// if it becomes too large, WriteRune will panic with [ErrTooLarge].
func (b *Buffer) WriteRune(r rune) (n int, err error) {
	// Compare as uint32 to correctly handle negative runes.
	if uint32(r) < utf8.RuneSelf {
		b.WriteByte(byte(r))
		return 1, nil
	}
	b.lastRead = opInvalid
	m, ok := b.tryGrowByReslice(utf8.UTFMax)
	if !ok {
		m = b.grow(utf8.UTFMax)
	}

			t.Fatalf("ReadRune(%U) after UnreadRune got %U,%d not %U,%d (err=%s)", r, r2, nbytes, r, size, err)
		}
	}
}

func TestWriteInvalidRune(t *testing.T) {
	// Invalid runes, including negative ones, should be written as
	// utf8.RuneError.
	for _, r := range []rune{-1, utf8.MaxRune + 1} {
		var buf Buffer
		buf.WriteRune(r)

	switch {
	case !utf8Valid1 || !utf8Valid2:
		// Name and Comment definitely not UTF-8.
		f.NonUTF8 = true
	case !utf8Require1 && !utf8Require2:
		// Name and Comment use only single-byte runes that overlap with UTF-8.
		f.NonUTF8 = false
	default:
		// Might be UTF-8, might be some other encoding; preserve existing flag.
		// Some ZIP writers use UTF-8 encoding without setting the UTF-8 flag.

}

// WriteRune writes a single Unicode code point, returning
// the number of bytes written and any error.
func (b *Writer) WriteRune(r rune) (size int, err error) {
	// Compare as uint32 to correctly handle negative runes.
	if uint32(r) < utf8.RuneSelf {
		err = b.WriteByte(byte(r))
		if err != nil {
			return 0, err
		}
		return 1, nil
	}
	if b.err != nil {
		return 0, b.err
	}
	n := b.Available()

</li>

<li>
Converting a slice of runes to a string type yields
a string that is the concatenation of the individual rune values
converted to strings.

<pre>
string([]rune{0x767d, 0x9d6c, 0x7fd4})   // "\u767d\u9d6c\u7fd4" == "白鵬翔"
string([]rune{})                         // ""
string([]rune(nil))                      // ""

type runes []rune

		File: []ZipTestFile{
			{
				Name:    "世界",
				Content: []byte{},
				Mode:    0644,
				// Name is valid UTF-8, but format does not have UTF-8 flag set.
				// We don't do UTF-8 detection for multi-byte runes due to
				// false-positives with other encodings (e.g., Shift-JIS).
				// Format says encoding is not UTF-8, so we trust it.
				NonUTF8:  true,
				Modified: time.Date(2017, 11, 6, 13, 9, 27, 0, timeZone(-8*time.Hour)),

Amery, Memo Akten, Michael Heilman, Michael Peteuil, Nathan Daly, Nicolas
Fauchereau, @ninotoshi, Olav Nymoen, @panmari, @papelita1234, Pedro Lopes,
Pranav Sailesh Mani, RJ Ryan, Rob Culliton, Robert DiPietro, @ronrest, Sam
Abrahams, Sarath Shekkizhar, Scott Graham, Sebastian Raschka, Sung Kim, Surya
Bhupatiraju, Syed Ahmed, Till Hoffmann, @timsl, @urimend, @vesnica, Vlad Frolov,

pkg testing, func RunBenchmarks(func(string, string) (bool, error), []InternalBenchmark)
pkg testing, func RunExamples(func(string, string) (bool, error), []InternalExample) bool
pkg testing, func RunTests(func(string, string) (bool, error), []InternalTest) bool
pkg testing, func Short() bool
pkg testing, method (*B) Error(...interface{})
pkg testing, method (*B) Errorf(string, ...interface{})