Things to check when you are applying hard fork upgrade.
There are few jobs and check points to increase the confidence of your code change.
Test Your change on devnet:
Merge your change into dev-upgrade branch. And update your hard fork block number. Code will auto deploy to devnet.
Apply your hard fork block ahead of current block and witness before and after. Blockchain grows as usual.
Create one node from your end, synchronize from the scratch to new change state.
Check Miner log whether there is error pumping out.
- Ask protocol team to check devnet's log.
- Check your local node logs
Check related API returning new data.