Given all this, it probably makes sense to test the software (or rather a zkSNACKS server behavior) in another way, namely by feeding it with outputs that any blockchain surveillance firm will deem dirty and then looking if some of these outputs are never getting accepted into a CoinJoin round.
The problem with this idea is that it will always be an
O(1), i.e. it could be a one-off 'bug' or 'temporary server issue'.
If there is no clear GUI message, any occurrence of blacklisting could be dismissed as a technical problem or bug.
It's also possible that no matter how hard you try, you can't outsmart their algorithm and purposely trigger it.
That's what I meant earlier. Meanwhile there could be someone on the other end of the world who got blacklisted and there's no way of knowing. It's impossible to know that blacklisting has not happened.
it's just quite hard to prove someone did get blacklisted, and impossible to prove that nobody got blacklisted.
Proving the absence of something is just very, very hard. You would need to have data about every single mixing / CoinJoin attempt to make a statement such as 'they do not even blacklist yet'.