func ToTitleSpecial(c unicode.SpecialCase, s []byte) []byte {
	return Map(c.ToTitle, s)
}

// ToValidUTF8 treats s as UTF-8-encoded bytes and returns a copy with each run of bytes
// representing invalid UTF-8 replaced with the bytes in replacement, which may be empty.
func ToValidUTF8(s, replacement []byte) []byte {
	b := make([]byte, 0, len(s)+len(replacement))

	{"\xFC\x80\x80\x80\x80\xAF", "\uFFFD", "\uFFFD"},
}

func TestToValidUTF8(t *testing.T) {
	for _, tc := range toValidUTF8Tests {
		got := ToValidUTF8([]byte(tc.in), []byte(tc.repl))
		if !Equal(got, []byte(tc.out)) {
			t.Errorf("ToValidUTF8(%q, %q) = %q; want %q", tc.in, tc.repl, got, tc.out)
		}
	}
}

func TestTrimSpace(t *testing.T) { runStringTests(t, TrimSpace, "TrimSpace", trimSpaceTests) }