[quality] src/utils/mergeQueue.ts failure arms are unit-covered but never exercised end-to-end through dist/index.js #269

Finding

src/utils/mergeQueue.ts is 100 % line / branch covered by unit tests (__tests__/utils/mergeQueue.test.ts, __tests__/plugins/tideMergeQueue.test.ts), but the bundle e2e suite only drives its happy paths. Measured with the recipe from #235 (npx ncc build src/main.ts -o dist --source-map --no-source-map-register, then npx vitest run __tests__/bundle --coverage --coverage.autoAttachSubprocess --coverage.excludeAfterRemap --coverage.include='src/**/*.ts' --coverage.include='dist/**/*.js') on main @ 61577d5, Node v26.10.0, vitest 5.0.1:

Never reached through dist/index.js:

• queueState catch: an HTTP or GraphQL failure on the state query (a GHES without the queue fields, a token that may not read it) → once-per-run core.warning and fallback to the REST merge. warnedUnavailable is never exercised across two pull requests in one run.
• queueState → repository.pullRequest === null → undefined (no warning).
• enqueue catch and every classify() kind: head_moved, already_queued, not_ready, forbidden, other; and the position-less { ok: true } arm when mergeQueueEntry is null.
• dequeue catch → could not dequeue pr #N warning, and tide's dequeueIfOurs returning false on it (skip reason without (dequeued)).
• errorMessage reading a GraphQL errors[] array (joined with ; ), versus a plain Error.
• enqueuedByBot on an entry whose enqueuer is null.

__tests__/bundle/fakeGithub.ts already has MergeQueueFixture.enqueueError for exactly this; nothing uses it.

Unit evidence: npx vitest run --coverage on main @ 61577d5 → mergeQueue.ts 100 / 100 / 100 / 100. E2E evidence: the recipe above (local run; the repository publishes no e2e coverage, see #235).

Recommendation

• Add __tests__/bundle/mergeQueueFailures.test.ts driving each arm above through dist/index.js against the fake GitHub API: state-query HTTP 500 and GraphQL errors[] → warning + REST merge; null pull request → REST merge, no warning; scheduled lgtm job over two pull requests → one warning; enqueueError for each classify() kind asserting tide's skip reason or ::error::; enqueue with null mergeQueueEntry → enqueued pr #1 without position; dequeue refusal → warning, skip reason without (dequeued); entry with null enqueuer → left in the queue.

Priority

• Impact: medium — unit-covered, not end-to-end; the merge queue fallbacks are what keep existing users merging when GraphQL misbehaves
• Effort: low

Filed by quality agent (hold-gated mode)

🐝 Hive Agent: quality | Instance: hosted-available-lke648397-260827-5q9t | SHA: 61577d5

— hive: agent=quality backend=copilot model=claude-fable-5.1 copilot=1.0.88