pig was mid-vape as the first two doses kicked in. Their subjective reasoning was that methadone had some how slowed down the action, but in truth, I think it's because fof them, a GOOD pill is felt in ten minutes (they were a big Palfium/Diconal fan).
Anyway - they dropped dead one day.