feat(tests): add zero edge cases for modexp eip7883 gas cost tests

[bshastry]

🗒️ Description

This PR adds additional zero edge cases to the ModExp (EIP-7883) gas cost tests. These new test cases improve coverage by testing various combinations of empty and zero-valued inputs for base, exponent, and modulus parameters.

The changes specifically add test cases Z1-Z7 and Z11-Z15 to test edge cases where:

• Empty strings are used for base, exponent, or modulus
• Large zero-filled inputs (1024 bytes) are tested
• Combinations of empty and zero values are explored
• Edge cases with single non-zero bytes at the end of otherwise zero-filled inputs

🔗 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.

[spencer-tb]

cc-ing @LouisTsai-Csie

[LouisTsai-Csie]

Thanks a lot! Could you please help update the table below:

There is a script that might help: #1929 (comment)

[bshastry]

Thanks a lot! Could you please help update the table below:

There is a script that might help: #1929 (comment)

Thank you for your review. I have updated the table. The coverage framework in the table is very good. I just complemented it with some edge cases wrt implementation (spec coverage is excellent).

[LouisTsai-Csie]

No problem from my side! Let's wait for final review and get merge. cc @spencer-tb

[LouisTsai-Csie]

@bshastry I am currently working on some refactoring PR for eip7823 & eip7883, it will give you an overview of test coverage like this.

Additionally, I update the testing infra in the PR for eip7823, to ensure all the output and gas usage is correct. Please feel free to add more cases to test the upper bound.

[spencer-tb]

Amazing!! Thanks 🫡