`zcashd` converts the PoWLimit into a compact representation before
using it to perform difficulty filter checks.
The Zcash specification converts to compact for the default difficulty
filter, but not for testnet minimum difficulty blocks. (ZIP 205 and
ZIP 208 don't specify this conversion either.) See #1277.
* Implement Expanded to Compact Difficulty
* Implement Arbitrary for CompactDifficulty
Remove the derive, and generate values from random block
hashes.
* Implement Arbitrary for ExpandedDifficulty and Work
* Use Arbitrary for CompactDifficulty in Arbitrary for Block
* Test difficulty on all block test vectors
And cleanup some duplicate test code
* Round-trip tests for compact test cases
* Round-trip tests for compact difficulty in block test vectors
* Make Add for Work return PartialCumulativeWork
Remove AddAssign for Work
Rewrite a proptest using Sub for PartialCumulativeWork
Use Arbitrary for Work
* Add roundtrip work sum tests
* Add roundtrip comparison difficulty tests
* Add failing proptest cases due to test bugs
* Use Some(_) rather than _.into()
* Reduce visibility of difficulty type inner values
* Split work and other difficulty proptests
This change makes sure that rejected work values don't disable property
tests on other types.
teor