fails:Integer#upto [stop] when self and stop are Fixnums does not yield when stop is less than self
fails:Integer#upto [stop] when self and stop are Fixnums yields once when stop equals self
fails:Integer#upto [stop] when self and stop are Fixnums yields while increasing self until it is less than stop
fails:Integer#upto [stop] when self and stop are Fixnums yields while increasing self until it is greater than floor of a Float endpoint
fails:Integer#upto [stop] when self and stop are Fixnums raises an ArgumentError for non-numeric endpoints
fails:Integer#upto [stop] when self and stop are Fixnums returns an Enumerator
