fails:String#count counts occurrences of chars from the intersection of the specified sets
fails:String#count raises an ArgumentError when given no arguments
fails:String#count negates sets starting with ^
fails:String#count counts all chars in a sequence
fails:String#count raises if the given sequences are invalid
fails:String#count returns the number of occurrences of a multi-byte character
fails:String#count calls #to_str to convert each set arg to a String
fails:String#count raises a TypeError when a set arg can't be converted to a string
