t.Fatal("Expected at least one PAX header to be written.")
	}

	// xattr bar should always appear before others
	indices := []int{
		bytes.Index(buf.Bytes(), []byte("bar=bar")),
		bytes.Index(buf.Bytes(), []byte("baz=baz")),
		bytes.Index(buf.Bytes(), []byte("foo=foo")),
		bytes.Index(buf.Bytes(), []byte("qux=qux")),
	}
	if !sort.IntsAreSorted(indices) {
		t.Fatal("PAX headers are not sorted")
	}
}

		t.Fatal(err)
	}
	if err := w.Close(); err != nil {
		t.Fatal(err)
	}
	b := buf.Bytes()

	var sig [4]byte
	binary.LittleEndian.PutUint32(sig[:], uint32(fileHeaderSignature))

	idx := bytes.Index(b, sig[:])
	if idx == -1 {
		t.Fatal("file header not found")
	}
	b = b[idx:]

	if !bytes.Equal(b[6:10], []byte{0, 0, 0, 0}) { // FileHeader.Flags: 0, FileHeader.Method: 0