for _, v := range vectors {
		got, err := formatPAXRecord(v.inKey, v.inVal)
		ok := (err == nil)
		if ok != v.ok {
			if v.ok {
				t.Errorf("formatPAXRecord(%q, %q): got format failure, want success", v.inKey, v.inVal)
			} else {
				t.Errorf("formatPAXRecord(%q, %q): got format success, want failure", v.inKey, v.inVal)
			}
		}
		if got != v.want {
			t.Errorf("formatPAXRecord(%q, %q): got %q, want %q",

	if len(paxHdrs) > 0 || isGlobal {
		// Write each record to a buffer.
		var buf strings.Builder
		// Sort keys for deterministic ordering.
		for _, k := range slices.Sorted(maps.Keys(paxHdrs)) {
			rec, err := formatPAXRecord(k, paxHdrs[k])
			if err != nil {
				return err
			}
			buf.WriteString(rec)
		}

		// Write the extended header file.
		var name string
		var flag byte
		if isGlobal {