this question will be a bit of a coding challenge perhaps, as I am not sure what exactly has gone wrong in the 400-odd lines of the class in question (though I suspect it will be related to either compareSalesWithCampaigns(), getMaxCampaignBonusForDate(), isProductEligibleForCampaign(), getCampaignBonus(), getCampaignBonusForDate() or isCampaignDateValid() ).