fails:Enumerable#min_by returns an enumerator if no block
fails:Enumerable#min_by returns nil if #each yields no objects
fails:Enumerable#min_by returns the object for whom the value returned by block is the largest
fails:Enumerable#min_by returns the object that appears first in #each in case of a tie
fails:Enumerable#min_by uses min.<=>(current) to determine order
fails:Enumerable#min_by is able to return the maximum for enums that contain nils
