fails:String#tr_s returns a string processed according to tr with newly duplicate characters removed
fails:String#tr_s accepts c1-c2 notation to denote ranges of characters
fails:String#tr_s pads to_str with its last char if it is shorter than from_string
fails:String#tr_s translates chars not in from_string when it starts with a ^
fails:String#tr_s tries to convert from_str and to_str to strings using to_str
fails:String#tr_s returns subclass instances when called on a subclass
fails:String#tr_s taints the result when self is tainted
fails:String#tr_s can replace a 7-bit ASCII character with a multibyte one
fails:String#tr_s can replace multiple 7-bit ASCII characters with a multibyte one
fails:String#tr_s can replace a multibyte character with a single byte one
fails:String#tr_s can replace multiple multibyte characters with a single byte one
fails:String#tr_s does not replace a multibyte character where part of the bytes match the tr string
fails:String#tr_s! modifies self in place
fails:String#tr_s! returns nil if no modification was made
fails:String#tr_s! does not modify self if from_str is empty
fails:String#tr_s! raises a RuntimeError if self is frozen
