Come on... This is the signature of the function:

std::string declareWinner(Fighter* fighter1, Fighter* fighter2, std::string firstAttacker)

This function has obviously 3 parameters.

This kata is 6 years old and was solved 2,134 times in C++. Do you really think it's possible there's such an error in sample tests and nobody saw it before you?...

BTW, sample tests are the same as in other languages.

There's a third parameter...

Tests are not the same.