fails:String#tr returns a new string with the characters from from_string replaced by the ones in to_string
fails:String#tr accepts c1-c2 notation to denote ranges of characters
fails:String#tr pads to_str with its last char if it is shorter than from_string
fails:String#tr raises an ArgumentError a descending range in the replacement as containing just the start character
fails:String#tr raises an ArgumentError a descending range in the source as empty
fails:String#tr translates chars not in from_string when it starts with a ^
fails:String#tr supports non-injective replacements
fails:String#tr tries to convert from_str and to_str to strings using to_str
fails:String#tr returns subclass instances when called on a subclass
fails:String#tr taints the result when self is tainted
fails:String#tr can replace a 7-bit ASCII character with a multibyte one
fails:String#tr can replace a multibyte character with a single byte one
fails:String#tr does not replace a multibyte character where part of the bytes match the tr string
fails:String#tr! modifies self in place
fails:String#tr! returns nil if no modification was made
fails:String#tr! does not modify self if from_str is empty
fails:String#tr! raises a RuntimeError if self is frozen
