fails:String#chr returns a copy of self
fails:String#chr returns a String
fails:String#chr returns an empty String if self is an empty String
fails:String#chr returns a 1-character String
fails:String#chr returns the character at the start of the String
fails:String#chr returns a String in the same encoding as self
fails:String#chr understands multi-byte characters
fails:String#chr understands Strings that contain a mixture of character widths
