Testing against either CooperateBot or DivergeBot is risky. Some opponents could cooperate with CooperateBot for meta reasons, while others may fail to halt when faced with a DivergeBot.

The safest case would to see what the opponent does against a DefectBot (most opponents that defect at all would defect against it) except IncrediblyInnocentBot can't generate a DefectBot on its own, either.

EBot (which always returns 'E rather than 'C or 'D) might be a safer version of DivergeBot to use, but it isn't completely fool-proof either. Then again, IncrediblyInnocentBot can check if the opponent returns 'E against EBot -- in that case, it should probably cooperate rather than "do the other thing that's not 'C, whatever it is", to avoid a (0,0) payoff when faced with MimicBot.