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