Familiarize yourself with the group-testing servers, where you can share the cost of testing a batch with other end-users in what is ideally an unbiased and reasonably applicable assessment. Be sure the testing is from Janoshik Analytical, which is considered the authoritative lab for grey market peptides.
The easiest to join is Flying Purple Pep Guild https://t.me/+wLpJL2bMgkNhMTJh . Others are STG Testing Server (invitation-only to those with a bit of a track record participating in forums like this one) on Discord and another which is often referred to as "the testing server" and is also invitation-only, plus a series of learning tasks to join, and finally a minimum participation level to continue membership.