I think it's not compulsory in every fight as some fighters AFAIK don't go with that process. That would only be required if the other camp would want that they will be tested before the fight, correct me if I'm wrong.
In the case of Mayweather vs Pacman, the former initiated or asked the commission that they will be tested by random and in a surprising manner.
I don't think that the fight will be canceled because of this issue because neither fighter is doing this doping thing.
Donaire does not ask for it in his previous fights IIRC, so can we call this an insult on Casimero's camp? For me, it shows that he doesn't trust Casimero and believes that he is using an enhancing drug to increase his stamina and power, how about you, what message did you see in this news?