{"a\xe0\x80cd", not(isValidRune), 1, 2},
}

func TestIndexFunc(t *testing.T) {
	for _, tc := range indexFuncTests {
		first := IndexFunc([]byte(tc.in), tc.f.f)
		if first != tc.first {
			t.Errorf("IndexFunc(%q, %s) = %d; want %d", tc.in, tc.f.name, first, tc.first)
		}
		last := LastIndexFunc([]byte(tc.in), tc.f.f)
		if last != tc.last {

		// then add only one delete marker if requested
		sort.SliceStable(fivs.Versions, func(i, j int) bool {
			return !fivs.Versions[i].Deleted
		})
		if idx := slices.IndexFunc(fivs.Versions, func(fi FileInfo) bool {
			return fi.Deleted
		}); idx > -1 {
			fivs.Versions = fivs.Versions[:idx+1]
		}
		dedupVersions = append(dedupVersions, fivs)
	}