if atEOF && len(data) == 0 {
		return 0, nil, nil
	}
	return 1, data[0:1], nil
}

var errorRune = []byte(string(utf8.RuneError))

// ScanRunes is a split function for a [Scanner] that returns each
// UTF-8-encoded rune as a token. The sequence of runes returned is
// equivalent to that from a range loop over the input as a string, which

func TestScanRune(t *testing.T) {
	for n, test := range scanTests {
		buf := strings.NewReader(test)
		s := NewScanner(buf)
		s.Split(ScanRunes)
		var i, runeCount int
		var expect rune
		// Use a string range loop to validate the sequence of runes.
		for i, expect = range test {
			if !s.Scan() {
				break
			}
			runeCount++

pkg bufio, func NewScanner(io.Reader) *Scanner
pkg bufio, func ScanBytes([]uint8, bool) (int, []uint8, error)
pkg bufio, func ScanLines([]uint8, bool) (int, []uint8, error)
pkg bufio, func ScanRunes([]uint8, bool) (int, []uint8, error)
pkg bufio, func ScanWords([]uint8, bool) (int, []uint8, error)
pkg bufio, method (*Reader) WriteTo(io.Writer) (int64, error)
pkg bufio, method (*Scanner) Bytes() []uint8