_, err := NewReader(bytes.NewReader(b), size)
	if err != ErrFormat {
		t.Errorf("zeroes: error=%v, want %v", err, ErrFormat)
	}

	// repeated directoryEndSignatures
	sig := make([]byte, 4)
	binary.LittleEndian.PutUint32(sig, directoryEndSignature)
	for i := 0; i < size-4; i += 4 {
		copy(b[i:i+4], sig)
	}
	_, err = NewReader(bytes.NewReader(b), size)
	if err != ErrFormat {
		t.Errorf("sigs: error=%v, want %v", err, ErrFormat)