mode := f.Mode()
	if want == 0 {
		t.Errorf("%s mode: got %v, want none", f.Name, mode)
	} else if mode != want {
		t.Errorf("%s mode: want %v, got %v", f.Name, want, mode)
	}
}

func TestInvalidFiles(t *testing.T) {
	const size = 1024 * 70 // 70kb
	b := make([]byte, size)

	// zeroes
	_, err := NewReader(bytes.NewReader(b), size)
	if err != ErrFormat {