Add MIP-8 page commit tests.

[mijovic]

ENG-1132

🗒️ Description

🔗 Related Issues or PRs

N/A.

✅ Checklist

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

  just static

• All: PR title adheres to the repo standard - it will be used as the squash commit message and should start type(scope):.
• 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.

Cute Animal Picture

Greptile Summary

This PR adds a new test file, test_paged_storage_trie.py, that covers the MIP-8 page-based storage commitment primitives page_commit and storage_root_paged. The tests are split into two categories: self-referential known-answer vectors for page_commit (with an appropriate disclaimer in the module docstring) and structural property tests.

• Known-answer vectors pin six page_commit outputs (single slot, pair, multi-level, full page, sparse even) to catch accidental ISMC regressions, with a clear warning that they must be cross-checked against the Monad reference client.
• Property tests cover zero-page rejection, length invariants, determinism, slot-value sensitivity, insertion-order independence, multi-page root distinguishability, and a manual keccak-MPT reconstruction against the single-page codepath.

Confidence Score: 5/5

This is a test-only addition with no changes to production code; safe to merge.

The PR adds only a new test file. No production logic is modified. The known-answer vectors carry a clear self-referential disclaimer, and all structural property tests are independently correct. The two pre-existing review thread concerns (the functionally duplicate empty-storage test and the dead < 32 branch in the manual reconstruction) are style/coverage issues already on the author's radar and do not introduce incorrect behaviour.

No files require special attention.

Important Files Changed

Filename	Overview
packages/testing/src/execution_testing/forks/tests/test_paged_storage_trie.py	New test file adding characterization vectors and property tests for MIP-8 page-based storage commitment; no logic bugs introduced, known limitations flagged in prior review threads.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A[_storage helper\nslot→Bytes32 key mapping] --> B[storage_root_paged]
    C[_page helper\noffset→4096-byte page image] --> D[page_commit]

    subgraph "page_commit tests"
        D --> E[test_page_commit_known_vectors\n6 parametrized vectors]
        D --> F[test_page_commit_length_is_32]
        D --> G[test_page_commit_rejects_all_zero_page]
        D --> H[test_page_commit_deterministic]
        D --> I[test_page_commit_sensitive_to_value]
        D --> J[test_page_commit_sensitive_to_offset]
    end

    subgraph "storage_root_paged tests"
        B --> K[test_empty_storage_is_empty_trie_root]
        B --> L[test_storage_root_length_is_32]
        B --> M[test_storage_root_order_independent]
        B --> N[test_storage_root_distinguishes_pages]
        B --> O[test_storage_root_clears_to_empty_when_slots_omitted]
        D --> P[test_single_page_root_matches_manual_reconstruction\nmanual keccak-MPT cross-check]
        B --> P
    end

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flowchart TD
    A[_storage helper\nslot→Bytes32 key mapping] --> B[storage_root_paged]
    C[_page helper\noffset→4096-byte page image] --> D[page_commit]

    subgraph "page_commit tests"
        D --> E[test_page_commit_known_vectors\n6 parametrized vectors]
        D --> F[test_page_commit_length_is_32]
        D --> G[test_page_commit_rejects_all_zero_page]
        D --> H[test_page_commit_deterministic]
        D --> I[test_page_commit_sensitive_to_value]
        D --> J[test_page_commit_sensitive_to_offset]
    end

    subgraph "storage_root_paged tests"
        B --> K[test_empty_storage_is_empty_trie_root]
        B --> L[test_storage_root_length_is_32]
        B --> M[test_storage_root_order_independent]
        B --> N[test_storage_root_distinguishes_pages]
        B --> O[test_storage_root_clears_to_empty_when_slots_omitted]
        D --> P[test_single_page_root_matches_manual_reconstruction\nmanual keccak-MPT cross-check]
        B --> P
    end

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_{Reviews (4): Last reviewed commit: "Fix lint in paged storage trie tests" | Re-trigger Greptile}

[greptile-apps]

if len(encoded) < 32 branch is dead for all parametrized cases

For a single-page leaf the MPT root_node encodes to a [hex-prefix-path, rlp(commitment)] structure where the path alone is 33 bytes (0x20 || 32-byte keccak key) and the value is 33 bytes. rlp.encode(root_node) is therefore always well above 32 bytes, so the keccak256(encoded) path on line 200 is never exercised by this test. The assertion on line 203 ends up testing only the else / Hash32(root_node) branch. This is consistent with what the production code does for these inputs, but if the threshold condition was accidentally inverted in either place the test would not catch it.

Prompt To Fix With AI

This is a comment left during a code review.
Path: packages/testing/src/execution_testing/forks/tests/test_paged_storage_trie.py
Line: 187-203

Comment:
**`if len(encoded) < 32` branch is dead for all parametrized cases**

For a single-page leaf the MPT `root_node` encodes to a `[hex-prefix-path, rlp(commitment)]` structure where the path alone is 33 bytes (`0x20` || 32-byte keccak key) and the value is 33 bytes. `rlp.encode(root_node)` is therefore always well above 32 bytes, so the `keccak256(encoded)` path on line 200 is never exercised by this test. The assertion on line 203 ends up testing only the `else` / `Hash32(root_node)` branch. This is consistent with what the production code does for these inputs, but if the threshold condition was accidentally inverted in either place the test would not catch it.

How can I resolve this? If you propose a fix, please make it concise.

[pdobacz]

LGTM, this is a great addition to the tests of the mEELS implementation of MIP-8, but note it is not a new spec test (the remaining 3 points from your list you've sent me seem to be new spec tests)

[pdobacz]

the CI failure, seems like it needs a formatter run:

uv run ruff format src packages tests && uv run ruff check src packages tests --exclude tests/fixtures --fix --unsafe-fixes

is my go-to line for this

just static

to check afterwards