test(tests): add BLOCKHASH genesis hash availability test

[bshastry]

🗒️ Description

Add minimal regression test for BLOCKHASH opcode to verify genesis hash availability in blockchain tests. This test ensures that BLOCKHASH(0) returns the genesis hash (non-zero value) when executed in block 1, validating that blockchain test infrastructure properly initializes the block_hashes mapping before execution.

Context: This is a regression test for a bug found in the revm blockchaintest runner where block_hashes weren't being populated, causing BLOCKHASH(0) to incorrectly return 0. This broke tests using dynamic address computations like BLOCKHASH(0) | TIMESTAMP, where the computed address would be wrong, leading to test failures.

The test validates infrastructure correctness by:

1. Executing ISZERO(BLOCKHASH(0)) in a contract deployed in block 1
2. Verifying the result is 0 (false), proving the genesis hash exists and is non-zero
3. Ensuring future tests with BLOCKHASH-derived addresses will work correctly

🔗 Related Issues or PRs

N/A.

✅ Checklist

• All: Ran fast tox checks to avoid unnecessary CI fails, see also Code Standards and Enabling Pre-commit Checks:

  uvx --with=tox-uv tox -e lint,typecheck,spellcheck,markdownlint

• All: PR title adheres to the repo standard - it will be used as the squash commit message and should start type(scope):.
• All: Considered adding an entry to CHANGELOG.md.
• All: Considered updating the online docs in the ./docs/ directory.
• All: Set appropriate labels for the changes (only maintainers can apply labels).
• Tests: Ran mkdocs serve locally and verified the auto-generated docs for new tests in the Test Case Reference are correctly formatted.
• Tests: For PRs implementing a missed test case, update the post-mortem document to add an entry the list.
• Ported Tests: All converted JSON/YML tests from ethereum/tests or tests/static have been assigned @ported_from marker.

📝 Additional Notes

File Added: tests/frontier/opcodes/test_blockhash.py

• Test: test_genesis_hash_available (57 lines)
• Valid from: Frontier (earliest fork with BLOCKHASH support)
• Test type: BlockchainTestFiller (requires multiple blocks)

Quality Checks Passed:

• ✅ ruff check - no linting issues
• ✅ ruff format - properly formatted
• ✅ mypy - no type errors
• ✅ uv run fill --fork=Frontier - generates valid fixtures
• ✅ uv run fill --fork=Cancun - works across all forks

Suggested PR Title:

test(tests): add BLOCKHASH genesis hash availability test

[bshastry]

CC @rakita who asked for such a test (upstream fix PR bluealloy/revm#3024)

[rakita]

Would be great to add additional block, and in block 2 to fetch block 1 hash, so that we can test both genesis and first executed block insertion.

[LouisTsai-Csie]

The current test structure looks good, but it is worth considering @rakita’s suggestion to include an additional scenario.

[bshastry]

Would be great to add additional block, and in block 2 to fetch block 1 hash, so that we can test both genesis and first executed block insertion.

Thank you for your feedback. I have updated the test accordingly such that after both blocks in the test are executed, the storage at key 0, 1 are expected to be zero (as per the logic of iszero(blockhash(0)) and iszero(blockhash(1))). Hope this change is fine @LouisTsai-Csie 🙏

[marioevz]

LGTM, thanks!