test(stm): split the IVC prover monolith into separated tests

[hjeljeli32]

Content

prove_all_scenarios ran eight scenarios in one test to amortize a single setup. It costs 1393.9 s on the nightly and, with the two keygen-only prover_setup tests of the single-threaded ivc-snark-sequential group, forms an 1830 s serial tail, 59 % of the job's 3116 s test step.

Splitting it naively costs more than it saves: at user / real = 7.39 the test already saturates the runner's four vCPUs and peaks at 11.02 GiB against 16 GB, so the group must stay serial and each extra process adds 70-125 s. The split is paid for by removing proving instead — the five rejection scenarios generate no proofs, and the six prove_with_transcript calls cover only four distinct (transition type, transcript) pairs. Warm and local: 175.5 s to 126.0 s, −28 %. On CI, normalised against the two untouched keygen-only tests of the same group, the two replacements cost 951 s against the monolith's 1264 s (−313 s, −25 %) taking the serial tail to 1408 s and the job's test step to 2348 s.

Changes

• Rejection scenarios to the fast tier (prover_input.rs, proof.rs): four run_rejects_* helpers become prepare tests asserting typed IvcCircuitError variants instead of is_err(), at ~0.36 s on every PR rather than nightly only, each failed inside prepare, which since Recover the ignored IVC prover input preparation tests #3466 needs no SRS, keygen or cache. The fifth duplicated prepare_rejects_invalid_snark_proof and is deleted.
• Monolith split, mature next-epoch proving removed (proof.rs): prove_bootstrap_produces_first_epoch_proof_and_rolling_state (3 proofs) and prove_same_epoch_produces_proof_without_rolling_state (1 proof) share a plain build_slow_test_context(), no OnceLock, which amortizes nothing under nextest's process-per-test model. run_next_epoch_path adds no new pair, and prepare_at_next_epoch_carries_lookahead_protocol_parameters already pins its state and accumulator against the same asset.
• Context decoupled from asset generation (proof.rs): the slow context builds Global and the genesis bootstrap input from the committed genesis fixture rather than AssetGenerationSetup. No measurable wall-time change — setup spans 7.1-8.7 s for identical artifacts and the ~1.0 GB proving key deserialize dominates — so it is kept for the decoupling, not for speed.
• Unchanged: .config/nextest.toml and filter-slow-tests.sh match on module path, so the renamed tests stay grouped and watched. The coverage the reduction rests on still passes; restore a mature next-epoch proving case if production later couples transition type with accumulator provenance, public inputs or transcript selection.

Pre-submit checklist

• Branch
  • Tests are provided (if possible)
  • Crates versions are updated (if relevant)
  • CHANGELOG file is updated (if relevant)
  • Commit sequence broadly makes sense
  • Key commits have useful messages
• PR
  • All check jobs of the CI have succeeded
  • Self-reviewed the diff
  • Useful pull request description
  • Reviewer requested
• Documentation
  • No new TODOs introduced

Issue(s)

Closes #3468

[github-actions]

Test Results

     5 files  ± 0     221 suites  ±0   1h 57m 34s ⏱️ + 1h 1m 50s
 3 567 tests +62   3 567 ✅ +62  0 💤 ±0  0 ❌ ±0 
11 683 runs  +71  11 683 ✅ +71  0 💤 ±0  0 ❌ ±0 

Results for commit 3de9bf0. ± Comparison against base commit 69572a0.

♻️ This comment has been updated with latest results.

[Copilot]

Pull request overview

This PR restructures the IVC prover tests to reduce CI runtime by splitting the former “monolith” scenario test into focused cases and moving rejection-path coverage to faster prepare-only tests, while decoupling slow-test setup from asset-generation machinery.

Changes:

• Added fast IvcProverInput::prepare rejection tests that assert typed IvcCircuitError variants (tampered message, mismatched AVK, corrupted previous IVC proof, mismatched Global).
• Replaced the prove_all_scenarios monolith with two standalone slow prover tests (bootstrap and same-epoch), using a shared slow-context builder.
• Built slow-test Global and genesis bootstrap input from committed genesis fixtures and verification-context assets (not asset-generation setup).

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
mithril-stm/src/proof_system/ivc_halo2_snark/prover_input.rs	Adds fast-tier prepare rejection tests using committed assets and typed error assertions.
mithril-stm/src/proof_system/ivc_halo2_snark/proof.rs	Splits the slow prover monolith into two tests and rebuilds slow context from committed fixtures/assets.

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[jpraynaud]

LGTM 👍

[damrobi]

LGTM 👍