Extracted and tested "calculateVotesForCandidate" into a class of its own
Renamed VotesByCandidateCalculation to VotesForCandidateCalculation, because that's what it actually calculates
Extracted calculateVotesByCandidate into it's own, tested, static helper class VotesByCandidateCalculation
Added a static import for calculateVotesByCandidate; candidateStates-Map ist wieder mutable