test(rpc): cover BatchSizeLimitMiddleware with max_entries=0

[Kewe63]

Summary

BatchSizeLimitMiddleware accepts a max_entries: usize and rejects any batch whose length exceeds it. The CLI value parser parse_max_batch_entries rejects 0 with must be >= 1, so the runtime cap is always at least 1. However, the in-process BatchSizeLimitMiddleware::new constructor has no such guard — callers can intentionally build a "no batches allowed" layer with max_entries = 0, and the middleware must behave sensibly in that case.

This corner case had no test coverage.

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Fix

Added a focused test locking in the documented behavior for max_entries = 0:

• Any non-empty batch is rejected with BATCH_TOO_LARGE_ERROR_CODE, and the error message names the offending size and limit.
• Empty batches are deliberately not asserted on: MockRpcService rejects empty batches with a different error code (-32600 "Invalid request"), and pinning the middleware's response shape on top of that quirk would lock in the wrong contract. The empty-batch case is left to the JSON-RPC layer below the middleware.

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Changes

File: crates/arc-evm-node/src/ (batch size limit tests)

• Added batch_size_limit_max_entries_zero test covering the max_entries = 0 case with non-empty batch inputs.

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How to Test

# Batch size limit tests
cargo test -p arc-evm-node --lib batch_size_limit
# ✅ 7 passed, 0 failed

# Format & lint
cargo fmt --check -p arc-evm-node
cargo clippy -p arc-evm-node --tests -- -D warnings
# ✅ Both clean

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Risk & Impact

None. Test-only addition — no production code modified. Locks in correct middleware behavior for an untested constructor edge case.

Type: 🧪 Test coverage

[ZhiyuCircle]

Hi @Kewe63,

Thank you for your interest in contributing to Arc Node, and apologies for the delay in getting back to this PR.

We're closing out the pull request backlog that predates our current contribution policy. This PR is being closed because it does not reference a GitHub issue. All PRs must reference an existing issue using the format Closes: #XXX, and the author must be assigned to that issue before the PR is opened.

This is not a judgement on the change itself. If you'd still like to land it:

1. Open an issue describing the problem, or find the existing one
2. Comment on the issue requesting assignment, and wait for maintainer approval
3. Open a fresh PR once you have been assigned

Please see CONTRIBUTING.md for details. Thanks again for taking the time to contribute.