refactor(coprocessor): improves test coverage on host-listener

[PanGan21]

Summary

Adds unit tests on host-listener files:
reorgs

• test_get_missing_ancestors_shallow_reorg — walk back to a known ancestor
• test_get_missing_ancestors_deep_reorg — walk back blocks through a long gap
• test_get_missing_ancestors_beyond_max_depth — stop at max depth limit
• test_check_missing_ancestors_not_ready — skip reorg detection when history < configured blocks

dependence chains

• test_dependence_chains_empty_logs — empty input returns no chains
• test_dependence_chains_across_blocks_false — past dependency ignored when across-blocks flag is off
• test_dependence_chains_connex_two_past_chains_merge — two past chains merge in connex mode

slow lane

• classify_slow_disconnected_components_at_threshold_are_fast — exactly at-threshold chains are not slow
• classify_slow_single_chain_at_boundary — slow lane condition is respected
• propagate_slow_lane_non_linear_dependency — non linear DAG

health check

• is_alive_after_blockchain_tick_update — alive after blockchain tick
• is_alive_after_timeout_tick_update — alive after timeout tick
• is_alive_after_database_tick_update — alive after database tick
• is_alive_after_all_ticks_update — alive after all ticks
• is_alive_at_creation — alive at creation

Closes: https://github.com/zama-ai/fhevm-internal/issues/1155

[github-actions]

Changed Lines Coverage

Coverage of added/modified lines: 97.0%

Per-file breakdown

Diff Coverage

Diff: origin/main...HEAD, staged and unstaged changes

• coprocessor/fhevm-engine/fhevm-engine-common/src/utils.rs (100%)
• coprocessor/fhevm-engine/host-listener/src/cmd/mod.rs (100%)
• coprocessor/fhevm-engine/host-listener/src/database/dependence_chains.rs (100%)
• coprocessor/fhevm-engine/host-listener/src/database/ingest.rs (89.7%): Missing lines 495,513,523,543,547,551
• coprocessor/fhevm-engine/host-listener/src/health_check.rs (100%)

Summary

• Total: 259 lines
• Missing: 6 lines
• Coverage: 97%

coprocessor/fhevm-engine/host-listener/src/database/ingest.rs

  491         );
  492 
  493         assert!(
  494             slow.is_empty(),
! 495             "no chain should be slow at exactly the threshold"
  496         );
  497     }
  498 
  499     // Single chain with exactly max_per_chain ops is not slow.

---

  509             max,
  510         );
  511         assert!(
  512             at_boundary.is_empty(),
! 513             "exactly at threshold should be fast"
  514         );
  515 
  516         let over_boundary = classify_slow_by_split_dependency_closure(
  517             &chains,

---

  519             max,
  520         );
  521         assert!(
  522             over_boundary.contains(&chains[0].hash),
! 523             "one over threshold should be slow"
  524         );
  525     }
  526 
  527     // Non linear: A -> B, A -> C, B -> D, C -> D

---

  539 
  540         assert!(slow.contains(&chains[0].hash), "A should be slow");
  541         assert!(
  542             slow.contains(&chains[1].hash),
! 543             "B should be slow (depends on A)"
  544         );
  545         assert!(
  546             slow.contains(&chains[2].hash),
! 547             "C should be slow (depends on A)"
  548         );
  549         assert!(
  550             slow.contains(&chains[3].hash),
! 551             "D should be slow (depends on B and C)"
  552         );
  553     }
  554 }

---

[mergify]

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lgtm

[PanGan21]

@mergify queue

[mergify]

Merge Queue Status

• ✅ Entered queue — 2026-03-25 09:48 UTC · Rule: main
• ✅ Checks passed · on draft merge queue: embarking main (bfc89a5) and #2119 together #2175
• ✅ Merged — 2026-03-26 00:37 UTC · at f49b9c5dff00d6734cb05d6ed82c5ee2ed36508b

This pull request spent 14 hours 49 minutes 28 seconds in the queue, including 13 hours 48 minutes 53 seconds running CI.

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