Probably would add this as a test fixture instead, but sure? Was there any reason why this might not work?

All of the tests will currently pass if the 32 is removed from line
https://github.com/bitcoinjs/bitcoinjs-lib/blob/master/src/hdnode.js#L217, and changed into:

this.keyPair.d.toBuffer().copy(data, 1)

Instead of:

this.keyPair.d.toBuffer(32).copy(data, 1)

So this test covers that case.

There may be one more at, that isn't covered: https://github.com/bitcoinjs/bitcoinjs-lib/blob/master/src/hdnode.js#L193

Most of the fixtures have a seed, the seed is unknown here.

@braydonf just so we didn't need to change our testing fixtures dramatically with more branching (though, my refactoring did that anyway), I generated a fixture that had 5 leading leading zeros here

Whatever, we'll merge both