Encoding/decoding test vectors for BigSize

[douglaz]

I was taking a look at https://github.com/lightning/bolts/blob/master/01-messaging.md#bigsize-decoding-tests

But after searching the code I couldn't find the corresponding test vectors, specially for the decoding part.

Is this really missing? If so, would it be worth to include such tests, perhaps as an easy "good first issue"?

[TheBlueMatt]

Yea, we probably never bothered to copy those over, would make sense IMO, please feel free to add them!

[AdvaitPote]

Hi @douglaz. I would love to work on this. Please tell me where should I start?

[douglaz]

Hi @douglaz. I would love to work on this. Please tell me where should I start?

A minimal start would be to add two functions (one for decoding and the other for encoding) to mod tests on lightning/src/util/ser.rs.

For instance, to test the following cases given on https://github.com/lightning/bolts/blob/master/01-messaging.md#bigsize-decoding-tests:

    {
        "name": "eight byte high",
        "value": 18446744073709551615,
        "bytes": "ffffffffffffffffff"
    },
    {
        "name": "two byte not canonical",
        "value": 0,
        "bytes": "fd00fc",
        "exp_error": "decoded bigsize is not canonical"
    },

You can create something like:

#[test]
fn bigsize_decoding() {
	let mut stream = std::io::Cursor::new(::hex::decode("ffffffffffffffffff").unwrap());
	assert_eq!(super::BigSize::read(&mut stream).unwrap().0, 18446744073709551615);
	let mut stream = std::io::Cursor::new(::hex::decode("fd00fc").unwrap());
	assert_eq!(super::BigSize::read(&mut stream).err(), Some(crate::ln::msgs::DecodeError::InvalidValue));
}

And to test the last case on https://github.com/lightning/bolts/blob/master/01-messaging.md#bigsize-encoding-tests:

{
    "name": "eight byte high",
    "value": 18446744073709551615,
    "bytes": "ffffffffffffffffff"
}

This would do:

#[test]
fn bigsize_encoding() {
	let mut stream = super::VecWriter(Vec::new());
	super::BigSize(18446744073709551615).write(&mut stream).unwrap();
	assert_eq!(stream.0, ::hex::decode("ffffffffffffffffff").unwrap());
}

Then add the other tests cases, comments, and perhaps use a function/macro/loop to avoid code repetition.

After adding all the tests cases just create a pull request. See https://github.com/lightningdevkit/rust-lightning/blob/main/CONTRIBUTING.md#contribution-workflow