fails:String#encode transcodes to the default internal encoding with no argument
fails:String#encode raises UndefinedConversionError if the String contains characters invalid for the target     encoding
fails:String#encode replaces invalid characters
fails:String#encode replaces xml characters
fails:String#encode replaces xml characters and quotes the result
fails:String#encode returns self when called with only a target encoding
fails:String#encode returns a String with the given encoding
fails:String#encode! transcodes to the default internal encoding with no argument
fails:String#encode! raises UndefinedConversionError if the String contains characters invalid for the target     encoding
fails:String#encode! replaces invalid characters
fails:String#encode! replaces xml characters
fails:String#encode! replaces xml characters and quotes the result
fails:String#encode! tags the String with the given encoding
