test: Check submitblock return values #18745

Add assert_equal in some tests to check the submitblock return value

ACK fa262712ca0981cb0ee68cd3dd99a214a20dcbf1

Updated tests pass locally for me.

Future follow-ups:

• Does it make sense to document the RPC API strings like block-validation-failed somewhere?
• It looks like there are a few other test files that call submitblock without checking the return value; should those be updated as well?

It looks like there are a few other test files that call submitblock without checking the return value; should those be updated as well?

I'd say no. Most of them just send a valid block, so the result is None. If the block wasn't valid, the tests would fail for that reason already.

Does it make sense to document the RPC API strings like block-validation-failed somewhere?

Doesn't the documentation of submitblock tell that those are BIP22 reasons?

The documentation does say they're BIP22 reasons:

Result:
null    (json null) Returns JSON Null when valid, a string according to BIP22 otherwise

However, BIP22 doesn't give a full list of possible strings. For example, it doesn't include inconclusive, block-validation-failed, bad-witness-nonce-size, or bad-witness-merkle-match.

My question was whether it's important to document the full list of reasons somewhere. I don't have a strong opinion about this: mostly I am trying to understand how you think about what documentation is important.

No opinion on whether all detailed reasons should be documented. This seems unrelated to this test change either way?

Correct, it doesn't block this change at all.

When I said "Future Follow-Ups" I meant it as a way to get your input about future work (possibly that I might do) in separate PRs. Sorry I distracted from the main point of this change.