test: Check why a blockchain test block was rejected

[chfast]

A blockchain test block expected to be invalid counted as correctly rejected however evmone rejected it, so a block failing a rule other than the one the test is about still passed. The header-mismatch branches were the weakest: any difference from the claimed header ended the case silently.

Compare the rejection against the fixture's exception at every exit: block validation, a rejected transaction, requests collection, and each header mismatch, which now names the BlockException it is the symptom of.

Two known gaps are documented rather than checked: transaction senders come from the fixture instead of the signature, so a broken signature surfaces only as a state-root mismatch, and ommer headers are not validated.

🤖 Generated with Claude Code

[codecov]

Codecov Report

❌ Patch coverage is 82.92683% with 7 lines in your changes missing coverage. Please review.
✅ Project coverage is 97.70%. Comparing base (8ec683f) to head (8068e29).

Files with missing lines	Patch %	Lines
test/blockchaintest/blockchaintest_runner.cpp	80.55%	6 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1623      +/-   ##
==========================================
- Coverage   97.73%   97.70%   -0.04%     
==========================================
  Files         171      171              
  Lines       15565    15593      +28     
  Branches     3604     3606       +2     
==========================================
+ Hits        15213    15235      +22     
- Misses        263      269       +6     
  Partials       89       89              

Flag	Coverage Δ
eest-develop	88.61% <77.50%> (-0.09%)	⬇️
eest-develop-gmp	26.66% <4.87%> (-0.05%)	⬇️
eest-legacy	17.19% <65.85%> (+0.17%)	⬆️
eest-libsecp256k1	28.86% <4.87%> (-0.05%)	⬇️
eest-stable	88.61% <77.50%> (-0.09%)	⬇️
evmone-unittests	93.13% <4.87%> (-0.18%)	⬇️

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Components	Coverage Δ
core	96.08% <ø> (ø)
tooling	91.86% <82.92%> (-0.22%)	⬇️
tests	99.80% <ø> (ø)

Files with missing lines	Coverage Δ
test/utils/block_transition.cpp	100.00% <100.00%> (ø)
test/utils/error_matching.cpp	95.83% <100.00%> (+0.37%)	⬆️
test/utils/t8n.cpp	96.74% <100.00%> (ø)
test/blockchaintest/blockchaintest_runner.cpp	83.51% <80.55%> (-0.63%)	⬇️

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[Copilot]

Pull request overview

Tightens blockchain-test rejection checks so invalid blocks must fail for the fixture’s expected reason.

Changes:

• Preserves structured transaction errors for matching.
• Validates transaction, request, block, and header-mismatch rejection reasons.
• Documents signature-recovery and ommer-validation gaps.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
test/utils/t8n.cpp	Renders preserved transaction errors.
test/utils/block_transition.hpp	Stores rejection error codes.
test/utils/block_transition.cpp	Propagates transaction error codes.
test/blockchaintest/blockchaintest_runner.cpp	Adds rejection-reason verification.

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[Copilot]

Pull request overview

Copilot reviewed 6 out of 6 changed files in this pull request and generated 1 comment.

Suppressed comments (2)

test/blockchaintest/blockchaintest_runner.cpp:396

• This disables reason checking for every executed block that contains an ommer, not only fixtures whose expected failure is an unvalidated ommer-header rule. Consequently, an unrelated block with an ommer can fail any header check above for the wrong reason and still be counted as correctly rejected. Gate the exemption on the specific unsupported ommer exception(s), rather than merely on a nonempty ommer list.

                const auto expect_fixture_names = [&](std::string_view names) {
                    if (!names_spec_exception || ommers_not_validated)
                        return;

test/blockchaintest/blockchaintest_runner.cpp:334

• The new rejection-reason behavior has no regression coverage: the existing test/integration/blockchaintest/*.json cases contain no invalid block with expectException. Add invalid fixtures that verify both a matching reason and a deliberately different reason (including validation, rejected-transaction, and computed-header exits), so future broad matching or silent exits cannot reintroduce false positives.

                    EXPECT_TRUE(
                        is_expected_block_exception(block_error, test_block.expected_exception))

[chfast]

Agreed on the coarseness, and I have added a comment stating it: nine validate_block() branches share INCORRECT_BLOCK_FORMAT, so to the matcher these four names are interchangeable, and separating them needs a distinct code per branch.

Worth noting it is not new behaviour introduced here. Before this commit the loader's map_legacy_exception rewrote those same three spec names to INCORRECT_BLOCK_FORMAT outright, so the interchangeability already existed — it was just hidden in the loader, and it destroyed the fixture's stated expectation on the way. This change removes those rewrites and puts the equivalence in one visible table, which is what makes the granularity gap reviewable at all. Giving the branches distinct codes is a change to state/errors.hpp plus validate_block(), deliberately outside this PR.