Array not enough elements or too much elements.

If you have an array with a fixed number for the count.

{
  "name": "numbers",
  "type": [
    "array",
    {
      "count": 3,
      "type": "li32"
    }
  ]
}

And you serialize less elements than the count.

  { "numbers": [1,2] }

Then the buffer should probably zero fill to look like this.
<Buffer 01 00 00 00 02 00 00 00 00 00 00 00>
Or have an error.

Currently it looks like this.
<Buffer 01 00 00 00 02 00 00 00>

Yet if I go over 3 values like so.

  { "numbers": [1,2,3,4] }

It actually over-flows the space in which I would expect it to be allowed to write in.
<Buffer 01 00 00 00 02 00 00 00 03 00 00 00 04 00 00 00>

Then the parsing would be wrong, because the extra data would not be for the same packet.

I guess this is really two concerns.

1. Undefined to be 00 filled if count length is fixed number. (An option maybe to zero fill or error?)
2. Over-writing past count to throw an error? (Silent ignore could also be a thing maybe an option?)

Reproduce the fixed-count array serialization using the schema and payload examples in this issue, checking both fewer and more than three elements. Review the serializer entry point and existing tests for fixed-length arrays; done should be a documented, tested decision for padding or rejecting short arrays and for handling excess elements.